Computational Fracking: 3D Numerical framework for multiphysics modelling of propagating fractures in rock

计算水力压裂：岩石传播裂缝多物理场建模的 3D 数值框架

• 批准号: 323760362
• 负责人: Professorin Dr. Xiaoying Zhuang
• 金额: --
• 依托单位: Institut für Photonik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/323760362?language=en
• 关键词: Computational; Fracking; 3D; Numerical; framework

Advances in underground exploration technology made in recent years have allowed for developments at great depth of subsurface rock for unconventional gas/oil mineral exploitation. For example, recent advances in hydraulic fracturing (HF) have allowed for commercially viable extraction of oil/gas from deep underground shale formations previously deemed uneconomical to exploit. However, the use of HF in unconventional oil/gas extraction has generated controversy, so that several countries have imposed moratorium on its use for unconventional hydrocarbon extraction. Opponents of HF claim that its use poses severe environmental risks such as contamination of groundwater resources, that it depletes freshwater supply and induces seismicity. To gain a better understanding of the HF-process, the applicant proposes to develop, implement, verify and validate a 3D computational multiphysics framework. The HF model should allow for fluid flow through porous media and discrete cracks for evolving complex three-dimensional fracture patterns such as crack branching and crack coalescence. It should be applicable to model at least two stages. The extended finite element method (XFEM) will be employed and devised to model the fluid flow through the fracturing network. Smaller fractures will be accounted for by a porous media model that links the permeability to the porosity which in turn depends on an anisotropic damage tensor. Phenomena including the increase of pore pressure across the discontinuity, the fluid lag, the fracture opening by the proppant particles and the crack induced permeability increase will be taken into account. The proposed computational framework will be validated by comparison to experiments and site data to be collected. Parameter studies will be performed in order to answer some of the most pressing issues in HF, e.g. the interaction between fracture networks at different stages, the possibility of the fracture network encroaching into adjacent layers of rock or the interaction of fractures with existing natural faults that intersect the shale seam, to name a few.

近年来，地下勘探技术的进步已经允许在地下岩石的大深度处进行开发，以进行非常规油气矿产开采。例如，水力压裂（HF）的最新进展已经允许从以前被认为开采不经济的深地下页岩地层中商业上可行地提取油/气。然而，HF在非常规石油/天然气开采中的使用产生了争议，因此一些国家已经暂停其在非常规烃类开采中的使用。HF的反对者声称，它的使用会造成严重的环境风险，例如污染地下水资源，耗尽淡水供应并引发地震活动。为了更好地理解HF过程，申请人提出开发、实施、验证和确认3D计算多物理场框架。HF模型应考虑流体流过多孔介质和离散裂缝，以形成复杂的三维裂缝模式，如裂缝分支和裂缝合并。它应该适用于至少两个阶段的模型。扩展有限元法（XFEM）将被采用和设计来模拟流体通过压裂网络的流动。较小的裂缝将由多孔介质模型来解释，该模型将渗透率与孔隙度联系起来，而孔隙度又取决于各向异性损伤张量。将考虑的现象包括孔隙压力的增加跨越不连续性，流体滞后，裂缝开口的支撑剂颗粒和裂缝诱导的渗透率增加。建议的计算框架将通过与实验和现场数据的比较进行验证。将进行参数研究，以回答HF中一些最紧迫的问题，例如，不同阶段裂缝网络之间的相互作用，裂缝网络侵入相邻岩石层的可能性，或裂缝与页岩层相交的现有天然断层的相互作用，仅举几例。