Hydrocarbon Generation And Expulsion Characteristics Of Paleogene Source Rocks In The South Of Lufeng Sag And Their Controlling Effects On Hydrocarbon Accumulations

In recent years,the exploration in Lufeng sag of Zhuyi depression in the South China Sea has made remarkable achievements and progress.Although it shows good resource prospects,the commercial success rate of exploration is low,which needs further research.The hydrocarbon generation and expulsion characteristics of source rocks are an important basic problem of oil and gas resource evaluation.At present,there are two major problems to be solved in the study of source rocks in the study area:1.Lack of deep and highly evolved source rock samples;2.The rock quality and organic matter content of source rock pyrolysis data are greatly lost,so it is impossible to accurately evaluate the resource potential.In view of the above problems,this paper has selected the Paleogene source rocks in the south of Lufeng sag,Zhuyi depression,Pearl River Mouth Basin as the research target,and carried out the research on the generation and expulsion characteristics of source rocks and the evaluation of oil and gas control.Through the systematic evaluation of source rocks in the study area,the distribution and geochemical characteristics of Paleogene source rocks have been clarified;Based on the rock pyrolysis data and the improved hydrocarbon generation potential method,a model for evaluating the hydrocarbon generation and expulsion characteristics of source rocks has been established and applied to the resource potential evaluation of Wenchang and Enping source rocks.The hydrocarbon expulsion history of Lufeng south area has been restored by forward modeling method.The results show that the Paleogene petroleum system can be divided into two stages:16 Ma～8 Ma and 8 Ma～present;The maximum hydrocarbon generation intensity and hydrocarbon expulsion intensity are 35130×10~4t/km~2 and 34480×10~4t/km~2;The whole Paleogene source rock in the south of Lufeng Sag has a hydrocarbon generation of 27.49 billion tons and a hydrocarbon expulsion of 24.23 billion tons.The lower Wenchang Formation source rock is the main hydrocarbon generation and expulsion horizon.The quantitative relationship model of hydrocarbon source rock controlled reservoir distribution suitable for Lufeng south area is established;The most favorable deepening exploration zone is determined:around Lufeng 13 East depression and twice the hydrocarbon expulsion radius,and the most favorable field is around the lower Wenchang source rock and upper and lower horizons.