Numerical and analytical solutions for the problem of hydraulic fracturing from a cased and cemented wellbore

Numerical and analytical investigations of the hydraulic fracture propagation problem, from a cased and cemented wellbore, have been pursued in this communication. A two-dimensional plane model has been used. Pure bond and pure slip boundary conditions, along the steel/cement and the cement/rock interfaces have been implemented, as two extreme cases. Both the in-plane and the anti-plane problems have been considered. Analytical and numerical methods have been applied to the problem of a straight fracture, while in the curved crack case only a numerical solution has been adopted. Crack turning is found to depend on the elastic properties of the rock in the pure bond case, while in the pure slip case no turning occurs. Results indicate that in the pure slip case, a larger pressure than that of the pure bond case, is required at the first propagation step. Results related to a starter (i.e. at the first propagation step) crack lying parallel to the plane of the maximum remote principal stress while the elastic modulus of the rock varies, indicate that bigger values, for both the pressure and the mode I crack opening displacement (COD) at the open hole, develop in the pure slip case than in the pure bond case. Results concerning a starter crack, inclined at varying angles with respect to the plane of the maximum remote principal stress, show that the mode II COD at the open hole is bigger in the pure bond case than in the pure slip case, for all the angles of inclination