Comparison of surface and subsurface limestone reservoir properties: key insights derived from the analysis of geological and geophysical datasets

Abstract

Fimkassar Oil Field (FOF) is located in the Potwar Sub Basin, having a fractured carbonate supply that includes reservoir formations (Chorgali-Sakesar). The Sakesar Limestone, considered a significant and established reservoir in numerous oil and gas fields in the Potwar Plateau, was evaluated for reservoir potential in the current work. This study conducts a petrophysical analysis to evaluate hydrocarbon potential, as well as an analysis of outcrop and core samples to investigate the porosity and permeability of the Sakesar Limestone. Seismic data structure interpretation was performed to assess the subsurface structure patterns, and seismic attributes were employed to identify fractures in Sakesar Limestone. The reservoir petrophysical properties were compared with the core samples analysis results of the Sakesar Limestone. The porosity and permeability of outcrop and core samples of Sakesar Limestone were determined in the laboratory. Two wells of the FOF have been taken for well log interpretation. The porosity calculated from the outcrop and core samples is 0.68 %–11.65 % and 3.86 %–10.76 %, respectively. The permeability calculated from the outcrop samples ranges from 0.0 to 26.82 mD. The lithological cross-plots were used to identify the lithology, and rock physics analysis provided information on the fluid type present in the formation. The correlation of the reservoir properties indicated that Sakesar Limestone has hydrocarbon potential and is a good reservoir.