Journal: Computational Geosciences

Abbreviation

Comput. geosci

Publisher

Springer

Journal Volumes

ISSN

1420-0597
1573-1499

Description

Filters

Reset filters

Search Results

Publications 1 - 10 of 22
  • Analytical solution and Bayesian inference for interference pumping tests in fractal dual-porosity media
    Item type: Journal Article
    Hayek, Mohamed; Younes, Anis; Zouali, Jabran; et al. (2018)
    Computational Geosciences
  • Simulation of hydro-mechanically coupled processes in rough rock fractures using an immersed boundary method and variational transfer operators
    Item type: Journal Article
    von Planta, Cyrill; Vogler, Daniel; Xiaoqing, Chen; et al. (2019)
    Computational Geosciences
  • Modelling of hydro-mechanical processes in heterogeneous fracture intersections using a fictitious domain method with variational transfer operators
    Item type: Journal Article
    von Planta, Cyrill; Vogler, Daniel; Chen, Xiaoqing; et al. (2020)
    Computational Geosciences
    Fluid flow in rough fractures and the coupling with the mechanical behaviour of the fractures pose great difficulties for numerical modeling approaches due to complex fracture surface topographies, the non-linearity of hydro-mechanical processes and their tightly coupled nature. To this end, we have adapted a fictitious domain method to enable the simulation of hydro-mechanical processes in fracture intersections. The main characteristic of the method is the immersion of the fracture, modelled as a linear elastic solid, in the surrounding computational fluid domain, modelled with the incompressible Navier-Stokes equations. The fluid and the solid problems are coupled with variational transfer operators. Variational transfer operators are also used to solve contact within the fracture using a dual mortar approach and to generate problem-specific fluid meshes. With respect to our applications, the key features of the method are the usage of different finite element discretizations for the solid and the fluid problem and the automatically generated representation of the fluid-solid boundary. We demonstrate that the presented methodology resolves small-scale roughness on the fracture surface, while capturing fluid flow field changes during mechanical loading. Starting with 2D/3D benchmark simulations of intersected fractures, we end with an intersected fracture composed of complex fracture surface topographies, which are in contact under increasing loads. The contributions of this article are as follows: (1) the application of the fictitious domain method to study flow in fractures with intersections, (2) a mortar-based contact solver for the solid problem, (3) generation of problem-specific grids using the geometry information from the variational transfer operators.
  • Analysis and numerical approximation of Brinkman regularization of two-phase flows in porous media
    Item type: Journal Article
    Coclite, Giuseppe M.; Mishra, Siddhartha; Risebro, Nils H.; et al. (2014)
    Computational Geosciences
  • On the upstream mobility flux scheme for two-phase flows in a porous medium with changing rock types
    Item type: Journal Article
    Mishra, Siddhartha; Jaffré, Jérôme (2010)
    Computational Geosciences
  • Modeling of shear failure in fractured reservoirs with a porous matrix
    Item type: Journal Article
    Deb, Rajdeep; Jenny, Patrick (2017)
    Computational Geosciences
    A finite volume-based numerical modeling framework using a hierarchical fracture representation (HFR) has been developed to compute flow-induced shear failure. To accurately capture the mechanics near fracture manifolds, discontinuous basis functions are employed which ensure continuity of the displacement gradient across fractures. With these special basis functions, traction and compressive forces on the fracture segment can be calculated without any additional constraints, which is extremely useful for estimating the irreversible displacement along the fracture (slip) based on a constitutive friction law. The method is further extended to include slip-dependent hydraulic aperture change and grid convergent results are obtained. Further, the change in hydraulic aperture is modeled using an asymptotic representation which respects the experimentally observed behavior of pore volume dilation due to shear slip. The model allows the initial rapid increase in hydraulic aperture due to shear slip and asymptotically approaches a finite value after repeated shearing of a fracture segment. This aperture increase is the only feedback for mechanics into the fluid flow for a linear elastic mechanics problem. The same model is also extended to include poroelastic relations between flow and mechanics solver. The grid convergence result in the case of poroelastic flow-mechanics coupling for flow-induced shear failure is also obtained. This proves the robustness of the numerical and analytical modeling of fracture and friction in the extended finite volume method (XFVM) set-up. Finally, a grid convergent result