ABSTRACT

Pakistan's offshore area consists of two distinct geological provinces: the Indus Offshore Basin, and the Makran Offshore Basin. Combined, both basins encompass an area greater than 250,000 sq. km. The Indus Offshore Basin is an Atlantic-type passive margin, underlain partly by the continuation of the continental crust of onshore Indus Basin, and partly by the oceanic crust of the Arabian Sea. The Makran Offshore Basin is an active subduction zone and accretionary prism.

In the regional context, offshore Pakistan is an anomalous gap in the prolific petroliferous belt extending from Oman and Iran in the west, to the giant offshore Bombay High complex in the east. However, this gap is probably due to lack of exploration rather than the absence of attractive prospects, as giant fields have been discovered in similar geological settings elsewhere in the world, (i.e. Canada's Mackenzie-Beaufort Basin and offshore east coast, and Eastern Venezuela-Trinidad).

Only 9 wells have been drilled in this vast area, 8 offshore Indus and one offshore Makran. From this total, 4 wells were abandoned (including the only one off Makran) for technical reasons prior to reaching target depths. One well, drilled with Canadian assistance, tested gas at 3.7 MMCF/D (104.8 10³m³) from Miocene sands. Others were drilled on poorly defined prospects and encountered minor shows.

Fairly extensive seismic coverage is available: 28,545 km offshore Indus, and 8,883 km offshore Makran. Most of this is 24 to 60 fold data of good to excellent quality. Another 10,000 km is planned.

In the Offshore Indus Basin, prospects of giant field potential have been seismically identified. These relate to various Tertiary deltaic and

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submarine fan environments well documented in the areas mentioned above. In addition, carbonate bank development analogous to the Bombay High environment, and reefal development along the Eocene paleo-shelf edge have been postulated. Deeper prospects in Cretaceous rocks, similar to the adjacent productive southern onshore Indus Basin, also cannot be ruled out.

The hydrocarbon potential of offshore Makran has not yet been substantiated by drilling. One onshore well had tested oil geochemically similar to the heavy crude of some Omani fields. There are numerous oil and gas seepages along the entire Makran coastline, associated with mud volcanoes; some are also visible on offshore seismic. Attractive structural and stratigraphic prospects exist in the shelf to slope and turbidite environments. Some large structures have been seismically identified, and await confirmation by drilling.

Substantial long-term Canadian assistance in the public petroleum sector, some already used in offshore seismic and drilling, has created respect for Canadian technology and general goodwill toward this country.

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