ORAL PRESENTATIONS
April 23: Monday Morning
Structure and Tectonics: From Micro-fractures to Plate Boundary Faults
Co-Chairs: H. Stang, C. Marshall
 
8:10am - 8:30am
Tectonic Implications from the 1992 Mv 7.3 Landers Earthquake Seismic Gap Between Johnson Valley and Long Canyon Faults, San Bernardino County, California
D. Crane
The 85km long surface rupture associated with the 1992 Mv7.3 Landers earthquake exhibits a 5km gap in both the surface expression, and seismic events from south of the Johnson Valley fault to north of the Long Canyon fault. A review of aftershocks reveals a reduction in hypocenter activity south of the Pinto Mountain fault (PMF) that terminate abruptly along a north-dipping line plunging 77 degrees, to a depth of 12 km. This line originates from the surface trace of the Pinto Mountain fault and implies the Pinto Mountain fault under-thrusts the Mojave Desert block, as evidenced by high-angel reverse faulting complex within the Sawtooths hills. Recent work by Gabriel et. al, (2016) proposes strain transference from the San Andreas fault into the Eastern California Shear Zone (ECSZ) byway of the Pinto Mountain Fault. Gravimetric basin models support this hypothesis, suggesting the Long Canyon fault is not an extension to the Johnson Valley fault. Lastly, a curvilinear fault surface traces occupy the gap region that may reflect local warping of earth stresses in responds to interplay between the PMF and the Mojave Desert block.
 
8:30am - 8:50am
Using Stable Isotope Stratigraphy as A Tool to Constrain Structural Models: An Example from San Joaquin Basin, California
A. Maldonado
The use of chemostratigraphy (the study of chemical variations in rocks to determine stratigraphic relationships) in the oil and gas industry is largely confined to geochemical applications such as oil typing, source rock evaluation, source-to-sink studies, among many others. A less commonly used application of chemostratigraphy in the industry is stable isotope stratigraphy. Applications of stable isotope stratigraphy are commonly utilized to make inferences regarding paleoenvironments and paleotectonic settings. However, this study is attempting to use stable isotope signatures, namely δ13Corg and δ18O, as a tool to unravel stratigraphy in complex structural environments where the typical stratigraphic succession has been disrupted via tectonic processes (e.g. faulting, over-turned beds). This methodology is a relatively inexpensive and easy way to acquire data that provides insight into the stratigraphic framework where log signatures are highly disrupted and don’t adhere to the ‘type’ profile. The geologic units present in the study area are the Etchegoin, San Joaquin, and Tulare formations. Each formation has well established depositional model(s) presented in the literature and, importantly, each model(s) represents distinct depositional environments. This distinction is critical to the methodology because perturbations in isotopic signatures are uniquely characteristic of each paleoenvironment. Depositional environments range from primarily open marine to restricted basin to lacustrine. Establishing baselines signatures for each formation is an important first step so that these ‘fingerprints’ can then be carried into areas where the stratigraphy is more challenging to determine. This is an ongoing study and methodology as well as preliminary findings will be presented.
 
8:50am - 9:10am      
Petroleum Geology Comparison of the San Andreas Fault Plate Boundary, California, USA to the Sagaing Fault Plate Boundary, Myanmar (Burma): Structural Style, Oil Field Traps, Tectonic Setting and Basin Development            
T. Davis
The San Andreas fault (SAF) and the Sagaing fault (SF) are the principal structures of seismically active transpressional plate boundaries with similar structural style, ages of deformation, and oil-trapping mechanisms. Both faults have ~300 km of post-Oligocene right-lateral slip, adjacent to fold and thrust belts developed since the late Miocene, oil fields with numerous structural traps, and actively-generating petroleum systems. The oil-rich basins along the SAF plate boundary are data-rich and concepts learned over the last 50 years can be used to explore in the Central Burma Depression (CBD) and to develop its oil fields. Along the SAF plate boundary, the results of exploration drilling, oil field development, reflection seismic data, and earthquake characteristics are consistent with development of a fold and thrust belt that results from strain-partitioning of plate motions. Within the belt are fault-related folds and thrust faults that flatten with depth, providing subthrust exploration traps with known oil source and reservoir rocks. The oil-rich CBD is deformed in a similar style and opportunities, and many of its oil field traps are fault-propagation- and detachment-origin anticlines in need of development drilling. The SF plate boundary between the Indian and Sunda (Asia) plates is comparable to the pre-Oligocene setting along the western edge of North America with similar, spatially-arranged tectonic elements. That is the Farallon and India subducting plates, California Coast Ranges and Indo-Burma Ranges fold and thrust belts and accretionary wedges, pre-Oligocene San Joaquin basin and CBD, and Sierra Nevada and Popo-Taungthanlon magmatic arcs. Temperature differences between the subducting plates may explain the differing positions of the SF and SAF in this arrangement. The petroleum potential differences between the CBD and the California oil basins result from post-Oligocene basin development, shallow-marine versus deep-marine, respectively.
 
9:10am - 9:30am
Why Structural and Stratigraphic Surface Observations in the Monterey and Sisquoc Formations are Critical Elements to Better Understand the Quality and Style of Miocene Structures in the Subsurface
Y. Wirtz
The distribution and intensity of deformational patterns in fault related folds of siliceous sedimentary rocks are generally controlled by time-transgressive interplays of sedimentation, kinematic history, burial diagenesis, and thickness of competence contrasting stratigraphic layers at different scales. Structural surface analysis of the primarily diatomaceous Sisquoc Formation and the chiefly cherty/porcelanitic Monterey Formation in the southern Santa Maria basin, CA documented significant strain variation along fold strike due to competence contrasting layers at formational scale. At outcrop-scale a variety of structural responses within alternating mechanical packages showed that even in a single anticlinal structure fold kinematics may be dramatically different in various positions of a stratigraphic section. In other words, qualitative characterization of reservoir rocks in structural traps may differ dramatically over short stratigraphic distances that are difficult or impossible to capture if not integrating surface observations. Structural surface studies, outcrop photographs, and cross-sections serve as examples that observations made at the surface can be used to reinterpret deformation in the subsurface that is not always easy to capture by just using geophysical data.
 
10:00am - 10:20am
23 Years of Historic Hydrocarbon Seep Studies in Santa Maria Basin, Offshore California Using Seismic and Stratigraphic Data (1995 through 2018)
J. Saenz, T. O'Neil, D. Denison, P. Fischer, and J. Vernon
Historical seismic and stratigraphic records were used to understand the relative effects of active tectonics on hydrocarbon seeps in the Santa Maria Basin (SMB), offshore California. The study confirms that hydrocarbon seeps are associated with the Hosgri-Purisima-Lompoc fault zones tapping into a single major reservoir, the Monterey Formation. These Monterey reservoirs occur in growing anticlinal folds that are faulted and fractured by the Hosgri Fault zone, acting as a major conduit for gas and oil seeps. The stratigraphy of the offshore SMB is known from seismic surveys, cores, electric logs, and 73 mud logs within the basin. Over 60 multi-sensor, shallow drilling hazard and deep seismic reports provided data sets of seeps, seafloor features, and geologic structure. We find an abundance of evidence to suggest continuous or episodic upward movement of fluids as migrating gas plumes from deeper sediments into surface sediments. The analysis shows that bright spots on the seismic reflection profiles are gas-plumes, linked to the highest geothermal gradients and controlled by active tectonics. Gas, deeply sourced in the Monterey Formation migrates upward along faults, anticlinal folds, and steeply dipping beds into shallow sediment from depth. Gas chromatograph analysis from mud logs samples in wells near gas plumes also show the highest concentrations of continuous total gas, methane, ethane, propane, and butane. Within close proximity to the Hosgri Fault zone, lithologic analysis also revealed three areas where siliceous Monterey rocks have been diagenetically altered to glassy cherts related to average downhole temperatures (118°F to 248°F), and reservoir pressures (2115 psig to 3385 psig). Active tectonics has subsequently fractured these brittle rocks throughout the study area. The fracturing is significant, as it allows migration pathways to the reservoirs and to faults that serve as conduits for hydrocarbon seeps emanating from the seafloor.
 
10:20am - 10:40am
Spatial and Geochemical Characterization of Anomalous, Map-scale Dolomite Breccia in the Monterey Formation, Santa Maria Basin, California
M. Davis and R. Behl
An approximately eighteen square kilometer dolomite breccia mapped by Dibblee and Erhenspeck in 1988 outcrops at or near the base of the Monterey formation in the southern margin of the SMB. Although not recognized as such by the original mappers, it marks the location of an extensive detachment surface, along which large amounts of fluids flowed that dolomitized and cemented an undulating fault zone, or detachment surface. This surface is key to allowing excess folding of Monterey strata relative to older strata. The dolomite breccia exposed in the old Grefco Quarry road cut is analyzed in detail using outcrop description, macro- and micro- rock fabric description, thin section petrography, X-ray diffraction data, carbon and oxygen isotopes, and trace element geochemistry. Deformation, mineralogy, and isotope signatures are consistent with hydrothermal dolomite (HTD) emplacement from evolved, Monterey-sourced connate fluids that ranged in temperature from 36.6 to 99.5oC. Clasts of dolomite, Monterey siliceous rocks and sandstone from underlying formations are locally supported by >35% micritic dolomite and microcrystalline quartz cement in a dilation breccia. A minimum of 128,000-231,000 cm3 of fluid per cm3 of breccia volume were required to deposit the dolomite cements.
 
10:40am - 11:00am
Timing of Structural Growth and Hydrocarbon Charging of Traps, Elk Hills Field, California
T. Reid and P. Cowell
Miocene through Pleistocene stratigraphy at the Elk Hills Field reveals insights into polyphase structural evolution of multiple folds and constrains the timing of hydrocarbon charging. Initial structural indications are subtle and the lack of widespread basin floor turbidites on the 29R anticline during the B Shale interval of the Monterey may indicate initial stages of structural deformation. More significant deformation occurred during deposition the uppermost portion of the Monterey. On the seafloor, major turbidite systems are deflected from emerging anticlinal crests, with folding accommodating over 1,500 feet of sand in the 26R turbidite system. Deformation continued through deposition of the lower part of the Reef Ridge Shale. Pliocene deposits represent the progressive filling of the basin to near sea level and indicate a prolonged period of structural quiescence. Pleistocene lake beds within the Tulare Formation indicate Elk Hills was the lowest point in the basin, possibly continuing to as late as 1 Ma. However, the youngest Tulare deposits are absent at Elk Hills, and stratigraphic trends indicate units including the Corcoran Clay onlap the growing structures, documenting an episode of significant late Pleistocene structural growth. Peak generation of oil in the Monterey Formation occurred between 2.5 and 3.5 Ma, but only one Elk Hills trap had formed by this time and was charged with early-maturity heavy oil. All other traps formed with the late Pleistocene deformation, and were charged with moderately mature mid-gravity hydrocarbons.
 
11:00am - 11:20am
Intensive Natural Fracture Study of Elk Hills Monterey Formation to Better Understand Production Variability
R. Gales, R. Sobczyk, and N. Harvey
Elk Hills, initially designated as Naval Petroleum Reserve No. 1, is a large anticlinal field discovered in 1911 in the southern San Joaquin Valley of California. Elk Hills is a complex structure with multiple pays and highly fractured. Focus will be on the Antelope Shale (Antelope) member of the Monterey Formation which has variability in production due to variations in net pay and degree of natural fracturing. The goal of this project was to understand the natural fracture complexity of the Antelope interval and influence on production variability and provide insight for development.
 We focus on the scope of work and workflows used to provide information obtained in a study involving 188 image logs over the Elk Hills structure. The study was designed to identify variability in fracture type, orientation, aperture and relationship to bedding over the field. We will also outline the systematic approach from Scope of Work, project Quality Control and final results including the benefit of a field wide approach compared to prior small area studies. The approach involved selection of high quality data sets that provided geographic coverage vertically, laterally and by tool type. Data sets came from different vendors showed that each tool type gave consistent response that could be used for comparable evaluation of fracture type, orientation and aperture. The fractures in the target section were picked in considerable detail focussing not so much on one particular fracture type but providing a spatially well populated and distributed data set allowed for the mapping of orientation, fracture type, aperture and frequency by zone, which provided insights into the nature and extent of the fracture distribution by zone within the Antelope Interval. A positive comparison to production was achieved by integrating weighted fracture intensity and reservoir quality from the petrophysical model. We present an approach for handling large borehole image data sets and presenting the information in a way that is beneficial to selection of production intervals and understanding the character of different fracture sets across a field or an exploration area. The techniques presented are applicable across a wide range of environments provided there is the data available.
 
Geology and Data: Leveraging Old Data, New Data, Smart Data, and Big Data
Co-chairs: S. Bhattacharya, L. Huang
 
8:10am - 8:30am
The Digital Visualization of an Oil Field (Belridge Field, California)
S. Chehal and K. Beecher
Big data is a broad term referring to large volumes of data, which can be complex to analyze using traditional data processing applications. In the upstream oil and gas industry, there is an abundance of data collected ranging from subsurface geologic data to down-hole well bore and surface equipment data to satellite imagery. This data is dispersed through a plethora of mediums including physical files, static digital files in various formats, and real-time data, which is stored in various locations- data warehouse, personal hard drives, or offsite storage facilities. This often leads to spending more time searching for data than actually analyzing it. Big data is simply described in terms of three “V’s”: Volume, Velocity, and Variety, each presenting a respective barrier for efficient use. However, a significant barrier of big data is inaccessibility of data, thus, from a user perspective the most valuable “V” is Visualization. In a proactive effort to utilize “structured” and “unstructured” data, the Light Oil Recovery and Evaluation Team at Aera Energy, LLC has proactively made multiple data connections to visualize data stored in various formats. The Light Oil Team has generated data connections and standardization to visualize data related to the Diatomite reservoir in ArcGIS, Tableau, and OpenWorks. The proactive data organization has enhanced collaboration between the reservoir management team and other departments, reduced training time of new team members, retained information related to previous projects, and improved access to data warehouses. The standardization and organization promotes ease of data access, efficient visualization, and incorporation of data for analysis.
 
