The Himalayas, subdivided into Sub Himalayas, Lesser Himalayas and Higher Himalayas, represent the most extensive and active collision zone in the world, extending westward from Burma, through northern India, Nepal and southern Tibet, into northern Pakistan. The study area lies in the southeastern part of the Potwar Plateau (Figure 1), which is a broad zone of Himalayan foreland thrusting in northern Pakistan. The Potwar Plateau is the foreland fold-and-thrust belt, lies to the north of the Salt Range Thrust. The post collisional molasse deposits, the Kamlial, Chinji, Nagri and Dhok Pathan formations cover the study area.
Many geological and geophysical studies have been carried out in this area. This area was initially mapped by Gee (1934) and the oil discovery was made by Attock Oil Company (AOC) in 1944. The anticlinal structure of Joya Mair was delineated by AOC purely on the basis of surface geology. Later on Pakistan Oilfields Limited (POL) conducted geological and seismic survey in the area and defined the structure on the basis of these studies. The total estimated reserves in Joya Mair Oilfield are 23-25 million barrels (mmbbl). The recoverable reserves are estimated as 10.45 mmbbl (Pakistan Energy Yearbook, 2004). The main objectives of the current study include to delineate the subsurface structure and to locate the prospective zones in the Chak Naurag and Joya Mair area and to assess the remaining recoverable reserves of Joya Mair Oilfield.
Pennock et. al. (1989) incorporates more than 1600 km of multi-channel seismic reflection lines from the Eastern Salt Range/ Potwar Plateau (SR/PP), released by Amoco and Chevron. The interpretation of this seismic data reveal a variety of structural styles that may be related to several factors, including changes in distribution and thickness of a basal evaporite sequence, basement faults and flexures, and low dip of the basement. Shami and Baig (2002) focus on the remodeling of the Joya Mair Oilfield to find out the possible remaining reserves. The work represents the geomodelling of Joya Mair oil field by using geologic, structural, borehole, seismic and fracture data. The Joya Mair structure appears as an open anticlinal structure on the surface. It is concluded on the basis of the study that the Joya Mair structure is the combination of thrust and back-thrust, forming a triangle zone at subsurface. The triangle zone is the result of two phases of Himalayan thrusting. These thrust and antithrust phases in Salt Range/Potwar Fold Belt (SRPFB) are the result of northwest-southeast Himalayan compression.