Integration of seismic and well data for a 3D model of the Balkassar anticline (Potwar sub-basin, Pakistan)

Abstract

The Potwar sub-basin is an important hydrocarbon producing zone of the Upper Indus basin and has significant oil and gas potential. The Balkassar area is the main oil field of the Potwar sub-basin and oil is mainly produced from Eocene carbonates. The Chorgali Formation is of Eocene age and is the main reservoir rock in this area. Structurally, the Potwar sub-basin is complicated, and surface features often do not reflect subsurface structures. This is due to the presence of detachments at different levels. In such cases, it is necessary to integrate seismic data with geological information for an accurate delineation of subsurface structures. Eleven seismic profiles were interpreted to understand subsurface structural style. To correlate well data with seismic data, a synthetic seismogram has been generated. Time, velocity and depth contour maps have been prepared. A 3D model for the Chorgali Formation has been prepared which confirms that this is a four-way anticlinal structure bounded by faults. It makes this structure more favorable for hydrocarbon accumulation. Moreover, a cross section has been prepared for five wells to show that the Chorgali Formation is spreading. Based on it, to show the relationship between compressional tectonics and basement slope, a 3D structural model has been prepared. In this case study, the Balkassar anticline was interpreted as a four-way closure pop-up structure which provides a structural trap for the accumulation of hydrocarbons. This study will help us understand the accumulation of hydrocarbons in the same type of structural traps in the Potwar sub-basin and in similar kinds of basins. It is also relevant to oil exploration within Pakistan.