Rock fabric controls on pore evolution and porosity–permeability trends in oolitic grainstone reservoirs and reservoir analogs

Abstract

Although the general influence of rock fabric on porosity and permeability (Φ-k) within carbonates is well documented, if and how pore evolution and Φ-k scatter quantitatively relate to depositional fabric remains poorly constrained. This project empirically explores this uncertainty within oolitic grainstones from a range of geologic ages and diagenetic histories to understand depositional sediment-pore relationships, and how they can evolve with lithification.Integrating data from point counting, digital image analysis, nuclear magnetic resonance and core analysis of Holocene, Pleistocene, Pennsylvanian, and Mississippian oolitic grainstones reveals quantitative relations among rock fabric, pores, and petrophysical parameters. Oolitic grainstones of similar sedimentology taken from distinct diagenetic scenarios display a unique combination of pore size, shape, spatial distribution, and Φ-k character. Within each scenario, grain size, sorting, and type are correlated more closely with pore attributes and k than cementation and compaction. Collectively, these results are interpreted to suggest that diagenesis defines the absolute values of pore attributes and petrophysical parameters, but sedimentology controls the trends or variability within an oolitic succession. The implication of these findings is that petrophysical variability within oolitic reservoirs closely follows sedimentologic trends, which may be predictable within a stratigraphic framework.First and foremost, I am especially grateful for my advisor Gene Rankey. I am eternally grateful for him believing in me and giving me the opportunity to work under him. Gene's investment in his students' overall success is unmatched. His guidance and patience embodies the exemplary advisor. His technical and non-technical support gave me the opportunity to be successful as a geologist and person throughout life. I also recognize my advisory committee members of Drs.Chi Zhang and Lynn Watney. Chi's NMR laboratory facilities were crucial to the completion of this study, and she provided valuable guidance on petrophysical methodologies and interpretation. Lynn's experience and knowledge of Kansas geology was instrumental in shaping this study.I thank Nikki Potter and the Kansas Geological Survey for lending their time and facilities during the selection and collection of the core samples in this study. I also would like to highlight the KGS for their exceptional organization and documentation, which provides aspiring scientists with the public resources and structure to contribute to the greater geoscience community. In addition, I thank Dr. Jon Smith at the KGS for allowing me to use his petrographic facilities, which allowed me to obtain data that was fundamental to this study. I am also grateful for the fellow students in Dr. Rankey's research group, who provided countless conversations, brainstorms, and feedback that helped me progress throughout my time at KU. v I cannot conclude without thanking my friends and family. My friends at KU kept me positive and prod...

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