Effect of vugs on hydraulic fracture propagation with phase field method

The interaction between hydraulic fracture and vugs affects the formed fracture pattern, which is of great significance for developing carbonate reservoirs efficiently. To investigate the effect of vugs on hydraulic fracture propagation, a hydromechanical coupling model is established based on the phase field method. Fluid flow in the porous media with vug is described by using phase field indicator functions. The pressure, displacement, and phase fields are solved by finite element approximation and iterative method, and the proposed model is validated against analytical solution. Some influencing factors including vug geometry and property are analyzed, and results show that the vug has important impact on hydraulic fracture propagation. The fracture diverts to the vug, and it could propagate across a small vug but be arrested by a large vug. As the distance between fracture and vug increases, the effect becomes weaker until it disappears. Besides, the modulus of vug fillings determines the fracture propagation pattern. The increase of vug filling modulus makes the fracture direct crossing difficult. The study could provide some guidance for hydraulic fracturing design of carbonate reservoirs.