Of particular significance in the Indonesia oil search was the discovery of the Attaka oil field, offshore East Kalimantan (Borneo), in late 1970. After confirmation drilling from September 1970 to February 1971, field development and facility installation began in early 1971. First production was achieved in November 1972.

This major field is in the Tertiary Balikpapan basin. Production occurs mainly from sublittoral to deltaic sands of the "Attaka Series," of Pliocene and Miocene ages. The age of the deepest bed penetrated in the field area is middle Miocene. Well logs and paleontologic data indicate a predominately regressive sequence of deposition. Highly permeable pay sands, 34 in number, occur at intervals from 2,000 to 7,800 ft measured depth.

The structure is a faulted anticline. Faults and stratigraphic variations in part control accumulation and affect fluid properties. The oil is very low in sulfur content, and has a range of gravity from 35 to 52° API. Both saturated and undersaturated reservoirs are present.

Development drilling was accomplished from 6 platforms with nearly all wells completed using dual tubing strings. After fluid processing at a production platform, further treating occurs at the onshore Santan terminal, where oil storage capacity is 2,000,000 bbl. Tankers are loaded at an SBM (buoy) anchored offshore. The maximum size of tanker that can be loaded is 125,000 DWT. With the completion of wells and facilities, it is anticipated that field production will exceed 100,000 BOPD during 1973.

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