Causes And Mechanism Of The Shallow Gas Reservoir In Liaohe Basin Xinglongtai Oil Field

The research carried out in the causes and accumulation controlling factors of shallow gas, not only is theoretically significative, but also is conducive to guiding the adjustment of the old areas natural gas tapping potentially, and timely adjust the ideas and direction of exploration and development.Based on the research of maturity composition feature components and carbon isotope composition(C1-C4) of shallow gas in the Dongying Group Xinglongtai oil field,we contrast the genetic of gas,research the types of shallow gas,natural gas distribution characteristics, forming mechanism and controlling factors, in combination with geological basic research on the favorable area has been optimized deployment. Main achievement as the following understanding:Carbon isotope composition of natural gas determines the causes and sources impertant, in which ethane is less affected by maturity, has obvious parent material inheritance, which is the best way to sub-consciousness distinguish the forming types of natural gas. Sapropel-type natural gasδ13C2?27.5‰, hybrid natural gas sector between the two.The use of methane and ethane carbon isotope composition determines the characteristics of different types of natural gas, according to classification results, the type of shallow gas in Xinglongtai oil field is divided into sapropel type, humus type and mixed three types.Based on the careful analysis of geochemical characteristics of natural gas,full understand of the distribution and maturity of the area around the main hydrocarbon source rock,we use the relationship of the carbon isotope of natural gas and gas source rock maturity to speculate gas source rocks. With the evolution history of the hydrocarbon source rock in CHENJIA sag, PANSHAN sag ,and QINGSHUI sag, we suggest the gas source rocks of Xinglongtai area shallow gas is hydrocarbon source rocks from sand one and three paragraph.With the detailed analysis of the distribution characteristics,the relationship of crude oil dissolved gas-oil ratio and gas-forming,the forming mechanism of shallow gas in Dongying group,we establish the reservoir-forming pattern of shallow gas in Xinglongtai Dongying group.Combined the configure relationship of gas source rocks,reservoir and cap rock,trap conditions,transporting channel, formation pressure,we analyze the controlling role of different gas reservoir, and get main controlling factor of accumulation clearly.The research of the shallow gas reservoir causes and mechanism of Liaohe Basin Xinglongtai oil field connects with actual production closely, guides the development of natural gas effectively,and is applied in Chen 1, Xing 28, Xing 20 areas in Xinglongtai oil field with the research result. 25 shallow wells have been tired totally, the oil-producing is 1.62×104t, gas-producing is 1.57×108m3 already, which has achieved remarkable social and economic benefits, with the contribution to the increase of reserves and stable production in Liaohe oil field.