摘要:随着石油工业的发展，低渗透油气藏所占比例越来越大，低渗透砂岩储层中的裂缝能够起到很好的储集和导流作用，对裂缝的研究具有十分重要的意义。牛庄洼陷牛35断块沙三中发育低渗透砂岩，为主要含油层系，前人对研究区低渗砂岩储层中的裂缝研究较少。运用岩心观察、镜下薄片观测及CT扫描技术对牛35块沙三中低渗致密砂岩储层裂缝的发育及演化规律进行研究，得出牛35块宏观裂缝主要发育低、高角度斜交剪切缝，长度在2～20 cm之间，分布间距大，但整体裂缝密度仅为0.27条/m，裂缝很不发育，难以构成有效的裂缝系统；微观裂缝较发育，包括粒内缝和粒间缝，改善了储层的连通性，有助于油气的储集和运移；与牛104井、河125-1井相比，牛35井岩石矿物接触关系更加不稳定，胶结程度更低，更容易在荷载作用下产生裂缝，裂缝由上到下呈辫状发育，裂缝体积随着施加荷载的增大呈线性增加。
关键词: 裂缝/
裂缝演化/
低渗透储层/
沙三中/
牛庄洼陷
Abstract:With the development of the petroleum industry, the proportion of low-permeability oil and gas reservoirs is increasing. Fractures in low-permeability sandstone reservoirs can play a good role in storage and diversion, which is of great significance to the study of fractures. The Middle of the Third Member of Shahejie Formatiom of the Niu35 fault block in Niuzhuang Sag is the main oil-bearing strata with low-permeability sandstones; the previous studies on the fractures in the low-permeability sandstone reservoirs in the study area are less. Scanning technology studies the development and evolution of fractures in low-permeability tight sandstone reservoirs in the middle of the Third Member of Shahejie Formation of the Niu35 fault block. The macroscopic fractures in block Niu35 mainly develop low and high angle oblique shear fractures. The length is between 2~20 cm, and the spacing is large. The overall linear fracture density is only 0.27/m, fractures are not well developed to form an effective fracture system; micro fractures are relatively developed, including intragranular fractures and intergranular fractures, which improve the connectivity of the reservoir and contribute to the accumulation and migration of oil and gas. Compared with the well Niu104 and well He125-1, the mineral contact relationship of well Niu35 is more unstable, and the degree of cementation is lower, and the cracks develop easier under loading in braid shape from top to bottom with the crack volume increases linearly.
Key words:Fracture/
Fracture evolution/
Low permeability reservoir/
Middle of the Third Member of Shahejie Formatiom/
Niuzhuang Sag
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