On the hydraulic fracturing in naturally-layered porous media using the phase field method: Fid-Bau Portal

On the hydraulic fracturing in naturally-layered porous media using the phase field method

Zhuang, Xiaoying / Zhou, Shuwei / Sheng, Mao / Li, Gengsheng

Highlights • A phase field framework is applied to investigate hydraulic fracturing in layered media. • No penetration criteria are required atmaterial interfaces. • Hydraulic fractures in the soft to stiff and stiff to soft configurations are investigated. • Different inclination angles of the layer interface are included. • The penetration, singly-deflected, and doubly-deflected scenarios can be predicted by phase field modeling.

Abstract In the hydraulic fracturing of natural rocks, understanding and predicting crack penetrations into the neighboring layers is crucial and relevant in terms of cost-efficiency in engineering and environmental protection. This study constitutes a phase field framework to examine hydraulic fracture propagation in naturally-layered porous media. Biot's poroelasticity theory is used to couple the displacement and flow field, while a phase field method helps characterize fracture growth behavior. Additional fracture criteria are not required and fracture propagation is governed by the equation of phase field evolution. Thus, penetration criteria are not required when hydraulic fractures reach the material interfaces. The phase field method is implemented within a staggered scheme that sequentially solves the displacement, phase field, and fluid pressure. We consider the soft-to-stiff and the stiff-to-soft configurations, where the layer interface exhibits different inclination angles $θ$ . Penetration, singly-deflected, and doubly-deflected fracture scenarios can be predicted by our simulations. In the soft-to-stiff configuration, $θ = 0 °$ exhibits penetration or symmetrical doubly-deflected scenarios, and $θ = 15 °$ exhibits singly-deflected or asymmetric doubly-deflected scenarios. Only the singly-deflected scenario is obtained for $θ = 30 °$ . In the stiff-to-soft configuration, only the penetration scenario is obtained with widening fractures when hydraulic fractures penetrate into the soft layer.