摘要
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。
In combination with the characteristics oi geotogtc structute evutu ical and stable isotopic compositions of natural gases and the formation water chemistry from the Jiannan Gas Field, Sichuan Basin,China, were investigated to elucidate the origin of the gas,precursor source, preservation and to reconstruct the gas-filling history for different reservoirs. All natural gases in the Jiannan Gas Field are dominated by CH, with low amounts of non-hydrocarbon（e, g-COz,HzS and Nz） compo nents. The CHf content ranges from 87.26%-98.63% ,with an average of 95.31%. The gas dryness coefficient（C1/C1-3） is over 0.9,5. The non-hydrocarbon gases contain not only a given amount of CO2 and N2 ,but also H2S generally being in the range of 0 to 4.34% with an average of 0.75% ,so it belongs to low HzS content gases. δ^13C1,δ^13 C2 and δ^13C in the range of -37.4‰ to -30.8‰,-41.8‰ to -33.7‰ and -27.6‰ The δ^13 C1, δ^13C2 and δ^13Ca values are to -40.8‰, respectively. Carboniferous gas was derived from the Silurian shale while the gas in the Upper Permi- an Changxing Formation was sourced from the Permian source rocks. The gas in the Lower Triassic Feixianguan and Jialingjiang formations was migrated from the Upper Permian gas through faults at later. The carbon isotopic trends of gaseous alkanes are generally of ^13 C1≥^13C2〈^13 C3, probably related to the TSR alteration rather than the mixing of gases from Silurian and Permian source rocks. Natural gases of the Carboniferous mainly come from oilcracked gases and some kerogen-cracked gases from the Lower Silurian Longmaxi Formation shale,and the I.ower Permian Liangshan Formation shale acts as an effective seal. Changxing Formation biothermal gas accumulated dur ing the process of oil cracking and formation of effective traps. Source rocks are mainly mudstone of the Upper Per mian Longtan Formation,with a certain contribution from the Silurian source rocks. The sulfide-bearing gases in the Lower Triassic gas pool are mainly sourced from the
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2015年第4期657-666,共10页
Natural Gas Geoscience
基金
国家自然科学基金(编号:41173035
4132201)联合资助
关键词
建南气田
天然气
地球化学
TSR
地层水
成藏方式
Jiannan Gasfield
Natural gas
Geochemistry
TSR
Formation water
Accumulation model
