川东小河坝砂岩天然气成藏地球化学研究

天然气成藏地球化学研究包括气源、生烃时期、烃源灶及圈闭形成时间等内容。从天然气组成、碳同位素分析入手,确定川东下志留统小河坝砂岩天然气气源为龙马溪组黑色页岩、深灰色泥岩;通过有机相分析、埋藏史分析、TTI计算,认为源岩生烃潜力大,晚三叠世至早侏罗世达到生烃高峰期,形成两个大面积的烃源灶,可提供充足的烃源;再利用构造演化史、流体包裹体均一温度确定关键时刻为晚三叠—早侏罗世。在天然气成藏地球化学分析的基础上,建立小河坝砂岩的天然气成藏体系。

GEOCHEMISTRY RESEARCH ON NATURAL GAS RESER-VOIR FORMATION OF XIAOHEBA FM OF LOWER SIL-URIAN IN THE EASTERN SICHUAN BASIN

The source rock, hydrocarbon generation, source kitchen and trap formation are discussed aimed at Xiaoheba FM of lower Silurian in the eastern Sichuan Basin, which is called natural gas reservoir geochemistry researches. First, through natural gas components, carbon isotope and organic faces analyses, dark shale and gray mudstone of longmaxi FM having high hydrocar-bon generation potential are thought as the source tock of Xiao-heba Natural gas reservoir. Second, the peak moment of hydro-carbon generation is clear and two large-scale source kitchens are determined by buried history research andTTIcalculation. Third, structure trap formation moment is in accordance withthe peak moment of hydrocarbon production.Forth,the result of fluid inclusion analysis testifies that the critical moment is late Triassic-early Jurassic.In the end,the system of reservoir forma-tion is constructed and natural gas reservoir forming process is clear.