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Fracture Characterization and Prediction in Unconventional Carbonates, “Mississippian Limestone”, Central and Northeastern Oklahoma


Unconventional Mississippian oil and gas reservoirs in central and northern Oklahoma and southern Kansas are characterized by porosities of 1–2 percent or less, and permeability values measured in fractions of millidarcies. As such, natural fractures are an important part of reservoir performance in the ‘Mississippi Lime’. Understanding the types and distribution of fractures in these carbonate rocks and how they may be related to facies and sequence stratigraphic architecture, may increase the predictability of fracture-enhanced permeability in the subsurface. Three cores were analyzed in Payne and Osage County. Fracture types were identified in the cores and various fracture properties were measured. This data was used in conjunction with the established high-resolution sequence stratigraphic framework to analyze the distribution of fractures within petrophysically-significant facies. Four facies types were defined in the three cores. The packstone-grainstone facies had the highest fracture density in the Elinore and Winney cores (2.57 fractures/foot and 2.10 fractures/foot). The glauconitic sandstone facies had the lowest fracture density (0 fractures per foot). In the Orion core the bioturbated wackestone-packstone facies had the highest fracture density (2.92 fractures/foot) and the burrowed mudstone-wackestone facies had the lowest fracture density (1.49 fractures/foot). The data from the cores suggests that fracture density is facies dependent.