Major Gas Field in Pakistan from Fractured Carbonates and Sandstones

Izabella Csiki¹, László Csontos¹, Katalin Lõrincz¹, József Tóth², and Athar Ali^3
1MOL PLC, Budapest, Hungary
²MOL PLC, Szolnok, Hungary
³MOL Pakistan PLC, Islamabad, Pakistan

MOL Pakistan and Partners (OGDC, PPL, POL, DGCP) had several major discoveries in the NW frontier Province of Pakistan, in the Kohat plateau. The area comprises the buried thrust front of the Himalayan orogeny. These discoveries extend the historical Potwar plays further to the west, in a new area.
The gas and minor liquid hydrocarbons are reservoired in Paleocene, Jurassic limestones and Cretaceous, Paleocene sandstones. These rocks are tight, non-porous at outcrop and are all strongly cemented. Their reservoir characteristics are controlled by fracturing during folding. Folding is generated by the India-Eurasia collision, which has created E-W striking major antiformal stacks of the target succession. Surface structural features only mimic the structures of the reservoir horizons at depth, since there are two thick detachment horizons between exposed Eocene and subcrop Paleocene-Mesozoic successions. The lower detachment, a Paleocene shale forms the main seal on the reservoirs. Fracturing in the reservoirs was developed as a systematic jointing during folding or as minor thrusts within the reservoir. Two later phases of strike slip faulting along the main E-W antiformal trend created en échelon folds and another intense fracture network, enhancing secondary porosity. Folding and fracture formation are all Pliocene in age. Trap formation is thus synchronous with major burial and hydrocarbon generation beneath thick fluviatile molasse sediments in front of the Himalayas.
Acid wash and matrix acid stimulations were conducted in carbonate reservoirs to enhance the wells' deliverability.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece