川西坳陷中段须家河组天然气藏凝析水地球化学特征及其意义

Geochemical Characteristics and Its Significance of Condensate Water in Gas Reservoirs of Xujiahe Formation in The Middle of Western Sichuan Depression

川西坳陷中段须家河组天然气藏普遍产出凝析水,具有矿化度低、HCO-3百分含量高的特征,水型以NaHCO3水为主,推断其为地层水蒸发之后与天然气发生混合作用的产物。由于分馏效应,导致凝析水的氢氧同位素明显偏低。凝析水是天然气高产的标志,产出水只能由其向地层水转化,随之出现产出水量增大,产气量减少,水气比增大的现象。凝析水的出水量、矿化度、离子含量等的变化特征与天然气产量的关系密切,可为气藏的进一步勘探开发提供参考。

Condensate water have been developed in the gas reservoirs of Xujiahe formation in western Sichuan depression. The condensate water can be featured with low salinity ,high HCO3- content and NaHCO3 water type. It was thought that condensate water may originate from formation water and then affected by complicated mixing interactions. Because of isotopic fractionations ,theδD‐δ18 O value of con‐densate water is low. Condensate water is considered the sign of high gas production. And the produced‐water only changes from condensate water to formation water. When the transition from condensate wa‐ter to formation water happened ,the gas production became less ,water production became high ,there for the water steam ratio increases. The relationship between condensate water and the production of hy‐drocarbon is very close. It can give some references to gas exploit.