FITZSIMMONS, ROY, JAMES BUCHANNAN, Conoco Inc., Houston; and CHRIS IZATT, BG plc, Reading

Abstract: Initiation of Collision: Tectonics and Sedimentation within the Suliaman Fold Belt, NW Pakistan

The British Gas operated Sulaiman concession lies within the Sulaiman fold and thrust belt of western Pakistan. This fold belt formed as part of the Himalayan orogeny as the Indian plate collided with Eurasia and associated plates.

The block lies in the Cretaceous/Paleocene clastic fairway.The litho and chronostratigraphy of these intervals in this part of Pakistan are poorly defined. This uncertainty has led to problematic correlation's and poorly constrained paleo-geographic depositional models for key reservoir units.As in many fold belts, one of the main challenges faced by the exploration team was the prediction of the sub-surface reservoir thickness and distribution. The volume of effective reservoir was a key uncertainty in the economic analysis as no wells or seismic were available within the block.

Fieldwork focused upon the potential reservoir units (Cretaceous Mughal Kot/Fort Munro/Pab Formations and Paleocene Ranikot Formation) defined from the previous studies. Over 2000m of stratigraphy was measured enabling detailed depositional models to be constructed. The Upper Cretaceous system comprised a major progradational clastic succession of linked fluvial, shoreline, slope and basin-floor depositional systems. Depositional trends were affected by incipient growth of major structural features, reflecting early collision of the Indian and Arabian plates. As the collision continued, basin (and ultimately coastline) morphology changed, resulting in a change to the deltaic/tide dominated systems of the Ranikot Formation. When seismic was obtained across the block, initial seismic-facies supported the depositional model developed from the outcrop studies. Reservoir thickness, tested within the subsurface was within 10% of pre-drill predicted thickness.

AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England