3D Modeling of Subsurface Stratigraphy and Structural Evolution of Balkassar Area, Eastern Potwar, Pakistan

Abstract

Balkassar area is located in the eastern part of Potwar sub-basin on the southern flank of Soan Syncline in Himalayan collisional regime. Borehole data obtained from wells drilled in Balkassar area indicate about 4km thick succession of Precambrian to Pliocene sedimentary rocks interrupted by four unconformities present at Precambrian-Eocambrian, Cambrian- Permian, Permian-Paleocene and Eocene-Miocene time. On the basis of information rendered by ten exploratory/development wells and eleven seismic lines, five distinct reflecting surfaces were marked. The Balkassar structure is a long, northeast southwest trending doubly plunging anticline that was created by north-south directed Himalayan forces with the inflow of evaporates form the sides thereby producing shortening in the overlying sedimentary sequence. Compression generated a Thrust 1 at the southeastern limb followed by Thrust 2 in NW direction to the earlier thrust. The structure is bounded by two thrusts at the SE side and a back thrust at the northwestern side of the anticline. At a later stage, a SE dipping back thrust at the northwestern side of the Balkassar anticline was created to merge the Thrust 1 and 2 over the décollement in the Salt Range Formation. Information from 3D models depicts steep limbs at the northwestern side whereas the flanks of anticline are gentle on the southeastern side, both truncated by faults. The Balkassar structure may have reservoirs of Chorgali, Sakesar and Khewra formations levels. At the level of Paleocene Lochkart limestone and Eocene Sakeasr limestone two fault bounded closures are observed which may act as possible prospects for Hydrocarbon exploration.