Integrating Microfacies, Diagenesis and Sequence Stratigraphic Control On Reservoir Character of Eocene Sakesar Limestone, Nw Pakistan

The tectonic deformation by Himalayan orogeny had resulted in the development of sedimentary basins with multiple petroleum plays especially in the Eocene stratigraphy. Previous studies on the Eocene rocks broadly discuss the depositional environment, diagenesis, and outcrop features. However, the present work includes both outcrop and wireline log data to incorporate the microfacies analysis, diagenetic control, and sequence stratigraphic patterns for reservoir characterization of the Sakesar Limestone both at surface and sub-surface level. Light to medium grey, massive, and nodular, fractured, fossiliferous limestone mainly classified as wackestone and packstone microfacies. Although, cementations, neomorphism, compaction, and calcite filled fractures reduced the pore network, but wireline logs show sonic porosity of 5.3% and 3.16% effective porosity sufficient for carbonate reservoirs. Furthermore, dissolution, dolomitization and fracturing enhance the reservoir pore spaces especially in bioclastic wackestone facies where the porosity may reach up to 14%. Thickening upward and massive carbonate beds interpreted as highstand System tract in the Sakesar Limestone suggests the prograding depositional pattern. The outcome of this work is to highlight the potential reservoir intervals based on microfacies variations, diagenetic impact, and sequence stratigraphic controls for refinement in exploration and production strategy for Early Eocene Sakesar Limestone.