Unocal Indonesia Ltd. is delineating a significant new oil and gas fault block discover near Serang field off East Kalimantan's Mahakam Delta.
Unocal SA-10 well cut 166 ft of new gas pay and 23 ft of new oil pay in Miocene sands in a deeper fault block that is geologically distinct from Serang oil field. The well was drilled directionally from the Serang platform in 328 ft of water to 14,600 ft TD.
Completed in the oil zone, SA-10 currently is producing 5,000 b/d of oil and 4.2 MMcfd of gas. John Imle, president of Unocal's energy resources division, said the fault block may hold significant additional reserves. The company conducted two drill stem tests in SA-10 to verify additional potential from separate pay zones in the fault block prior to its completion as an oil producer. The tests yielded a combined flow rate of 4.3 MMcfd of gas and 288 b/d of condensate with 2,350 psi flowing tubing pressure. On May 31, Unocal spudded a step-out to delineate the find.
The SA-10 well successfully tested improvements in 3D seismic processing that enabled Unocal to obtain accurate images beneath shallow carbonates, which distort seismic images.
The fault block discovery plus additional development drilling have boosted Unocal's gross oil production in Indonesia to 100,000 b/d, its highest rate there since 1981 and a 41% increase from an average 71,000 b/d in 1993. Unocal's Indonesian gas production is 251 MMcfd, up 23% from 204 MMcfd in 1993.
Serang started up in late 1993 and is currently averaging 17,000 b/d of oil and 25 MMcfd of gas, exceeding expectations of peak output of 15,000 b/d. Further drilling will boost Serang output to more than 20,000 b/d. Under a production sharing contract with Indonesia's state owned Pertamina, Unocal operates six fields off East Kalimantan. Unocal holds a 100 % interest in Serang, Sepinngan, Melahin, Kerindingan, and Yakin fields and a 50% interest in supergiant Attaka field, which is about 8 miles south of Serang (see map, OGJ, Jan. 24, p. 14).
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