Efficient Coupled Multiphase-Flow and Geomechanics Modeling of Well Performance and Stress Evolution in Shale-Gas Reservoirs Considering Dynamic Fracture Properties

Abstract

Summary Significant conductivity losses of both propped hydraulic fractures and unpropped natural fractures are widely observed by laboratory experiments and field studies in shale-gas reservoirs. Previous studies have not well-considered the effects of dynamic fracture properties, which limit the accurate prediction of well performance and stress evolution. In this study, an efficient coupled flow and geomechanics model is proposed to characterize the dynamic fracture properties and examine their effects on well performance and stress evolution in complex fractured shale-gas reservoirs. In our proposed model, a unified compositional model with nonlinear transport mechanisms is used to accurately describe multiphase flow in shale formations. The embedded discrete fracture model (EDFM) is used to explicitly model the complex fracture networks. Different fracture constitutive models are implemented to describe the dynamic properties of hydraulic fractures and natural fractures, respectively. The finite-volume method (FVM) and finite-element method (FEM) are used for the space discretization of flow and geomechanics equations, respectively, and the coupled problem is solved by the fixed-stress split iterative method. The coupled model is validated against classical analytical solutions. After that, the proposed model is used to investigate the effects of hydraulic-fracture and natural-fracture properties on production behavior as well as pressure and stress evolution of shale-gas reservoirs. With the dynamic fracture properties incorporated, our model can predict the well production more accurately, and provide more realistic stress evolution that is essential for the design and optimization of refracturing and infill-well drilling.

Iteratively Coupled Flow and Geomechanics in Fractured Poroelastic Reservoirs: A Phase Field Fracture Model

“…The injection point is located at the center of the domain and the injection rate was chosen as 2:5e − 4m 2 /s. Although depletion tests can be dealt with straightforwardly in an identical manner, we defer interested readers to the study of geomechanical response during depletion [43,44]. Material parameters were chosen as follows: Young's modulus E = 17 GPa, Poisson's ratio ν = 0:2, matrix bulk modulus K m = 36 GPa, fluid bulk modulus K f = 2:2 GPa, Biot's coefficient α = 0:8, porosity ϕ por = 0:2, permeability k = 9e − 15 m 2 , the initial pore pressure p = 1 MPa, and fluid viscosity μ f = 0:89 mPa • s. For simplicity's sake, the homogeneous Dirichlet/Neumann boundary conditions (i.e.…”

Applying two-grid method on unstructured tetrahedra to study fault stability and surface deformation in multiphase geomechanics

“…As shown in Fig. 2b, the two-grid approach is built on top of a staggered solution algorithm in which the flow and geomechanics subproblems are solved sequentially and iteratively using a fixed stress split iterative scheme [22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,21,46,47,48,49,50,51,52]. The accuracy of the two-grid method has been demonstrated for the classical Mandel's problem [53,54] in our earlier work [21].…”

Coupled Geomechanics and Flow Modeling of Fractured Reservoirs considering Matrix Permeability Anisotropy

“…Sangnimnuan et al [23] presented a coupled flow and geomechanics model using the EDFM to predict stress evolution in unconventional reservoirs during production. Liu et al [24] investigated the effects of hydraulic fracture and natural fracture properties on production behavior as well as pressure and stress evolution of shale gas reservoirs using the EDFM and FEM coupled simulations. Bai et al [25] developed a coupled compositional flow and geomechanics simulator using the EDFM and investigated the effect of confined phase behavior in shale oil reservoirs.…”