MOL Plc has been present in North Pakistan for 22 years. This is the first petroleum hub of the country near the Himalayan thrust front. The historic finds were located in the Potwar plateau, a hilly area around Islamabad; MOL’s main assets are located in the westward neighbouring Kohat plateau, west of the Indus River. Both plateaus are squeezed between the Main Boundary Thrust in the north, and the southern limiting thrust of the Himalaya system, exposed in the Salt range-Surghar range mountains. All these rocks are the scraped off sedimentary cover of the northwards subducting Indian continent.

During our exploration activity, MOL and Partners OGDC; PPL; POL; GHPCL have found nine fields with a success rate of 60%, mostly containing gas-condensate. Further targets await drilling. As such, our key asset is amongst the richest in the country and provides a production basis to become the fifth-largest gas producer, second-largest oil producer and top LPG producer in the country.

The petroleum system is based on Lower Cretaceous and Lower Jurassic, deltaic shale source rocks that yield their petroleum into fractured Mesozoic through Paleocene carbonates and sandstones. A thick Paleocene shale sequence provides the general seal and there may be internal Mesozoic seals as well; however, intense fracturing enables effective pressure communication between the reservoirs. Traps are four- and three way closed, thrust-linked anticlines. Structure formation has occurred in several episodes from Paleocene to Recent. The present trap topographies are however the result of Pliocene to younger structuration.

The first important structural episode occurred in the Paleocene, when the Indian continent collided with the Kohistan arc. Primitive nappes of oceanic and continental slope origin (Kurram nappes) were thrust from NW to SE on the future Kohat plateau. As a result, a large foredeep was developed where sandstones and shallow water carbonates (our key reservoirs) and deep marine restricted facies shales (our main seals and secondary source rocks) were deposited.

A second, Early to Middle Miocene event created detached individual nappes. Southward directed thrusting propagated from north to south and from east to west. This propagation is testified by the shift of depocentres of massive continental molasse, thickness of which can reach 7 km. In our Kohat area we have two thicker nappe stacks, comprising 5 to 3 nappes. The northern root of these nappes provides for individual kitchens, where the Mesozoic source rocks can be matured. There is a clear variance in source rock composition since each of our fields has a different hydrocarbon composition.

The original subsurface nappe geometry was later modified by a sequence of tectonic events (from assumed oldest to youngest): 1, by an E-W right lateral wrenching creating elongated pop-up structures, hence long linear traps; 2, by a NW-SE thrusting, an effect of the continent-scale Quetta-Chaman left lateral shear zone, materialized by the Kurram fault zone. This deformation cut up the earlier nappes and created secondary anticlines in the NW; 3, by a NE-SW shortening and resulting EW left lateral wrenching, overprinting the previous pop-ups; and 4, by a N-S differential shortening creating lateral shear zones of roughly N-S orientation. It is very hard to define the precise timing of these young events, and their timing might overlap or alternate, as local stress build-ups changed through time.

The several young tectonic episodes not only influenced trap geometry, but also enabled a dense fracture network to develop. This fracture network provides an essential fracture porosity and a good permeability in our otherwise tight reservoirs.

As a conclusion, we can see that structuration has an overwhelming influence on each element of the petroleum system and contributes to the massive exploration success of MOL in Pakistan.