Abstract

The Attaka field is the first commercial offshore oil field to be discovered in Kalimantan, Indonesia, After its discovery in 1970 and the drilling of confirmation wells during 1970 and 1971, a development programme involving 50 wells from six platforms was begun. The field is 12 miles off-shore from the East Kalimantan coast in 200 ft of water.

Areal and vertical closures of the Attaka structure are 26 square miles and 600 ft respectively, and the areal extent of oil accumulation is some 9.8 square miles. The Attaka structure is located in the Tertiary Kutei basin which contains Early Tertiary to Quaternary sediments, and the oil in the Attaka field is in numerous deltaic sands deposited during a Late Miocene advance of the ancestral Mahakam River delta.

Seismic velocity and well velocity survey data indicate the presence of a low velocity region more or less coincident with the limits of oil and gas accumulation on the crest of the Attaka structure. Use of lower RMS stacking velocities in this crestal area in comparison with the RMS stacking velocities required on the flanks produces continuous seismic events in the crestal area. The diminished interval velocities on the crest may be due to the presence of oil and gas.

Gravity of the Attaka oil ranges from 35° to 43° API and its sulphur content is 0.1% by weight. Production rates from individual completions range from 400 to 4300 barrels of oil per day and by late 1973 or early 1974 when all wells are on stream the production rate will be about 100,00 barrels of oil per day..