Thermal maturity modelling for the source rocks in blocks 10 and 11.1, Nam Con Son basin

Abstract

Blocks 10 and 11.1 are located at the western boundary of the Nam Con Son basin, offshore southern Vietnam. Hydrocarbon shows have been encountered in many wells as the Gau Chua (GC), Ca Cho (CC), Gau Ngua (GN), Phi Ma (PM), Than Ma (TM), etc. In the CC and GN fields, the oil and gas were discovered in Miocene sandstone reservoirs and in fractured granite basement. The Cau and Dua formations are active source rocks in this area. Oil and gas discovered in wells were generated from coal and coaly claystone sediments which deposited under oxidation conditions to weak reducing in fluvio-delta to estuarine environments, in which land plants develop very abundantly. The 2D modeling results suggested that hydrocarbons discovered in the study area mainly derived from the local source rocks. The large quantity of hydrocarbons yields from source rocks in deeper part of southeastern kitchen migrated both vertically and laterally into the overlaying formations. Hydrocarbon strongly migrated lost through open fault. Prospects located near kitchen can trap hydrocarbons if they have a good seal. Block 10 and western block 11.1 face high risk of hydrocarbon charge due to the distance from the kitchen, weak top seal and fault seal. Of seal scenario, the composition of hydrocarbons accumulated in GC structure contains 87.5% volume of liquid and 12.5% volume of gas that derived from local Oligocene source rock. The composition of hydrocarbons in accumulation in CT (Ca Ty) structure of contains 99% volume of liquid and 92.5% volume of gas that derived from local Oligocene source rock.