天然裂缝性储层压裂液滤失研究

裂缝性储层压裂液滤失对裂缝的几何尺寸、支撑剂的分布都有较大的影响。现有裂缝性储层压裂液滤失模型都对天然裂缝进行了简化处理，认为天然裂缝对基质均匀切割，这与实际不符，不能准确反映裂缝分布的非均质性对压裂液滤失的影响。基于储层裂缝统计资料，应用概率统计、随机理论、Monte–Carlo 等方法，建立储层二维离散裂缝网络模型，并借助等效渗透率张量原理将裂缝性介质转化为均质各向异性连续介质，建立了基于渗透率张量的裂缝性储层压裂液滤失数学模型。计算结果表明，天然裂缝分布及其与水力裂缝的位置关系的不同使得沿裂缝长度方向，滤失速度变化较大，若天然裂缝与水力裂缝连通，则压裂液滤失主要发生在连通处，文中模拟了天然裂缝和人工裂缝存在三处连通的情况，这三处的滤失量占裂缝总滤失量的45% 以上，建议对天然裂缝进行封堵。

A Study on Fracturing Fluid Leak-off in Naturally-fractured Reservoirs

Fracturing fluid leak-off in naturally fractured reservoirs has a great impact on fracture geometry and proppant placement. Existing fractured reservoir fracturing fluid loss models all simplified natural fractures，considering that natural fractures cut evenly on the matrix，which does not truly reflect the effect of heterogeneity of fracture distribution on fracturing fluid loss effects. Based on reservoir fracture statistics and by applying probability and statistics stochastic theory，Monte-Carlo and other methods，the two-dimensional discrete fracture network model of the reservoir was established. And on this basis，by translating fractured media into homogeneous anisotropic continuum medium，we established fracturing fluid filtration model of fractured reservoir. The results show that along the direction of fracture，fracturing fluid filtration rates vary widely due to the distribution of natural fractures and its positional relationship with hydraulic fracture. If natural fractures connects with hydraulic fracture，the fracturing fluid loss occurs mainly in the connected department. This paper simulates the three artificial connections filtration，which account for 45% loss in total. Therefore，it is recommended to seal natural fractures in fractured reservoir fracturing.