Numerical modeling of fully coupled hydraulic fracture propagation in naturally fractured poro-elastic reservoirs

The effect of a pre-existing natural fracture on the extension of a hydraulically induced fracture has been modeled based on poro-elastic behavior. The approach of Warpiniski and Teufel was adopted to evaluate the fracture propagation that would occur after an induced fracture intersects an existing natural fracture. This two dimensional numerical model will simulate the interaction between an induced propagating fracture and natural fracture. The model departs radically from current models in that poro-elastic behavior is not used, uniform pressure inside the natural fracture was used in practice this is not true and effect of fracture toughness ignored. A modified leak-off model for intersecting fracture based on poro-elasticity is introduced as the leak-off is increased in the intersection. Besides these previous model used startup solution using PKN model. In this model a triple system of wellbore-fracture-formation is considered and the fracture will initiate first then propagate some extent then interact with natural fracture. A poro-elastic solution for the stresses in the interaction zone has been used as a basis for hydraulic/natural fracture interaction criteria. The criteria compares favorably with the experimental results. Comparison of the numerical results with experimental results has shown that the main effect of the natural fractures is the width constriction that occurs when the induced fracture propagates into the natural fracture. Numerical and experimental studies for such propagation indicate a near wellbore width and effective length reduction due to the additional normal stress acting on the plane of the induced fracture Keywords: Hydraulic fracturing; Shear strength; Fracture interaction; Fracture geometry; In-situ stresses; Fracture orientation; Stress regime; In-situ stress; Coupled fluid and poroelastic medium.