基于扩展有限元的水平井改进拉链式压裂数值模拟

Numerical simulation of modified zipper-type hydraulic fracture propagation in horizontal wells based on extended finite element method

为了研究水平井改进拉链式压裂的裂缝扩展规律,根据水力压裂流-固耦合理论,采用扩展有限元方法分析改进拉链式压裂过程中簇间距、地应力等因素对各条裂缝扩展形态和缝间诱导应力场的影响。结果表明:裂缝间距越大,簇间应力干扰作用越小,但对每条裂缝的影响程度不同;较大的裂缝间距能够保证压裂后形成的各条裂缝具有相似的形态,且压裂缝的长度更长并能从射孔处向两侧均匀延伸,从而实现储层的均衡开发;地应力差越大,各条裂缝的扩展越均匀,减少了裂缝发生偏转的可能,并能在一定程度上降低邻井裂缝发生沟通的风险。

In order to study the crack propagation of modified zipper-type fractures in horizontal wells, based on the fluid-solid interaction theory, an extended finite element method was utilized to study the influences of fracture cluster spacing, crustal stress, and other factors on the pattern of fracture propagation and the induced rock stress in the process of modified zipper-type fracturing. The results show that large crack spacing can decrease the stress interferences between fracture clusters, while its influence to each crack is different. Large cluster spacing can cause the zipper-type fracturing cracks which have more similar morphology and long length. It also can make the cracks evenly extending from the perforation to both sides in the rock matrix, thus leading to stable development of the reservoirs. Large crustal stress can make the crack propagation more uniformly and reduce the risks of crack deflection. To some extent, it can decrease the risk of crack mergence between two horizontal wells.