Abstract

Since the discovery of Kasim oil field in 1972, some eighty-five wells have been drilled by Petromer Trend in the Salawati Basin. This subsurface information, together with earlier Shell Oil and Pertamina data, provides a fairly complete picture of basin history with its Miocene reef growth, burial, tilt and subsequent deformation.

Until Eocene time the basin deepened southward. Mio-Pliocene northward tilt accompanied by left-lateral displacement on the Sorong fault, resulted in the present basin shape.

Near surface geothermal gradients three times normal are common; the high gradients decrease with depth.

Subaerial exposure of the porous Miocene carbonate reservoirs resulted in an active brackish-water drive.

The Walio reef complex is part of barrier and pinnacle reef system at the edge of a carbonate platform that extends southwestward from Klamono to Misool Island. Walio oil field exhibits many of the above characteristics - Late Neogene plate-margin kinematics affected reservoir properties, type of sediment enclosing the reef, fresh water influx, and possibly the abnormal geothermal gradient. Twenty-eight Walio wells presently produce 36,000 b/d of 35° API low-sulfur oil from a depth of 2,400 to 2,900 feet.