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

Although the general influence of rock fabric on porosity and permeability (Phi-k) within carbonates is well documented, if and how pore evolution and Phi-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 Phi-k character. Within each scenario, pore attributes and k are correlated more closely with grain size, sorting, and type than with cementation and compaction. Collectively, these results are interpreted to suggest that sedimentology controls the trends or variability within an oolitic succession but that diagenesis defines the absolute values of pore attributes and petrophysical parameters. These findings suggest that petrophysical variability within oolitic reservoirs may closely follow sedimentologic trends, which may be predictable within a stratigraphic framework.