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四川盆地须家河组天然气的干燥系数、甲烷碳同位素、乙烷碳同位素和甲烷氢同位素在平面上具有相似的分布特征,即“西高东低、北高南低”。在纵向上,干燥系数和甲烷碳同位素有随深度变浅而变小(低)的特点,与须一段、须三段和须五段烃源岩的演化特征一致,说明须家河组天然气都属于就近运移成藏。川西须家河组天然气碳同位素出现了部分倒转现象,天然气碳同位素的倒转可能与高—过成熟演化、多期天然气充注以及煤系烃源岩中煤和暗色泥岩生气贡献率不同有关。海相成因天然气的氢同位素值高于陆相成因天然气,氢同位素值高于-160‰的天然气基本为海相成因,而低于-160‰为陆相成因,同时,氢同位素也受成熟度的影响。
The drying coefficient of natural gas in the Xujiahe Formation in the Sichuan Basin shows similar distribution characteristics of methane carbon isotope, ethane carbon isotope and methane hydrogen isotope in the plane, ie, “high in the west and low in the east and low in the north and high in the north.” In the longitudinal direction, the drying coefficient and methane carbon isotopes are smaller (lower) with decreasing depth, consistent with the evolution characteristics of the source rocks of the Xu-5, Xu 3, and Xu-5 Member Stones, indicating that the Xujiahe Formation gas Belong to the recent migration into a reservoir. The carbon isotope of natural gas in the Xujiahe Formation in western Sichuan shows a partial inversion phenomenon. The inversion of carbon isotope of natural gas may be related to the evolution of high-over-maturation, multi-period gas filling and the contribution rate of coal and dark mudstone in coal-bearing source rocks. The hydrogen isotope value of natural gas is higher than that of continental gas, and the natural gas with hydrogen isotope value above -160 ‰ is marine origin, while below -160 ‰ is continental origin, and hydrogen isotopes are also affected by maturity Impact.