Characteristics of Fluid Dynamic Field and Its Significance to the Accumulation of Hydrocarbons in Haizhong Sag of Beibuwan Basin

Haizhong Sag, located in the south part of North Depression of Beibuwan Basin, is considered to be quite good in the geological conditions for hydrocarbon accumulation and favorable for the exploration. Under the guidance of the dynamic theory for hydrocarbon accumulation, the authors, based on the integrated study of basin modeling technique and petroleum geology, analyzed the characteristics of fluid dynamic field including geothermal field, pressure field, fluid potential field and stress field, dissected the relationship between the fluid dynamic field and hydrocarbon accumulation, laid a foundation for the deep understanding on dynamics of hydrocarbon accumulation in Haizhong Sag. The study indicates that both of the present geothermal field and paleo-geothermal field are characterized with relative higher temperature in the Haizhong Sag. The abnormal high pressure is mainly distributed in the deeply buried mudstone interval of middle-deep lacustrine facies Liushagang Formation of the sag, and the abnormal high pressure evolution was successive in the geological history. The potential energy difference could drive hydrocarbon generated from mature source rock from high potential area in the sag to the lower potential area and accumulate. There are many normal faults in Middle Eocene, which are beneficial to the hydrocarbon vertical migration. The strong compressional inverse occurred in late Miocene is favorable to the hydrocarbon preservation.