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结合四川盆地地质与构造演化特征,利用天然气组分、稳定碳氢同位素组成和气田地层水地球化学指标,探讨了建南气田天然气成因类型、母质来源、油气保存条件以及不同类型气藏的成藏方式。建南气田天然气以烃类气体为主,CH4含量占87.26%~98.63%,平均为95.31%,干燥系数均大于95%,属于典型的干气。非烃气体除含有一定量的CO2和N2外,天然气中普遍含有H2S,含量占0~4.34%,平均为0.75%,属于低含H2S天然气。天然气δ13 C1值介于-37.4‰~-30.8‰之间,δ13C2值介于-41.8‰~-33.7‰之间,δ13 C3值介于-27.6‰~-40.8‰之间。石炭系天然气主要来自志留系烃源岩,而上二叠统天然气主要来自二叠系烃源岩,下三叠统飞仙关组和嘉陵江组天然气为后期气藏调整过程中上二叠统天然气调整运移形成。建南气田烷烃气碳同位素普遍存在δ13C1≥δ13C2<δ13C3的特征,可能与TSR改造有关,不存在志留系与二叠系生成天然气的混合。建南气田地下水化学特征表明飞三段、长兴组、石炭系储层中,地层水矿化度普遍大于35g/L,且以CaCl2型为主,指示油气藏保存条件良好,可能与嘉陵江组膏岩有效地阻止了地表水向下交替有关。嘉陵江组因局部地区受断层影响,膏岩遭受地表的淡水淋滤,水型以Na2SO4为主,矿化度低,油气封存能力变差。
Based on the geologic and tectonic evolution characteristics of Sichuan Basin and using the composition of natural gas, stable hydrocarbon isotope composition and formation water geochemical indicators in gas field, the genetic type, parent material source, hydrocarbon preservation conditions and accumulation of gas reservoirs in Jiannan gas field are discussed the way. Natural gas in Jiannan gas field is mainly hydrocarbon gas, with CH4 content accounting for 87.26% ~ 98.63%, with an average of 95.31%. The drying coefficient is more than 95%, which is a typical dry gas. In addition to non-hydrocarbon gas containing a certain amount of CO2 and N2, the natural gas containing H2S, content of 0 ~ 4.34%, an average of 0.75%, belonging to low H2S natural gas. The δ13C1 value of natural gas ranges from -37.4 ‰ to -30.8 ‰, the δ13C2 value ranges from -41.8 ‰ to -33.7 ‰, and the δ13C3 value ranges from -27.6 ‰ to -40.8 ‰. The Carboniferous natural gas mainly comes from the Silurian source rock, while the Upper Permian natural gas mainly comes from the Permian source rocks. The Lower Triassic Feixianguan Formation and the Jialingjiang Formation natural gas are the Upper Permian Natural gas to adjust the formation of migration. The characteristics of δ13C1≥δ13C2 <δ13C3, which are common to the carbon isotopes of alkanes in Jiannan gas field, may be related to the transformation of TSR. There is no mixture of Silurian and Permian gas. The chemical features of groundwater in Jiannan gas field indicate that the salinity of formation water is generally above 35 g / L in the Feisanpai, Changxing Formation and Carboniferous reservoirs, and CaCl2 is the dominant type, indicating that the reservoirs are well conserved and may be associated with Jialingjiang Formation paste Rock effectively prevents the surface water from turning down. The Jialingjiang Formation is affected by faults in some areas. The gypsum is leached by freshwater from the surface. The water type is mainly Na2SO4 with low salinity and poor oil and gas sequestration ability.