中国主要气区海相沉积层序特点与大中型气田分布规律

我国大中型气田已发现68个,其中大部分分布于海相或海陆过渡相中,勘探实践证实海相层序富集大中型气田。3大气区克拉通海相沉积层序,整体上经历了两次大的海侵和两次大的海退沉积,形成了纵向上多套优质的生储盖组合,而且经历了多期次的大型构造运动,形成震旦纪中晚期和志留、泥盆纪两次大的不整合和其他次级不整合,有利于地层岩性风化壳天然气藏类型的发育。海相、海陆过渡相地层中,存在4种天然气藏类型,即(1)古隆起控气下的地层岩性天然气藏;(2)古隆起控气下的受晚期构造运动调整的构造背斜气藏;(3)生物礁、鲕滩、河流相砂体等岩性气藏;(4)大型挤压背斜圈闭天然气藏。海相、海陆过渡相天然气的分布,受古隆起控制,同时各种沉积环境下形成的碳酸盐岩储集场所及河流相砂岩有利相带的分布也制约着天然气藏的富集,而且与多期次构造运动对原生气藏的破坏和调整有关。 

MARINE SEDIMENTARY SEQUENCES AND MAJOR GAS FIELDS IN CHINA

Presently sixty-eight major natural gas fields have been discovered in marine and transitional continental-oceanic sequences in China and marine sedimentary sequences are favorable for exploration of natural gas.The marine sedimentary sequences in three cratonic basins are composed of two major cycles of transgression and regression,in which multiple combination of source rocks,reservoirs and seals was formed.In addition,as a result of tectonic movement many unconformities were formed and stratigraphic-lithological gas pools were developed.There are 4 kind of gas fields in marine sequences:(1) stratigraphic-lithological gas traps related with old uplift;(2) anticlinal gas pools related with old uplift and late tectonic movement;(3) lithological gas pools of reef,oolite beach or sandbody;(4) large anticlinal gas pools under compressional background.In one word,distribution of natural gas is closely related with old uplift,reservoir conditions and tectonic activity.