The impact of stress state on the propagation of hydraulic fractures near bedding plane

Hydraulic fracturing is widely used in exploiting coal,oil and gas and the emerging unconventional gas.Controlling the hydraulic fractures expand horizontally in specified strata and confining the number and length of fractures outside the specified strata is an effective way to improve the efficiency of hydraulic fracturing and protect the strata environment.The stress state of bedding plane is one key factor affecting the propagation of hydraulic fractures.With using RFPA^2D-Flow,crack propagation behavior,such as hydraulic cracks initially meet the bedding plane,the maximum crack length along the bedding plane and the hydraulic crack failure mode are simulated under different stress states.The results show that:①Stress environment has no effect on crack expansion when hydraulic cracks initially meet the bedding plane;②the curve of the maximum hydraulic fracture expansion length along the bedding plane and the principal stress ratio is hyperbola;③when the maximum principle stress equals the minimum principal stress,the influence range along the bedding plane caused by hydraulic fracturing reaches the maximum;④ with the increase of the principal stress ratio,the impact of the bedding plane on hydraulic crack expansion gradually reduces and the hydraulic cracks penetrate the bedding plane perpendicularly to the minimum principle stress.