8:30am - 8:50am
Data Analytics for Greenfield Production Forecasting: A Case Study of Antelope Shale
M. Lal and T. Kim
In this paper, we discuss the case study of four vertical wells drilled in the McKittrick field in San Joaquin Valley targeting the Opal CT and Quartz phases of the Antelope Shale reservoir. All four wells came on at good Initial Production (IP) followed by a steep decline. The results showed opportunities for a horizontal development plan but were challenged by operational issues, limited analog data set, higher cost, poor economics, and comparison with traditional heavy oil projects. An analog study of unconventional shale plays with both vertical and horizontal producers in San Joaquin Valley and the Permian was done to understand the relative performance of horizontal and vertical wells. This along with the actual production data from the four vertical wells was used to forecast the horizontal wells production using Decline Curve Analysis (DCA). This statistical method of production forecasting is an inverse problem that is well suited to multivariate correlating technique like Support Vector Machine (SVM). A stochastic model using SVM was developed incorporating the geological, geomechanical, fracture stimulation, production, and zonal contribution data. This model was trained, tested, and then used to forecast oil production. The results of the SVM model compared reasonably well with the analog method of production forecasting, thus validating the DCA forecast using analog data set. In lack of a reservoir simulation model, the SVM model offers a relatively quick and less expensive way of forecasting oil production using parametric supervised learning. As more production data becomes available, the uncertainty associated with the SVM model should decrease (or the accuracy of the SVM model should increase) which will enable using a deterministic SVM model rather than a stochastic model. This practical application of machine learning opens the opportunity to utilize large volumes of multi-dimensional data and translate them into actionable insights. Use of machine-led intelligence can result in cost and time savings while providing a technology roadmap for forecasting production in a greenfield in lack of suitable analog data and reservoir simulation model. This can be particularly more useful in a low oil price environment.
 
8:50am - 9:10am      
Bi-Modal Shaly-Sand Model             
D. Hill and D. Seevers
Clay minerals affect essentially every measured petrophysical property. They destroy effective porosity and permeability, as well as contaminate essentially all wireline measurements.
A simplified mixing model consisting of coarse and fine grains of about two-orders of magnitude difference offers qualitative, if not quantitative insight on these effects. The qualitative results predicted from this simplified model are remarkably similar to those observed from a Canadian Arctic shaly-sand well and published by Alan Heslop, in the mi-1970s.
 
9:10am - 9:30am
Machine Learning-Assisted Prediction of Daily Hydrocarbon Production using Fiber-optic, Petrophysical, Geomechanical, Engineering, and Surface Data 
S. Bhattacharya, P. Kavosui, and T. Carr
The study demonstrates the application of machine learning to predict hydrocarbon production using high-frequency fiber-optic, petrophysical, geomechanical, completions, and surface data from an unconventional reservoir in North America. The main objectives of this study are to better understand the well performance in terms of different subsurface and surface drivers, and forecast the daily gas production. The 28-stage horizontal well drilled in the shale formation, contains a plethora of multi-scale and multi-sensor-based spatio-temporal data, such as Distributed Acoustic Sensing (DAS), Distributed Temperature Sensing (DTS), petrophysical logs, geomechanical logs, production logs, surface pressure, and surface temperature. A Support Vector Machine (SVM), a powerful machine learning algorithm, was trained using 18 input parameters to predict the daily gas production from each completed stage. The data-driven model was trained on 414 days of gas production and then tested for subsequent 102 days for validation purpose. The SVM model shows accuracy of ~94% in predicting daily gas production. 102 days of the test data shows that the SVM model has a mean absolute error of 9.83 MCF/day for the gas production. Sensitivity analysis was performed on the data set, which gives a robust understanding of the key drivers for hydrocarbon production. The results show that fiber optic measurements (DAS and DTS), temperature, pressure, stage length, gamma log, Poisson’s ratio, brittleness, and minimum horizontal stress are the most important parameters to predict hydrocarbon production.
 
10:00am - 10:20am
Deep Learning Research for Geological Subsurface Classifications
L. Huang and X. Dong
The objective of the research is to apply the latest breakthroughs in data science, especially in the deep learning technology, to address the grand challenge of hydrocarbon exploration. Precise classifications of Earth subsurface features will help scientists better understand the Earth’s fine structures and geological history. Besides the significant advances in knowledge and practices of geology and geophysics, the data science provides a new approach to tackle the challenge via the capability of analyzing massive data sets and building sophisticated deep learning models. In this research, we built a variety of deep learning models to automatically classifying the geological subsurface features from seismic data. We also identified a group of geophysical attributes to enrich the deep learning models with the combined knowledge in the geophysics and statistics to improve its accuracy. We have built multiple deep learning networks with transfer learning functionality, which utilizes the existing well-trained deep learning models for low-level features. The results are very encouraging for our geological subsurface features classification study. We will show the geological faults detected from West Cameron seismic data sets in the Gulf Coast area, which is close to human expert interpretation result. Data science opens a new door to allow interdisciplinary scientists work together to conquer many grand challenges with the data-driven approach, which leads to better decision-making based on pure facts. The research demonstrated that we are able to better interpret the Earth subsurface features with deep learning models that extract valuable insights from massive data sets. We are working on further enhancing the research by integrating more geological and geophysical knowledge into the statistical learning process.
 
10:20am - 10:40am
Differentiating Biogenic Silica from Other Forms of Silica Found in Detrital Sediments Using the Rock-DNA Method
J. Little
The Monterey Shale in California’s San Joaquin Basin contains a mixture of sediments ranging from organic rich mudstones, arkosic turbidite sands and siltstones to siliceous shale typically all stacked together. Siliceous shale reservoirs by themselves are unusual as they are distributed throughout the world in only a few select locations and production characteristics are unlike those found in other types of conventional reservoirs. Primary composition is diagenetically altered diatomaceous (biogenic silica) also known as diatomaceous claystone and porcelanite. In general, this type of sedimentation has a relatively high porosity while exhibiting a very low permeability, creating a situation where acid stimulation or hydraulic stimulation is required to produce oil at economic rates. Identifying the sweet spots to focus completion expenses in the best reservoir sections starts by being able to identify and quantify the volume of biogenic silica.
Over the past decade Schlumberger and its business partners have been evaluating both conventional and unconventional reservoir rocks as a part of the California Mineralogy Project. The purpose of this effort was to investigate what improvements might be made in the application of capture spectroscopy logging data to this depositional basin and thus improve characterization efforts. What has emerged is a new methodology which utilizes chemical elemental ratios to quantify biogenic silica bSi, this method or workflow is called Rock-DNA. This new Petrophysical method produces results which show dramatic improvement in estimates for both grain density and porosity in the Monterey formation, both of which have a large impact on reservoir characterization efforts and the estimation of oil in place calculations.
 
10:40am - 11:00am
Recovering Dip Data from Vintage Dipmeter Logs (V 2.0)
T. Howard
 When original Dipmeter log interpretation deliverables, i.e. tadpole log and related plots, are suspect or no longer available, interpretable and useable dip data can still be recovered from paper or electronic copies of “Vintage” raw field Dipmeter logs, i.e. three or four pad, single or two button logging tools. Satisfactory to excellent results can be obtained from a 5 inch = 100’ paper log plot (or scanned tiff); in some instances, useable dip data can be recovered from 2” logs. Interpretations based on resurrected data may be better than any original computer-generated interpretation, as the workflow centers on: 1) An experienced analyst manually picking, editing and interpreting “events” or picks, and 2) that our analyst can integrate iterative feedback from the end-user geologist. Most resurrected picks will likely be structural bedding dips; however, it may be possible to speculate about some picks which are otherwise including: faults, sedimentological dips, and/or fractures. The general workflow is as follows: capture, clean up, orthorhomb-ize and then digitize the desired Dipmeter log tiff. Next load to suitable software and perform various QA/QC evaluations. Continue and make appropriate picks of the “events” seen on the Dipmeter log, and consider in light of additional, field-wide data. Finally, plot and refine any interpretation, using various analysis tools including: classic tadpole patterns, other plots such as SCAT and walkout diagrams, input from well histories, and lastly, but importantly, input from the end-user geologist.
 
11:00am - 11:20am
Using Deep Learning and Distributed Machine Learning Algorithms to Forecast Missing Well Log Data
C. Ejimuda and E.C.I. Ejimuda
With limited amount of prospects available within producing fields, the holistic and realistic evaluation of well logs represent an important parameter to guide development, production and investment decisions within the field. However, some wells with log data have missing curves or erroneous values while some wells have no log data. We propose using deep learning and distributed machine learning model which effectively models the non-linearity within well log files to forecast a realistic estimate of missing well log data. Authors of previous papers used commercial applications to generate such missing log data. Such applications are limited in their analysis and cannot handle big data unlike ours. However, our methodology used cloud distributed computing resources and open source tools to develop the deep learning and machine learning algorithm. Additionally, we applied it to about 15,000,000 rows of data where such commercial applications are unable to scale or model complexities that exist amongst variables. Additionally, our work will further assist petrophysicists, reservoir engineers and geologist build a more robust geologic and reservoir simulation model and guide management’s current or future investment decisions in an asset. We used python programming language, Apache Spark and Tensorflow APIs to perform this work. We scraped and downloaded about 985 well log data (log ascii files) of Cook Inlet basin wells to the cloud. We extracted their actual data and metadata for all the wells. We subsequently saved the data into feather file format which allows for quick file reads and writes. Furthermore, we preprocessed the well log data, normalized and scaled it to ensure all features were within the same scale and thus, reduce computational expense. Initially, applying Apache Spark’s distributed machine learning model, our overall accuracy was very low (about 10%). However, currently, we are using an auto encoder and convolutional neural network ResNet deep learning architecture. Preliminary results are promising and expect further model architecture and parameter tuning to yield results with even higher accuracy. These and more will efficiently forecast well log data with missing values and wells without log data.
 
11:20am - 11:40am
Application of Volumetric Seismic Attributes for Complex Fault Network Characterization in the North Slope, Alaska
S. Bhattacharya and S. Verma
Volumetric seismic attributes can be significantly useful to unravel the structural complexity and deformation history of subsurface formations. In this study we apply an ensemble of volumetric seismic attributes to better understand the polyphase history of faulting by detecting fault architecture over different geologic horizons. Different seismic attributes, such as most-negative curvature (long-wavelength and short-wavelength), most-positive curvature (long-wavelength and short-wavelength), and aberrancy (magnitude and azimuth) were computed on the Shublik shale and Kekiktuk horizon, which is considered as economic basement. Seismic attribute-assisted horizon mapping reveals presence of two dominant styles of faulting on the Shublik horizon: NW-SE oriented normal fault and a conjugate set of faults oriented NE-SW and NW-SE, whereas the Kekiktuk horizon mostly shows NW-SE oriented faults. However, a complex pattern of discontinuities can be observed on the Kekiktuk horizon, some of which are below the seismic resolution. Long-wavelength curvature shows fault pattern that is difficult to visualize in the conventional seismic, whereas short-wavelength curvature map illustrates detailed fracture pattern within intense and highly localized fracture systems. A relay ramp structure can be observed near the NW corner of the 3D seismic survey. Curvature and aberrancy maps also reveal that the basement has an impact on fault development on the overlying sedimentary horizons.
 
April 23: Monday Afternoon
PS-SEPM: Sedimentology and Stratigraphy: From Lacustrine to Deep-water Reservoirs
Co-Chairs: G. Gordon, T. Green
 
1:20pm - 1:40pm
Integrated Reservoir Characterization of a Miocene Submarine-Fan System, Midway-Sunset Oil Field, San Joaquin Basin, California, USA
O. Olabisi
The Midway-Sunset Oil Field (MWSS) is one of the largest oil fields in California. Deposits of deep-water clastics constitute prolific hydrocarbon reservoirs in this field. The Reservoir A is one of several deep-water clastics located in the MWSS Oil Field; it is a new development opportunity in a very mature area and is the subject of this study. It represents the uppermost clastic unit within the upper Miocene Antelope shale at the MWSS Oil Field. A well was cored to be able to better characterize the Reservoir A sands. Core recovery was poor due to the conglomeratic nature of the rocks. Core data was integrated with other wire log tools to characterize the reservoir. Data pertaining to total porosity, effective porosity, permeability (facilitated by the nuclear magnetic resonance tool, CMR), lithology and facies, hydrocarbon occurrence, oil and water saturations, and frequency/effectiveness of naturally occurring fractures were gotten by integrating core data with CMR, image, and triple-combo logs. The approach used was to depth-tie recovered core intervals to wireline log as best as possible. Image log, FMI was used extensively to define lithology, facies, & sedimentary structures including open/healed/cemented fractures and to correlate to core intervals. CMR log results was also correlated with whole and sidewall cores to determine facies. The CMR data (particularly CMR porosity, CMR free fluid index, and CMR permeability as well as bulk volume irreducible water - BVI) with the porosity and saturation tools was used to infer reservoir properties for other wells with no CMR logs. A 3D static geologic model was built by incorporating the interpreted facies and “bias to facies” reservoir properties to illustrate reservoir interpretations of the Reservoir A depositional system. This allows us to better define the reservoir architecture, establish criteria for oil in place estimation and develop strategies for reservoir management, and production enhancement of the Reservoir A sands in the MWSS Oil Field. The Reservoir A sands were deposited within a southeast-trending trough at the MWSS Oil Field. The Reservoir A is a deep water, submarine fan system composed mainly of channel and lobe deposits. They are interpreted to be deposits of turbidity currents, sandy debris flows, bottom-current-rework, pelagic and hemipelagic settling depositional processes. The reservoir has a thickness of up to 550ft thick. Porosity types in this reservoir include depositional and diagenetic porosity (caused by dissolution of cements, feldspars, and other frame work grains), and fractures (microfractures, and through-going fractures). Porosity averages 29% and permeability ranges to as high as 8446 mD. This study presents a detailed integrated methodology that better describes the reservoir distribution, geometry, and quality of the Reservoir A sandstones including how they are controlled by depositional processes. The integrated methodology presented here have application in other deep water, heavy oil reservoirs; especially where core recovery is poor.
 
