涠洲11-1油田角尾组低阻油藏成因机理及测井评价方法
FORMING MECHANISM OF LOW RESISITANCE RESERVOIR IN JIAOWEI FORMATION OF WEIZHOU11-1 OILFEILD AND ITS LOGGING EVALUATION
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摘要: 涠洲11-1油田角尾组二段油层普遍具有低电阻率特征,在复杂的地质条件下使得低阻油层与水层的识别难度增大,为此,利用岩心分析化验、录井、测井、构造及试油等资料,从宏观和微观地质因素入手,对该区低阻油层成因机制进行了系统深入的剖析。结果表明,角尾组低阻油层的主要宏观地质成因是构造和沉积特征,它们共同为涠洲11-1地区低阻油层的形成和分布创造了条件;微观低阻成因是在水动力条件较弱的滨海沉积环境下发育的岩性粒度细、泥质含量高、黏土矿物附加导电性以及低幅度构造背景下的高束缚水饱和度所致。在此基础上,结合成因提出了改进后的自然伽马相对值与视地层水电阻率的交会图、改进后的自然电位相对值与深感应电阻率的交会图以及束缚水饱和度—视地层水电阻率的交会图来综合识别低阻油层,结果表明,该方法显著提高了低阻油层的识别能力,展示出良好的应用前景。Abstract: Low resistivity oil reservoirs are common in some oil fields. Due to their complex forming mechanism, it is difficult to identify or separate them from water reservoirs in well logging curves. They are often ignored or misinterpreted. Therefore,it is of great significance to make in-depth study of the formation mechanism of low resistance oil reservoirs so as to select effective methods to identify them in later period for increase in oil reserve and production. Through a comprehensive analysis of research findings,it is found that tectonic and sedimentary characteristics control the formation and distribution of low resistance oil layers in the Weizhou 11-1 oil field from a macroscopic point of view. In terms of microscopic aspects, they are controlled by bound water, lithology, content of clay minerals and specific conductive minerals and other factors. Upon the basis of integrated study, we adopted a variety of methods to identify the low resistance reservoirs, such as, using the relationship between the improved relative gamma values and apparent formation water resistivity,the diagram of improved sp relative versus deep induction resistivity, and the cross plot of irreducible water saturation against apparent formation water resistivity and movable water analysis. The methods are proved effective in improvement of identification of low resistivity reservoirs.