Hot dry rock (HDR) hydraulic fracturing propagation and impact factors assessment via sensitivity indicator

Hot dry rock (HDR) is abundant of geothermal energy, without pollution or emissions, thus its mining methods have received extensive attention. Although the predecessors have discussed the law of initiation and propagation of hydraulic cracks comparatively consummate, the sensitivity comparative analysis of parameters (displacement and viscosity of fluids, horizontal in-situ stress difference and elastic modulus of rock mass) is still not mentioned. A three-dimensional fluid-solid coupling hydraulic fracturing model for vertical well is established to analyze the factors which affected crack extension. And a visual expression of the prominence of fracture morphology variation under the effect of factors mentioned above also be exposed. Through the analysis of sensitivity indicator, it is found that, if fracture morphology deform to a certain specific degree under the condition of only one variable parameters, the magnification of viscosity is far greater than the other three. The main crack of HDR is more sensitive to rock elastic modulus than horizontal in-situ stress difference. And the variation of fluid displacement have a greater impact of fracture morphology than viscosity. The results provide a scientific basis and a engineering guidance for the parameter optimization of vertical well hydraulic fracturing in enhanced geothermal system (EGS). (C) 2019 Elsevier Ltd. All rights reserved.