Hydraulic Fracture Propagation in Layered Rocks: Research Combining 3D FEM Modeling and Laboratory Experiments

The complex morphology of hydraulic fractures has been reported in layered formations due to the frequent occurrence of bedding. The success of hydraulic fracturing heavily depends on the vertical growth of hydraulic fractures. However, hydraulic fracture propagation in laminated rocks poses a complex problem due to the heterogeneity of the formations and bedding plane properties. This study employs a 3D finite element modeling considering bedding plane properties to simulate hydraulic fracture propagation in multi-lithologic interbedded strata and then validate the results with laboratory experiments. The hydromechanical coupled model proposed in this paper accounting for contact types, bedding friction coefficient and conductivity, rock layer distribution, stress and viscous fluid flow, which can well simulate the mutual interaction between hydraulic fractures and bedding planes. Numerical predictions are in good agreement with true triaxial fracturing experiments conducted. According to the numerical simulation and experiments results, the hydraulic fracture can exhibit one of the following behaviors: it may pass through the interface directly, extend along the interface after turning, or stop before reaching the interface. The results indicate that higher overburden pressure promotes the cross-layer propagation of hydraulic fractures. Only when the coefficient of variation between the vertical stress and the minimum horizontal stress reaches a certain threshold can the fracture penetrate the bedding. Hydraulic fractures may be arrested at the interface due to weak bedding strength or roughness. In the presence of multiple interfaces, hydraulic fractures may propagate along weakly-bonded interfaces with conductivity, which can lead to a decrease in the effective fracture area and a reduced efficiency of hydraulic fracturing. This study conducts further investigations and discussions on the influence of parameters, such as interlayer roughness and strength, interface permeability, on the fracture propagation. This research can provide insights into the mechanics of hydraulic fracture propagation in layered rocks and contribute to the development of unconventional reservoirs with more effective hydraulic fracturing techniques.