SEISMIC DATA INTERPRETATION OF BALKASSAR AREA USING SEISMIC AND WELL

Abstract

Two-dimensional seismic interpretation has been carried out in upper Indus Basin, Balkassar area to reveal as clearly as possible the subsurface structure of the Balkassar Anticline and to infer the possibility of hydrocarbon occurrence in deeper horizons of the sedimentary sequence. The well data of Balkassar Oxy # 1 was used to confirm the reflectors depth. The interpretation includes the construction of time and depth contour maps, 3D displays and surfaces of Chorgali, Sakesar and Khewra horizons. Time contour maps of the reflectors were produced using two way time of the reflectors. Average velocities were used to find the depths of the formations for the seismic section. The interpretation of geoseismic section showed that the area was structurally deformed due to salt decollement and compressional tectonic movements. The Balkassar Structure is a long, northeast southwest trending double plunging anticline. The structure is bounded by tear and reverse faults. The northwestern flank of the structure is steeply dipping and is terminated by southeast dipping reverse fault. Estimated horizontal closure of Balkassar Anticline is 80 sq.km and the vertical closure is 365 meter. Two decollment surfaces are present, one in the Pre-Cambrian Salt, the other in Neogene Sediments. The compressional tectonic of the structure is obvious from the reverse faults that bound the plunge of the structure. The geoseismic section along PBJ-04 and PBJ-05 show a salt-cored Pop-Up structure, which is one of the most favorable structures for oil and gas accumulation. Based on the Petrophysical analysis we find out different properties of rocks ( volume of shale, Porosity ,permeability, water saturation and hydrocarbon saturation) which helped us to find out hydrocarbon potential zones. Different cross plots have been generated to discriminate between different lithologies, this helped us to separate reservoir from shale. Some oil zones were recognized in both Chorgali and Sakesar formation. These zones were thinner but in Chorgali formation, due to higher hydrocarbons content these zones are recognized as potential hydrocarbon zones. Some oil shows could be found by correlating different logs in Sakesar formation but the zone as a whole is not very productive.