Geochemical Characteristics Of The Gas And Source And The Hydrocarbon Generation Potentialof Xujiahe Formation In Middle Of Sichuan Basin

In sichuan basin,especially central Sichuan area,lithologic gas reservoir is difficult to prospect and explore Based on Structural geology, sequence stratigraphy,sedimentary petrology, reservoir geology, natural gas accumulation zone theory, the source control theory, the dynamic balance theory of natural gas, many scholars have studied the gas reservoir types main controlling factors in Xujiahe formation. In this paper, we ues the theory of organic geochemical approach,to study the gas accumulation,hydrocarbon generation and accumulation. In combination with organic geochemical characteristics of source rocks and geochemical characteristics of oil and gas, to analyze hydrocarbon source rock distribution characteristics and oil and gas sources. Using the hydrocarbon-generating intensity calculation method,to evaluate the hydrocarbon generation capacity comprehensively in Xujiahe formation. The main research results of papers obtained as follows:1?The Upper Triassic Xujiahe Formation in central Sichuan basin is a lake, river of fluvial facies strata.Hydrocarbon source rocks mainly occurs in thefifth,the third and thefirst member of Xujiahe Formation,also the coal and dark mudstone beds in the sixth,the fourth and the second member of Xujiahe Formation.2?The kerogen type in Xujiahe Formation is mainly belong to type?2~?, the organic macerals of coal mainly are vitrinite and inertinite.The type of organic matter predominantly is the sapropel and evolution of source rock is during the mature and high mature stage,abundance of organic matter is relatively high.3?The type of gas in Xujiahe Formation is mainly wet gas, at the same time reflects the typical characteristics of terrigenous coal type gas, and the organic matter type is type?;Condensate oil here is coal-type oil and has the characteristics of the root cause of the high mature humic type.4?Although the upper and lower strata in Xujiahe Formation has many sets of hydrocarbon source, the region tectonic activity is very weak.Combined with correlation of oil?gas and their supposed source rocks,it indicates that oil and gas inreservoir mainly comes from the hydrocarbon source rock itself.5.The cumulative hydrocarbon gene-(ration) intensity in Xujiahe Formation of central Sichuan area approximated to 10 ~ 30×108m3/km2, an average of23.0×108m3/km2(SPI=2.35). Accumulation model is auto-product and auto-reservoir?Hydrocarbon source rock and reservoir is interbed type composite, and the contact area is not large.Oil and gas filling ability of hydrocarbon source rocks is medium.