四川盆地P_2—T_2沉积发展史及其对烃类聚集的影响

SEDIMENTARY HISTORY AND ITS EFFECT ON HYDROCARBON ACCUMULATION FROM LATER PERMIAN TO MIDDLE TRIASSIC IN SICHUAN BASIN

从东吴运动后(P_2)到印支运动前(T_2),四川盆地内在海侵的背景下自下而上形成了一个由含煤地层、深缓坡碳酸盐岩、开阔海台地碳酸盐岩、局限海台地碳酸盐岩和蒸发岩组成的大型复合向上变浅的地层层序。对这套地层的储集岩的岩石学及地球化学研完表明燕山运动前(K)储集层中以液烃的运移、聚集为主。喜山运动前(N)则以气烃运移、聚集为主。在由液烃向气烃演化时烃类曾多次运移,气烃向层序上部迁移并导致不同源气混合。层序上部的膏盐层是封堵这些气烃的重要盖层,故现今在这些含膏盐岩的地层中发现了为数众多的气藏。综上所述,本文指出在这套地层中应注意在成盐盆地及其周围寻找气田。

A mega-complex shallowing-upward sequence, ranging from deep ramp carbonates, open platform carbonates to restricted platform carbonates and evaporites, was formed in Sichuan region during the ingression from Dongwu Movement (Later Permian) through Yinzhi Movement (Middle Triassic). Petrological and geochemical studies of the reservoir showed that the multiple migration of hydrocarbon, dominantly liquid before Cretaceous and gaseous after Neogene, occured during the thermal-evolution of hydrocarbon. The multiple migration resulted in the mixing and accumulation of noncognate gaseous hydrocarbon in the upper part of the mega-complex sequence. They were finally sealed by evaporites, as seen in the gas reservoirs discovered. So more exploration will be significant in the salt-bearing basins of Later Permian --Midle Triassic in Sichuan basin.