ABSTRACT: Re-development of structural-stratigraphic traps in the Wanda Area, Sunda Basin, Southeast Sumatra, Indonesia
Yudistira, Gunawan Juniarto, Sri Lestari, Agusandi Isdiawan, Jarot P. Adi, Mulyo Hadisantoso, and Rob Hull , YPF Maxus Southeast Sumatra B.V, Jakarta, Indonesia
Wanda field is located in the Sunda Basin, 60 km north of Jakarta, Indonesia. The first development was in 1984-1986 utilizing 2D seismic data after the 1982 Wanda-1 discovery and 12 delineation wells. Further development was considered uneconomic by 1991 due to rapid production decline and poorly understood sand distributions. However, the area was included in a 3D seismic survey shot in 1993, and interpreted in 1995. Since that time seismic-influenced sand trend interpretations led Maxus to successfully develop 3 production caissons with 17 wells. Production soared from 1000 BOPD in 1995 to a peak of 19,000 BOPD in mid-1998.
Production is from Talang Akar formation "Gita" sandstones that trend southwestwards and stratigraphically trap on the N-S structural grain of faulted eastward dipping units. The reservoirs are fluviatile sands up to 12 feet thick, interbedded with shales and coals deposited in meander floodplain settings. Six depositional units, A through F, are identified based on coal and shale markers, and the E and C-3 sands form the main reservoirs.
Thin sands and coals have made it difficult to detect individual sands with the 3D seismic's frequency content but isochron has successfully outlined composite E and F sand distribution after cokriging with well data. Isochron has also been used in combination with detailed fault mapping to identify C-3 sand thicks where syndepositional structural lows developed. In addition, 2D seismic modeling has been used in a more complex stratigraphic sequence to support the presence of C-2 sands.
AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia