Significance of gypsum-salt rock series for marine hydrocarbon accumulation

With further exploration and research, the gypsum-salts rock series as good caprocks attracted a lot of attention. The gypsum-salt rock series played an important role during migration, preservation and trapping of hydrocarbons. Recently, major breakthroughs have been continuously made in marine petroleum exploration of gypsum-salt rock series in the eastern Ordos Basin, the central Tarim Basin and the western Sichuan Basin in China, and the high-evolution and low-abundance gypsum-salt rock series as hydrocarbon source rocks become possible. Besides research advances in the reservoir-caprock assemblage of gypsum-salt rock series, development and hydrocarbon-generation potential of source rocks in the gypsum-salt rock series were well studied in terms of source-rock development environment and hydrocarbon generation mechanism. Results showed that the gypsum-salt rock series, including high-evolution and low-TOC gypsum-salt rock series in China, could be regarded as good source rocks. This understanding was a breakthrough to previous traditional viewpoint that low-TOC gypsum-salt rock series could not act as effective hydrocarbon sources. The key to understand hydrocarbon-generation mechanism was that abundant and high-quality hydrocarbon-generation materials, large amount of hydrocarbon generation and conversion in geological history, and hydrocarbon-generation materials occurred in the form of carboxylates, were developed in the high-evolution and low-TOC gypsum-salt rock series.