2D seismic interpretation and integration of well data with seismic data of Balkassar area, Potwar plateau, upper Indus basin, Pakistan (P-1083) (MFN 4003)

Abstract

Seismic lines PBJ-2, PBJ-4, PBJ-6, PBJ-8, and PBJ-10 obtained from Directorate General of Petroleum Concessions (DGPC) was shot by OGDCL in 1980 in the area of Balkassar which lies in the central Potwar on the southern flanks of Soan syncline.Seismic line PBJ-2, PBJ-4, PBJ-6 are dip lines and PBJ-8, PBJ-10 are strike line. Five prominent reflectors are R1 (Chorgali Formation), R2 (Sakesar Formation), R3 (Lockhart Formation), R4 (Tobra Formation) and R5 (Khewra Formation) were marked on the seismic section on the basis of observed seismic reflection. A fault was marked which continuities along the Precambrian basement. Two more thrust faults were marked which showed fault propagating folds in the form of anticlines of Balkassar. A time section was produced from the seismic section using the vibrating point and two way time (TWT) of the reflectors and faults. The TWT were posted on the base map to make a time contour map of the formations as it was continuing throughout the area. The seismic velocities given in the velocity windows on the seismic section were used to find the average velocities of the formations. These average velocities were then used to find the depths of the formations for the seismic section. The well data of Balkassar Oxy 1 was used to confirm the depth of reflectors.The geo seismic section showed that the area was structurally deformed due to salt decollement and compressional tectonic movements. Traps for hydrocarbons were developed in the anticline as they truncated against the thrust fault. Salt probably moved into these anticlines due to compressional movements and a pop-up structure was formed. The Balkassar anticline was the prospective zone and was primary targets for oil exploration, where the depth of the Chorgali Formation was almost 2400m, favorable for drilling.