The Origin and Mechanism of Formation of Hydrocarbon Deposits of the Vietnamese Shelf

Abstract

This paper presents the results of studies of the main factors that are responsible for the formation conditions and localization of oil and gas deposits within the Cenozoic sedimentary cover and Pre-Cenozoic granite basement of the Vietnamese shelf. Our structural–tectonic model of the Cuu Long Basin allows the identification of the formation conditions of regional and local structures with hydrocarbon (HC) deposits, mechanisms of origin of HC traps and reservoirs, the genesis of HCs, including those occurring in the basement rocks, and the possible mechanisms of migration and accumulation of HCs in the basement rocks. Abundant traps are real or potential HC reservoirs in the crystalline basement body. The structural–tectonic processes in the basement resulted in origination and evolution of positive morphostructures (domes and protrusions), whose cores are filled by disintegrated (granulated) basement rocks. For the interpretation of chronothermobaric conditions of origination and evolution of HC sources, formation conditions, and principles of occurrence of oil and gas deposits at the Vietnamese shelf we conducted 3D modeling of the generation and accumulation HC systems using basin modeling in PetroMod program software (Schlumberger, Ltd., United States). The studies of HCs–biomarkers of oils of the deposits of the Cuu Long Basin including those located in the crystalline basement showed similar biomarker parameters of oils and organic matter, which is evidence of the organic nature of the oil deposits of the basement at the Vietnamese shelf.