中国煤型气区的构造环境、典型气藏及勘探方向Ⅱ--中、新生界煤型气

本篇论述中、新生界煤型气的有关问题。中生界煤型气资源集中分布在北方,气源岩以侏罗纪煤系为主,以西北区资源前景最好。其中吐-哈盆地最具代表性,构造环境反转是本区煤层气形成并富集的特殊构造条件。新生界煤型气资源则集中分布于大陆架裂谷系,第三纪煤系为主力气源岩,裂谷高温构造环境是源岩热演化生烃的有利条件,而背斜-断层圈闭是最有利成藏的构造类型。崖13-1气田为本区典型代表并具自生自储的特点。

The Tectonic Environment,Typical Gas Pools and Exploration Direction of Coal type Gas Provinces in China

The coal type gas resource of Mesozoic mainly concentrates on the North China where the Northwest area is the most favorable region, and the gas source rocks are almost Jurassic coal series.The Turpan Basin is a typical coal type gas basin where C₁/C_1-5 value of HongTai 2 gas pool is 0.887,and its δ13C_1-4 values and 40Ar/ 36Ar ratio are -39.1‰,-26.5‰,-25.4‰,-25.2‰ and 571,respectively.And these indicate that the Middle Jurassic series are self generated and self reservoired coal type gas pools,and the reversion of tectonic environment is the special structural condition for source rock to generate and concentrate coalbed gases. The coal type gas resource of Cenozoic mainly concentrates on the rift valleys of continental shelf along the seawest of the East China,and the Upper Tertiary coal series and their chief source rocks,The Ya 13 1 gas field located in the South of HaiNan Province is also a typical one that its δ13C₁,value varies from -39.9‰ to -35.5‰,δ13C₂ value varies from -26.8‰ to -24‰,and its gas belongs to pyrolysis genesis.The high temperature tectonic environment (thermal gradient of the Earth exceeds 4℃/100 m)is the favorable factor for the Tertiary to generate hydrocarbon,however,anticline and fault trap is the most helpful structural condition of concentration and reservation.