南堡凹陷东营组巨厚堆积的关键控制要素及其油气地质意义

以南堡凹陷东营组为研究对象,采取时空演化与对比的方法,从东营组发育期构造活动的独特性出发,判别出凹陷边缘断裂的活动性在古近纪晚期进一步增大的同时,凹陷整体的坳陷作用也在进一步增强。在上述边界断层强烈活动和基底沉降强烈增速的"双强要素"联合作用下,南堡凹陷的沉降中心、沉积中心均远离边界断层而发育于凹陷中心,并导致了在东营组堆积期大面积深湖相沉积的发育;其内部堆积了厚层的深湖相泥岩和大量的深湖浊积体,同时在凹陷北部的断控陡坡部位发育了大量的扇三角洲体系,在南部缓坡部位则发育了辫状河三角洲沉积,从而使东营组内部储层非常发育,且类型齐全;新近系巨大的地层厚度导致了东营组的烃源岩进入生烃门限而生烃、排烃,从而构成了良好的"自生自储"组合。东营组堆积期及其后的新构造运动又导致了大量的同沉积断层活动和晚期的再活动,这些断层有效地将东营组储集体与下伏Es3+Es2+Es1的"烃源灶"沟通,并将下部油气垂向运移至东营组乃至更浅层位的储集体内聚集成藏,从而造就了东营组巨大的油气勘探潜力。

The key control factors and its petroleum and geological significance of extra-thick deposition in Dongying Formation,Nanpu Sag

This study is focused on the Dongying formation in Nanpu sag.Based on the uniqueness of tectonic activity of the development period of Dongying formation,through the method of spatial-temporal comparison,it is determined that in late Paleogene,both the activity of boundary faults and the depression effect of the whole sag increased simultaneously.Under the combined control of‘two important elements’from the intense fault activity and the acceleration of basement subsidence,the subsidence center and depocenter both migrated away from the boundary faults and developed in the central of the sag,which resulted in the development of wide distribution of deep lacustrine facies in Dongying formation and accumulation of thick lacustrine mudstone and turbidity sandbodies.Meanwhile,agreat deal of fan delta in the northern steep slope zone and braided river delta in the southern gentle slope zone deposited,which led to well developed and various reservoirs in Dongying formation.The extra-thick Neogene strata caused source rocks reaching the threshold of hydrocarbon generation and hydrocarbon expulsion,which formed favorable self-generated and self-contained combination.The tectonic movements during the Dongying formation deposition period and Neotectonic movements caused the activation of many synsedimentary faults and reactivation later.These faults effectively connected reservoir bodies with main hydrocarbon kitchen of Es3,Es2,and Es1below and vertically transported the lower hydrocarbon to the reservoir bodies in Dongying formation or even shallower strata.All of these lead to the great potential of hydrocarbon exploration in Dongying formation.