Balkassar Salt-Cored Anticline Structure: An Interpretation For Potential Hydrocarbon Prospect

The Potwar Basin is known to be one of the greatest and oldest oil producing provinces in Pakistan. The subsurface of the Potwar Basin consists of large anticlines, mostly bounded by reverse faults. The area selected for this study is in Balkassar Oilfield situated in Potwar Basin, which is a compressive structure belonging to the active Fold and Thrust Belt of northern Pakistan. We interpreted subsurface structural geology until Khewra Formation (3050 m depth) and hydrocarbon potential by identifying, folds, faults, structural trends, styles and trap type using well logs and 2D seismic data. Seismic interpretation reveals the presence of an anticline in the center of the area, bounded by seven major blind faults, one normal fault in the basement, four faults are present at the south-eastern limb, and two faults are present in the north-western limb. The six major faults structure were earlier normal faults that were reactivated as reverse faults by salt diapirism. Moving in the northeast direction from first seismic line, an increase in disturbance can be observed caused by Salt Range uplift forces and Himalayan orogeny. This structure in the sub-surface of the Balkassar block is recognized as a Salt-Cored anticline. The Balkassar structure is the active diapirism pillow stage 2. The 3-D map from seismic interpretation shows that the anticline structure dips steeply towards NW, and gently towards SE. Limbs terminated by the faults occur on both sides of the anticline. The Chorgali Formation, covering the anticline top flat surface, also indicates a four-way closure for hydrocarbons accumulation. At the level of Sakesar Limestone in the northwest side, a broad contour closure has been identified, which may act as a potential prospect for hydrocarbon accumulation in the Balkassar block bounded by faults from both sides.