AbstractsChemistry

Laboratory Measurements of Electrical Resistivity of Kerogen in Organic-Rich Mudrocks

by Gama Firdaus




Institution: Texas A&M University
Department:
Year: 2015
Keywords: Kerogen; organic-rich mudrock; electrical resistivity; maturity; graphite-like
Posted: 02/05/2017
Record ID: 2102233
Full text PDF: http://hdl.handle.net/1969.1/155751


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 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. Advisors/Committee Members: Heidari, Zoya (advisor), Ayers, Walter (committee member), Kronenberg, Andreas (committee member).