UNOCAL DRILLS ANOTHER BIG FAULT BLOCK STRIKE OFF KALIMANTAN

Unocal Indonesia Ltd.'s seismic technology advances continue to pay dividends off East Kalimantan.

The company late last month disclosed its second significant fault block oil and gas discovery off East Kalimantan and plans to proceed with its development. The strike, in Santan field on the prolific Mahakam Delta, confirms a separate fault block that extends Santan field southwest (see map, OGJ, Jan. 24, p. 14).

In June, Unocal reported it is delineating a fault block oil and gas discovery near Serang oil field in the same area (OGJ, June 27, p. 32).

UNOCAL DISCOVERY

Unocal's 8 Santan well, drilled directionally to 13,191 ft from the Galveston Key jack up in 262 ft of water, cut a net 70 ft of gas pay and 110 ft of oil pay in Miocene sands.

Two drill stem tests yielded as much as 9 MMcfd of gas and 2,255 b/d of oil through a 56/64 in. choke from intervals at 9,945-11,115 ft with 775 psi flowing tubing pressure. Shallower oil and gas zones were not tested but will be tapped when the field is developed.

Bottomhole location is 6,600 ft south-southwest of Unocal's 1 Santan discovery well. The field, discovered in 1971, was not developed because follow-up drilling did not adequately delienate the field.

Unocal plans to install a platform in Santan field in 1997. Production, expected to start in August 1997, could reach 50 MMcfd of gas and 6,000 b/d of oil.

EXPLORATION ADVANCES

"Detailed regional studies of the effects of shallow carbonates together with 3D seismic interpretation, have enabled us to refine our picture of the subsurface," said John Imle, Unocal Corp. president. "This significantly reduces the exploration risk, particularly with a subtle and difficult to define fault block like we found with the 8 Santan well."

Imle noted Unocal's success in applying 3D seismic interpretation techniques to its East Kalimantan prospects. "We have been able to see faults we couldn't see before and extend old discoveries very successfully," he said. "This has dramatically improved the effectiveness of our East Kalimantan exploration program."

Unocal plans four or five more exploratory wells this year on a number of prospects off East Kalimantan. Another 13 or so exploratory wells are planned for 1995-96, but the exact number will depend on success of the 1994 program.

Many of the prospects are in areas where data gathering is difficult because of shallow carbonates. Before beginning its current exploration program, Unocal conducted an East Kalimantan regional study that examined all aspects of petroleum geology systems in the area.

Unocal holds a 100% interest in Santan field.

It will sell Santan gas to Indonesian state oil company Pertamina for export as liquefied natural gas through Pertamina's Bontang LNG plant north of the Mahakam Delta. Santan oil will go to the open market.