Hydraulic Fracture Height Predictions in Laminated Shale Formations Using Finite Element Discrete Element Method
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AbstractLaminated structures in shale formations typically result in anisotropic elastic properties, including Young's modulus and the Poisson ratio, which highly influence hydraulic fracturing treatment execution. The lamina can confine the hydraulic fracture height growth and they sometimes act as weak interfaces for potential fracture propagation path. Hydraulic fracture geometries are highly affected by these properties. In order to make more accurate prediction of hydraulic fracture pattern, especially fracture height, these factors cannot be ignored.We utilized a recently developed Finite Element-Discrete Element Method (FEDEM) code to simulate the complex fracture propagation in shale formations. This coupled fluid flow and geomechanics simulation can also models multi-fracture, multi well fracture propagation scenarios. For simulating fracture height growth, the bedding planes module (with corresponding mechanical anisotropy properties generation) are incorporated. Both 2D and 3D hydraulic fracture propagation studies can be performed.Our simulation results show that without considering the mechanical anisotropy effect, the treatment design will be corrupted by the inaccurate prediction of fracture height. To be more specific, in typical mechanical anisotropic formation, fracture height is always smaller than the fracture height in mechanical isotropic formation, and the fracture tends to propagate (at least temporarily) along the bedding plane interfaces. Different bedding plane properties, including bedding plane dipping angle, permeability etc., also have strong influence on the predicted fracture height. We also consider fracture height growth in multi fracture schemes. The stress shadowing effects give rise to non-planar vertical growth and possible fracture branching. The simulations show that hydraulic fracture height growth is substantially restricted in laminated formations.This paper provides a framework for more realistic prediction of fracture height and fracture pattern evolution in laminated shale formations exhibiting mechanical anisotropy.
