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

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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.