1:40pm - 2:00pm
Reinterpretation of Tulare Depositional Environments and Reservoir Distribution, a Case for Two Depositional Sources in North Midway Sunset, San Joaquin Basin, CA
E. Fisher
The Midway Sunset (MWSS) oil field is a prolific field in the western San Joaquin Basin that has produced over 3 BBO since its discovery in 1909. Early production was mainly in the Miocene Potter turbidite sand. The Plio-Pleistocene Tulare was developed as a secondary reservoir starting in the early 1980s. The Tulare represents a variety of depositional environments, reservoir qualities and productivity. It has been targeted for development by various operators in North MWSS, yet little has been published about this unit, and what publications exist are at a regional scale compared to detailed, production-scale mapping presented here. Previous regional interpretations of the North MWSS depositional environment for the Tulare assume a single depositional source from the Temblor Range, gradually changing in depositional environment from a bajada/alluvial system to fluvial systems, then into a lacustrine environment, from west to east respectively (Nielson, 1989). Recent regional mapping of the Tulare at North MWSS shows an abrupt unconformity that puts the reservoir sands laterally adjacent to a shale interval. In light of this data, I present a new depositional model that has two sources one from a bajada/alluvial system flowing west to east which ends at a sinuous unconformity. The geometry of the unconformity is likely controlled by the Midway Syncline and the Globe Anticline. The second depositional source on the eastern portion of the field flows from north to south in a pro-delta system in a lacustrine environment. This presents a different distribution of sand and possible reservoirs for economic production in the Tulare. The different orientations and changes in depositional environment explain the previously inexplicable differences in oil production by areal extent. It also brings up questions of the uplift history in North Midway Tulare, not previously explored. The Tulare represents a variety of depositional environments, reservoir qualities and production potential. Its heavy biodegraded oil (8-12 API) that requires tight well spacing, down to ¾ acre well spacing in heterogeneous alluvial fans or very thin-bedded lacustrine settings. This localized variation warrants different development strategies and will lead to varying production results. Mapping these environments at a local level could lead to more appropriate strategies and predictions for oil production in the Tulare.
 
2:00pm - 2:20pm
The Gatchell Sand Truncation Play: East Flank San Joaquin Basin, CA: A 25-Year Exploration Status Update
P. Penoyer
A trap component shared by the two largest conventional oil fields in North America (Prudhoe Bay Field, Alaska and East Texas Field, Texas) is sand pinchout by truncation. On the San Joaquin basin’s west flank, the Lower Eocene Gatchell sandstone produces in excess of 600 MMBO with >500 MMBO from East Coalinga Ext. field alone beneath the base Domengine regional unconformity. Pinchout by truncation of the Gatchell sand in the largely structureless, homoclinal dip (2° - 3°) of the east flank remains untested from the Five Points area south to the Bakersfield Arch. Well control integrated with approximately 1000 miles of reprocessed seismic data show the nearest test well to the seismically mapped 70-mile sand pinchout trend has 90 feet of sand. With past structural tests having drilled mostly time closures and nearly half of the Gatchell Sandstone penetrations (~17 of 40 wells) in this trend having oil shows, a significant hydrocarbon charge to this untested sand pinchout in the homoclinal dip setting seems reasonable. Oil shows and production are largely absent from intervals surrounding the base Domengine unconformity in up dip progressively truncated areas indicating the overlying Kreyenhagen Shale coupled with glauconitic, clay-rich and calcite cemented Domengine Grit provides a viable seal below the 10,000+ foot depth of this play. High resolution, strike-oriented seismic in the area of the Gatchell sand subcrop and pinchout is needed to define a permeability barrier in the spill direction along geologic strike of the sand subcrop beyond the four untested stratigraphic closures mapped against the sand pinchout to date. Hydrocarbon charge to a possible sand-filled gorge/submarine canyon along the truncation edge similar to the 600+ feet of sand observed in the Five Points area West Bay well supports targeting this sand truncation in areas directly up dip from thermally mature Kreyenhagen shale below 14,000 feet.
 
2:20pm - 2:40pm
Shelf Origins to the Abyssal Sink of the Arguello Submarine Canyon System Off Southern California
K. Marsaglia, B. Rodriguez, D.S. Weeraratne, H.G. Greene, N. Shintaku, and M.D. Kohler
The Arguello submarine canyon/channel system extends more than 300 km from the continental shelf off Point Arguello along the Pacific margin of California. The area where the canyon system originates is characterized by apparently active morphologic fluid-flow features linked to fluid leakage from the underlying hydrocarbon basin. The continental slope dissected by the channel exhibits features consistent with large-scale mass wasting. The deposits at the base of the slope (a.k.a., Arguello submarine fan) exhibit large channel meanders and ridges that are more consistent with mass transport deposits rather than deep-sea fan depositional lobes. Mass wasting may have been triggered by seismicity or gas venting and hydrate dissociation. The canyon/channel continues due south following the structural grain of underlying oceanic basement until it reaches the E-W striking Arguello transform, where it makes 90° turn (bend) to the west, then developing into a meandering channel system. The channel continues west, curving around a thickened crustal bulge then emptying into an 800 m-deep basin depocenter. The age of the system is estimated as Miocene. Further work is needed to clarify the age and origin of this complex feature.
 
3:10pm - 3:30pm
Status Report on the Long Beach Monterey and Related Sediments Project (MARS):
Part 1: Lithology and Stratigraphy
R. Behl
The Miocene Monterey Formation is the primary source rock and an important reservoir of petroleum in California. It is also an unmatched archive of paleoenvironmental data. Because of its excellent and widespread exposures and abundant subsurface penetrations, the Monterey serves as a primary laboratory for understanding the sedimentology, stratigraphy, diagenesis and deformational styles of siliceous/ diatomaceous sediments around the globe. In 2011, the Long Beach MARS Project (Monterey and Related Sediments) was created by a consortium of 8 energy companies and the CSULB Department of Geological Sciences. At a foundational meeting of industry professionals and academic researchers with several 100 years of combined experience working in the Monterey Formation, the key unresolved scientific problems were identified and approaches to investigating them discussed. Since then, 12 complete Masters theses and numerous other projects have investigated the sedimentology, composition, lithostratigraphy, chemostratigraphy, diagenesis, rock properties and structural deformation of the Monterey and related formations in California. Key findings from this research will be reviewed and are outlined below and in the following abstract (Part 2). Two stratigraphic sections outcropping in the San Joaquin and Los Angeles basins (Chico Martinez Creek and Malibu) were publically described in detail for the first time and characterized by spectral gamma-ray to aid correlation with subsurface sections. Compositionally-based lithostratigraphic members of the Monterey were identified in 5 subsurface wells and in the Malibu Beach section in the Los Angeles basin, even within sandstone-dominated turbiditic successions. The unique mineralogy of fine-grained detritus in different basins requires creation of different equations to determine relative amounts of biogenic/diagenetic silica. Trace metal geochemistry is a valuable tool for correlation and environmental interpretation.
 
3:30pm - 3:50pm
Status Report on the Long Beach Monterey and Related Sediments Project (MARS):
Part 2: Diagenesis, Rock Properties and Deformation
R. Behl
In the past 6 years, the MARS Project has investigated outcrop and subsurface sections of the Miocene Monterey to understand the linkages between sedimentology, stratigraphy, diagenesis and deformational styles of siliceous/ diatomaceous sediments. Biogenic silica from diatoms and radiolarians undergoes dramatic and surprising diagenetic transformations after deposition. The porosity of siliceous sediments is well known to decrease in abrupt steps with the transformation of opal-A to opal-CT to quartz, but the pore sizes and structures undergo an unexpected progression starting with large inter-and intraparticle pores in diatomaceous sediment, followed by much smaller, partially isolated nanopores in opal-CT phase rocks, then larger, more connected equidimensional micropores in quartz phase rocks. Significant silica mobility, and localized cementation or secondary porosity develops when different silica phases are juxtaposed during halted burial or tectonic uplift. Hardness also increases with each diagenetic step and the overall decrease in porosity, but within any one diagenetic stage or burial depth, hardness increases with diagenetic silica content and increased porosity. Contrasting lithologic composition from the bed-scale to member-scale results in distinct styles and mechanisms of deformation. Within a contractive regime, diatomaceous sediment horizontally compacts and develops widely spaced, penetrative fault or fracture sets that cross primary stratification. Diagenetic enhancement of bedding in the opal-CT and quartz phases produces a highly contrasting mechanical stratigraphy prone to bed-confined fractures, detachment faulting and fault- and breccia-related folding. Large-scale differences in rock properties due to silica phase or stratification produce distinct mechanical behavior and large-scale detachments within or at the base of the Monterey Formation, some of which become important fluid-flow pathways or significant petroleum reservoirs.
 
3:50pm - 4:10pm
Developing a Method of Chemostratigraphic Correlation for the Monterey Formation in the San Joaquin Basin, California
A. Sedlak and R. Behl
Despite over a century of study, precise dating and long-distance correlation within the Monterey Formation remains a problem for stratigraphers. The widely used benthic foraminiferal stages are time-transgressive and of long duration, but there are few viable alternative methods due to diagenesis or discontinuous accumulation of microfossil taxa. One underdeveloped alternative is correlation through chemostratigraphy. Our goal is to characterize the geochemical stratigraphy of the Monterey Formation in the San Joaquin basin in order to develop a reproducible, robust method of correlation. Unfortunately, the most common chemostratigraphic methods such as oxygen isotopes typically require continuous occurrence of carbonates, which generally restricts usage to the lower and middle parts of the formation, yet it is often the upper section that is of interest to petroleum geologists. It is therefore necessary to use a method that is applicable to a wider array of lithologies. To this end we have chosen to analyze major, minor, and trace elemental abundances within the Monterey Formation, with a particular focus on redox and productivity-sensitive trace elements that potentially have a basin-wide signature that can be traced independent of lateral facies changes due to depositional process or environment. Geochemical analysis was performed on 290 samples of cleaned, refined cuttings from 3 wells in the southern San Joaquin Basin. These wells represent a west-side to central basinal transect. When combined, the wells are a composite record of the middle-to-upper sections of the Monterey Formation, with a particular focus on the McDonald and Antelope members due to their high organic content and potential for dramatic, correlative events. Our analysis shows that it is possible to use cuttings to identify distinct geochemical submembers within the Monterey Formation utilizing trace elemental abundances. These submembers appear to be correlative between distinct depositional environments.
 
4:10pm - 4:30pm
Monterey Formation lithofacies:  Linking a Complex Story of Deposition and Diagenesis to Help Unravel Stratigraphic Relationships
J. Schwalbach, K. Bohacs, and W. Berelson
The Monterey Formation is well known as a heterogeneous fine-grained rock of significant economic interest. Its role as a reservoir, source rock, and seal has been documented in many studies. Much less work has been done, however, trying to understand and use individual lithofacies and lithofacies associations for the purpose of stratigraphic evaluation, and ultimately predicting lithofacies distributions. Casual workers often assume a relatively simplistic process of pelagic settling of biogenic material as the primary depositional process. The Monterey, however, contains a significant component of fine-grained terrigenous clastics. Mud and mudstone studies over the past few decades revealed a range of transport processes, from hypo- and hyperpycnal flows to dilute gravity flows, that distribute fine-grained sediments far into the basin. Both the fine-grained clastics and biogenic components are stripped from the water column and delivered to the seafloor by flocculation, organic aggregation, and biogenic pelleting. Muds on the sea floor are subject to reworking by a variety of bottom currents. The Monterey contains evidence of all these processes. After deposition, diagenesis takes over within the first meter of burial. Diagenetic reactions are a function of sediment composition as well as rate of burial and pore water chemistry. Precipitation from pore waters can account for greater than 50 percent of the rock volume for some bedsets. The resultant lithofacies and lithofacies associations are diagnostic of depositional environment. The lithofacies associations, including stratal stacking patterns, change laterally moving from one basinal environment to another. We can improve our predictions of source, reservoir, and seal by looking more closely at basic rock data and using proxies such as well logs and seismic data to map lithofacies distributions relative to specific depositional environments.
 
4:30pm -4:50pm
Mineralogical Characterization of the Miocene Olcese Formation of the Kern River Oil Field, California
K. Lopez, J. Guo, and D. Baron
The early to middle Miocene Olcese Formation in the southern San Joaquin Valley of California consists of shallow marine shelf sands in its lower and upper parts, and non-marine sands in its middle part, and varies in thickness up to 1800 ft. There is little known as to the origin, nature, quantity, and distribution of clay minerals throughout the formation. This study examined 95 sidewall core samples from three wells in the Kern River Oil Field. Well samples were from depths between 1,800 and 4,000 ft. Qualitative and quantitative mineralogy including clay minerals of the sidewall samples and selected cutting samples was determined by powder X-ray diffraction (XRD). XRD analyses were supplemented by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). The main minerals of bulk samples include composite clay, quartz, potassium feldspar/plagioclase, calcite with minor amounts of dolomite, clinoptilolite, and opal-A/cristobalite. Content of composite clay varies between 21% and 93%. The clay-size fraction is predominantly composed of smectite, illite, kaolinite and chlorite with smectite being the most abundant. Smectite and clinoptilolite may be the alteration products of deeper burial of volcanic materials. The formation permeability could be significantly lowered by these authigenic minerals.
 
