Geology and Hydrocarbon Potential of the Makran Thrust Belt, Southwestern Pakistan

By

 James C. Pol¹, Dana M. Jurick¹, Oscar E. Gilbert¹, David A. Nollsch¹, Shaji Alam², John D. Smewing³

(1) Ocean Energy Inc, Houston, TX (2) Ocean Pakistan, Ltd, Islamabad, Pakistan (3) Earth Resources, Ltd, Swansea, United Kingdom

 New 3D seismic data, geological mapping, shallow coring, and quantitative structural reconstructions allow improved understanding of the Makran hydrocarbon system. Thick turbidite sands, clearly-defined structural traps, and evidence of an active hydrocarbon system encourage further exploration.

The 500-meter thick sands of the Miocene Panjgur Formation were deposited on oceanic crust as part of the proto-Indus Fan, and later buried by prograding slope mudstones of the Parkini Formation. These sediments were scraped off the Indian Plate to form the present Makran thrust belt. Syntectonic sedimentation of the Parkini is indicated by angular unconformities visible in outcrop, and downlap sequences apparent from seismic data. Prograding Pliocene through Holocene slope to paralic sediments buried the thrust ridges and provide a vertical hydrocarbon seal. Balanced reconstructions suggest approximately 40-50 percent structural shortening.

Much of the offshore Makran thrust belt is covered by recent 2-D seismic, and a new 2100 square km 3D survey. 3D imaging to seven seconds permits interpretation of thrust fault planes to the decollement surface. The 3D has delineated thirteen structures along a series of imbricate thrusts. The average areal extent of the closures is 3100 acres.

Due to structural complexity, four wells drilled in the last fifty years failed to test Panjgur sands observed in outcrop. Gas seeps, gas plumes observed in the 3D data, and hydrocarbon observations in wells indicate an active hydrocarbon charge. Gas is economically attractive here because of the proximity to major South Asian markets with a constantly increasing appetite for clean gas fuel