库车前陆冲断带盐下深层压力特征及其油气勘探意义

库车前陆冲断带盐下深层气藏埋深大, 普遍发育超压。通过收集大量盐下深层压力实测数据, 开展压力分布规律研究, 揭示其与气藏的形成及分布之间的联系。结果表明, 库车前陆冲断带盐下深层压力分布为85~127 MPa, 压力系数分布为1.5~1.9, 为超压特征。平面上, 地层压力和压力系数分布表现为南北分带、东西分段的特征。侏罗系烃源岩距白垩系巴什基奇克组砂岩顶部为1 500~4 000 m之间, 平均为3 000 m, 源储压差在70 MPa以上, 超压流体为天然气强充注成藏提供动力条件, 是形成高效气藏的必要条件。平面上, 盐下深层大气藏(田)的分布与超压分布区叠置;纵向上, 气藏群位于超压集中发育的封闭楔形冲断体内, 成排成带分布。

Characteristics of formation pressure and its significance for the subsalt deep layer in foreland thrust belt of Kuqa depression

The gas reservoirs with deep burial developed high formation pressure. Large amount of tested pressure data were collected and formation pressure framework and distribution were analyzed, and revealed their relationships with gas reservoirs. The results showed that the values of formation pressure and pressure coefficient are 85~127 MPa and 1.5~1.9, respectively. Pressure and pressure coefficient both displayed features of different zones in north and south, different parts in east and west. The top distance between Jurassic source rock and Cretaceous Bashenjiqike sand is 1 500~4 000 m, averaging 3 000 m, the pressure difference between source rock and reservoirs is over 70 MPa, which provided the dynamical conditions for gas charging strongly and forming gas reservoir efficiently. Distribution of high formation pressure and subsalt deep large gas field superimposed in the plane, and vertically gas reservoir group distributed as a row and belt shape, locating in the thrust wedge with high formation pressure.