Bulletin of the Geological Society of Malaysia, Volume 37, July 1995, pp. 55 – 75
P.T. Caltex Pacific Indonesia, Rumbai, Sumatra
Abstract: The Kelabu-Jingga area, located in the Kiri Trough of the Central Sumatra Basin, produces gas from the Paleogene Pematang Group. The Pematang Group consists of sandstones, claystones, organic-rich shales and conglomerates deposited in fluvial and fresh-water deltaic and lacustrine environments. Deposition occurred during regional tectonism associated with a major plate reorganization in the Pacific and Indian Oceans during the Paleogene. Subsequent rifting and basin development occurred in the Kiri Trough area in Central Sumatra. Syngenetic listric faults and associated “rollover” folds formed during rifting. The Pematang Group was deposited in deep, transtensional pull-apart grabens and shallow extensional rifts. Tectonics strongly influenced the geometry and lateral continuity of the fluvial-deltaic sands.
During the Neogene, oblique convergence of the Indian Ocean plate with the Asian plate resulted in a regional dextral-wrenching event in the Central Sumatra Basin that overprinted the earlier extensional style of faulting. In the Kiri Trough, both extensional and compressional features are evident. Interpretation of a 3D seismic survey, wireline logs (including dipmeter and FMS data) and core data has delineated fault styles and depositional trends within the Pematang Group in the Kelabu-Jingga Fields. The resultant maps and cross sections reveal hydrocarbon reserves and new drilling opportunities.