Abstract: Concepts and Techniques Utilized in Successful Exploration for Oil-Bearing Reefs in Indonesia

Richard R. Vincelette, Norman H. Foster

Exploration activity since 1971 has resulted in the discovery of significant oil reserves in Miocene reefs in the Salawati basin of northwestern Irian Jaya, Indonesia.

The success of the program was the result of a combination of exploration techniques, including: (1) detailed facies analysis from preexisting outcrop and subsurface control; (2) recognition of the potential of Tertiary reefs as exploration targets; (3) recognition of the geomorphic expression of subsurface reefs and detailed interpretation of aerial photographs and remote-sensing imagery to determine location of reefs; (4) application of modern multifold seismic techniques to map reefs in the subsurface; and (5) use of helicopter-transported rigs and modern engineering techniques in drilling exploratory wells in remote jungle terrain. Utilization of these fundamental exploration concepts and techniques has resulted in significant oil discoveries.

The reservoir and trap are highly porous and permeable Miocene reefs, which have produced as much as 32,000 BOPD from individual wells. Reef heights are in excess of 1,600 ft (490 m) and range in areal extent from 2 to 48 sq mi (5 to 124 sq km). Porosities within reefal carbonate rocks are as much as 43 percent and average 20 to 30 percent.

The knowledge gained from the current exploration program concerning reef morphology, porosity variations, tectonic history, surface expression and seismic response of reefs, and other factors which control these oil accumulations should expedite future exploration efforts in this and similar basins.

AAPG Search and Discovery Article #90973©1976-1977 AAPG Distinguished Lectures