琼东南盆地深水区天然气运移规律与成藏组合

Natural Gas Migration Rule and Play in Deep-water Area in Qiongdongnan Basin

为解决琼东南盆地深水区新区天然气勘探中遇到的天然气运移认识不清的难题,在实验(数值)模拟和大量调研基础上,综合钻井、构造和地震等资料,利用盆地模拟软件,开展了深水区天然气运移规律系统研究。结果显示,深水区天然气运移主要受到“流体势场”—“通道场(输导体系格架)”—“约束场(区域盖层)”3场耦合的控制。高势生烃凹陷内的底辟带和晚期活化沟通气源断裂发育区的陵水组区域盖层完整性被破坏,天然气垂向运移为主,利于在区域盖层之上形成多个中小规模气藏组成的浅层大中型岩性型气田;部分凹陷边缘—低凸起及之上地区陵水组区域盖层保存完整,断裂—砂体—构造脊汇聚型复合输导体系发育,天然气运移侧向为主,利于在区域盖层之下形成深层整装构造型大中型气田,而新构造运动是深水区晚期大中型气田形成的重要诱因。深水区最终形成了浅层和深层两套成藏体系和3套有利成藏组合。成果指导勘探,在松南低凸起深层成藏组合勘探中首次获得突破性发现,继续拓展,有望在中央峡谷外找到新的大中型气田群。

In order to solve the problem of unclear understanding of natural gas migration in the new area of deep-water area of Qiongdongnan Basin,based on the experimental(numerical)simulation and a large number of investigations,the systematic study of natural gas migration law in deep-water area is carried out by using basin simulation software and integrated drilling,structural and seismic data.The results show that the gas migration in deep water area is mainly controlled by the coupling of“fluid potential field”,“path field(transport system)”and“restraint field(regional seal)”.In the diapir zone and the late active deep and large fault development area in the high potential hydrocarbon generation depression,the integrity of Lingshui formation regional cap rock are destroyed,and the natural gas vertical migration is dominant,which is conducive to the formation of shallow,large and medium-sized lithologic gas fields composed of a number of small and medium-size gas reservoirs above the regional cap rock;the regional cap rock of the Lingshui formation is well preserved in some depression margins,low bulges and upper areas,the“Fault-Sand-Ridge”composite transport system is developed,and the gas migration is mainly lateral,which is conducive to the formation of deep-seated integrated structural large-medium sized gas fields under the regional caprock,and the neo-tectonic movement is an important inducement for the formation of late large and medium-sized gas fields in the deep-water area.The deep-water area finally formed two sets of reservoir-forming systems:shallow and deep reservoir-forming system,and three sets of favorable reservoir-forming assemblage similar to the Santos basin in the South Atlantic Ocean.The results guided exploration and made major breakthroughs.Further expansion is expected to find new large and medium gas fields outside the Central Canyon.