An Integrally Embedded Discrete Fracture Model with a Semi-Analytic Transmissibility Calculation Method

Shao, Renjie; Di, Yuan

doi:10.3390/en11123491

Cited by 14 publications

(4 citation statements)

References 36 publications

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“…However, this approach only accounts for the case of two intersecting fractures 46 . Shao and Di 47 developed the integrally embedded discrete fracture model (iEDFM), which improves pressure calculation for intersecting fractures and accuracy of the pressure gradient in the matrix by lowering the number of elements by grouping them and applying a semi‐analytic transmissibility equation to matrix‐fracture connections.…”

Section: Introductionmentioning

confidence: 99%

Consistent treatment of shear failure in embedded discrete fracture models using XFVM

Conti,

Deb,

Matthäi

et al. 2023

Num Anal Meth Geomechanics

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Understanding deformations and fluid flow in fractured rocks is of central importance for many subsurface flow applications. Thus, numerical frameworks are needed that capture the coupled mechanical and hydraulic behaviour, including scenarios with complex fracture networks. This paper employs the extended finite volume method to represent fracture manifolds in a poroelastic matrix domain and to compute shear and tensile displacements of fracture segments. However, using embedded fractures with non‐conforming grids can lead to severe convergence issues while computing shear slip and tensile opening of intersecting and parallel fractures, particularly if they have similar slopes. Our proposed solution of this problem is to slightly deform the fracture geometry by merging critical segments. We discuss and show examples of which attributes the merged segment has to adopt to ensure the correct slip behaviour at an intersection. Thereby it is crucial that the flow topology remains unaltered. Analysing failures of kinked fractures and fracture intersections show the flexibility of the devised algorithm. Moreover, it is demonstrated that deformation and opening patterns of a natural network with more than 200 fractures are qualitatively predicted very well. This method is a simple solution to treat multiple fracture segments in a grid cell, hence it can be used for any model embedding fractures in non‐conforming grids.

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Section: Introductionmentioning

confidence: 99%

Consistent treatment of shear failure in embedded discrete fracture models using XFVM

Conti,

Deb,

Matthäi

et al. 2023

Num Anal Meth Geomechanics

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“…Traditional EDFM cannot precisely model the anisotropic flow between fracture and matrix due to the oversimplified linear pressure distribution assumption applied in the EDFM [30]. Shao et al [31,32] developed an integrally embedded discrete fracture model (IEDFM), where fractures are envisioned as series of point sinks to derive the semianalytical pressure distribution around the fractures. e IEDFM allows for the calculation of matrix-fracture connection transmissibilities considering the anisotropy of rock matrix, which is used to calculate the fluid exchange between the rock matrix and fracture.…”

Section: Introductionmentioning

confidence: 99%

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

2022

Geofluids

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The effect of geomechanics is crucial in the modeling of fractured reservoirs since fractures can be more stress-sensitive than the rock matrix. In fractured reservoirs, the microscale fractures are often homogenized into the matrix continuum leading to matrix permeability anisotropy. The embedded discrete fracture model (EDFM) is becoming increasingly popular for numerical simulation of fractured reservoirs and has been successfully employed in the simulation of coupled geomechanics and flow systems. However, the anisotropic permeability of matrix cannot be considered in traditional EDFM. An approach of coupled geomechanics and flow modeling is proposed for fractured reservoirs considering anisotropic matrix permeability. In order to calculate the fluid exchange between fractures and rock matrix in an anisotropic formation, an integrally embedded discrete fracture model (IEDFM) is used. The geomechanics model of the proposed approach uses an equivalent continuum approach, which introduces an equivalent material to represent the overall deformation of the fractured rock under normal and shear stresses. The constitutive relations of the equivalent continuum are derived rigorously from stress-strain analysis, where the stress-dependent moduli of natural fractures are included. The coupled geomechanics and flow system is solved using the fixed-stress split iterative coupling strategy with the dynamic hydraulic parameters of matrix and fractures updated separately. Several examples are performed to demonstrate the applicability of the proposed approach for modeling the coupled geomechanics and flow system in fractured reservoirs considering anisotropic permeability. The effect of anisotropy is investigated, which indicates that the dynamic behavior of a fracture is highly orientation-related due to initial stress anisotropy and matrix permeability anisotropy. Simulations also show that the anisotropic matrix permeability affects the compaction in the reservoir domain, which reflects on the performance of production.

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“…e oversimplified assumption in the EDFM may lead to errors in calculating the transmissibilities of matrix-fracture connections [29]. An integrally embedded discrete fracture model (IEDFM) [30] has been proposed to improve the transmissibility calculation of the EDFM. In the IEDFM, the transmissibilities of matrix-fracture connections are derived semi-analytically, which obtains the more realistic pressure distribution near the fracture surfaces and improves the accuracy of modeling flow in fractured reservoirs.…”

Section: Introductionmentioning

confidence: 99%

A New Projection-Based Integrally Embedded Discrete Fracture Model and Its Application in Coupled Flow and Geomechanical Simulation for Fractured Reservoirs

2022

Geofluids

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The embedded discrete fracture model (EDFM) has been popular for the modeling of fractured reservoirs due to its flexibility and efficiency while maintaining the complex geometry of fracture networks. Though the EDFM has been validated for single-phase flow simulations, some recent cases show that the EDFM might result in apparent errors in multiphase flow situations. The projection-based embedded discrete fracture model (pEDFM) and the integrally embedded discrete fracture model (IEDFM) are two recently developed methods, which intend to improve the accuracy of the EDFM. In this study, a projection-based integrally embedded discrete fracture model (pIEDFM) is proposed, which combines the advantages of the pEDFM and the IEDFM. Similar to the pEDFM, the pIEDFM uses a kind of additional connections between fracture and nonneighboring matrix cells to obtain more physically authentic velocity fields. As a significant improvement, a semi-analytical cone-shaped pressure distribution that follows the IEDFM is adopted in the pIEDFM to capture the sharp pressure change near the fracture surfaces. Comparisons with benchmark results and explicit-fracture fine grid simulation results show that the pIEDFM provides accurate solutions using a moderate amount of grids. The proposed pIEDFM is also applied to coupled flow and geomechanical simulation for fractured reservoirs. Comparison of our coupled simulation results with that of the EDFM shows that the pIEDFM is applicable for the coupled simulation, and the different methods for matrix-fracture transmissibility between the pIEDFM and the EDFM may lead to deviations in stress fields predicted by geomechanical modeling, which eventually affects the oil production, water cut, and oil saturation profiles.

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An Integrally Embedded Discrete Fracture Model with a Semi-Analytic Transmissibility Calculation Method

Cited by 14 publications

References 36 publications

Consistent treatment of shear failure in embedded discrete fracture models using XFVM

Consistent treatment of shear failure in embedded discrete fracture models using XFVM

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

A New Projection-Based Integrally Embedded Discrete Fracture Model and Its Application in Coupled Flow and Geomechanical Simulation for Fractured Reservoirs

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