Source Rocks And Accumulation Dynamics Of Tight Gas From He-8 Member In The Sulige Gas Field

Based on modern accumulation dynamics theory and advanced test and analysis technology,this study uses macroscopic and microscopic,simulated experiment and geological comprehensive analysis.The spatial distribution,geochemical characteristics and hydrocarbon generation potential of source rocks are detail analyze with a large amount of data.Based on the study of the characteristics of reservoir fluid inclusions petrographic and microscopic temperature measurement,this study uses the state equation combined with the basin simulation method to restore the paleo-pressure and pressure evolution history of reservoir and source rock formation,and determines the pressure state of natural gas main charging into the reservoir period.This study probes and quantifies into the contribution of abnormal pressure,diffusion and expansibility to the driving force of reservoir formation,and determines into the relationship with natural gas accumulation.In this study,the Upper Paleozoic source rocks in 1167 wells are interpreted,and the thickness of coal seam is range from 0.4m to 27m,which the distribution characteristics of thin in the west and south,and thickness in the east.Organic carbon content range from40.37%to 91.32%.Type?is the main type,and there are also some type?and mixed kerogen.Maturation is range from 1.2%to 2.0%,which is in mature to high-mature stage and low in northeast.The hydrocarbon generation intensity is high in the east and south,the west and relatively low in the north,the subject is between the(10 to 26)×10~8 m~3/km~2,the west of S212-S14-S31-Z59 is a complex zone of gas and water,the hydrocarbon generation intensity is generally less than 14x10~8m~3/km~2,and the maturity is generally less than 1.8%.The inclusions captured in the main oil and gas charging period are mainly developed in the healing fissures and the secondary quartz outgrowth edges,the abundance of hydrocarbon inclusions is larger.The homogenization temperature is distributing from 120 to 150?,and the corresponding geological age is Early Cretaceous(140 to 105 Ma).The formation mainifests abnormal low pressure currently,the paleo-pressure of reservoir is 49.2~67Mpa,and the paleo-pressure of source rocks is between 61.44 to 88.85Mpa,and all of which have paleo-overpressure.The evolution of formation pressure in He-8 Member has roughly undergone four stages:continuous pressurization—weak depressurization—secondary sharp pressurization—secondary pressurization.The ancient overpressure caused by hydrocarbon generation is the main dynamics for natural gas to enter reservoir accumulation through migration channel from source rock,and in 18.42 to 39.49MPa,the result of(2.47 to 3.95)×10~8 m~3/km~2 charging intensity of H-8 Member is diffusion action.The pressure decrease 18.4to 36.73MPa,0.86 to 2.38MPa,2.71 to 16.33MPa for temperature,pore rebound,expansibility respectively.The abnormal pressure is closely related to the distribution of oil and gas reservoirs,and the hydrocarbon generation intensity macroscopically controls the distribution of gas-water complex zone and pure gas-producing area,and the ancient overpressure caused by hydrocarbon generation determines the charging degree of oil and gas reservoirs.