Sacramento Basin Exploration and Development
Co-chairs: K. Weberling, S. Hector
 
1:40pm - 2:00pm
What is Next for the "Mature" Sacramento Basin? The West Side Story, A Brief Look into the Lower Cretaceous and Upper Jurassic Rock
R. Sterling
The Sacramento Basin has seen little in the way of exploration for the last number of years. Traditional productive areas have been heavily exploited through the use of 2D and 3D seismic such that smaller and smaller targets were successfully drilled and produced. An effort to look for another possible exploration province was undertaken beginning in the 1990’s by this author. The Lower Cretaceous and Upper Jurassic sediments that form the outcrop belt along the western side of the Sacramento Basin have had a disjointed drilling history filled with shallow wells, heavy mud, and no commercial results. The Lodoga and Stoney Creek Formations represent the earliest deposition into the forearc basin formed by the subduction of the Farallon Plate underneath the North American Plate during the Late Jurassic and early Cretaceous periods. Middle to Late Cretaceous sediments were deposited further east as the early basin was filled. Approximately 45,000 feet of measured section has been observed in the outcrop belt. Sediments are composed of marine shales and sands. The sands were deposited as deep water turbidites and range from fine grained sands interbedded with silty shales to thick conglomerates. Sediments tend to be high in lithic content due to the provenance of early Sierra Nevadan volcanic rocks. Recent drilling by various operators have tested several concepts for these rocks with confidential results. The most recent well with data publicly available is the CRC Tulainyo #1 in section 7 T18N R4W which was abandoned in January 2015 after encountering mechanical difficulties. This well encountered interesting indications of gas while drilling and logs indicate saturation of gas in the sands, though the area is very structurally complicated.
 
2:00pm - 2:20pm
Back to Basics at Rio Vista field:  Successful Revival of Geologic Interpretation Methods Below the AVO Anomaly Window in the Sacramento Basin
K. Weberling, D. McCuan, and J. Anderson
The Sacramento Basin in Northern California is one of the most prolific onshore dry gas basins in North America with over 11 Tcf of cumulative production. The first significant discoveries in the basin, including Rio Vista field (4 Tcf CUM) were discovered on single-fold 2D seismic in the 1930’s. Multi-fold 2D data in the 1960’s contributed to the next round of large discoveries including Grimes, Malton-Black Butte, Lathrop and Union Island. Curiously, the prolific acquisition of 3D seismic during the late 1980’s – mid 2000’s did not add a similar corresponding bump to the basin EUR creaming curve like earlier 2D acquisition efforts. This lack of additional reserve adds is largely a factor of 3D surveys being designed to highlight AVO anomalies to identify new pools and increase drilling success within existing fields. Very few true exploration 3D surveys have been shot in the basin. Mapping amplitude anomalies for identification of gas-charged reservoirs is a highly successful technique, yet because AVO anomalies are largely identified at depths shallower than 8,500 feet, only a small percentage of wells in the basin have been drilled below 10,000 feet. This lack of deep wells provides operators and explorers with opportunities in deeper reservoirs that have largely been ignored within proven fields. California Resources Corporation acquired Rio Vista Field in 2011 and focused on identifying conventional structural traps in the deeper, overlooked Winters and Peterson Formation reservoir intervals. These reservoirs are at 10,000-12,000 feet and below the traditional AVO anomaly windows. The subsequent drilling campaign based on revised interpretations was largely successful and contributed significantly to the daily production, future reserve potential, and revival of the historic Rio Vista field.
 
2:20pm - 2:40pm
Natural Gas Fields at the Sutter Buttes Volcanic Complex
S. Hector, S. Muir, and K. Blake
The Sutter Buttes are a topographic anomaly, a small mountain range of volcanic origin that protrudes out of the otherwise flat floor of the northern Sacramento Basin, California, with an elevation near sea level. The Buttes rise roughly 2000 feet above the surrounding flatlands. The Buttes are composed of numerous silicic and intermediate composition intrusive domes and complex shaped dikes that forcibly intruded through Late Cretaceous, Paleogene, and Neogene marine sediments. The volcanic activity lasted from 2.4 to 1.36 million years before present. One of the largest accumulations of high-quality natural gas in California is found next to (and partly on) the Buttes. A total of 1.5 trillion cubic feet of natural gas has been produced from fields lying west and south of the Buttes. Almost all of the gas has been produced from the Late Cretaceous Kione and Forbes sandstones. While much of the gas has come from the Sutter Buttes and Grimes fields, some fields lying farther away from the volcanic field appear to be on structures formed by volcanic plugs. Gas fields associated with volcanic intrusions include Wild Goose, Butte Sink, Moon Bend and Sycamore. Relatively recent drilling has been used to compliment gravity and magnetic survey results published by Muir and others (1992) and continuing exploration in this part of the Sacramento Basin. This study shows that the effective area of volcanism extends some 10 miles beyond the surface volcanic outcrop area.
 
3:10pm - 3:30pm
​The Mid-Tertiary Succession on the Northeast Flank of Mount Diablo - a Record of Tectonic Events at the Plate Boundary
​R. Sullivan, S. Edwards, R. Wagner, and A. Deino    
The mid Tertiary succession on the northeast flank of Mount Diablo is part of the uplifted margin of the Sacramento Basin. The succession contains two major hiatuses below and above the Kirker Formation of Oligocene age. The Eocene succession below the first mid Tertiary unconformity is composed of a cyclic succession of turbidite sandstone and shale deposited in the rapidly subsiding Sacramento Basin during late stages of subduction. The marine forearc basin of the early Tertiary changed to a continental setting with the onset of transform in the Oligocene. Volcanic ash and detritus, largely absent in the lower Tertiary section, appears in the Kirker Formation of Oligocene age above the first unconformity. Volcanism was the result of steeping and roll back of the retreating subducting plate that created a major volcanic center to the east over Nevada. Dating of the Kirker Tuff at 29 Ma establishes the onset of eruptions of silicic ignimbrites that filled the drainage systems in the Sacramento basin. A second unconformity separates the Oligocene succession from the overlying upper Tertiary rocks. During late Miocene, NW-SE transextension in the crust created the Sierran microplate and intensified proto-Cascade volcanism. These volcanoes generated large volumes of andesitic debris flows, lahar and ash falls across and into the Sacramento basin. Dating the volcanic tuffs has enabled the accurate timing of these late Miocene events. These include Cierbo tuff dated at 10.93 Ma and the top of the Neroly Sandstone at 9.7 Ma. Contemporaneously and later at the western transform plate margin, slab-window volcanism in the wake of the northward-migrating triple junction produced north-younging eruptive centers. Tephras from these volcanic events are also time markers in the upper Tertiary succession on the flanks of Mount Diablo.
 
3:30pm - 3:50pm
Oil and Gas Field Around Mount Diablo ​​
T. Elam and S. Hector
Mount Diablo is one of the most dramatic mountains of the Coast Ranges of California. It rises to almost 4000' in elevation and is located at a conspicuous location between the San Francisco Bay and the Great Valley. What many who see this mountain do not know is that it is ringed by oil and gas basins and fields. This paper explores these, including fields in the Livermore Basin south of the mountain and fields of the Sacramento Basin both north and east of it. The tectonic history of the mountain and its effect on basin morphology and hydrocarbon capture and re-capture will be discussed. Topics will include the probable Eocene basin that once had the Livermore and Brentwood fields together, now severed by the mountain, and discussion of the gas fields with multiple thrust sheets on the northern side of the mountain (due to compression of the Suisun Sub-Basin?).
 
3:50pm - 4:10pm
Northern Ucayali Basin, Peru: Unraveling Multiple Phases of Fault Slip on Reactivated Structures
J. McGregor, N. W. Eichelberger, and A. Nunns
For basins that have undergone varying stages of contraction and extension, it is important to distinguish the timing, amount, and style of deformation associated with different tectonic environments. Folded growth strata record the timing and kinematics of deformation; however, it can be difficult to quantify these patterns. The deformational history of a seismically-imaged Subandean contractional structure, with evidence of multiple extensional and contractional events, is quantitatively analyzed using a combination of sequential restoration and structural modeling techniques. The northern Ucayali Basin in Peru is a flexural foreland-style basin that contains an early Paleozoic rift architecture thought to control source rock deposition and Andean structural trends. The Paleozoic rift system was then contractionally reactivated in the Miocene during Andean shortening. The seismic section clearly shows contractional deformation in the upper part of the well-imaged hangingwall, but less distinguishable footwall correlations at greater depths. In the interpretation there is a strong angular unconformity in the hanging wall between Permian – Ordovician and overlying, contracted strata, with significant missing section in the footwall. Structural restoration of the top Cretaceous reveals the timing of two phases of contraction on the reactivated rift structure. Structural modeling is able to constrain horizon depths for the missing section as well as validate footwall correlation of the top Ordovician within the structural framework, and provide independent measures of fault slip for intervals deformation. An iterative process of retro-deforming seismic data above and below stratigraphic horizons improves identifying pre-growth/ growth strata, pertinent to unraveling the timing of multiple-phase deformation. This combined with forward modeling of fold geometries, enables the definition and quantification of structural development through time.
 
4:10pm - 4:30pm
Groundwater Basins of the Sacramento Basin ​​
S. Hector and K. Blake
Geological boundaries of the Sacramento Valley have formed multiple groundwater basins within it. Features such as the Sutter Buttes volcanic field have greatly affected the location, shape, and depth of groundwater reserves. The Sustainable Groundwater Act of 2014 has set goals of sustainability through local management. Many of the groundwater basins in the Sacramento Valley are overdrafted and listed as having medium priority for action under the Act. This paper looks at these basins, identifies their areas and Lead Agencies, and looks at how data from oil and gas wells can aid in their interpretation.
 
April 24: Tuesday Morning
Pacific Exploration: Mature Basins and Prolific Reservoirs
Co-Chairs: A. Hosford Scheirer, A. Auffant

8:10am - 8:30am
Recoverable Petroleum Beneath the City of Los Angeles
D. Gautier
Southern California oil accumulations, including those in the City of Los Angeles, are extraordinary because: (1) they exhibit what may be the world’s highest natural concentration of crude oil, and (2) they underlie a modern mega-city with tens of millions of inhabitants. In spite of L.A.’s early and enthusiastic embrace of both the petroleum industry and the gasoline-powered automobile, oil development and urbanization have been in conflict from the start. Early day town-lot drilling, competing land use practices, and fickle societal acceptance have conspired to severely limit production. As a result, recovery efficiency is low in nearly every accumulation and many fields have been abandoned prematurely, leaving large volumes of recoverable oil behind. A new evaluation of the oil fields within the L.A. city limits suggests that about 1.6 BB of additional oil (mean estimate) could be recovered with existing technology. The study was done in two steps: First, published USGS estimates of remaining recoverable oil in Inglewood, Torrance, and Wilmington-Belmont fields were allocated to the field areas falling within L.A. city limits. Second, the volumes of recoverable oil in the seventeen other L.A. basin oil fields within the city were assessed by means of a methodology similar to that used by USGS. The original oil in place was calculated from a standard petroleum engineering equation using data from the California Department of Conservation, the USGS, and the peer-reviewed literature. Potential recovery efficiencies were estimated from recovery efficiencies modeled in engineering studies, achieved in similar reservoirs in other basins, or indicated by laboratory results reported in technical literature. Resource allocations to the City of Los Angeles were based on maps of historically productive areas within municipal boundaries, modified as necessary by other considerations.
 
8:30am - 8:50am
Organofacies and Paleoclimate Controlled Genetic Oil Families in the Onshore/Offshore Santa Maria Basins, California
K. Peters, P. Lillis, T. Lorenson, and J. Zumberge
Chemometric analysis of 21 source-related biomarker and stable carbon isotope ratios for 48 crude oil samples from the onshore and offshore Santa Maria basins identifies six genetic oil families. The data comprise a training set that was used to create a chemometric decision tree to classify newly collected oil samples. The geochemistry and map/stratigraphic distributions of these families reflect different organofacies within the Miocene Monterey Formation source rock controlled by differing oxicity during diagenesis and carbonate versus siliceous-detrital input in ‘carbonate’, ‘marl’, and ‘shale’ organofacies like those in the lower calcareous-siliceous, carbonaceous marl, and clayey-siliceous members of the Monterey Formation found elsewhere in coastal California. The corresponding lithofacies and organofacies appear to be linked to middle Miocene paleoclimatic cooling after ~13.9 Ma, a systematic up-section increase in the stable carbon isotope compositions of the generated oil samples, decreased preservation of calcium carbonate shells from planktic foraminifera and coccoliths, and increased preservation of clay-size siliceous shells of diatoms and radiolarians. Multiple biomarker parameters indicate that the six oil families achieved early oil-window maturity in the range 0.6-0.7% equivalent vitrinite reflectance despite generally high sulfur content. The results show that organofacies within the Monterey source rock are responsible for many of the geochemical differences between the oil families. This organofacies model for crude oil from the Monterey Formation can be used to enhance future exploration efforts in many areas of coastal California.
 
8:50am - 9:10am      
Characterization of Five Unconventional Diatomaceous (Opal-A) Reservoirs, Monterey Formation, San Joaquin Valley, California
D. Larue, C. Hager, T. Merrifield, G. Evola, D. Crane, and P. Yorgensen
Unconventional Opal-A and Opal-CT diatomaceous reservoirs in the Monterey Formation of the San Joaquin Valley in California have been produced for more than 30 years. Although the reservoirs can be grouped into a single category as “diatomaceous reservoirs,” they are characterized by considerable heterogeneity in structural setting and style, lithology, 3D distribution of rock properties, and production character. Here, five diatomaceous reservoirs in the Monterey Formation are described, with locations at Lost Hills, Cymric, McKittrick and two at Midway-Sunset Fields, all in the San Joaquin Valley. Three occur in anticlinal traps (Lost Hills, Cymric, and Westates anticline at Midway-Sunset), one occurs as a combined structural and stratigraphic trap (9C at Midway-Sunset), and one is present in a complex thrust belt (McKittrick). Characteristics of depth to reservoir, lithology, oil gravity api, porosity and oil saturation are described. Puzzling features of the diatomaceous reservoirs are considerable. Oil saturation is largely continuous through the reservoirs, indicating there are few or no “non-net” lithologies. Oil-water contacts for the diatomaceous reservoirs are poorly defined: only the 9C reservoir has a defendable oil-water contact. Strong 3D variations in oil saturation occur, and the edges of the reservoir appear wet at Lost Hills and for the Westates anticline, and possibly at Cymric 1Y. The transition from Opal-A to Opal-CT occurs at low formation temperatures, yet the fold amplitudes at Lost Hills, Cymric and Westates are thousands of feet, indicating that the crestal portions of these reservoirs have likely never been more deeply buried than they are today. The Opal-A to Opal-CT transition has been folded, but more gently than bedding. In general, the best producing diatomaceous reservoirs have the best oil saturations (>45%, Cymric and McKittrick Field) or are thick (>1000 ft, Lost Hills Field). Negative characteristics are deeper reservoirs (>1500 ft) with lower oil saturations (<40%, Section 9C, Midway-Sunset Field), and reservoirs that are very shallow (<500 ft) (McKittrick Field). These insights provide general guidance about characterization of unconventional diatomaceous reservoirs, and the identification of factors that most dramatically influence performance.
 
