Characteristics of Fluid Inclusions and Determination of Hydrocarbon Accumulation Period of Caofeidian 18-1/2Buried Hill Reservoirs in Bozhong Depression,Bohai Bay Basin

The study area Caofeidian 18-1/2 structure is located in the Shadongnan structural belt at the southeast subduction end of the Shaleitian salient in the western Bohai Sea. The characteristics of reservoirs and fluid inclusions from 13 core samples near the buried hills in the study area are studied,and regional geology and conditions for reservoir formation are analyzed to reveal the characteristics and the processes of reservoir formation. Phase I oil and gas inclusions are mainly developed,and the abundance of oil and gas inclusions in this period is high( GOI is about 15%). The homogenization temperature of the hydrocarbon-containing brine inclusions accompanying them is mainly 90-120 ℃ . The simulation results of burial history and thermal history show that the main charging period of oil and gas is the present Himalayan tectonic movement period since 8 Ma,and mainly through unconformities,faults,and drainage systems,they are migrated and accumulated into fault anticline traps of Dongying Formation mudstone( E_d).