LABORATORY MEASUREMENTS OF ELECTRICAL RESISTIVITY OF KEROGEN IN ORGANIC-RICH MUDROCKS A Thesis by GAMA ADAM FIRDAUS Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Chair of Committee, Zoya Heidari Committee Members, Walter B. Ayers Andreas Kronenberg Head of Department, Daniel Hill August 2015 Major Subject: Petroleum Engineering Copyright 2015 Gama Adam Firdaus ABSTRACT Reliability of conventional resistivity-porosity-saturation models (e.g., dual water and Waxman-Smits) is questionable in organic-rich mudrocks, which often leads to overestimation of water saturation. Previous publications showed that the interpretation of electrical resistivity logs for such rocks is challenging because of the presence of highly mature kerogen and pyrite connected networks that can influence electrical resistivity measurements. However, the electrical properties of kerogen in these rocks have not yet been quantified experimentally. Separation of kerogen from mudrocks and subsequent removal of pyrite from the kerogen, both requirements for successful laboratory experiments, remain challenging. This research quantitatively evaluated the electrical resistivity of mature kerogen using an experimental approach. This thesis was designed to assess the impact of maturity on electrical resistivity of the isolated kerogen and organic-rich mudrock samples at heat-treated samples ranging from 25°C to 800°C. Kerogen isolation was performed on mudrock samples, using a physical method, chemical techniques, and pyrite removal that involved acidic chromium chloride solution under a nitrogen (N2) atmosphere. The isolated kerogen powder sample was then compressed to form a homogeneous consolidated disk using a mold frame designed for this purpose. The next step was to synthetically mature both mudrock and isolated kerogen samples by heat-treating. Finally, the last step of the experimental work is to measure the electrical resistivity and geochemical properties of each set of molded samples at different ii maturity levels. The actual electrical resistivity of kerogen was estimated by minimizing the difference between the numerically simulated and measured effective electrical resistivity of the molded kerogen samples. The experimental work successfully isolated kerogen from Haynesville mudrock samples. X-ray fluorescence (XRF) measurements confirmed the absence of carbonates, silicates, and pyrite in the isolated kerogen samples. The electrical resistivity measurements of these samples recorded a significant decrease (i.e., up to four orders of magnitude) upon elevating the heat-treatment temperature from 300°C to 800°C. The decrease of electrical resistivity at high maturity levels could be attributed to the presence graphite-like sheets and/or the appearance of aromatic components in the organic matter. Further investigation is required to accurately separate the impact of different factors affecting electrical resistivity in the isolated kerogen and organic-rich mudrock samples. The outcomes of this thesis can potentially improve interpretation of electrical resistivity logs in organic-rich mudrocks, which can lead to enhanced well-log-based assessment of in situ hydrocarbon saturation. iii DEDICATION This thesis is dedicated to my creator, ALLAH SWT, to my lovely and amazing mother, father, sister, and to my home country, Indonesia. iv ACKNOWLEDGEMENTS In the name of ALLAH, the Beneficent, the Merciful. I would like to express my gratitude to my creator, ALLAH SWT, for giving me strength, knowledge, and guidance to finish this master thesis. All praise is for Him, who gives mankind the knowledge they never had before. I would like to thank my advisor, Dr. Zoya Heidari, for her guidance, constructive comments, valuable insights and analysis, remarks and engagement through the conduct of this thesis. I also appreciate the help and support from the members of my committee, Dr. Walter B. Ayers and Dr. Andreas Kronenberg for suggestions, guidance, assistance and patience from time to time during the process of this research. I would like to thank Dr. Thomas A. Blasingame for his attendance in my thesis defense as the substitute committee and his constructive comments on my thesis. I thank all my colleagues in the Multi-Scale Formation Evaluation Research Group, especially, Huangye Chen, Emmanuel Oyewole, Abdelrahman Kotb, and Angie Yang for their help and support in the completion of this thesis. I appreciate all the companies and organizations that fund and support this research, such as: American Chemical Society, Crisman Institute for Petroleum Research, and SPE International and the Multi-Scale Formation Evaluation Joint Industry Project. Thanks also goes to the Harold Vance v Department