Distribution of temperature at the bottoms of Cenozoic source rocks in the Bohai Bay Basin
Gong Yuling1, Wang Liangshu2, Liu Shaowen3, Li Cheng2, Han Yongbing2, Li Hua2, Cai Jingong4
1. Department of Exploration and Information Technology, East China University of Technology, Fuzhou, Jiangxi 344000; 2. Department of Earth Sciences, Nanjing University, Nanjing 210093; 3. School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210093; 4. School of Ocean and Earth Science, Tongji University, Shanghai 200092
Based on the geotemperature data from more than 2 000 wells in the Bohai Bay Basin,stratigraphical and lithological descriptions,and stratification and well logging data,the paper calculated the temperature at the bottom surfaces of different Cenozoic source rocks in the basin.The results showed that the temperature at the bottom of the Shahejie Formation in most sags of the basin rangeed from 90 ℃ to 150 ℃,satisfying the condition for oil generation,while it was less than 90 ℃ for the same formation in areas of uplifts or some highs,which was not enough for oil generation.The Dongying and Kongdian Formations might be possible for oil generation in temperature to some extent.It was also found that the temperature showed a close relationship with the buried depth of the strata,namely,the temperature increased with the increasing buried depth.The sags where the sediments were relatively thicker had a larger temperature than that in the uplifts and highs with relatively thinner sediments,indicating that the depth of the formation should be a key factor for controlling its temperature,and the influence of the geotemperature gradient might be relatively small.