A continuum non-local damage-transport model for hydraulic fracturing

We present a novel non-local damage-transport model for hydraulic fracture in porous media. The new model is sought to provide an enhanced description for the long-range damage and transport interactions in the fracture process zone. The model is derived from thermodynamic principles, leading to a non-local transport description and reliable damage growth via a permeability-stress relationship. The modeling approach prescribes Darcy flow inside and outside the fracture zone, which preserves the continuity of all quantities within the domain and eliminates the stress discontinuities at fracture boundaries. This continuum definition is obtained through a non-linear permeability constitutive law that allows for elevated fluid velocity in the crack zone. In order to verify the model validity, the proposed model is used to simulate hydraulic fracture propagation. The verification process confirms that the model can predict: pressure development in initial stage, pressure development in wellbore pressurization stage, breakdown pressure, and pressure decline post end of pumping. In addition, the model captures the variation of elevated fluid flow speed inside the hydraulic fracture. The significance of the non-local transport modeling is demonstrated through modeling hydraulic fracturing in materials with pre-existing high permeability zones and multiple concurrently propagating hydraulic fractures. The incorporation of non-local transport effects in hydraulic fracture modeling is proved to uncover possible flow paths through preexisting high permeability zones. In addition, the model provides a physical basis for the prediction of the formation of frac-hits growing between fractures. This model provides a new approach for well optimization and cluster design. Improving the prediction and minimization of frac-hits effects can lead to substantial increase in recovery rates and more economic hydraulic fracturing.