四川盆地二叠系玄武岩非常规气藏气源及勘探前景分析

ANALYSIS OF GAS SOURCE AND EXPLORATION POTENTIAL OF PERMIAN BASALT UNCONVENTIONAL GAS RESERVOIR IN SICHUAN BASIN

根据川西地区周公山构造周１井在二叠系玄武岩中钻获工业气流的气体组分、碳氢同位素值等地球化学表征，并结合以往研究与勘探成果，对天然气来源、勘探前景进行了论证。研究表明，玄武岩非常规气藏之天然气具高含甲烷、高干燥系数、高同位素值、低重烃、无硫化氢（三高一低一无）特征，属有机成因的煤系高成熟晚期气。天然气主要来自同一层系（上二叠统煤系Ⅲ型母质烃源层）。天然气甲烷碳同位素虽然显示重值，但明显低于典型无机成因的甲烷碳同位素值，无疑属有机成因气。天然气成熟度与Ｐ_２ｌ煤系区域热演化趋势展示吻合，成烃强度大，有足够的烃源供给。以此为据，认为四川盆地上二叠统龙潭组玄武岩、致密砂岩、碳酸盐岩有获得类似气藏的可能性，预测其勘探有利地区：玄武岩在成远－宜宾－叙永一线以西；其它岩类则以龙女寺、江津富烃区及其邻区有利。

In the light of gas components, carbon isotope value of commercial gas flow of Zhou-1 well drilled in Permian basalt of Zhougongshan structure in west area of Sichuan and the geochemistry features, combining the for mer researches and explorative achievements, the gas source and exploration potential are expounded. The gas of basalt unconventional. Reservoir is high maturation paulopost one of organic origin coal measure and has the characteristics of high methane, high drying coefficient, high isotope value, low heavy hydrocarbon without H_2S. The gas maturity is identical with the show of thermal evolution tendency in P_2l coal measure area, having enough hydrocarbon source supply. It is possible to obtain the same gas reservoirs in Longtan formation of Permian basalt, tight sand and carbonate rock in Sichuan Basin. The favourable explorative area of basalt is to the west of the line of WeiyuanYibin-Xuyong and the other rocks for availably exploring are the rich hydrocarbon areas of Longnusi, Jiangjin as well as the vicinal regions.