Research On The Law Of Oil And Gas Accumulation In The South Of Jinhu Depression

Jinhu Depression is one of the the major oil and gas producing areas in North Jiangsu Basin, which is located in the western part of Dongtai Hollow. Rich in oil and gas accumulation, the South Jinhu Depression is of great significance for the study of hydrocarbon accumulation, because there are a lot of faults, a complicated accumulation process and a great exploration potential. In this paper, analyses of oil and gas accumulation condition are conducted. Through studying the directional change of the crude oil property and geochemical indexes, the possible direction of the migration of crude oil can be determined. Likewise, the analyses of oil and gas accumulation conditions can be used to determine the path of hydrocarbon with the study results of conduit system with oil and gas migration; Based on the current distribution of oil and gas and exploration practice, typical reservoir dissecting can be performed; Through analyzing controlling factors of oil and gas accumulation, establishing migration patterns and summarizing the law of hydrocarbon migration and accumulation, new exploration targets will be found out.Fault–nose and fault-block oil reservoirs distribute in most areas of Dongyang, with a high concentration of crude oil. It comes from the source rocks of E₁f₂. The sand body is developed, the faults in Fuâ…¡and Fuâ…¡open both laterally and vertically. The deposition relationship between source rock and sand,sand and faults are both very good. The condition of reservoir and cap rock is excellent. The oil and gas are mainly distributed along the sand, passing through the faults sites to migrate to the structurally high part. The altitude of hydrocarbon layer ascends from the center of oil, with the properties of crude oil deteriorating. The cause of heavy oil is mainly primary-secondary. Fault–nose and fault-block oil reservoirs distribute in most areas of Chajian. Crude oil is not so concentrated, mainly comes from the source rock of E₁f₂-E₁f₄. The sand has developed extensively and the lateral closure of the faults which are next to the sub-sag are better compared with the slope. The lateral closure of the faults is good while the vertical closure is moderate or bad. The deposition relationship between source rock and sand,sand and faults of Fuâ…¡are both very good .The oil is largely moderated in the fault zone. The cause of heavy oil in E₁f₄ and E₁f₂ is distinctive. Most reservoirs of Longgang area are kind of fault–nose,fault-block and lithology.. The sand of Fuâ…¡is better when compared with that of Fuâ…¢and Fuâ…£.The lateral closure of the faults is good while the vertical closure is moderate or bad. The deposition relationship between source rock and sand,sand and faults in the area of Duntang,Yangjiaba and Biandong are all ideal. Hydrocarbon which is expelled from the source rock of Fuâ…¡migrates along the faults in the oil sand. Once encountered with the faults, it will form accumulations. The cause of heavy oil in the east and west is different.The abundant source of oil is the basis of accumulation. The efficiency of oil dipping is determined by the the deposition relationship between sand and the source rock. The effective migration system controls oil migration. The growth of the seal decides the possibility of accumulation. In addition, the ideal deposition relationship of structural fluctuation,the forming time of the traps, accumulation period and the high pressure of Fuâ…¢will also influence the accumulation.The traps of E₁f₂- E₁f₄ are good for accumulation as a result of splendid ability of vertical conduction. The traps which are near the furrow in Chajian area have a great possibility of accumulating oil while oil tends to accumulate in E₁f₄ and E₂d in Longgang area.