基于三维莫尔圆的裂缝有效性评价方法及应用

复杂储层裂缝评价是储层研究的重要内容。针对复杂储层现今裂缝有效性定量评价的难题,通过阵列声波测井、电成像测井提取的地应力及裂缝参数信息,采用基于临界应力断层假说的三维莫尔圆方法定量分析裂缝有效性的方法,通过井眼周围应力场分布特征,选取合理的地应力模型计算地层三维应力并根据成像测井拾取的裂缝倾角、倾向等属性。在此基础上根据岩石强度理论通过三维莫尔圆计算裂缝面上岩石正应力与切应力,求取岩石裂缝面上的摩擦系数,采用临界应力断层假说定量分析裂缝有效性特征。渤海地区JZ油田应用结果表明,通过三维莫尔圆计算的裂缝摩擦系数能够反映裂缝有效性的差异,与产能匹配较好,可以用于产能分析,是裂缝定量评价的一种有效手段。

Method for fracture effectiveness evaluation based on 3D Mohr Circle and its application

Fracture evaluation in complex reservoir is an important part of reservoir research. Aiming at the difficulties of quantitative evaluation on present fracture effectiveness in complex reservoir, three-dimensional Mohr Circle method based on critical stress fault hypothesis is used to quantitatively analyze fracture effectiveness using geo-stress and fracture parameters acquired by array acoustic logging and resistivity imaging logging. According to the distribution characteristics of stress field around the borehole, a reasonable geo-stress model is selected to calculate the three-dimensional stress of the layer. Moreover, fracture dips, strikes and other properties are collected through imaging logging. On this basis, according to rock strength theory, the normal stress and shear stress of rock on the fracture surface are calculated by three-dimensional Mohr Circle, so as to obtain the friction coefficient of rock fracture surface. The critical stress fault hypothesis is used to quantitatively evaluate fracture effectiveness characteristics. The application in JZ oilfield of Bohai Sea indicate that the friction coefficient calculated by three-dimensional Mohr Circle can reflect the differences in fracture effectiveness, matching well with productivity and able to be used for productivity analysis, so it is an effective method for fracture quantitative evaluation.