致密油水平井分段压裂裂缝延伸规律数值模拟

Numerical simulation of the fracture extension law for the staged fracturing in the tight-oil horizontal well

簇间距和段内簇数是致密油水平井分段压裂设计的重要参数。为了弄清簇间距和簇数对于致密油水平井压裂裂缝延伸的影响规律,建立了水平井段内多簇压裂数值模型,采用扩展有限元数值模拟了不同簇间距和段内不同簇数条件下的裂缝延伸形态,评价了簇间距和段内簇数对于裂缝延伸的影响。结果表明:随着簇间距的减小,裂缝的偏转程度会增大,同时会对中间裂缝形成抑制,影响中间裂缝的延伸;裂缝平均缝长与簇数的多少呈反比例关系,段内簇数越多,平均缝长越短;外侧裂缝的偏转角度与簇数的多少呈正比例关系,段内簇数越多,外侧裂缝的偏转角度越大。实际监测井底压力和压后产能测试表明,该压裂模型的数值模拟计算结果与实际数据偏差很小(0.5%~7.4%),模拟结果合理。

Cluster spacing and cluster number are important parameters for the design of the staged fracturing for tight-oil horizontal wells. In order to clarify the influences of the cluster spacing and cluster number on the fracturing fracture extension in the tight-oil horizontal wells, the numerical simulating model of the multi-cluster fracturing in the horizontal well intervals was established, the fracture extension patterns under different cluster spacings and cluster numbers within the interval were simulated respectively by the extended finite-element numerical simulation. And moreover the impacts of the cluster spacing & cluster number on the fracture extension were evaluated. The results show that with the decrease of the cluster spacing, the deflection degree of the artificial cracks will increase, at the same time, these conditions will restrict the formation of the intermediate cracks, and moreover the extension of the intermediate cracks will be inhibited;the average length of the cracks is inversely proportional to the number of the clusters, the more the clusters in the interval, the shorter the average length of the fractures;the deflection angle of the outboard fractures is in direct proportion to the number of the clusters,the more the clusters in the segment, the bigger the deflection angle. The bottomhole pressure and postfra productivity tests for the actual measuring wells show that there is little deviation between the mumerical simulation calculted results of the fracturing model and actual data(0.5%-7.4%), so the simulated results are reasonable.