Organic geochemical characteristics of Enping Formation source rocks in Wenchang A sag, Pearl River Mouth Basin, China

The Wenchang A sag has abundant oil and gas resources with great potential for exploration and development. The source rocks are mainly developed in Enping Formation (Ep). However, earlier work has only focused on basin evolution and reservoir characteristics of Wenchang A sag, without a systematic study of Ep source rocks. In this study, Wenchang A sag is divided into four blocks (A, B, C, and D) by the structural and sedimentary characteristics. The quality of Ep source rocks in four blocks is evaluated, and the organic geochemistry characters and sedimentary environment characteristics are analyzed by using 139 geological and geochemical data. The results show that source rocks in blocks B and C have higher of organic matter abundance compared with the blocks A and D. Meanwhile, the blocks A, B, and C source rocks were deposited in more reductive environment than block D and are dominated by Type II kerogen. On the whole, the blocks B, C, and D source rocks are in the stage of mature, while those of the block A are in the stage of low mature. Vertically, the hydrocarbon expulsion threshold of the Ep source rocks is 3600 m.