Macrobenthic red algae and their hydrocarbon generation in the Paleogene deep-water source rocks, Qiongdongnan Basin

To solve the contradiction between the discovery of natural gas field in the deep water area of Qiongdongnan Basin under the background of low organic matter abundance of Paleogene (Oligocene) source rocks and the current recognition of higher plants as the main source material, selects four exploration wells in the study area for the first time with the help of “mild” maceration kerogen identification technology and scanning electron microscopy observation, and finds that the source materials are mainly marine macrobenthic red algae with high abundance rather than the before thought higher plants. The marine macrobenthic red algae have the characteristics of early oil generation and late gas generation, especially in the high to over mature stage, which has a good gas prospect. It is the first time to find the source rocks with carpospores and the disk-shaped hard pads as the main source materials in China and abroad, which indicates that macrobenthic red algae are a kind of source materials that should not be ignored, which provides a possible explanation for the formation of large gas fields in the deep water area of Qiongdongnan Basin under the background of low organic matter abundance of source rocks.