井打在溶洞外的缝洞型油藏数值试井模型
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摘要
缝洞型碳酸盐岩油藏多发育大尺度的溶洞和裂缝,非均质性极强。这类油藏不能使用常规的连续介质理论描述。根据缝洞型碳酸盐岩油藏的特征,结合地震、地质等资料,建立了井未钻遇溶洞的缝洞型碳酸盐岩油藏数值试井物理数学模型。利用有限元方法对模型进行求解并绘制了试井样版曲线,对影响井底压力动态的主要因素进行了分析。研究表明:当井打在洞外时,由于洞内的渗透性远优于洞外地层,压力导数曲线后期出现明显下掉,溶洞的尺寸主要影响压力导数曲线的下掉幅度。模型解释结果与实测数据对比分析表明,该试井模型具有较高的预测精度,能够为碳酸盐岩油藏的试井分析提供理论指导。
Conventional continuous multiple medium theories are not suitable for describing the fractured- cavernous carbonate reservoir with big- size fractures and caves. An interpretation model for well test of naturally fractured vuggy reservoir has been developed with consideration of wells drilled outside a big cavity. The model equations are solved with the finite-element method. The analysis of the affecting factors of dynamic pressure at well bottom indicates that the pressure derivative curve of the late stage will go down and form a concave because of the high permeability of the cave. The scale and permeability of the cave mainly affect the amplitude of the pressure derivative reduction. The predicted model has a good agreement with the field test. This can provide a theoretical basis and guidance for well test interpretation of carbonate reservoir.
Conventional continuous multiple medium theories are not suitable for describing the fractured- cavernous carbonate reservoir with big- size fractures and caves. An interpretation model for well test of naturally fractured vuggy reservoir has been developed with consideration of wells drilled outside a big cavity. The model equations are solved with the finite-element method. The analysis of the affecting factors of dynamic pressure at well bottom indicates that the pressure derivative curve of the late stage will go down and form a concave because of the high permeability of the cave. The scale and permeability of the cave mainly affect the amplitude of the pressure derivative reduction. The predicted model has a good agreement with the field test. This can provide a theoretical basis and guidance for well test interpretation of carbonate reservoir.
引文
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[2]Barenblatt G I,Zheltov J P,Kochina I N.Basic concepts in the theoryof seepage of homogeneous liquids in fissured rocks strata[J].Journal ofApplied Mathematics and Mechanics,1960,24(5):852-864.
[3]Warren J E,Root P J.The behavior of naturally fractured reservoirs[J].Society of Petroleum Engineers Journal,1963,3(3):245-255.
[4]Closmann P J.An acquifer model for fissured reservoir[J].Society ofPetroleum Engineers Journal,1975,15(5):385-398.
[5]刘慈群.三重介质弹性渗流方程组的精确解[J].应用数学和力学,1981,2(4):419-424.Liu Ciqun.Exact solution for the compressible flow equations through amedium with triple-porosity[J].Applied Mathematics and Mechanics,1981,2(4):419-424.
[6]吴玉树,葛家理.三重介质裂-隙油藏中的渗流问题[J].力学学报,1983,19(1):81-85.Wu Yushu,Ge Jiali.The transient flow in naturally fractured reservoirs withthree-porosity systems[J].Acta Mechanica Sinica,1983,19(1):81-85.
[7]常学军,姚军,戴卫华,等.裂缝和洞与井筒连通的三重介质油藏试井解释方法研究[J].水动力学研究与进展,2004,19(3):339-346.Chang Xuejun,Yao Jun,DAI Weihua,et al.The study of well testinterpretation method for a triple medium reservoir[J].Journal ofHydrodynamics,2004,19(3):339-346.
[8]Snow D T.Anisotropie permeability of fractured Media[J].WaterResources Research,1969,5(6):1273-1289.
[9]Neale G H,Nader W K.The permeability of a uniformly vuggy porousmedium[J].Society of Petroleum Engineers Journal,1973,13(2):69-74.
[10]李亚军,姚军,黄朝琴,等.裂缝性油藏等效渗透率张量计算及表征单元体积研究[J].水动力学研究与进展,2010,25(6):1-7.Li Yajun,Yao Jun,Huang Zhaoqin,et al.Calculation of equivalentpermeability tensor and study on representative element volume formodeling fractured reservoirs[J].Journal of Hydrodynamics,2010,25(6):1-7.
[11]徐轩,杨正明,祖立凯,等.多重介质储层渗流的等效连续介质模型及数值模拟[J].断块油气田,2010,17(6):733-737.Xu Xuan,Yang Zhengming,Zu Likai,et al,Equivalent continuousmedium model and numerical simulation of multimedia reservoir[J].Fault-Block Oil&Gas Field,2010,17(6):733-737.
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