In the sandstone reservoir of ultra-low permeability, high initial water cut often occurs when the oil well is put-ting into operation. To find out the cause, we analyzed the factors affecting initial water cut of this kind of reservoir from macroscopic and microscopic perspectives. Macroscopic factors assessment showed that there was no obvious relationship between the structure of the studied area and the initial water content;the types and physical property of sandstone was in-fluenced by sedimentary microfacies, which led to bigger difference in initial water saturation; a large number of effective pores came into being due to the development of secondary pores, and clastic dissolution particles and authigenic clay ac-companied by the formation of large dissolved pores seriously affected the water saturation;the interlayer was opened after fracturing, which connected the oil bearing space and water bearing space and resulted in bigger difference e of initial water cut. Microscopic factors research showed that the smaller the rock pore throat was, the higher the initial water saturation got; the crude oil could not flow smoothly due to the Jiamin Effect caused by water lock effect caused in the process of drill-ing and fracturing and the water lock effect during drilling and fracturing process and the Jamin effect caused by capillary pressure;micro fractures and start-up pressure gradient were also main factors leading to high initial water content of oil wells.%特低渗透砂岩油藏中经常发生油井投产后初始含水率高的现象, 为了搞清这种现象的成因及机理, 从宏观和微观角度分析了特低渗透砂岩油藏初始含水率的控制因素. 宏观影响因素评价表明: 研究区构造与初始含水率没有明显关系; 沉积微相影响砂岩类型及物性, 从而导致储层原始含水饱和度存在较大差异变大; 次生孔隙的发育, 形成大量的有效孔隙, 伴随着大溶孔形成, 产生的碎屑溶蚀微粒和自生黏土严重影响含水饱和度; 压裂投产压开隔夹层, 沟通了含油和含水空间, 使得初始含水率变化较大. 微观因素研究表明, 岩石的孔喉越细小, 原始含水饱和度越高; 钻井和压裂过程中造成的水锁效应及毛细管压力导致的贾敏效应使得原油无法顺利流动; 微裂缝和启动压力梯度的存在, 也是导致油井初始含水率较高的主要因素.
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