Abstract:
The study area (Fimkassar and Turkwal oil fields) is located in the Central Potwar Basin, District Chakwal, Punjab, Pakistan. It consists of Fimkassar-01, 02 and Turkwal deep-01 wells. Fimkassar-01 and Fimkassar-02 wells are being operated by Oil and Gas Development Company Limited (OGDCL) while Turkwal deep-01 is being operated by Pakistan Oil Field Limited (POL). Fimkassar -01 is exploratory well while Fimkassar-02 is development well. They produce oil and gas. Turkwall deep-01 is an exploratory well and is suspended. Effective reservoir at field lies within the Sakesar and Chorgali formations. Organic rich shales of the Paleocene (Patala Formation) can be considered as the source of the area. Both structural and stratigraphic traps are present in the Potwar Basin. Structural traps have been developed due to thin-skinned tectonics, which has produced anticlines, pop-up and positive flower structures above Pre- Cambrian salt (Pennock et al., 1989). The Potwar Basin is filled with thick infra Cambrian evaporite deposits overlain by relatively thin Cambrian to Eocene age platform deposits followed by thick Miocene Pliocene molasse deposits (Shami and Baig, 2002). This whole section has been severely deformed by intense tectonic activity during the Himalayan Orogeny in Pliocene to middle Pleistocene time(Shami and Baig, 2002). The Salt Range Formation is best developed in the Eastern Salt Range. The Salt Range lies unconformably on the Precambrian basement. For petrophysical evaluation of Fimkassar-01, 02 and Turkwal deep- 01 wells two formations (Chorgali Formation and Sakesar Limestone) are tested for the assessment of hydrocarbon saturation. The hydrocarbon saturation noted other than shale volume, average porosity, effective porosity, resistivity of water and saturation of water, amount 66 %, 71 %, and 0 % in the Chorgali Formation of Fimkassar-01, 02 and Turkwal deep-01 wells, respectively. Sakesar Limestone of Fimkassar-01 and 02 wells give 65 % and 55 % hydrocarbon saturation respectively. Based on this study the Chorgali Formation when compared with Sakesar Limestone seems to be a prospect zone in Fimkassar-01 and 02 wells. Structurally Fimkassar-01 and 02 wells show no disturbance whereas in Turkwal deep-01 well there is a thrust fault conformed by repetition of the strata in which older rocks lay over younger rocks. The thickness of both the Corgali Formation and Sakesar Limestone decreases from SW to NE.
