Depositional and diagenetic controls on reservoir properties of the lower Cambrian Khewra Sandstone, eastern salt range, Sub-Himalaya, Pakistan

Abstract

This study aims to determine the interdependence of deposition, tectonics and diagenesis in a prolific hydrocarbon reservoir. This has been achieved through an integrated field study, petrography, scanning electron microscope (SEM), zircon microscopy and X-ray diffraction (XRD) in the fluvio-deltaic sandstone of the Lower Cambrian Khewra Sandstone. Sandstones are subarkose, sublitharenite and feldspathic litharenite subjecting to compaction, cementation, dissolution and replacement. The pore types are intergranular, vuggy, and fractures. The paragenetic sequence suggests a multistage diagenetic history for the sandstone under eogenetic, mesogenetic and telogenetic regimes. The telogenetic alterations are triggered by Himalayan orogeny. Both deposition and tectonics control the spatial and temporal distribution of diagenetic facies and sweet spots. The bounding unconformities and variation of compositional and textural patterns determine the reservoir quality. The dynamic interaction among deposition, tectonics and diagenesis yields a comprehensive understanding of reservoir potential on a global scale.