Eocene and Paleocene carbonate reservoir characterization using seismic inversion and geological synthesis of Dhurnal area, upper Indus basin, Pakistan (T-1545) (MFN 6358)

Abstract

Dhurnal block is located 74 Km southwest of Islamabad in Potwar Plateau of Upper Indus basin and covers an area of 64 Km2. The study block is situated in the Attock district Punjab. The major purpose of this research work is to carry out the reservoir characterization of Paleogene carbonate reservoirs using the advance seismic techniques and correlate it to well data. Total of four horizons were marked at Eocene and Paleocene level namely Chorgali, Sakessar, Patala and Lockhart, four thrust faults were also marked on the seismic sections. Time and depth contour maps were generated which showed a typical pop up anticline bounded by the thrusts based on the seismic interpretation. Late Paleocene shales of Patala Formation are responsible for the generation of hydrocarbon and Eocene reservoirs accumulated this hydrocarbon in the structural traps, and Mamikhel shales and basal Murree shales provided seal to this accumulation. Petrophysical analysis was carried out for the wells Dhurnal 03 and 06 to identify the reservoir potential and for the Formation evaluation to check the reservoir porosities and saturation of water. This evaluation showed that the Eocene carbonates have a good potential for the hydrocarbon accumulation in the study area which was later confirmed by the reserve estimation. Facies models were also made for these reservoirs which helped to identify that the Sakesar formation at Eocene level has more clean limestone as compare to Chorgali formation. In last, advance seismic technique (seismic inversion) is used for the reservoir characterization to get the lateral idea of the area away from the wells using them as a reference. Model based inversion was carried out to compute the acoustic impedance, as the inversion method converts the seismic reflectivity from the boundary property to a layer property (Porosity, Density). Porosity was computed along the reservoir Formations to check the lateral variation of the porosity in the area with the help of the well data and it showed that average porosity at well point is same as computed with the inversion which gives the correct lateral control of the reservoir property.