A hydro-mechanical-damage fully coupled cohesive phase field model for complicated fracking simulations in poroelastic media
A hydro-mechanical-damage fully coupled cohesive phase field model for complicated fracking simulations in poroelastic media
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DOI：
10.1016/j.cma.2022.115451
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发表时间：
2022-09
影响因子：
7.2
通讯作者：
Hui Li;Hongwu Lei;Zhenjun Yang;Jianying Wu;Xiaoxian Zhang;Shouding Li
中科院分区：
文献类型：
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作者：
Hui Li;Hongwu Lei;Zhenjun Yang;Jianying Wu;Xiaoxian Zhang;Shouding Li
建立了一种模拟多孔弹性介质中复杂准脆性破裂的流体-力学-损伤耦合数值方法。基于毕奥的孔隙弹性理论，建立了裂缝宽度与渗透率相关的统一流体连续性方程，用于裂缝和多孔介质中流体流动的同时模拟。将流体压力耦合到相场正则化凝聚区模型的控制方程中，该模型可以自动预测准脆性多裂纹的萌生、成核和扩展，而无需重新网格化、裂纹跟踪或其他方法所需的辅助场。在有限元框架内实现交替最小化牛顿-拉夫森迭代算法，以解决上述三场耦合问题的节点自由度的位移，流体压力和损伤。该方法首先验证了三个问题的解析解，一个问题的实验结果，和两个裂纹合并问题的数值结果在已发表的文献中，在注入的流体压力，裂纹宽度和长度的时间演变，并最终裂纹路径。然后模拟了具有平行水力裂缝和随机天然裂缝的水平井筒压裂问题，详细研究了射孔间距、数量和角度的影响。结果表明，该方法能够模拟均质介质和含天然裂缝的非均质介质中复杂的多裂缝压裂，为页岩油气开采的压裂设计优化提供了一种新的方法。
A hydro-mechanical-damage fully coupled numerical method is developed for simulations of complicated quasi-brittle fracking in poroelastic media. A unified fluid continuity equation with crack-width dependent permeability, based on the Biot’s poroelastic theory, is used for simultaneous modeling of fluid flow in both fractures and porous media. The fluid pressure is coupled into the governing equations of the phase-field regularized cohesive zone model, which can automatically predict quasi-brittle multi-crack initiation, nucleation, and propagation without remeshing, crack tracking, or auxiliary fields as needed by other methods. An alternate minimization Newton–Raphson iterative algorithm is implemented within the finite element framework to solve the above three-fields coupled problem with nodal degrees of freedom of displacements, fluid pressures, and damages. The method is first validated by three problems with analytical solutions, a problem with experimental results, and a two-crack merging problem with numerical results in published literature, in terms of time evolutions of injected fluid pressures, crack widths and lengths, and final crack paths. Horizontal wellbore fracking problems with parallel hydraulic cracks and random natural fractures are then simulated, with the effects of spacing, number, and angle of perforations investigated in detail. It is found that the developed method is capable of modeling complex multi-crack fracking in both homogeneous media and heterogeneous media with natural fractures, and is thus promising for fracking design optimization of practical exploitation of shale gas and oil.