Granular LCM migration and plugging behavior in shear-slip fractures

The redistribution of in-situ stress around the wellbore while drilling fractured reservoir is likely to induce fracture shear-slip and causes fracture deformation, consequently leading to changes in fluid flow, LCM (Lost circulation material) particles migration, and plugging in the fracture. In this work, the effects of mechanical shear on fluid flow anisotropy, LCM particles migration, and plugging in rough fractures were studied by numerical simulation. The simulation results show that the flow capacity in fracture generally goes up with the increase of the shear displacement, but when the fracture surfaces are extremely rough, the flow capacity in the fracture changes significantly. Both fracture permeability and LCMs plugging behavior show anisotropy, the particle-laden flow velocity in the direction perpendicular to the shear displacement greatly increases, making it more difficult for the LCMs to form effective plugging. The larger normal stress in shear fractures inhibits shear dilation, and circulation loss in the shear fracture is smaller, so it is easier for LCMs to form plugging in the shear fracture. In general, fracture shear slip is one of the important factors accounting for the drilling fluid loss and difficult plugging. But proper shear slip may be conducive to the plugging of coupling fractures and strengthening boreholes.