“井工厂”压裂模式下水力裂缝动态扩展模拟分析

Simulation analysis of dynamic propagation of hydraulic fracture under“well factory”fracturing mode

随着致密油气等非常规油气资源大规模开发,“井工厂”压裂工艺由于其作业效率高、能够充分利用应力干扰实现复杂裂缝网络等特点而受到青睐。然而,“井工厂”压裂过程中合理井距的选择始终是一个影响压裂效果的难题。以线弹性断裂力学为基础,基于扩展有限元理论构建了致密储层体积压裂多缝干扰延伸动力学模型,以苏里格气田苏平001井组为例,对常规“井工厂”水力压裂和拉链压裂这2种“井工厂”压裂模式下水力裂缝动态扩展规律进行了模拟分析和对比。研究结果表明,受水力裂缝延伸产生的诱导应力场影响,后续裂缝在延伸过程中其延伸方向会发生明显偏转,合理选择井间距离对改善井间诱导应力场对裂缝延伸影响具有重要意义;相对常规“井工厂”压裂模式下,采用拉链压裂能够更好降低井间裂缝干扰对裂缝动态扩展影响,增加水力压裂改造体积;在相同储层条件下,采用常规“井工厂”水力压裂合理井距为水力裂缝长度的1.7~1.8倍,而拉链压裂合理井距则为其1.4~1.5倍。

With the large-scale development of unconventional oil and gas resources such as tight oil and gas,the fracturing technology of“well factory”is gaining popularity because of its high efficiency and the ability to make full use of stress interference to realize complex fracture networks.However,the selection of reasonable well spacing in the fracturing process of“well factory”is always a difficult problem which affects the fracturing.Based on the linear elastic fracture mechanics and the extended finite element theory,a dynamic model of multi-fracture interference extension for volume fracturing in tight reservoirs was constructed.Taking the Suping 001 well group of Sulige gas field as an example,the dynamic extension laws of hydraulic fractures were simulated,analyzed and compared under two“well factory”fracturing modes,namely,conventional“well factory”hydraulic fracturing and zipper fracturing.The results show that under the influence of induced stress field generated by hydraulic fracture extension,the extension direction of subsequent fractures will be significantly deflected during the extension process,and it is important to select the well space distance to improve the influence of induced stress field on fracture extension.Compared with the conventional“well factory”fracturing mode,the zipper fracturing mode can better reduce the influence of the interwell fracture interference on the dynamic extension of fractures and increase the volume of hydraulic fracturing.Under the same reservoir conditions,the reasonable well spacing of conventional“well factory”hydraulic fracturing should be 1.7~1.8 times of the hydraulic fracture length,while that of zipper fracturing is 1.4~1.5 times of the hydraulic fracture length.