Modelling of stress disturbance due to hydraulic fracturing on RVE

Stress disturbance is a companying behavior with hydraulic fracturing volumetric opening,and has great effects on the unconventional gas production. In the present paper, in order to establish a theoretical model of stress disturbance on RVE,firstly,a numeric simulation on the meso-mechanism of stress disturbance is executed,by which,the skeleton of porous media are divided into neck and root according to the different stresses, that in the neck,the effective stress is generated,and in the root,the total stress is generated,which is sum of the initial in-situ stress and the stress disturbance. Next,the basic principle of effective stress change inducing hydraulic fracturing volumetric opening is clarified. and then,based on which,and using the compatibility of deformation,the stress disturbance model is established. The advantage of the model is that it can incorporate the effect of hydraulic fracturing propagation regimes on stress disturbance,which is the basic physics of hydraulic fracturing. Example shows that:① total stress is affected strongly by hydraulic fracturing regimes,and shows differentiation along fracture opening and parallel to fracture plane. For example,in viscosity dominated regimes,the peak stress σ_1max is about 2 times static stress,and falls to 0.93 times when fracture opening attains;while the peak stress parallel to facture plane σ_2,3max,is 2 times static stress and no stress falls in steady state. But in toughness dominated regimes,σ_1max is about 1.7-2. 7 times static stress,and falls to 0.59-0.73 times when steady fracture opening attains;while σ_2,3max is 2.19-2.91 times static stress and no stress falls. ② the most important feature that hydraulic fracture different from the anhydrous conditions is that,fluid leak-off plays the part of enhancing the glutinousness of fracture,and thus ad reducing fracture brittleness,which,therefore,contributes to larger hydraulic fracture opening and total stress differentiation along fracture opening and parallel to fracture plane.