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KADRI, IQBAL BAKHSH, Pakistan Petroleum Limited, Sindh, Pakistan

ABSTRACT: Cretaceous Source Rocks in Pakistan

Pakistan is located at the converging boundaries of the Indian, Arabian and Eurasian plates. Evolution of this tectonic setting has provided an array of environmental habitats for deposition of petroleum source racks and development of structural forms.

The potential Cretaceous source rocks in Central and South Indus Basin are spread over an area of about 300,000 sq km. With 2% cutoff on Total Organic Carbon the average source rock thickness is 30 to 50 m, which is estimated to have generated more than 200 billion bbl of oil equivalent.

To date production of more than 30,000 bbl of oil and about 1200 million cu ft of gas per day can be directly attributed to Cretaceous source.

This basin was an area of extensional tectonics during the Lower to Middle Cretaceous associated with slightly restricted circulation of the sea waters at the north-western margin of Indian Plate. Lower Cretaceous source rocks (Sembar Formation) were deposited while the basin was opening up and anoxia was prevailing. Similarly Middle to Upper Cretaceous clastics were deposited in setting favorable for preservation of organic matters.

The time and depth of burial of the Cretaceous source material and optimum thermal regime have provided the requisite maturation level for generation of hydrocarbons in the basin.

Central Indus basin is characterized by Cretaceous source rocks mature for gas generation. However, in South Indus Basin Cretaceous source rocks lie within the oil window in some parts, and have gone past it in others.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.