The Research on Dynamic Rules of Crack Extension during Hydraulic Fracturing for Oil Shale In-Situ Exploitation

It is a tough problem of low permeability for in-situ exploiting oil shale, while improving low permeability by hydraulic fracturing can generate permeable belts, and this is vital importance for oil exploitation. According to the layer property of oil shale, making full use of cohesive element to simulate, it established mathematical models for hydraulic fracturing and its fracturing rules, then conducted 3D numerical simulation. We can get: the shape of fractures is oval, and fractures extend along different directions are different, due to anisotropic property of oil shale and geostatic stress influenced, shown as from fig.9 to fig.10; the leak-off flow rate of fracturing fluid rises, reduces, and tends to a fixed value shown in fig.11; fracture opening is dependant on the volume and injection velocity of fluid injection and the rules of damage evolution and fracturing opening refer to fig.5, fig.6 and fig.13.