Abstract: Parallel Petroleum Systems in the West Java Sea and the East China Sea

David C. Bushnell

Analyses of the prolific petroleum system in the Sunda basin of the western Java Sea and the prospective, but unexplored petroleum system in the Wenzhou subbasin of the East China Sea indicate many fundamental similarities. Both are deep half-grabens of Tertiary age with well-defined rift and sag sequences. In the Sunda basin, the 3,000 meter thick rift sequence is dominated by low-energy fluviatile, paludal, and lacustrine facies containing rich petroleum source rocks. The rift sequence of the Wenzhou subbasin is of similar thickness and geometry but is undrilled. Newly reprocessed seismic data display a 1,500 meter thick, seismically transparent interval which is interpreted to represent deep lacustrine facies similar to those which occur in some basins of eastern China In both basins, drilling shows the younger part of the rift sequence to be dominated by fluviatile or deltaic facies with abundant reservoir sand, which can be mapped in trap position on the basin flanks. In the Sunda basin, the Gumai shale covers the petroleum system like a lid, trapping virtually all the generated hydrocarbons within the basin. The 300 meter Wenzhou shale provides a similar regional cover on the Wenzhou subbasin. Regional subsidence and source maturation in the Sunda basin, occurring well after the petroleum systems were in place, generated and expelled nearly a billion barrels of recoverable oil. In the Wenzhou subbasin, 1,200 meters of Neogene subsidence with the same relative timing may also have generated and expelled large quantities of hydrocarbons.

AAPG Search and Discovery Article #90960©1995 AAPG Southwest Section Meeting, Dallas, Texas