Eocene carbonate microfacies distribution of the Chorgali Formation, Gali Jagir, Khair-e-Murat Range, Potwar Plateau, Pakistan: approach of reservoir potential using outcrop analogue

A detailed study on the microfacies and depositional setting in the context of reservoir assessment of the Eocene Chorgali Formation exposed in the Khair-e-Murat Range, Pakistan, has been conducted. The investigation is based on carbonate rock samples collected from two stratigraphic sections. Five microfacies are identified including (1) non-laminated mudstone, (2) algal laminated mudstone, (3) dolomitized mudstone, (4) wackestone, and (5) siliciclastic mudstone. The Chorgali Formation was deposited in a predominantly tidal environment. The vertical distribution of the facies shows cyclicity that affects reservoir characteristics. All three genetic porosity types (i.e., depositional, diagenetic, and fracture porosity) are observed. The primary porosity types include fenestral and intracrystalline/intraparticle porosity (modified and enhanced by diagenesis, i.e., dissolution), while the secondary pore types identified are intercrystalline, moldic, vuggy, and fracture porosity. The vuggy and fracture porosities are the dominant secondary porosities disclosing that diagenesis and fracturing played a vital role in the development of porosity of the Chorgali Formation.