By OGJ editors
HOUSTON, Apr. 16 -- Unocal Corp. subsidiary Unocal Rapak Ltd. reported strong oil and natural gas flows from an appraisal well in the deepwater Ranggas oil field off Indonesia.
"The test results are another step towards commercializing our third deepwater oil field in Indonesia," said Brian Marcotte, president of Unocal Indonesia Co. He said the company plans to spud the Ranggas-5 appraisal well, also on the main Ranggas structure, before the end of April.
The Ranggas-4 appraisal well was tested at a rate of 8,158 b/d of oil and 6.4 MMcfd of gas from a single interval at a depth of 10,174-10,224 ft true vertical depth subsea (TVDS). The drill stem test had flowing tubing pressure of 1,223 psi through a 56/64-in. choke.
The test rates were constrained by equipment, but initial production rates from a well producing from this single zone are estimated at 10,000 b/d of oil and 8 MMcfd of gas.
The Ranggas-4 well encountered 181 ft of net oil pay and 57 ft of net gas pay. The well was drilled in 5,208 ft of water to TD at 11,252 ft TVDS. The well is 2.4 miles north of the Ranggas-1 discovery well and 1.2 miles south of the Ranggas-3 appraisal well (OGJ Online, Sept. 4, 2001).
With the results of the Ranggas-4 well, Unocal estimates the gross discovery volume for the main Ranggas structure at 200-350 million boe, with additional potential on other prospects on the same trend. Earlier, Unocal had estimated the unrisked exploration potential of the entire Ranggas complex at 350-650 million boe.
Unocal has drilled six wells in the Ranggas complex, and all have found hydrocarbons.
Additional drilling
Two wells were drilled recently to test structures on both the northern and western parts of the large central Ranggas prospect.
The Ranggas Utara-1 well encountered 33 ft of net oil pay and 44 ft of net gas pay. The well was drilled in 5,258 ft of water to TD at 12,650 ft TVDS. The well is 2.5 miles north of the Ranggas-3 well. This accumulation was deemed subcommercial as an independent development at this time, but it demonstrated the potential for additional hydrocarbons to be found north of Ranggas field.
The Ranggas West-1 well encountered 85 ft of net gas pay in two intervals. The well was drilled to 9,955 ft TVDS in 4,483 ft of water. The well is 2.9 miles west of Ranggas-3. This accumulation could most likely be tied back to the future Ranggas development facilities via a single subsea well. Oil potential remains in the southern extension of this trend.
Marcotte added that several additional prospects on trend or adjacent to the main Ranggas structure remain to be drilled. This includes the Api prospect where the Api-1 well is being drilled.
Unocal Rapak operates the Rapak production-sharing contract area. It holds 80% interest and Lasmo Rapak Ltd., a subsidiary of ENI SPA, holds the rest.
