Hydraulic fracture extension characteristics of fractured formation based on phase field method

YI Liangping; ZHANG Dan; YANG Ruoyu; XIAO Jialin; LI Xiaogang; YANG Zhaozhong

doi:10.13809/j.cnki.cn32-1825/te.2022.04.008

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Hydraulic fracture extension characteristics of fractured formation based on phase field method
Issue 4, Pages: 604-616(2022)
Published：2022
DOI： 10.13809/j.cnki.cn32-1825/te.2022.04.008
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DOI：

YI Liangping, ZHANG Dan, YANG Ruoyu, et al. Hydraulic fracture extension characteristics of fractured formation based on phase field method[J]. Petroleum Reservoir Evaluation and Development, 2022, (4): 604-616. DOI： 10.13809/j.cnki.cn32-1825/te.2022.04.008.

摘要

基于相场法理论建立了多孔弹性地层中压裂裂缝延伸模型，在该模型中，流体流动遵循达西定律，岩石的渗透率各向异性，且是岩石最大主应变的函数。通过3个不同时间步长算例验证了模型的收敛性，并基于建立的模型，研究了原地应力差、相交角、注入速率和压裂液黏度对水力裂缝与天然裂缝相交后延伸轨迹的影响。研究表明：（1）水力裂缝只能开启天然裂缝的一翼；（2）相交角和原地应力差越小，水力裂缝越容易开启天然裂缝；（3）提高注入速率有利于完全开启天然裂缝，因此，压裂施工过程中，在井口装备和地下管柱强度允许的条件下应尽量提高施工排量；（4）注入压力随注入速率和流体黏度的增加而增加。最后通过将研究模型模拟结果和前人物理模拟实验结果进行对比，验证了模型的可靠性。

Abstract

Based on the theory of phase field method

a model of fracture propagation in porous elastic formation is established. In the proposed model

the fluid flow in the porous rock obeys Darcy’s seepage law

and the permeability of rock is anisotropic and a function of the maximum principal strain. The convergence of the model is verified by comparing the results of three different time steps cases. Meanwhile

based on the proposed model

the effects of the in-situ stress difference

intersection angle

injection rate

and fracturing fluid viscosity on the intersection behaviour of hydraulic and natural fractures are investigated. The results indicate that: ① The hydraulic fracturing can solely make one side of the natural fracture open; ② The smaller the intersection angle and in-situ stress difference

the easier the hydraulic fracture is to open the natural fracture; ③ Increasing injection rate is beneficial to completely open the natural fractures

therefore

in the process of fracturing construction

the construction displacement should be increased as much as possible under the conditions of wellhead equipment and underground string strength; ④ The injection pressure increases with the increase of injection rate and fluid viscosity. Finally

the reliability of this model is verified by comparing the simulation results of this model with those of previous laboratory experiments.