1. School of Geosciences, China University of Petroleum, Qingdao 266580, China
2. Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, China
3. State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
4. College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, China