川西前陆盆地碎屑岩天然气跨层运移过程中的相态演变

近年来 ,川西前陆盆地在侏罗系及白垩系非生烃层中发现大量的“次生气藏”。“次生气藏”是下伏一二千米以下上三叠统须家河组气源层纵向跨层运移聚集成藏的结果。跨层运移的动力是该区独具特色的须家河组含气封存箱内的异常高压 ,通过纵向发育的断层及裂缝系统 ,流体以混相涌流方式向上运移。在运移过程中 ,由于温度、压力的改变 ,流体相态不断发生变化。经计算定量地确定出运移进入不同层位时的各相态比例 ,从而恢复出天然气跨层运移过程中的相态演变历程。

PHASE STATE EVOLUTION IN THE CROSS FORMATIONAL FLOW OF NATURAL GAS IN THE WEST SICHUAN FORELAND BASIN

In the recent years, lots of secondary pools are found in the strata of Jurassic and Cretaceous nonproducing hydrocarbon formations of the West Sichuan foreland basin. The secondary gas pools are the result of gas cross formational flow. The gas is from the underlying gas resource zone of the Xujiahe Formation located at one or two thousand meters below. The driving force of the cross formational flow is an abnormal high pressure of the characteristic gas bearing compartment in the Xujiahe Formation. The cross formational is depends on the vertical fault and fissure system. In course of migration, the fluid phase state changes with the change of the temperature and pressure. In the present paper, the proportion of each phase state has quantitatively been assured, and the evolution of the phase states restored as well.