Reservoir evaluation of the Eastern Tethyan Middle Eocene Larger Benthic Foraminifera dominated carbonates

DOI: 10.48129/kjs.15597

Authors

  • anwar Qadir The University of Haripur
  • Dr.
  • Mr.
  • Mr.

DOI:

https://doi.org/10.48129/kjs.15597

Abstract

Eocene Larger Benthic Foraminifera limestones of the Tethyan margins are proven hydrocarbon reservoirs. This study examines the controls on porosity and permeability development of the producing middle Eocene Pirkoh Limestone of the Eastern Tethys on the well core data. The results concluded from petrography and core samples analysis lead to the identification of distinct sedimentological and reservoir characteristics of the non-reefal system of the Indus Basin (Pakistan). Petrographic studies of the limestone section of the Pirkoh Formation, producing reservoir interval, have allowed to recognize three microfacies comprising bioclastic packstone to floatstone, bioclastic wackestone and mud-wackestone microfacies. The allochems identified in these microfacies mostly belong to benthic foraminifera including Nummulites sp., Discocyclinids sp., Coralline algae, Assilina sp., Lockartia sp., and gastropoda along with the other bioclastic debris. These grains are embedded in the micritic matrix with extensive cementation of calcite. The diagenetic events include cementation, compaction, dolomitization, fracture filling and neomorphism. Based on microfacies identified and constituents, i.e., grains, matrix and cement, the environments of deposition of the Pirkoh Limestone are interpreted to be high energy zone of the middle ramp of the shallow marine environment. Subsurface core from the field area indicates that the porosity of the reservoir is low to high (6% to 27.47%) and permeability is low to fair (0.03 to 7.73 mD). Porosity development in these carbonates is closely related to depositional lithofacies and diagenetic modifications. This study is the first attempt to document the reservoir facies of the non-reefal carbonates of the Pirkoh Limestone unit that would help to exploit reservoir's potential of the carbonate platforms developed in similar settings worldwide.

Published

08-02-2022

Issue

Section

Earth & Environment