9:10am - 9:30am
Yowlumne Depositional Patterns Using Inversion Seismic
G. Henley II and K. Fox
In 2011 California Resources Company drilled a well in the northwest part of the field, with over 300’ of pay, where previous interpretations had projected 0’ of net pay. This prompted CRC to reprocess the seismic data and work out the channel systems at Yowlumne using seismic inversion and well log data.
Using the P-impedance seismic data, we were able to map out over 14 geobodies in the Yowlumne field and explain the observed production anomalies. The geobodies varied in thickness from 50-200’ with general northwest trends in depositional directions. The geobodies showed compensation stacking, likely a result of channel avulsion.
The high and low impedance geobodies could not be resolved into reservoir/non reservoir based on seismic data alone. Using well data, we were able to identify which geobodies were turbidite deposits, shales, and cherts. The seismic interpretation showed a series of time equivalent “88-4” sands with the oldest clearly cutting into the O Chert marker. The “Lower Main Sand” was resolved into three main channels and the “Main Sand” into two major channels; with all channels sharing a similar spill point. This suggests folding with local topographic uplift occurring prior to “Lower Main Sand” deposition.
While we could take the correlation from seismic back into the well logs, with some minor adjustments, all previous interpretations based on logs alone did not honor the seismic interpretation. The results of our work show opportunities in Yowlumne and suggest the relevance of our work flow towards finding value in other turbidite reservoirs.
 
10:00am - 10:20am
Building an Exploration Play in a Mature Basin- Concept to Wildcat Western San Joaquin Basin, CA
D. Miner and E. Fisher
The west central portion of the San Joaquin Basin is certainly one of the most maturely explored and developed areas for hydrocarbons in the United States. Can there possibly be any more exploration targets remaining in an area that dates back to 1911, has had over 100 exploration wells drilled and recovered in excess of 2.5 billion barrels of oil from at least 12 reservoirs? This presentation identifies the elements required to find more exploration opportunities in this challenging and maturely drilled area. The geological history that creates the opportunity are a complexly, faulted, folded and thrusted area coupled with compensating stratigraphy and heterogeneous rock properties of both the source and reservoir rocks. Advances in seismic processing of 3D seismic data enable imaging of this area after years of prospecting with 2D seismic and well data. We used play based analysis to map and combine the critical petroleum risk elements. This includes dry hole analysis of over 100 key wells, creating regional mapping and reservoir quality analysis for each reservoir, source rock charge maps made for the Monterey and Kreyenhagen source rocks, regional structural review including dip-meter SCAT analysis and basin wide reconstructions to determine areas of similar deformation style.
 
10:20am - 10:40am
In the Deep Sub-surface of the San Joaquin Valley, are the Monterey, Kreyenhagen and Moreno Formations Continuous Oil Accumulations Analogous to the Bakken Formation?
D. Larue, M. Mercer, and M. Smithard
Continuous oil accumulations are pervasive throughout large areas and are not affected by natural hydrodynamic influences. Three source rocks in the San Joaquin Valley are actively producing hydrocarbons and represent potential continuous oil accumulations: the Monterey, Kreyenhagen and Moreno formations. In 2014, the Energy Information Administration (EIA) announced that there are potentially 15 BB of recoverable oil in the Monterey Formation in California, spiking huge interest. Such a resource would make the Monterey by far the largest continuous oil accumulation in North America. This number has since been reduced dramatically to 600 MMBO for the state and 21 MMBO within the San Joaquin Valley. In this study, first the concept of the continuous oil accumulation is reviewed, and differentiated from other non-conventional resources. Next, the subsurface character of the Bakken Formation of North Dakota is compared with the three source rocks in the San Joaquin Valley at oil window depths. To characterize these reservoirs, hundreds of well logs, core descriptions, and mud logs were studied. A technique to rank character of oil show data was developed in which Interesting, Possibly Interesting, or Not Interesting wells were located on thermal maturity maps. Interesting wells have significant oil shows, whereas Not Interesting wells show minor or no shows. In the Bakken Formation, the character of the oil show correlates with well productivity. Applying this same classification to the San Joaquin Valley source rocks leads to a more disappointing conclusion. Although there are oil shows in the source rocks of the San Joaquin Valley at oil window depths suggesting the presence of a continuous oil accumulation, the distribution of shows is both laterally and vertically heterogeneous and not predictable. Moreover, recent attempts to produce from source rocks at these depths have not been economically successful. We conclude that the three source rocks in the San Joaquin Valley represent heterogeneous and discontinuous oil accumulations at oil window depths in the subsurface. Likely there are billions of barrels of oil in these discontinuous oil accumulations. Source rocks in the Bakken are rated as world class: source rocks in the San Joaquin Valley are good to excellent quality. However, the quality of the oil shows in the San Joaquin Valley appears more discontinuous than the Bakken Formation. It is possible that effective drainage between the source rocks and the up-dip reservoirs has left large volumes of the source rocks at oil window depths with only residual oil saturation. Complex structural and stratigraphic architecture, heterogeneity and continuity create issues of predictability for optimal areas to target. Rapid rates of subsidence over the past few million years and accompanying thrusting and folding resulted in a complex subsurface pressure regime. The lack of clear hydraulic fracture targets, analogous to the middle Bakken, further complicates drilling decisions, and likely deliverability. In addition, the oil windows in the San Joaquin Valley are significantly deeper than the Bakken Formation which would result in substantially higher well cost. Recent drilling results support this study and suggest that heterogeneous and discontinuous oil accumulations in the San Joaquin are unlikely to become economic without dramatic changes in technology.
 
10:0am - 11:00am
Finding New Pays in Old Plays: Applications for Surface Geochemical Exploration in Mature Basins
D. Schumacher
Detailed surface geochemical surveys document that hydrocarbon microseepage from oil/gas accumulations is common, is predominantly vertical, and is dynamic. These characteristics create applications for surface geochemical surveys that are well suited for mature basins: early delineation of field limits, field development, reservoir characterization, identification of by-passed pay, near-field exploration, and monitoring patterns of hydrocarbon drainage. Combined with other uses of surface geochemistry like high-grading leads, and prospects based on likely hydrocarbon charge, these new applications show great promise for better prospect evaluation and risk assessment in mature basins. Because microseepage is predominantly vertical, the extent of an anomaly at the surface approximates the productive limits of the reservoir at depth. The detailed pattern of microseepage over a producing field can reflect reservoir heterogeneity and distinguish hydrocarbon-charged compartments from drained or uncharged compartments. Additionally, since hydrocarbon microseepage is dynamic, seepage patterns change rapidly in response to production-induced changes in fields and waterfloods. Determining the depth or identity of the reservoir responsible for the surface anomaly is challenging but can sometimes be inferred from hydrocarbon composition, from detailed anomaly shape, and from passive electromagnetic data. These applications require close sample spacing and are most effective when results are integrated with subsurface data, especially 3-D seismic data. The need for such integration cannot be overemphasized. Seismic data will remain unsurpassed for imaging trap and reservoir geometry, but only detailed geochemical or microbial surveys can reliably image hydrocarbon microseepage from those same reservoirs. This presentation will be illustrated with examples from the USA, Canada, and South America.
 
DEG: Geologic Applications in a Changing Regulatory Environment
Co-chairs: C. Campbell, A. Waggoner
 
8:10am - 8:30am
The State of the Aquifer Exemptions
J. Kimber and M.Van Grinsven
Oil and water will not mix unless sheared at high speeds, forming an emulsion. This is an interesting metaphor considering that a fierce emulsion of interests, tied to the Safe Drinking Water Act (SDWA), is churning around and about California’s aquifers. The driving question is this: What water should be protected? Although this question inspires ongoing discussions and disagreements between regulatory agencies, the public, and the State’s energy providers, a rational, data-based approach is beginning to prevail. Enacted in 1974, the SDWA is the federal law that protects public drinking water supplies throughout the nation. The SDWA assumes all groundwater with less than 10,000 mg/L (ppm) TDS is a potential source of drinking water and mandates its protection. Hundreds of oil and gas reservoirs throughout the state have been exempted from the SDWA, but the areas exempted are limited to the oil productive areas of 1973. Today, many oil & gas operators wish to expand their injection operations beyond these exempted areas and have submitted massive amounts of data to the DOGGR to demonstrate that the targeted aquifer areas meet exemption criteria. The State, in cooperation with the EPA and operators, works to evaluate the protected waters to determine if their classification as an underground source of drinking water (USDW) is warranted. The process, to be detailed during the presentation, has evolved over the last two years and is now more efficient and transparent. The presentation will include details on the rigorous scientific review of regional and subsurface parameters.
 
8:30am - 8:50am
Reinterpretation of the Vedder Sand/Walker Formation Boundary in Round Mountain Oil Field with the Aquifer Exemption Process
L. Bazeley and M. J. Wilson
The Round Mountain Oil Field, located to the northeast of Bakersfield, has been producing since 1927. On February 9, 2017, the US EPA approved the request to expand the existing aquifer exemption of the Jewett Sand, Pyramid Hill Sand, the Vedder Sand and the Walker Formation in the field. As part of the application process, the field-wide stratigraphy was reviewed and integrated with surface geologic maps, core data, lithologic descriptions, porosity and permeability data, paleontology, production data, and enhanced oil recovery data. Regional structural and stratigraphic cross sections were constructed to place the field in the context of the surface geology and the surrounding oil fields, particularly the Kern River Oil Field to the southwest and the Mount Poso to the north. Within the field, the Vedder is the primary producing zone and is productive in all five producing areas. With the exception of the east side of the field where the Walker is productive, the majority of the wells were only drilled to the upper portion of the Vedder. The lack of wells drilled to the Walker Formation or basement throughout the field led to the assumption that the Vedder section in the Main Area was similar in thickness to the section to the east in the Pyramid Hill Area. The regional analysis resulted in a reinterpretation of the boundary between the marine Vedder Sand and the underlying non-marine Walker Formation. The new interpretation, which is consistent with the Vedder thickness in the surrounding fields, shows the Vedder as a wedge, thickening toward the basin from approximately 100 feet on the east to approximately 900 feet in the Alma Area to the west. The new interpretation of the boundary has implications for operations in the Main Area of the field.
 
8:50am - 9:10am      
The Tulare Formation: A Regional Perspective for an Old Friend
C. Campbell
Recent projects submitted for regulatory review to the California Division of Oil, Gas, and Geothermal Resources (DOGGR) involving the Tulare Formation, a Pliocene to Holocene sediment consisting of mainly unconsolidated clays, silts, sands and gravels, have resulted in project delays due to the wide use of lithostratigraphic nomenclature when describing the formation. This delay has occurred both internally, and across multiple agencies. In trying to pin-point the true cause for the delay, the author has seen mixed consensus as to the subsurface characterization, and use of lithostratigraphic nomenclature. In some cases, several questions raised by internal stakeholders and external reviewers focused around the lithostratigraphic nomenclature used (i.e. U. Tulare, L. Tulare, Basal Alluvial Clay) and the inconsistencies across fields. It is the authors belief that this localized-field use of terminology, as opposed to conformance and detailed stratigraphic nomenclature across the valley using sequence stratigraphic correlation, to further illustrate rapid changes in environment of deposition (EOD), and changes in facies will enable a clear understanding of the Tulare Formation, the regional and local sealing clays, and reservoir units. This talk will emphasize the audience to re-think what our old friend, the Tulare Formation, truly is; a complex assemblage of mixed EOD’s, facies, and stratigraphic hierarchy. Using regional to sub-regional examples, past literature, and current use of terminology, I will demonstrate that in describing and characterizing the Tulare Formation, we truly need to take a step back, and ensure we are taking the time to accurately interpret the subsurface.
 
9:10am - 9:30am
Stratigraphy of the Tulare Formation, Elk Hills and Buena Vista Hills, San Joaquin Basin, California
T. Reid, E. Greenwood, and J. Goodell
Outcrop exposures and subsurface data from the Elk Hills (EH) and Buena Vista Hills (BVH) region document a nearly complete record of the Pliocene and Pleistocene Tulare Formation in the southwestern San Joaquin Basin. In this region, the section is finer grained and muddier than in areas more proximal to the basin’s margins. The lowermost portion of the Tulare contains an interval of laterally continuous sands interbedded with mudstone layers and is interpreted to represent prograding lake shoreline and floodplain deposits. The overlying Tulare section contains laterally discontinuous sand bodies and mudstone, and likely were deposited in fluvial channel and floodplain environments. Channels become dominant and coarser grained toward the top of the section. Two major regionally continuous clay intervals occur within the fluvial section. The Amnicola Claystone is present throughout central and western EH and across all of BVH. A second interval of clay and sand, locally called the Tulare Clay, is present in outcrop across EH and BVH. The distinctive regional clay intervals are excellent marker beds and assist correlation of the Tulare into adjacent basin areas. An additional younger section of the Tulare that contains the E-Clay (or Corcoran Clay) is present in the basin but absent on the hills. The two regionally continuous clay intervals represent lake-bed deposits and occurred before uplift of the EH and BVH structures. The younger section containing the E-Clay was deposited after uplift of the structure began. Age constraints on lake-bed deposits place initiation of uplift at about 1 Ma.
 
