Study of interaction mechanisms between multiple parallel weak planes and hydraulic fracture using the bonded-particle model based on moment tensors

Outcrop and core observations show that discontinuities are well developed in unconventional reservoirs. Presence of these discontinuities can have beneficial or detrimental effect on hydraulic fracturing behaviors. Previous studies summarized several interaction modes between hydraulic fracture and a single-weak plane based on a large number of laboratory tests and theoretical analysis. In some cases, the reservoir contains a considerable number of parallel weak planes that make the fracture propagation more complex. The interaction mechanisms between hydraulic fracture and parallel weak planes remain unclear. In the present study, a bonded-particle model (BPM) coupling fluid-mechanical is used to study the driven force of those interactions. Moment tensor inversion is used to analyze the failure mechanisms of those weak planes. The results indicate that as the number of weak plane increases, the interaction mode becomes complex. Several modes (e.g. arrested, arrested with offsetting, crossing, and crossing with offsetting) are observed in the multiple parallel weak planes contained models. The interaction mode is closely related to a stress concentration around the intersection area between hydraulic fracture and weak planes. The arrested or crossing with offsetting mode is mainly caused by the shear slippage of the weak plane through moment tensor inversion analysis.