THE ORGANIC MATTER CHARACTERISTIC OF LOWER MIOCENE FORMATION IN CUU LONG BASIN

Cuu Long basin is located mainly in South Vietnam continental shelf and a part of mainland belonging to Mekong estuary area. It has an oval shape, convex seawards and lies along Vung Tau-Binh Thuan coast. Cuu Long basin adjoins mainland northwestwards, separates from Nam Con Son basin by Con Son uplift, southwest part is Khorat - Natuna uplift and northeast part is Tuy Hoa strike-slips separated from Phu Khanh basin. Recent oil and gas quantity exploited from Cuu Long basin is evaluated to be produced dominantly from Oligocene organic-rich sediments. Some studies suggested that organic matter of lower Miocene shale deposits fails to come up to standard of source rock or very poor source rock. Lower Miocene sediments considered how to play a role in providing production into trap is the subject studied more in detailed in this report. The organic carbon (TOC %) in lower Miocene source rocks contains mostly kerogene type III is 0.64-1.32%. The depositional environment of the organic matter in the lower Miocene sediments is terrestral. Therefore the lower Miocene formation may be considered the source rocks, but has not generated hydrocarbon, because it has not passed the oil window. The depositional environment of the organic matter in the lower Miocene sediments is terrestry.