Assess Late Syn-Rift Plays in Cuu Long Basin, Offshore Vietnam

Abstract Cuu Long basin is a Cenozoic rift basin located in the southeastern shelf of S.R. Vietnam, containing vast potential oil and gas resources. The basin was impacted by three main tectonic periods of pre-rift, syn-rift and post-rift tectonism. Major petroleum plays in Cuu Long basin are the Pre-Cenozoic fractured basement, Oligocene and lower Miocene sandstone reservoirs. Upper Oligocene sediments were deposited during late syn-rift phase of Cuu Long basin. The reservoirs in these strata (Oligocene C and D) were previously discovered in the center, southwestern and southeastern margins of Cuu Long basin with limited total reserves, up to 5%, of Cuu Long basin's discovered reserves. Recent exploration and appraisal results of St, Tg, Rg, Ct etc. show a greater potential of upper Oligocene reservoirs with a greater variety of trap types in many areas of Cuu Long basin than that of previous assessments. Therefore, additional studies and assessments of recently discovered trap types need to be carried out for the Cuu Long basin exploration and appraisal program. This article discusses the assessments of upper Oligocene trap types and identifications of several trap mechanisms utilizing the integration of exploration methods. The research results permit better understanding of the trapping mechanisms and possible distributions of various trap types in the upper Oligocene strata of the Cuu Long basin, thus leading to better planning of exploration/appraisal strategies in the basin.