COMPARISON OF SURFACE AND SUBSURFACE RESERVOIR (SAKESAR LIMESTONE) PROPERTIES: A CASE STUDY FROM FIMKASSAR OIL FIELD, PAKISTAN

Abstract

The Fimkassar is situated in the eastern part of the Potwar Sub Basin, having cracked carbonate supply includes reservoir formations (Chorgali-Sakesar). The present study aimed to understand the reservoir characteristics of the Sakesar Limestone of the Fimkassar oil field. The reservoir petrophysical properties were compared with the outcrop samples and the core analysis of Sakesar Limestone. Two wells of the Fimkassar oil field were taken for interpretation. The petrophysical interpretation of Sakesar Limestone of Fimkassar_01 estimated shale volume as 17.7% and porosity 16.68% and permeability 0.50 mD, respectively. The average hydrocarbon saturation was 55.16% and the water saturation was calculated as 44.33% and similarly, the reservoir characteristics of Fimkassar_02 were estimated. The porosity and permeability are the important features of the reservoir rock; therefore, the Sakesar Limestone’s outcrop and the core samples were examined in a laboratory for porosity and permeability. The porosity calculated from the outcrop sample was 0.68% to 11.65% and the core samples calculated porosity was 3.86% to 10.76%. The lithological cross plots were helpful in lithological identification and the cross plots of the modules versus density gives us the fluid type present in the Formation. We can observe that the lower modules values correspond to gas, relatively higher ones to the hydrocarbons. The correlation of the reservoir properties calculated from petrophysical interpretation, outcrop and the core data analysis show that Sakesar Limestone has hydrocarbon potential and is a good reservoir.