USING FORMATION RESISTIVITY DISCONTINUITIES TO TEST THE HYDROLOGIC SEALING NATURE OF A FAULT A Thesis Presented to the faculty of the Department of Geology California State University, Sacramento Submitted in partial satisfaction of the requirements for the degree of MASTER OF SCIENCE in Geology by Zachary David Levinson SPRING 2020 © 2020 Zachary David Levinson ALL RIGHTS RESERVED ii USING FORMATION RESISTIVITY DISCONTINUITIES TO TEST THE HYDROLOGIC SEALING NATURE OF A FAULT A Thesis by Zachary David Levinson Approved by: __________________________________, Committee Chair Dr. David Shimabukuro __________________________________, Second Reader Dr. Steven Skinner __________________________________, Third Reader Mr. Michael Stephens ____________________________ Date iii Student: Zachary David Levinson I certify that this student has met the requirements for format contained in the University format manual, and this thesis is suitable for electronic submission to the library and credit is to be awarded for the thesis. __________________________, Graduate Coordinator ___________________ Dr. David Shimabukuro Date Department of Geology iv Abstract of USING FORMATION RESISTIVITY DISCONTINUITIES TO TEST THE HYDROLOGIC SEALING NATURE OF A FAULT by Zachary David Levinson Water co-produced with petroleum—termed produced water—is often disposed of through subsurface injection. Regulations require that the injected fluid stays in the target zone and does not migrate into usable groundwater aquifers. While impermeable rock provides the primary barrier to fluid migration, faults have also been asserted to act as barriers to fluid flow, often without evidence of their degree of seal. In previous studies, discontinuities in salinity, measured in ppm TDS (total dissolved solids) were used as a method to determine if a fault seals. Here, discontinuities in formation resistivity (Rt) were used as proxy for TDS discontinuities to examine the sealing ability of the Kern Front and West Premier Faults on the east side of Kern County, California. A publicly-available online database of borehole geophysical logs and historical well records from oil and gas wells, maintained by the California Geologic Energy Management Division (CalGEM), was utilized to determine fault throw patterns and investigate the sealing ability of the Kern Front and West Premier Faults. Historical well records from wells in Kern Front and Kern River and geophysical logs from wells within v the Poso Creek field were used to map variations in fault throw. After fault throw patterns were determined, Rt data was collected from borehole geophysical logs from wells on either side of the fault. When a Rt measurement is taken in a 100% water saturated sand unit, free of any clay or hydrocarbon, it is denoted as Ro. A multiple linear regression model was used to test the statistical significance of the observed trends. Results show apparent Ro discontinuities across the Kern Front Fault, which vary in magnitude along-strike of the fault. A multiple linear regression analyses indicate the side of the fault in which the Ro measurement was taken was statistically significant and heavily impacted the prediction of log Ro (coefficient= 0.386, p=<0.001). Prediction of log Ro was also strongly dependent on an interaction term that measured the difference in Ro moving along strike of the fault (coefficient= -0.563, p=<0.001). The R-squared of this model was 0.38. Discontinuities in Ro suggest the Kern Front Fault creates a hydrologic seal in the Kern River Formation. Results from Poso Creek show only slight Ro trends near the West Premier Fault. These apparent trends suggest the West Premier fault does not create a lateral seal above the Macoma Claystone and groundwater can migrate across the fault plane. These observations were supported by a multiple linear regression model that showed no statistical difference in Ro from one side of the fault to the other Ro (coefficient= 0.0015, p=0.997). The R-squared of this model was 0.210. _______________________, Committee Chair Dr. David Shimabukuro _______________________ Date vi ACKNOWLEDGEMENTS I would like to recognize everyone that has supported me throughout graduate school and the development of this thesis. First and foremost, I would like to express my deepest gratitude to my advisor Dr. Dave Shimabukuro for providing me with all the tools and guidance I needed throughout my graduate career. Dave went out of his way to ensure my family and I were comfortable after our move to Sacramento and has provided an endless amount of support throughout this project. I would also like to thank Dr. Steven Skinner, who always had an open door when I had needed help along the way. I would also like to extend my gratitude to Michael Stephens for his guidance throughout this project. Michael has provided endless hours of advice and discussion that have not only benefited this project but helped me develop as a scientist. I would also like to say thank you to the California State Water Resources Board and the U.S. Geologic Survey for providing funding for this project. I truly appreciate the opportunity for collaboration with these organizations and I am thankful for the breadth of knowledge they provided. I also had the great pleasure of working with Water Resources Group at CSUS and I would like to thank all that supported my research. Special thanks to my parents, Harlan and Cecile, who have always supported me in all my endeavors. I cannot begin to express enough thanks to my wife, Kimberly, who has supported me throughout my academic career and always encouraged me to follow my passion. Finally, I would like to thank my children, Makenzie and Liam, for providing the motivation I needed to prosper in every step of my academic career. vii TABLE OF CONTENTS Page Acknowledgements .................................................................................................... vii List of Tables ................................................................................................................ x List of Figures ............................................................................................................. xi Chapter 1. INTRODUCTION ……..……………………………………………………….. 1 Project Background ........................................................................................... 1 Fault Zone Architecture and Permeability ...................................................... 3 Hydrocarbon Fault Seal Analysis ..................................................................... 4 Groundwater Fault Seal Analysis ..................................................................... 6 Recent Advances in Fault Zone Hydrology ..................................................... 8 Formation Resistivity as a Proxy for TDS ....................................................... 8 2. REGIONAL GEOLOGY ...................................................................................... 11 Regional Sedimentation History ..................................................................... 11 Regional Hydrology ........................................................................................ 12 Regional Tectonic and Structural Development ............................................. 14 Stratigraphy of Study Area ............................................................................. 15 Important Stratigraphic Relationships within Study Area .............................. 18 Structural Development of Study Area ........................................................... 19 3. METHODS ........................................................................................................... 22 viii Data for Formation Resistivity and Fault Offset Analysis.............................. 23 Formation Resistivity ...................................................................................... 24 Ro Data Collection........................................................................................... 24 Dataset A: Formation Resistivity near the Kern Front Fault .......................... 26 Dataset C : Formation Resistivity near the Premier Fault .............................. 26 Geologic Markers............................................................................................ 28 Dataset B: Geologic Marker Data ................................................................... 28 Dataset D: Clay Mapping near the Premier Fault ........................................... 29 4. RESULTS AND DISCUSSION ........................................................................... 31 Kern Front Fault in Kern Front and Kern River ............................................. 31 Kern Front Fault Offset ................................................................................... 31 Resistivity Near the Kern Front Fault ........................................................... 35 Interpretation of Ro Trends Near the Kern Front Fault ................................... 40 Premier Faults in Poso Creek .......................................................................... 43 Fault Offset in Poso Creek .............................................................................. 43 Resistivity Near the Premier Faults .............................................................. 45 Interpretation of Ro Trends Near the Premier Faults ...................................... 51 Comparison of Kern Front and Premier Fault Systems .................................. 53 5. CONCLUSIONS....................................................................................................55