In order to clarify the source and migration characteristics of natural gas in Xujiahe Formation and support efficient exploration of tight gas, northeastern Sichuan Basin. Based on the understanding of the structure, faults, and sedimentation, northeastern Sichuan Basin, comprehensive utilization of natural gas composition and stable carbon and hydrogen isotope data is carried out to analyze the geochemical characteristics, genesis and sources of natural gas; Furthermore, by combining formation pressure, migration characteristics was studied. The results indicate that the natural gas of T3x3 and T3x4 Members in Yuanba Area and T3x4 Member in Langzhong and Bazhong Area are mainly coal type gas, originating from the coal bearing source rocks of Xujiahe Formation. The natural gas of T3x2 Member in Yuanba Area is a mixture of coal type gas and oil type gas, sourced from Xujiahe Formation and Leikoupo Formation. The natural gas of T3x2 and T3x4 Members in Tongnanba anticline and Tongjiang depression is a mixture of oil type gas generated by Wujiaping Formation source rocks and its own coal type gas. Due to the different hydrocarbon supply of Xujiahe Formation, the carbon isotopes of different layers show regular changes. Natural gas has not undergone long-distance lateral migration, and there are two types of vertical migration characteristics: ①When the faults in Xujiahe Formation is underdeveloped and the thickness of T3x3 Members is large, natural gas has not undergone long-distance vertical migration. ②When the faults develop, high permeability fault-fractures bodies become channels for long-distance vertical migration of natural gas, promoting the mixing of gas in T3x2 and T3x4 Members, manifested as similar gas components and formation pressure characteristics.
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