10:00am - 10:20am
Aquifer Architecture and Groundwater Quality in the Tulare Formation, Lost Hills-Belridge Oil Fields Area, Kern County, California
J. Gillespie, M. Stephens, and T. Davis
As part of the California State Water Resources Control Board’s Regional Monitoring Program of Water Quality in Areas of Oil and Gas Production (RMP), formation and clay layer mapping, sequential pressure tests, geophysical log analysis, and groundwater sample lab analyses were used to determine: 1) the presence and extent of confining layers, 2) groundwater salinity and 3) depth to the base of protected groundwater (TDS <10,000 mg/l) within the Tulare Formation in the Lost Hills, North and South Belridge oil fields and adjacent areas. The Tulare Formation is erosionally thinned to about 300 feet where it crops out on the northern Lost Hills anticline. It thickens to over 2000 feet to the south and east. Sequential pressure tests indicate the presence of five locally confining layers within the formation. Pressure anomalies across confining layers are common. Calculation of formation water salinity using borehole geophysical logs indicates that salinity generally increases with depth and often changes markedly across confining layers. The base of protected groundwater usually occurs within the Tulare Formation. The elevation of the base of protected groundwater slopes southeast from sea level in the northwest part of the area to -1100 feet in the southeast. Several generations of produced water disposal wells were drilled in the area. Geophysical logs from older wells (pre-1985) show a linear increase in salinity with depth. Logs in newer wells (primarily 2012-2015) have irregular salinity patterns with depth and show saline waters at shallower depths than in nearby older wells. The presence of produced water disposed of in surface sumps can be seen in logs from newer wells where saline water (>10,000 mg/L TDS) has seeped into the alluvium overlying the Corcoran Clay equivalent in the uppermost Tulare. Historical groundwater sample data further downgradient to the east indicates that these saline waters reached saturated groundwater zones in places.
 
10:20am - 10:40am
A Comparison of Methods That Use Produced Water Geochemistry and Borehole Geophysics to Map Deep Groundwater TDS In and Around Oil and Gas Fields
D. Shimabukuro, M. Stephens, J. Gillespie, W. Chang, D. Finney, and E. Haugen
Several different methods using a combination of produced water geochemistry and borehole geophysics have been used to understand deep groundwater total dissolved solids (TDS) in and around oil and gas fields in the San Joaquin Valley. Produced water geochemical measurements alone can yield a TDS-depth relationship. These measurements can be supplemented with borehole geophysics, such as using observed deep resistivity-TDS relationships, or using deep resistivity, porosity, and temperature to calculate TDS using the Archie's-based resistivity-porosity method. These approaches are often one-dimensional in nature, yielding TDS as a function of depth for an entire well field. These techniques can be extrapolated into three dimensions using geostatistical methods, such as kriging, that allow spatial heterogeneity to be better represented. Such approaches include kriging produced-water geochemistry, kriging Archie's equation with standard or empirically-fit parameters, or machine-learning methods such as neural nets. Here, we discuss the advantages and disadvantages of each method, and how the availability of archived oil and gas data, along with field characteristics, such as vertical and lateral salinity gradients, the presence of diatomite, and thermal effects due to steaming, may affect the choice and accuracy of each method.
 
10:40am - 11:00am
Case Studies of an Effective Methodology to Collect Formation Water to Meet Regulatory Requirements for Formation Water Sampling
V. Tran, B. Tapan, and A. Nayi
New underground injection control (UIC) regulatory activity come with challenges. California regulatory agencies have enhanced scrutiny on underground injection projects. One of the requirements under the California UIC regulations is to collect formation water samples and submit water analysis results together with the application package to confirm whether the Total Dissolved Solids (TDS) of a formation or aquifer is greater than 10,000 ppm, which is non-underground source of drinking water (non-USDW) under the federal Safe Drinking Water Act (SDWA). Various methodologies for collecting water samples were evaluated before selecting wireline tools, to collect water samples. The water samples were collected open-hole using downhole special wireline equipment with high technologies to analyze/detect not only fluid types being pumped through tool’s flowline but also the contamination levels (due to mud filtrate invasion), to prove the representative formation fluid quality of the collected samples. This paper summarizes water sampling methods using two different types of wirelines sampling tools from two different leading wireline contractors. Depending on the key sensors each tool has, strategies to detect contamination levels were studied and developed. The following executions and on-the-fly decision making have proved this sampling method is the most suitable and cost-effective for the specific regulatory required sampling. Formation water samples were successfully collected with monitored contamination levels to prove the accuracy of the formation TDS of this sampling method compared to the log-derived TDS. This crucial data helps demonstrate the TDS and water quality in order to comply with California UIC requirements. This is a new sampling method that had never been used in the San Joaquin Valley region for formation water sampling. Despite initial concerns from regulatory agencies about the accuracy of this method, the regulators have not only accepted this formation water sampling technology, but now advocate for its use by other operators.
 
11:00am - 11:20am
Groundwater Salinity Mapping Using Geophysical Log Analysis Within the Fruitvale and Rosedale Ranch Oil Fields, Kern County, California
M. Stephens, D. Shimabukuro, J. Gillespie, W. Chang
This work presents a volume model of groundwater total dissolved solids (TDS) in the vicinity of the Fruitvale and Rosedale Ranch oil fields near Bakersfield, California. California Senate Bill 4 (2013) and the 1974 Safe Drinking Water Act authorize the protection of underground sources of drinking water (USDW), defined as non-exempt aquifers containing water with <10,000 parts per million (ppm) TDS. TDS data from produced water samples indicate that TDS increases with depth, but the depth at which TDS reaches 10,000 ppm varies greatly. Currently, the spatial distribution of available TDS data do not provide adequate coverage to clearly define the distribution of USDW near the oil fields, causing uncertainties in strategies for monitoring protected groundwater and management of wastewater injection operations. Therefore, geophysical logs from 50 oil and gas wells were evaluated to fill spatial gaps. Resistivity, porosity, and temperature data from these logs were used to model TDS concentrations in three dimensions. The model uses Archie’s Equation and kriging to predict TDS values (with uncertainties) within the volume. Model parameterizations are found by mathematical optimization with the sum of the squared residuals as the objective function to be minimized. Modeling shows the 10,000 ppm boundary is reached at ~3,200 ft (975 m) below sea level in Rosedale Ranch and deepens to the southeast in Fruitvale to ~4,200 ft (1,280 m). Mapping groundwater TDS concentrations at this resolution reveals that concentration is primarily controlled by depth, recharge, and stratigraphy, as well as faulting and facies changes in some places.
 
11:20am - 11:40am
The Kern River Reservoir of the Kern River Field: A Closed System
M. Van Grinsven
This study expands on the work of Coburn and Gillespie (2002), whose results suggest that a water management program to remove of excess water from the producing zones will increase steamflood efficiency. The current management plan bolsters the inward pressure gradient allowing fluids to be more efficiently produced and ensuring they remain in the bounds of the oil field. The previous work is limited to an up-dip section of the Field near the Kern River. To understand if the closed system assumption holds true for deeper western areas where there may be questions over the hydraulic connection to the SJ basin or and Upper Chanac formation below, a similar study was performed. There A correlation was found between increased production from interdiction wells and oil production and it is likely a result of a more efficient steam chest. Two causes for increased oil production may include greater accommodation space for the steam chest to expand caused by the reduction of reservoir fluids and/or a lower reservoir pressure required to maintain the steaming operations. Furthermore, in mature fields with a bottom water drive, it is common for the percentage of produced water to increase as oil production decreases with depletion. This is not the case for the Kern River Oil Field as the water-oil ratio has decreased over time. The decreasing water-oil ratio is strong evidence that the region acts as a closed system and maintains the economic viability of the oil field.
 

POSTER PRESENTATIONS
April 23 and April 24
 
Structure and Tectonics: From Micro-fractures to Plate Boundary Faults 
​(Presenters are expected to be at their posters from 8:00am to 11:30am on Tuesday, April 24) 
Alamo Schist North of Alamo Lake, Arizona
W.J. Elliott and J. Corones    
A small isolated outcrop of blue-gray schist occurs north of Alamo Lake, AZ. Visual comparison of this metamorphic rock was made with samples of Orocopia Schist on the northwest side of the Plomosa Mountains, AZ, and at Cemetery Ridge, AZ. At the hand-lens level of identification, save natural variation, these three schists appear to be all but indistinguishable, one from the other. Relative Probability U-Pb age date for detrital zircons obtained from the Alamo schist is 167 Ma (middle Jurassic). This appears to be compatible with U-Pb ages at Cemetery Ridge and at Plomosa Mountains. Massive quartz “breccia” bodies, with occasional well rounded quartz clasts, occur with Alamo schist. A tentative explanation may be that the “breccia” is a well-cemented collection of disaggregated ocean-bottom ribbon quartz combined with far-traveled quartz-pebble turbidite sequences from some distant shore. We tentatively suggest that this exposure may represent an isolated occurrence of Orocopia Schist – an artifact of an exhumed portion of the Farallon Plate.
 
Spatial and Temporal Characterization of Volcanic-filled Paleovalleys Dextrally Offset Across the Petrified Springs Fault in the Central Walker Lane, Nevada
A. Hoxey, J. Lee, and A. Calvert
The Central Walker Lane (CWL), NV, accommodates ~25% of Pacific-North American plate boundary dextral shear. In the CWL five faults are hypothesized to accommodate most of the dextral slip, but displacement magnitudes and initiation ages are poorly constrained. Review of 30+ year-old geologic maps suggests Cenozoic volcanic-filled paleovalleys (PVs) record offset across the five CWL faults, including the Petrified Springs fault (PSF). To test if PVs act as geologic markers across the PSF, we completed new geologic mapping and structural studies. Observations of paleosol developed stratigraphically on top of Mesozoic rocks and structural measurements in the overlying Cenozoic rocks document the geometry of the unconformity and offset magnitude across the PSF. The PSF is an ~65 km long, NW-striking dextral fault that offsets four geologic markers. The oldest marker is a series of four, nested PVs filled with Cenozoic lavas and tuffs. Dividing the ~10.3 km offset magnitude by the ~27.11 Ma Ar/Ar age reported for the youngest nested unit, Mickey Pass Tuff (Henry & Faulds, 2010), yields an ~0.4 mm/yr minimum slip rate. A younger PV is offset ~9.6 km and filled with an ~16.03 Ma andesite lava (preliminary Ar/Ar), yielding an ~0.6 mm/yr minimum slip rate. A 3rd PV is offset ~1.8 km across one splay and filled with a presumed Pliocene basalt (Ar/Ar in progress). A 4th marker is a normal fault, bounding an ~10.7 Ma basin (K/Ar age; Evernden et al., 1964). The normal fault is truncated by and dextrally offset ~3.3 km across the PSF, which yields an ~0.3 mm/yr minimum slip rate. Our ~0.4 mm/yr slip rate is within error of reported minimum slip rates along both the dextral, west-adjacent CWL faults: the Gumdrop Hills and Benton Springs faults (Mayberry & Lee, 2017; Dubyoski et al., 2016), and is within error of GPS-based block-model estimates for recent slip on the PSF of ~0.6 mm/yr (Bormann et al., 2016).
 
Settling of Heavy Liquid Metal During Planetary Core Formation
C. Martinez, D. Brand, C. Rains, J. Fleck, J. Rincon, and D. Weeraratne 
Descent of heavy metals during the differentiation of impacted and subsequently melted asteroids is an evolutionary and obscure process of planetary accretion. The process of metal segregation from rocky silicates is not fully understood and the extreme physical properties are difficult to model numerically. I present physical laboratory experiments that model the gravitational instability, descent, and settling of an emulsified liquid metal layer at the base of an impact induced magma ocean or reservoir. Using liquid gallium and glucose solutions experimental results have been gathered showing descent of emulsified metal drops through a viscous solution. The emulsified gallium drops are coated in a low density glucose solution which is entrained to the bottom of an experimental box. Residue created by viscous shearing forces experienced by liquid gallium during the descent process settle much slower due to increased drag from their flaky, elongated shape. This residue can possibly explain currently observed areas of significantly low shear (S) and compressional (P) wave velocities at the core-mantle boundary. Scaling to planetary interiors and high pressure mineral experiments indicates that Si, O, and H within molten silicates may be entrained to the Earth’s core and may explain the observed core density deficit. Subsequent upwelling of the buoyant material out of the core occurs slowly over several billion years as groups of rising plumelets providing a primordial source required for lower mantle shear velocity provinces observed today.
 
PS-SEPM: Sedimentology and Stratigraphy: From Lacustrine to Deep-water Reservoirs 
(Presenters are expected to be at their posters from 8:00am to 11:30am on Monday, April 23) 
Climate, Water Table, and Sedimentary Controls on the Evolution of a Wet Vertebrate Ecosystem, Lower Jurassic Aztec Sandstone, Valley of Fire State Park, Southern Nevada
M. V. Caputo and S. Rowland
Trackways made by arthropods, therapsids, and theropod dinosaurs have been discovered in relation to an anomalous, reddish lenticular bed in the Lower Jurassic Aztec Sandstone of eolian origin at Valley of Fire State Park, southern Nevada. At its maximum, the bed is 3.0 meters thick and is composed mostly of broken, folded, wavy, and flat laminae of mudstone, very fine grained sandstone, and dolomitic limestone. Sandstone beds are locally cross-laminated in sets 0.1-meter-thick and fill erosional scours a few centimeters deep. Bedding cycles, 0.8 to 1.0-meter-thick, show vertical trends in platy calcareous fragments that increase upward in size and abundance. Vertebrate tracks found within a few meters above this interval are absent below it. For this bed, we interpret traction, suspension, and biogenic sedimentation in a localized interdune swale now preserved among distinct eolian strata in the Aztec Sandstone. Because of subsidence of the sediment pile or a shift to a wetter climate, the water table rose and intersected a nearly lifeless interdune floor to create an ecosystem, vibrant with a diverse biota of plants and arthropods, therapsids, and carnivorous theropod dinosaurs. Limited areal extent of this interdune deposit suggests a short-lived, wet ecosystem that with time succumbed to drying conditions, lowered water table, more sediment available for wind transport, and burial by eolian dunes. Fine wind-blown sand was trapped by adhesion at the capillary fringe. Sporadic wadi floods moved small subaqueous dunes and scoured the interdune surface. Mudstone laminae settled from suspension in standing water and waning wadi flooding, and were later deformed by loading. Platy calcareous fragments may be remnants of organic mats that record vertical fluctuations in the water table in upward-wetting cycles.
 
U-Pb Age of Continental Red Beds North of Alamo Lake, Arizona
W. J. Elliott and J. Corones
Scattered, isolated outcrops of siliciclastic red beds occur throughout southeastern California and southwestern Arizona. Many attributes, including camel, dog, cat, and bird trackways found in fine-grained sediments near Lincoln Ranch, AZ, suggest a continental origin. Red and orange staining derives from post-depositional weathering of iron- bearing minerals such as hornblende and biotite in hot arid or semi-arid climates. North of Alamo Lake, AZ, an approximately 2-feet thick, crème to light green volcanic ash occurs within the red-orange Chapin Wash Formation. Basal ash was deposited on a dry, mud-cracked lake bed. U-Pb Zircon age of this igneous ash is: 12.53 +/- 0.16 Ma (middle Miocene).
 
3D Stratigraphic and Compositional Characterization of the Kreyenhagen Formation at Kettleman City and Kettleman North Dome:  San Joaquin Basin, California 
L. Giannetta and R. Behl
The Eocene Kreyenhagen Formation is an understudied, but potentially important siliceous, organic-rich mudstone of the San Joaquin Basin, California. Long known to be a source rock for the northern San Joaquin Basin, the Kreyenhagen has emerged as a potential unconventional resource. Yet, in comparison with the Miocene Monterey Formation, data from the Kreyenhagen is very limited. We will complete a high-spatial-resolution stratigraphic characterization of the subsurface Kreyenhagen and its lithostratigraphic subunits to better understand its internal compositional variability and depositional history. This study will integrate subsurface well logs, core, and cuttings analysis. First, a gross well-log correlation of the Kreyenhagen will be conducted near Kettleman North Dome, where cross-sections, structure, and isopach maps will define its regional framework. Subunits within a focused study area will be recognized based on stacking patterns, mineral composition, and geochemical properties. Petrophysical techniques will provide initial estimates of clay and organic carbon content. For calibration, rock samples will be analyzed for whole-rock major elemental composition and Total Organic Carbon. We will populate the subunits with the laboratory-derived data to refine their composition and reservoir properties. Ultimately, this approach will document vertical and lateral compositional variations within the subunits across the study area. This study will improve our understanding of the Kreyenhagen Formation’s unconventional resource potential and bathyal sedimentation within the San Joaquin Basin during the Eocene – one of Earth’s great intervals of biosiliceous sedimentation. Furthermore, we hope that results will illuminate the depositional controls on compositional facies variations in deep-water siliceous and organic-rich mudstones.
 
Differentiating Beach and Fluvial Conglomerates by Size and Shape Characteristics of Quartzite Clasts in the Cenozoic Tecuya and Kern River formations, Southern San Joaquin Valley, CA
S. McKinney, J. Buehler, and K. Watson
Coarse grained quartzite clastics in the San Joaquin Valley have been interpreted to have been deposited in both beach, fluvial, and alluvial environments with the location of marine/non-marine transitions poorly constrained. Quartzite clasts in modern fluvial gravels tend to plot in the prolate/sphere field on a Zingg diagram (Howard, 1992). The average 218 quartzite clasts from a single location in Miocene fluvial conglomerates of the Kern River Formation (QTkr) plot in the prolate/sphere field as expected but close to the boundary of the disc field. We attribute this to the large percentate of foliated micaceous metaquartzites in the QTkr that have anisotropies favorable for the creation of disc shaped clasts. We plan to test further locations in the QTkr, Quaternary Kern River terraces, and to subdivide the quartzite population into orthoquartzite and metaquartzite subpopulations. The Oligocene Tecuya Formation (Ttcq) also has sedimentologic and facies evidence for deposition in a similar braided river system as the QTkr but the quartzite population in fluvial conglomerates consists overwhelmingly of more isotropic orthoquartzite. Orthoquartzite from Ttcq plots (n=444) within the sphere field. We conclude that orthoquartztes are the preferable rock type to use when discriminating beach vs fluvial conglomerates. This is supported by beach/fluvial discriminant S/L vs (L-I)/(L-S) of Howard (1992) where the average of QTkr with more metaquartzite clasts plot in the discoidal beach field while orthoquartzites of Ttcq plot in the fluvial field. We plan to test additional locations in the KRF and Ttcq and to subdivide the quartzite population into orthoquartzite and metaquartzite populations. Sediment recycling of eroded beach deposits is also a possibility in QTkr, but there is more evidence of sediment recycling of beach and nearshore deposits in Ttcq. Metavolcanic clasts in QTkr do not plot in fluvial fields on either discriminant. In fluvial Ttcq, metavolcanics clasts do plot in the sphere field but are shifted towards the oblate field comparted to quartzites. On beach/fluvial S/L vs (L-I)/(L-S) plots metavolcanics clasts are not an effective discriminant. Plutonic+Metamorphic clasts are even less discriminating as to environment, with fluvial conglomerate clasts plotting in the oblate and beach fields.
 
Mineralogical and Geochemical Characterization of the Miocene-Oligocene Santos shale, Southern San Joaquin Valley, California
N. Mitchell and J. Guo
The Santos shale is a 29 ~ 20 Ma member of the Temblor Formation located in the southwest corner of the San Joaquin basin. It was deposited in an ocean basin along the slope and the basin plain. The Santos outcrops in the Temblor range along the western perimeter of the San Joaquin valley, where it dips and thins eastward into the subsurface under the valley. The goal of the study is to characterize the Santos shale through its mineralogical and geochemical properties to better understand depositional environment and it’s potential as a source rock or fractured shale reservoir. Forty samples were used for this study from the wells along the crest and the flank of the Belgian anticline, ranging in depths of 1,061’ in the west and 14,970’ in the east. XRD analyses revealed that the bulk composition of the average Santos is composed of 45% clays, 29% quartz, 15% carbonates and 11% feldspar. In the clay size fraction, the clays are on average composed of 45.5% smectite, 43.3% illite, 8.2% kaolinite and 3.0% chlorite. LOI reveals the Santos has an overall high TOC content that ranges from 1.4 to 15.8 wt.%, with an average of 7.7 wt.%. Geochemical analyses from XRF and ICP-MS indicate the Santos was deposited in a well oxygenated marine environment based on relationships between iron, TOC and total sulfur; and low trace element ratios used as paleoredox proxies such as Ni/Co vs. V(V+Ni), V/Sc vs. V(V+Ni), and V/Cr vs. Ni/Co. Redox conditions upon burial are indicated by enrichment in Ni, V and U within the Santos samples. High TOC content is attributed to the oxic ocean environment with productive paleo waters. The preservation of the organic matter is due to redox conditions upon burial at the ocean-sediment interface where the oxygen is quickly depleted from settling organic matter. High TOC values in the Santos imply very good potential for fracture development.
 
Quantitative Compositional Characterization of the Biosiliceous Miocene Lark Formation, Danish North Sea and Norwegian Margin
M. Mortimer-Lamb, R. Behl
The Miocene epoch is one of global biosiliceous sedimentation. A number of siliceous deposits co-occur or precede the Monterey Formation of California, yet most have not been characterized, or assessed as a reservoir or source of petroleum. One of these - the Miocene Lark Formation of the Norwegian Margin and Danish North Sea - was largely deposited before the establishment of the deep thermohaline circulation system that shifted biosiliceous sediments from the North Atlantic to the Pacific Ocean. Quantification of biosilica content during this transition could help constrain the timing of the “silica switch”. This study will develop a reliable biosilica quantification procedure via core sample analysis from three wells in the North and Norwegian Seas. This will better characterize the sediment, and inform our understanding of paleoceanographic circulation and paleoproductivity.
Quantification of biosilica must be multifaceted as two of the diagenetic phases, opal-A and opal-CT, are non- or poorly crystalline. These poorly crystalline materials are difficult to quantify by X-ray diffraction (XRD); therefore, XRD analyses must be calibrated by and combined with other techniques such as Inductively Coupled Plasma Mass Spectrometry, Fourier Transform Infrared Spectroscopy, and wet-chemical alkaline digestion and spectrophotometry.
This study will test the robustness of each quantification technique and generate an “excess silica” equation that can be applied to the Norwegian Margin and Danish North Sea and provide a template for use in California and elsewhere. Based upon an empirically derived biosilica to detritus ratio, the excess silica equation will be used to determine the amount of original biogenic opal-A, opal-CT or quartz phase silica that exists in the sedimentary rock. This information will help predict key reservoir properties including porosity, permeability, and hardness.
 
Compositional Trends in Izu-Bonin Mariana Arc Volcaniclastic Sandstones
I. Ruttenberg and K. Marsaglia
Integrated Ocean Discovery Program (IODP) Expedition 351 and Ocean Drilling Program (ODP) Leg 126 recovered cores of Late Oligocene volcaniclastic rocks (marine gravity-flow deposits) in the Izu-Bonin Mariana (IBM) Arc system from four drill sites, three in the forearc (Holes 787B, 792E, and 793B), and one in the reararc (Holes U1438B/D). These provide a record of IBM arc rifting and initiation of the Shikoku backarc basin. Pore-water samples were squeezed from cores throughout these intervals. Thin sections were prepared from 68 volcaniclastic sandstone samples first impregnated with blue-dyed epoxy for porosity recognition: Holes 787B (n=29; 119-310 meters below seafloor [mbsf]), 792E (n=9; 438-781 mbsf), 793B (n=10; 970-1369 mbsf), and 1438B/D (n=20; 165-493 mbsf). Petrographic point-count data were collected using the Gazzi-Dickinson point-count method after thin sections were stained for calcium and potassium silicate phases (feldspar and zeolites). Counted categories included various unaltered to partly altered mineral and glassy volcanic components, authigenic phases (zeolites and clay minerals), and primary and secondary porosity. Samples vary in their degree of alteration with total zeolite content ranging up to 50%, and clay cement up to 60%. Residual primary porosity ranges from 0-22% with 0-2% secondary porosity. Site 787 and U1438 samples are more felsic in composition and Site 792 and 793 samples are more mafic in composition, suggesting that each group had a different volcanic provenance. Correlation coefficient-based statistical analysis reveals that at each site and across all sites, original composition, authigenic phases, presence of component types, mean grain size, and pore water geochemistry are weakly correlated to each other (with correlation coefficients between -0.6-0.6) but have standard deviations too large to be statistically significant. However, some variables do correlate with each other across specific parameters.
 
Investigating the Macroinvertebrate Skeletal Contributions to Devonian Carbonate Records: Contrasting Patterns at Different Spatial and Temporal Scales
G. Valov and M. Brady
Much of the Paleozoic stratigraphic and fossil records come from carbonate-dominated shallow-marine epicontinental settings. Previous work suggests the extent of these depositional settings has declined through the Phanerozoic, while the contributions of skeletal material to carbonate sedimentation have increased over time. This study compares the contributions of skeletal grains across two coeval Devonian carbonate sedimentary basins: the thermally-subsiding continental margin in Nevada versus the stable continental interior in Iowa. These basins preserve comparable depositional environments and macroinvertebrate taxa, but exhibit distinct sediment accumulation rates over an ~5 m.y. interval: 40 m/year in Nevada versus 6-12 m/year in Iowa. The thicker stratigraphic record in Nevada is dominated by tidal flat and shallow subtidal facies and preserves a lower proportion of skeletal-rich facies compared to the thinner record in Iowa that is dominated by deep subtidal facies. However, when comparing skeletal-rich facies, Nevada exhibits a greater proportion of skeletal material relative to Iowa. Within each basin, there is a basinward increase in deep subtidal facies, but this trend is more pronounced in Iowa. Skeletal-rich facies make up comparable proportions of localities across the Nevada basin, but are most common away from the extreme shoreward and basinward localities in Iowa. Contrasting patterns at varying spatial and stratigraphic scales suggest that suppressed carbonate sedimentation in Iowa relative to Nevada led to a greater proportion of deeper subtidal and skeletal-rich facies, but also a lower proportion of skeletal grains within skeletal-rich facies. Distinct seawater conditions in the epicontinental seaway may have contributed to suppressed carbonate sedimentation rates. These findings may be used to better predict vertical and lateral trends in petroleum system characteristics in carbonate facies and settings.
 
Tight Oil Exploration in Monterey-like Biosiliceous Shale of Japan
S. Yokoi and T. Tsuji
In 2012, we started tight-oil exploration in the Onnagawa Shale, a Neogene biosiliceous mudstone unit in Japan. As the first step, we tried acid stimulation on this non-commercial shale reservoir in an existing deviated hole and achieved significant success with initial production over 300 BOPD. The well has produced over 100 thousand barrels of oil in the first year and a half.
Judging from the production profile, we can estimate some fracture contribution during initial production, and then a strong matrix contribution in the later stages of production. The former means successful acid stimulation from carbonate-cemented fractures with an injection pressure slightly above formation fracture pressure, whose effect is estimated to be equivalent to that of a bi-wing artificial fracture several tens meters long. The latter is supported by matrix pores of quartz-porcelanite, with pore sizes that are comparable to common shales.
Although this is the first case of acidizing in this type of mudstone in Japan, we can expect a stimulation performance similar to hydrofracturing under certain conditions. We are now modeling our acidizing job with some simulators (Tamagawa 2018, in application for PSAAPG), expecting further application as a cost-effective tool.
From the perspective of exploration, we are still in a structural or conventional trap, developing migrated tight oil, and the preservation of matrix pores in porcelanite will be a critical issue for further exploration in deeper parts of the basin where a continuous accumulation is expected.
 
