ABSTRACT: A Comprehensive Evaluation of the Exploration Potential of the Offshore Sibolga Area, West Coast Sumatra Island, Indonesia

Specht, Thomas D.¹, Triyanto Rahardjo¹, Frederic I. Frasse¹, Perry B. Dobson²
(1) PT Caltex Pacific Indonesia, N/A, Indonesia
(2) Texaco Inc, Bellaire, TX

The Sibolga PSC was acquired in October of 1996, with PT Caltex Pacific Indonesia (CPI) designated operator of the block. The exploration area covered some 10,000 square kilometers mostly lying offshore between Simelue Island and the West Coast of the Sumatra, western Indonesia. Water depths in the area range from onshore to greater than 2000 feet deep at the north and south ends of the block. The area's sedimentary section at its greatest is in excess of 20,000 feet thick.

The Sibolga Block is located in the Mentawai Forearc Basin. It is bordered by two positive tectonic elements; the outer arc and the Mesozoic-Paleozoic core and volcanic arc of Sumatra. The basin began to subside around 17 MA and received nearly continuous sedimentation throughout most of the Neogene. Wrenching along a series of regional right-lateral strike-slip faults produced important differences in the structural and stratigraphic evolution between the various sub basins along this fore-arc.

CPI conducted an exploration program that included the acquisition of 1959 kilometers of 2D seismic and gravity data, 1945 kilometers of magnetic data, conducting extensive field geological studies, interpreting these data and conducting an environmental baseline. The exploration program incorporated the existing multiple vintage 2D seismic data and the data from seven exploratory wells drilled in the late 1960's and early 1970's.

CPI's exploratory work demonstrated that shallow burial depths limited the size of biogenic accumulations and that classic low fore-arc heatflow suggests only a limited thermogenic petroleum system was developed.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia