层序演化对滩坝储集层成藏要素与分布的控制作用

湖相滩坝砂体储集层在中国东部渤海湾盆地古近系断陷湖盆演化过程中广泛发育。湖盆滩坝体系的形成与分布控制因素较多,着重讨论了层序地层的发育与演化对滩坝储集层的形成、分布及成藏的控制作用:构造层序控制了滩坝形成与发育时期;滩坝体系主要形成于断陷盆地二级构造层序形成的早期和断坳转换期,分布于三级层序的湖侵体系域;湖平面的升降和沉积物供给控制了滩坝四、五级旋回的形成及构成。滩坝沉积的旋回性是滩坝储集层储盖组合形成、分布以及储集层非均质性的重要控制作用之一;四级旋回内较大湖泛泥岩段作为区域或局部盖层,控制了滩坝储盖组合的形成与发育位置,在总体湖侵背景下,不同储盖组合分布范围与成藏潜力各异。图8参14

Control of sequence stratigraphic evolution on the distribution and hydrocarbon accumulation of beach and bar reservoirs

Beach and bar sandstone reservoirs are widespread in the Paleogene faulted lake basins, Bohai Bay Basin, East China. There are many factors which control the generation and distribution of the beach and bar depositional system. This paper focuses on the control of sequence stratigraphic evolution on the formation, distribution and oil-gas accumulation of beach and bar reservoirs. The formation stage of beaches and bars is controlled by tectonic sequences. Beaches and bars are mainly formed in the early stage of the formation of second-order tectonic sequences and in the transitional period from fault to sag. They are the important component part of the transgressive systems tract of third-order sequences. Lake level fluctuation and sediment supply control the formation and composition of fourth- and fifth-cycles of beaches and bars. The depositional cyclicity of beach and bar is an important factor controlling the formation and distribution of reservoir and seal assemblage and the heterogeneity of beach and bar reservoirs. The flooding mudstone interval in the fourth-order cycle acts as local or regional seal and also controls the formation and development of reservoir-seal assemblage. Reservoir-seal assemblages are varying in distribution and hydrocarbon potential.