Source-to-sink Analysis of the Tributary System That Fed the Mio-Pliocene Capistrano Formation Channel Complex at Dana Point Harbor, Dana Point, Orange County, California
D. Schwartz
A source-to-sink evaluation of the modern-San Juan Creek Watershed in Orange County, California was initiated to assess the origin and transport distance of distinctive breccia deposits exposed within the Mio-Pliocene Capistrano Formation (Tct) at Dana Point Harbor. Initial evaluation indicates that debris flows transporting tabular shaped cobble sized middle-late Miocene Monterey Formation (Tm) clasts were confined within channels in the submerged proto-San Juan Creek watershed. Cobble transport distance varies by channel location with respect to Monterey outcrops that were present in the Pliocene. There are three potential transport routes for the debris flows. Distance from source terrain to deposit varies from a minimum of 7.5 kilometers within proto-San Juan Creek, a minimum of 10.6 kilometers in the proto-Arroyo Trabuco Creek, and a minimum of 13.5 kilometers in proto-Oso Creek. Volumetric contributions of each tributary have not been determined. Breccia deposits in the Capistrano comprise over 20 percent of the channel fill. Rounded clasts of granule to cobble size derived from early Miocene to Triassic-Jurassic age strata within the proto-San Juan Creek watershed were deposited within pebbly sandstone and conglomerate beds in the Capistrano Formation (Tct) at Dana Point Harbor. These clasts and medium to course grained sands were transported via traction and grain flow processes within tributary channels for distances a minimum of 8.5 kilometers and a maximum of 45.7 kilometers.
 
Pacific Exploration: Mature Basins and Prolific Reservoirs
(Presenters are expected to be at their posters from 8:00am to 11:30am on Tuesday, April 24) 
Hybrid Fracturing Concept Based on Geologic Features of a Monterey-like Biosiliceous Shale, Japan
T. Tamagawa
We have made continuous efforts to develop a middle mioccene Monterey like bio-siliceous shale distributed in northern Japan since 2012 with governmental supports. The shale formation is called as Onnagawa formation and is roughly estimated to have an order of hundred million barrels of oil as an original in-place. Although we have successfully recovered a certain amount of oil from Onnagawa shale, cost-effective and efficient production methods to exploit oil from Onnagawa shale are still unclear. In our project, two different stimulation approaches were tried, those were multi-stage hydraulic fracturing and acidizing. In the multi-stage hydraulic fracturing job along a newly drilled horizontal well, we met a serious issue to occur screenouts at some frac stages. The prepared measures to prevent screenout, which were adoption of high viscous fluid slug and pre-injection of fine particles, didn’t work. From the detail investigation of microseismic event rates as well as pumping pressure responses, the cause of screenout is interpreted to be in excessive leak-off of fracturing fluid to natural fracture system. On the other hand, the acidizing job using mud acid system applied at an existing deviated-well was a great success. After the job, the oil production increased dramatically from 10 bbl/D to 315 bbl/D and shows 100,000bbl cumulative production for a year. The production improvement is inferred to come from contributions by stimulating natural fracture system filled with acid soluble minerals. Based on the interpretation of the two field trials and a preliminary acidizing simulation, a hybrid fracturing concept has come up as a cost-effective approach for Onnagawa shale. In the hybrid fracturing process considered, acid fracturing stimulate natural fractures developed in the deep field away from a wellbore and proppant fracturing injects proppant placed in the near-wellbore region to prevent closing of fractures from high draw down pressure at oil production.
 
DEG: Geologic Applications in a Changing Regulatory Environment
(Presenters are expected to be at their posters from 8:00am to 11:30am on Tuesday, April 24) 
​Impacts of the 2016 Erskine Fire on the Physical Properties of Soils
S. Haake, J. Guo, and W. Krugh
Wildfires over the past few decades have been impacting an increasingly larger area of the southern Sierra Nevada. The effects of wildfires on landscapes, and soils in particular, can increase the frequency of debris flow events, which pose a greater risk to people, as the wildland-urban interface expands into the Sierra Nevada. Alterations in the physical properties of burned soils are one such effect that can catalyze slope failure and debris flow events, and previous studies reveal that the degree of a soil’s physical alteration resulting from wildfire has been linked to burn severity. In this study, the physical properties of soils with varying degrees of burn severity are explored within the Erskine fire perimeter. The Erskine fire ignited in June 2016 in the southern Sierra Nevada, burning 48,019 acres, resulting in soils of unburned (or very low), low, moderate, and high burn severities. Unburned (VLBS), low (LBS), moderate (MBS), and high (HBS) burn severity soil samples were collected within the Erskine fire perimeter, and the influence of burn severity on the physical properties of soil are explored using X-ray diffractometry (XRD) analysis, grain size analysis, liquid limit, plastic limit, total organic carbon content, and shear strength tests. Total organic carbon (TOC) content increased with increasing burn severity. HBS soil has the highest liquid limit, followed by LBS, MBS, and VLBS soils. Plastic limit increased with increasing burn severity. Analyses from XRD, grain size, and shear strength testing are being finalized. Results from this study will be used to help constrain the effects of burn severity on the physical properties of soils and to assess debris flow hazard models within burned areas of the Kern River watershed in the southern Sierra Nevada.
 
Using Oxygen Stable Isotopes in Cements from Sandstones to Estimate Pore Water Salinity in the San Joaquin Valley, California
M. Loustale, D. Shimabukuro, and A. Wagner
Enactment of California Senate Bill 4 has renewed interest in determining groundwater quality, measured in parts per million total dissolved solids (ppm TDS), in and near oil fields in the San Joaquin Valley (SJV). Current efforts to map the distribution of underground sources of drinking water, or waters with less than 10,000 ppm TDS, rely on measured groundwater chemistry or processed borehole geophysical logs, but these efforts can be limited by lack of available produced-water chemistry. Previous work reveals a positive linear relationship between groundwater TDS and oxygen isotope composition. This, along with the well-known relationship between the oxygen isotope composition of groundwater and precipitated calcite, may allow for the determination of groundwater TDS using the oxygen isotope composition of calcite cements. Here, we test if oxygen isotope composition of calcite cements in local sandstones could be used to estimate groundwater salinity in the SJV. Samples from oil-and-gas drill cores were selected from a variety of SJV fields based on the criteria that they came from an interval with known TDS measurements. Samples were made into polished thin sections and the calcite cement was observed for cathodoluminescence and analyzed for δ18OPBD via secondary ion mass spectrometry (SIMS) at a 10-µm scale. The measured δ18OPDB in the cements and the bottom hole temperature from each well were used to calculate δ18OSMOW of the porewater. Preliminary results show a positive linear relationship with between observed cement oxygen isotope composition and measured TDS, indicating oxygen isotope composition present in calcite cements could be a good predictor of TDS in the SJV. Finally, since most samples had TDS measurements above 30,000 ppm, additional bulk sampling has been recently completed to further test the relationship at a wider range of salinities. Bulk sampling will be done in place of SIMS due to lack of significant intra-sample variation.
 
3-D Mapping of Groundwater Chemistry in the Midway-Sunset Oilfield Using Historical Produced Water Geochemistry
E. Haugen, D. Finney, D. Shimabukuro, and J. Gillespie ​
Much of the effort to characterize the distribution of water with less than 10,000 parts per million total dissolved solids (TDS) in and around oil fields has focused on the use of borehole geophysical methods. Here, we explore a method that uses historical produced water geochemistry and geostatistics to create a 3-d map of aquifer salinity in the Midway-Sunset oil field. Unlike geophysical methods, which require the use of Archie's equation and assumptions for empirical constants, groundwater geochemical data provides direct measurements of TDS and major ion composition of aquifers. The Midway-Sunset oil field, located on the west side of the San Joaquin Valley, consists of Cenozoic marine and non-marine units deformed into a series of northwest-trending anticlines by dextral transpression along the San Andreas Fault. It is an ideal oil field to test this method of salinity mapping due to the large number of geochemical measurements available at different producing horizons spanning a large depth interval. Produced water geochemical measurements were extracted from scanned DOGGR records. Values were validated by charge balance and evaluation of the source of the sample. For wells in which multiple measurements exist, the earliest measurement was used for the spatial analysis, while later measurements were used to understand the time-series behavior of TDS. TDS and select major ions were then kriged using standard geostatistical methods to create 3-d maps of groundwater quality. Preliminary results show that Midway-Sunset field has lower (<10,000 ppm) TDS values in the north and west. These fresher waters have high bicarbonate concentrations suggesting that surface recharge may be a major factor in producing localized zones of less saline groundwater.
 
Mapping Groundwater Salinity Using Borehole Geophysical Logs in the Heavily Steamed, Diatomaceous Midway-Sunset Oilfield, San Luis Obispo and Kern County, CA
​D. Finney and D. Shimabukuro
A detailed map of groundwater total dissolved solids (TDS) does not exist at the Midway-Sunset oilfield on the west side of the San Joaquin Valley. Existing groundwater geochemical measurements do not provide the spatial coverage required to clearly define the distribution of TDS within the field. One way to supplement existing groundwater geochemical measurements, which do not provide sufficient spatial coverage, is with borehole geophysics. The resistivity-porosity (RP) method, based on Archie’s equation, uses deep resistivity, porosity and temperature to calculate groundwater TDS. It is challenging to apply the RP method in the Midway-Sunset field due to decades of steam injection, which raises temperature, and the presence of diatomite, which yields inaccurate geophysical measurements of porosity. In order to avoid temperature effects, only geophysical measurement from wells more than 200 feet from pre-existing injection were selected for analysis. Porosity estimates were corrected in diatomite zones using a multiple linear regression model developed with density and neutron porosity logs and laboratory-measured core porosity. TDS was then calculated in clean, wet sands, and kriged to generate 3-d volumes of TDS. Preliminary results exhibit groundwater with less than 10,000 ppm TDS at depths greater than 2000 feet in the northwest. The TDS trend shallows from west to east and north to south. The observed west-east trend is more gradual in the north than in the south. We provide evidence that the observed salinity gradients are stratigraphically controlled.
 
Modeling to Determine Controls on Arsenic Release into Groundwater in the Kings Subbasin, California
V. Petela, A. N. Vankeuren, and K. R. Burow
Groundwater is a critical resource for California; it supplies approximately 40% of drinking water in the state. The Groundwater Ambient Monitoring and Assessment Program (GAMA) is a statewide, comprehensive assessment of groundwater quality designed to help better understand and identify risks to groundwater resources. GAMA is being implemented by the California Water Board.  The USGS is the technical lead for the Priority Basin Project (PBP), one of four GAMA components. The USGS is sampling groundwater at many locations across California in order to characterize its constituents and identify trends in groundwater quality.  The results of these tests will provide information for water agencies to address a variety of issues ranging in scale from local water supply to statewide resource management.
​GAMA data for samples collected between 2013 - 2014 within the Kings subbasin from primarily domestic wells as part of the PBP showed 8% of sampled wells had arsenic concentrations exceeding the state and federal maximum contaminant level of 10 µg/L. Continued exposure to these concentrations of arsenic is associated with an increased risk of cancer and other adverse health effects. Arsenic is an inorganic contaminant found in groundwater that is usually of natural origin but may be affected by human influence. Geogenic arsenic in this region is sourced from sediments deposited by the alluvial fan of the Kings River, which originates in the Sierra Nevada to the east. This type of arsenic is typically mobilized into solution by desorption in alkaline water or reductive dissolution of manganese and iron oxides. GAMA and U.S. Geological Survey National Water-Quality Assessment (NAWQA) data from wells along a transect near Fresno, California show water with mixed redox processes and pH levels mostly in the alkaline category. Mean groundwater ages estimated from Tritium-3Helium dating range from 16 to 47 years with up to 50% mixing with pre-modern water, and ages generally increase towards the center of the valley. Recharge temperatures determined from dissolved noble gas thermometry range from 16 – 21 ºC, similar to or a few degrees higher than the mean annual temperature in the Fresno area.  Drilling reports from 23 wells along the transect have been used to evaluate aquifer heterogeneity. These data will be used to assign aquifer properties in a MODFLOW groundwater model incorporating geochemical reactions. Modeling will investigate the influence of pH and redox condition on arsenic concentration, which varies from 0.7-19 µg/L along the flow path, to determine the strongest contributing factors to dissolved arsenic in this area.

Reducing Risk and Maximizing Productivity: Using Pre-Stack Seismic Inversion to Predict Pay Probability for Rose and North Shafter Step-outs
C. Sine
Historically a correlation between seismic amplitudes and charged reservoir has been demonstrated and used to help guide development and field extension of the Rose and North Shafter oil fields. However, ambiguities in the seismic anomaly associated with tuning of the seismic response have limited the usefulness of the seismic. We present results of a pre-stack seismic inversion that reduces pitfalls related to seismic tuning and provides volumes of elastic properties including compressional wave impedance (Ip), shear wave impedance (Is) and their derivatives including Vp/Vs ratio. Log data indicate that high porosity oil saturated reservoir is characterized by low Ip and low Vp/Vs ratio. This observation suggests that pay (high porosity and high hydrocarbon saturation) can be identified by isolating bodies of low Ip and low Vp/Vs ratio within the pre-stack inversion derivatives. Here we apply Bayesian classification to the seismically derived Ip and Vp/Vs volumes to create a pay probability volume over a study area that includes the North Shafter field and a prospective field extension area to the northwest. Comparison of North Shafter productivity indicators (Ip and EUR) for wells drilled inside the high pay probability area to wells drilled outside of the high pay probability area shows a nearly 2x increase in productivity. Therefore, moving away from current field boundaries, we expect the pay probability volume to reduce risk and maximize productivity by providing a more reliable guide, compared to seismic anomalies, for the identification and subsequent development of the highest quality reservoir.