of Petroleum Engineering staff and administration for being extremely helpful during my time in the department. I would like to thank Dr. Mike Tice, who trained me to use the XRF equipment and shared the knowledge to analyze the results. I appreciate Texas A&M Supercomputing Facility for providing computing resources used for the numerical simulations in this thesis. I further extend my appreciation to my best friends and roommates, Danar Sampurno and Farid Bakti, for all of their encouragement and help in cheerful and difficult times. They have been always there for me, and so will I. Thanks and gratitude are also given to all members of the Multi-Scale Formation Evaluation TAMU research group for sharing valuable knowledge, support, and cheers. I am indebted to Gia Alexander for the advice and constructive remarks through this thesis writing. Furthermore, I would like to express my big appreciation for John Maldonado and Don Conlee for supporting my experimental instruments and supervising the safety of the laboratory experiments. Beyond Texas A&M University, I am grateful to the research scientists of W.D. Von Gonten Laboratories, Devon McAfee, Eric Carter, Debora Berti, Scott Davis, Andrew Russell, and Michael Stewart for sharing technical assistance on experimental procedures and results with me. vi Last but not least, my sincere thanks and gratitude is to my mom, dad, and sister for warm love, endless support, and help throughout the entire process, both keeping me focus and helping me putting pieces together to finish this thesis. vii NOMENCLATURE List of Acronyms 2D Two-Dimensional 3D Three-Dimensional Al Aluminum Ca2+ Calcium CaCl2 Calcium Chloride CaCO3 Calcium Carbonate CaF2 Calcium Fluoride CrCl2 Chromium Chloride CO2 Carbon Dioxide CO Carbon Monoxide Cl- Chloride CT Computed Tomography DC Direct Current DCM Dichloro Methane EDXRF Energy Dispersive X-Ray Fluorescence F- Fluoride Fe Iron FeCl2 Iron Chloride viii FeS2 Pyrite FID Flame Ionization Detector HCl Hydrochloric acid HF Hydroflouric acid HI Hydrogen Index, mg HC/g TOC HNO3 Nitric Acid H2S Sulfuric Acid K Potassium LAH Lithium Aluminum Hydride Mn Manganese NaOH Sodium Hydroxide OI Oxygen Index, mg CO2/g TOC S Sulfur Si Silica TEM Transmission Electron Microscope Ti Titanium TiO2 Titanium Oxide TOC Total Organic Carbon, wt% XRD X-Ray Diffraction XRF X-Ray Flouresence Zn Zinc ix List of Symbols A Cross-Sectional Area, cm2 D Diameter, cm I Electric Current, A h Thickness, cm M Molarity N Normality R Electrical Resistance, ohm V Electric Potential, V ΔV Electric Potential Difference, V v/v Volume/Volume v/w Volume/Weight W Watt ρ Electrical Resistivity, ohm-m σ Electrical Conductivity, S/m x TABLE OF CONTENTS Page ABSTRACT .......................................................................................................................ii DEDICATION .................................................................................................................. iv ACKNOWLEDGEMENTS ............................................................................................... v NOMENCLATURE ............................................................................................... ........viii LIST OF FIGURES ........................................................................................................ xiii LIST OF TABLES .......................................................................................................... xvi CHAPTER I INTRODUCTION AND LITERATURE REVIEW ................................... 1 1.1 Background .............................................................................................................. 1 1.1.1 The Challenge of Petrophysical Evaluation in Organic-rich Mudrocks ........... 1 1.1.2 Kerogen Isolation .............................................................................................. 3 1.1.3 The Impact of Kerogen Isolation on Geochemical Properties .......................... 9 1.1.4 The Impact of Highly Mature Kerogen and Pyrite on Electrical Resistivity of Organic-Rich Mudrocks ........................................................................................... 10 1.2 Statement of the Problem ....................................................................................... 13 1.3 Research Objective ................................................................................................. 14 CHAPTER II KEROGEN ISOLATION AND GEOCHEMICAL CHARACTERIZATION ................................................................................................. 16 2.1 Kerogen Isolation ................................................................................................... 17 2.1.1 Physical Method