莺歌海盆地高温超压天然气成藏地质条件及成藏过程

莺歌海盆地高温超压天然气勘探的突破，使得该区域已成为勘探的热点，但关于其天然气成藏规律还存在许多不确定的因素。为此，对天然气成藏地质条件及成藏过程进行了分析，以期确定该盆地高温超压环境下游离天然气成藏的主控因素。结果发现：①莺歌海盆地烃源岩质量高、烃源灶范围大、生烃期时窗长、排烃期延迟；②高温超压环境有利于储层保持较高的孔隙度和渗透率；③盆地长期处于封闭、半封闭流体系统，发育多套盖层，有利于天然气富集和保存；④中深层底辟带半封闭式高温超压流体系统中，水溶气在不同级差压力下运移、释放、聚集并成藏，同时还找到了盆地中多个水溶相天然气出溶成藏的证据。该研究成果为莺歌海盆地下一步的天然气勘探提供了指向。

Geological conditions and pooling process of high-temperature and overpressure natural gas reservoirs in the Yinggehai Basin

With the breakthrough made in gas exploration in the high temperature and over-pressured environment of the Yinggehai Basin,this area has thus become the hot spot in present gas exploration.However,there are many uncertainties about the gas pooling patterns there.In view of this,through the analysis of geological conditions and gas pooling process in this area,the main controlling factors of free gas pooling in such high temperature and over-pressured environment of this basin are clarified.The following results are achieved in this study.(1) The hydrocarbon kitchen had a wide area with good quality source rocks,hydrocarbon generation took a long time,and there was a long lag in the time of hydrocarbon expulsion.(2) Such high temperature and over-pressured environment is good for the reservoirs to keep a rather high porosity and permeability.(3) Under closed and half-closed fluid system for a long time in this basin,multiple sealing rocks are well developed and favorable for gas accumulation and preservation.(4) In those half-closed high temperature and over-pressured fluid system in the diapiric structural zones of the middle and deep basin,water-soluble gas migrates,releases,and accumulates,as a result,a gas pool has come into being.Such evidences have been found in several water-soluble gas reservoirs in this basin.This study provides guidance for further gas exploration in the Yinggehai Basin.