Variation in catagenesis level and hydrocarbon generation in sedimentary rocks of the South Sumatra Basin, Indonesia

GALO system for basin modeling is utilized to restore numerically burial and thermal histories of Limau Graben in South Sumatra Basin from Oligocene to present time. Thermal and maturation history of Basin was considered on an example numerical reconstructions for sedimentary sections of six wells (Pandan-81, Petanang-1, Tepus-2, Tepus-1, Gambir-1 and Lembak-8) located along the profile crossing Limau Graben. Variations in tectonic subsidence suggest period of lithosphere extension in Oligocene and Miocene with amplitude increased from β = 1.12 at the flanks of the Limau Graben (well Lembak-8) to 1.32 in its centre (wells Tepus-1 and 2). The modeling shows that the Lemat source rocks are oil generating in the main part of Limau Graben. The rocks at the base and roof of the Talangakar formation can be considered as intensive oil generating excluding, may be, upper horizons of the formation in the must shallow areas of the Graben (w. Lembak-8). A peak of oil generation by the formation rocks occurred in the last 5 – 10 My. Oil generation by the rocks of the Gumai formation can be significant in the main part of the Graben. It is negligible only in fare flanks of the Graben (w. Lembak-8).