ABSTRACT:

Hydraulic fracturing induces formation response accompanying with complex fracture network. The extreme formation response potentially causes unfavorable consequences including wellbore instability, casing failure and fault reactivation etc. It is significant to predict formation behavior induced by hydraulic fracturing for a safe and efficient stimulation. Based on rock mechanic, experiments and micro-seismic events, fracture slip is identified, and casing failure mechanism is revealed. To quantitative evaluation, a hydro-mechanical coupled model is established to predict formation behavior under hydraulic fracturing. The hydraulic and natural fractures are embedded in formation with cohesive zone model. The pore pressure, fracture propagation, effective stress, and deformation of formation are analyzed. Results indicate that the proposed hydro-mechanical coupled model can predict the fracture growth and formation behavior under hydraulic fracturing. The pressurized zone is consistent with the fracture propagation. The effective stress along the wellbore fluctuates with time and space, which becomes lower at the location around fractures. The horizontal and vertical displacements along the wellbore increase during injection and decreases after shut-in. Especially, a distinct shear slip arises at the crossing point between the inclined natural fracture and horizontal wellbore. The well barrier will be subjected to the tensile and shear loads. The research findings can be applied to predict formation response and assess well integrity under hydraulic fracturing.

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