GEOCHEMICAL CHARACTERIZATION OF RESERVIOR FLUIDS FOR CONNECTIVITY AND ALTERATIONS, ADHI OIL FIELD, POTWAR SUB BASIN, PAKISTAN

Abstract

Potwar Sub-Basin is a Himalayan foreland fold and thrust belt in the Upper Indus Basin of Northern Pakistan. The Potwar Sub Basin is Pakistan's traditional oil-producing region, the basin has various formations that are essential for oil and gas development in the region, and it is one of Pakistan's most productive hydrocarbon-bearing sedimentary Basins. The Salt Range Formation, Khewra Sandstone, and Patala Formation are all probable source rocks in the Adhi oil field, whereas the reservoir rocks are Khewra Sandstone, Tobra Formation, and Sakesar Limestone. Due to the mismatch of source and depositional environments of organic matter, biomarkers and bulk stable isotopes were previously utilized to evaluate oils in the Potwar Basin of Pakistan. Saturated and Aromatic biomarker distributions were used to classify crude oils from the Potwar Basin, and the results were previously published but we know very little about the source potential and secondary alterations based on Light hydrocarbons characterization of Potwar Sub Basin. The geochemical characterization of Light hydrocarbons of Adhi Oil Field oil samples and their correlation is carried out using Thompson’s (1983) and Mango’s (1994) parameters. These parameters were used for the assessment of thermal maturity, organic input, source rock identification and secondary alterations. Five oil samples (A-10, A-11, A-15, A-16, A-17) of Adhi oil Field were studied for geochemical characterization. The parameter used for thermal maturity (Thompson’s 1983) revealed that the oil samples are normal oils except the sample A-11 which is Mature. The source related parameters indicates that oil samples have the same terrigenous source for hydrocarbons. The secondary alterations assessment parameters showed that none of the oil sample is biodegraded. The Aromaticity versus Paraffinicity and C₇ oil correlation star diagram represent that the oil samples are slightly altered by Evaporative Fractionation.