珠江口盆地(东部)油气地质特征、成藏规律及下一步勘探策略

Hydrocarbon geology,accumulation pattern and the next exploration strategy in the eastern Pearl River Mouth basin

在珠江口盆地东部地区,区域上先断后坳的构造演化造就了盆地的双层结构,先陆后海的沉积序列形成了盆地的多类型沉积相组合,地壳厚度向南逐渐减薄造成了几个坳陷带热演化的不均衡。在这种独特的地质背景下,多期成盆结构发育多套烃源岩,断坳叠置复合盆地发育陆、海相两大套储盖组合,多期构造活动形成多种类型的复式圈闭,油气围绕富生烃凹(洼)陷呈"北油南气"分布,并在二级构造带上复式聚集。综合研究认为,富生烃凹(洼)陷控制该地区的油气分布,烃源岩及其热演化的差异性造成了油气分布的分带性,复合输导体系和晚期构造活动控制了油气的复式聚集。基于油气的分布特征和成藏规律,提出该地区下一步勘探策略:对于已证实的富生烃凹(洼)陷,要坚持以复式油气勘探理念为指导,实现二级构造带立体饱和式勘探;对于潜在的富生烃凹(洼)陷,要从区域地质研究入手,系统评价其油气资源量,优选二级构造带,实现新区勘探突破。

In the eastern Pearl River Mouth basin,the regional tectonic evolution from the early rift ting to the late depressing has resulted in a dual configuration of basin,the sedimentary sequence from the early nonmarine facies to the late marine facies has formed various assemblies of sedimenta ry facies,and the southward gradual thinning of the crust has led to an uneven thermal evolution in multiple depressed zones.In this distinct geolog ical background,several sets of source rocks de veloped during multiple episodes of basin form ing,two reservoir seal combinations of nonmarine and marine facies formed in the riftting and de pressing stage respectively,and various types of composite traps occurred due to multiple tectonic events,resulting in a hydrocarbon distribution of ＂north oil and south gas＂ around the rich hydro carbon generation sags （subsags） and a type of composite accumulation in the second order struc tural belts.According to a comprehensive study,it could be considered that the oil and gas distribu tion in the region is controlled by the hydrocarbon generation sags （subsags）,the areal zonation of hydrocarbon distribution results from the differences in source rocks and their thermal evolution,and the composite accumulation of hydrocarbon is caused by a compound system of migration and the late tectonic movements.Based on the hydrocarbon distribution and accumulation pattern,the next exploration should be deployed around the rich hydrocarbon generation sags （subsags）.For the proven sags （subsags）,the conception of duplex exploration should be kept as a guide,in order to achieve the three-dimensional and saturated exploration in the second-order structural belts.For the potential sags （subsags）,it is needed to start from the regional geological study,evaluate systematically their hydrocarbon resources,select the best second-order structural belts and make the exploration breakthrough in new areas.