SOUTH SUMATRA BASIN PROVINCE, INDONESIA

U. S. DEPARTMENT OF THE INTERIOR
U.S. GEOLOGICAL SURVEY

SOUTH SUMATRA BASIN PROVINCE, INDONESIA: THE LAHAT/TALANG AKAR-CENOZOIC TOTAL PETROLEUM SYSTEM

by Michele G. Bishop¹

Open-File Report 99-50S

2000

ABSTRACT
Oil and gas are produced from the onshore South Sumatra Basin Province. The province consists of Tertiary half-graben basins infilled with carbonate and clastic sedimentary rocks unconformably overlying pre-Tertiary metamorphic and igneous rocks. Eocene through lower Oligocene lacustrine shales and Oligocene through lower Miocene lacustrine and deltaic coaly shales are the mature source rocks. Reserves of 4.3 billion barrels of oil equivalent have been discovered in reservoirs that range from pre-Tertiary basement through upper Miocene sandstones and carbonates deposited as synrift strata and as marine shoreline, deltaic-fluvial, and deep-water strata. Carbonate and sandstone reservoirs produce oil and gas primarily from anticlinal traps of Plio-Pleistocene age. Stratigraphic trapping and faulting are important locally. Production is compartmentalized due to numerous intraformational seals. The regional marine shale seal, deposited by a maximum sea level highstand in early middle Miocene time, was faulted during post-depositional folding allowing migration of hydrocarbons to reservoirs above the seal. The province contains the Lahat/Talang Akar-Cenozoic total petroleum system with one assessment unit, South Sumatra.

INTRODUCTION
The South Sumatra Basin Province 3828 consists of several structural sub-basins with Tertiary sedimentary section lying unconformably on the eroded and faulted topography of pre-Tertiary metamorphic and igneous rocks. The province ranks number 60 in known reserves exclusive of the United States (Klett and others, 1997, 2000). Known petroleum is estimated at 4.3 billion barrels of oil equivalent (BBOE) (Klett and others, 1997, 2000). Late Tertiary anticlinal traps account for more than 75% of the known oil and gas reserves in the province with sandstone being the dominant reservoir (Petroconsultants, 1996).

One total petroleum system (TPS) was identified, Lahat/Talang Akar-Cenozoic (382801) (Fig. 1), that is composed of Lahat lacustrine shale and Talang Akar lacustrine and coaly shales as source rocks along with Cenozoic clastic and carbonate reservoir rocks. This total petroleum system contains one assessment unit, South Sumatra (38280101). The U.S. Geological Survey assessment of the estimated quantities of conventional oil, gas and condensate that have the potential to be added to reserves by the year 2025 for this province is 469 million barrels of oil (MMBO), 18,250 billion cubic feet of gas (BCFG), and 239 million barrels of natural gas liquids (MMBNGL) in the South Sumatra assessment unit or 3.7 BBOE (U. S. Geological Survey World Energy Assessment Team, 2000). The assessment suggests that this is and will continue to be a gas-rich province.

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U. S. Geological Survey Open-File Report 99-50S