for seismic moment magnitude for single fracture and fracture network with random initial hydraulic and friction properties is also obtained. The b-value, which represents the slope of seismic moment occurrence frequency decay vs seismic moment magnitude, which is approximately constant in a semi-logarithmic plot, is estimated. The numerical method leads to converged b-values for both single fracture and fracture network simulations, as grid and time resolutions are increased. For the resulting linear system, a sequential approach is used, that is, first, the flow and then the mechanics problems are solved. The new modeling framework is very useful to predict seismicity, permeability, and flow evolution in geological reservoirs. This is demonstrated with numerical simulations of enhancing a geothermal system.
  • XFVM modelling of fracture aperture induced by shear and tensile opening
    Item type: Journal Article
    Conti, Giulia; Matthäi, Stephan; Jenny, Patrick (2024)
    Computational Geosciences
    In reservoir simulation, it is important to understand the mechanical behaviour of fractured rocks and the effect of shear and tensile displacements of fractures on their aperture. Tensile opening directly enhances the fracture aperture, whereas shear of a preexisting rough-walled fracture creates aperture changes dependent on the local stress state. Since fracture dilatation increases reservoir permeability, both processes must be included in a realistic and consistent manner into the mechanical reservoir simulation model. Here, we use the extended finite volume method (XFVM) to conduct flow and geomechanics simulations. In XFVM, fractures are embedded in a poroelastic matrix and are modelled with discontinuous basis functions. On each fracture segment the tractions and compressive forces are calculated, and one extra degree of freedom is added for both the shear and tensile displacement. In this particular XFVM implementation we assume that linear elasticity and steady state fluid pressure adequately constrain the effective stress. In this paper, shear dilation is not calculated a posteriori, but it enters the equations such that aperture changes directly affect the stress state. This is accomplished by adding shear dilation to the displacement gradients and therefore ascertains a consistent representation in the stress-strain relations and force balances. We illustrate and discuss the influence of this extra term in two simple test cases and in a realistic layer-restricted two-dimensional fracture network subjected to plausible in situ stress and pore pressure conditions.
  • Modeling wetting-phase relative permeability hysteresis based on subphase evolution
    Item type: Journal Article
    Khayrat, Karim; Jenny, Patrick (2017)
    Computational Geosciences
    A recently introduced subphase framework for modeling the nonwetting phase relative permeability is extended to the wetting phase. Within this framework, the wetting phase is divided into four subphases, which are distinguished by their connectivity; backbone, dendritic, isolated and corner-film subphases. The subphase saturations evolve according to inter-subphase volume transfer terms, which require modeling. An advantage of distinguishing the subphases is that wetting phase relative permeability relations as functions of these constituent subphases can be developed. In order to develop models for the inter-subphase volume transfer and the wetting phase relative permeability in a strongly wetted system, quasi-static flow simulations in pore networks were conducted to analyze the evolution of the wetting subphases during drainage and imbibition. The simulation results suggest that hysteresis trends apparent in experimentally obtained wetting phase relative permeability curves for Berea sandstone may be explained by accounting for corner-film flow.
  • A finite-volume method with hexahedral multiblock grids for modeling flow in porous media
    Item type: Journal Article
    Lee, S. H.; Jenny, P.; Tchelepi, H. (2002)
    Computational Geosciences
  • Predicting plume spreading during CO2 geo-sequestration: benchmarking a new hybrid finite element-finite volume compositional simulator with asynchronous time marching
    Item type: Journal Article
    Shao, Qi; Matthai, Stephan; Driesner, Thomas; et al. (2021)
    Computational Geosciences
    In this paper, we present the results of benchmark simulations for plume spreading during CO2 geo-sequestration conducted with the newly developed Australian CO2 Geo-Sequestration Simulator (ACGSS). The simulator uses a hybrid finite element-finite volume (FEFVM) simulation framework, integrating an asynchronous local time stepping method for multi-phase multi-component transport and a novel non-iterative flash calculation approach for the phase equilibrium. The benchmark investigates four standard CO2 storage test cases that are widely used to assess the performance of simulation tools for carbon geo-sequestration: (A) radial flow from a CO2 injection well; (B) CO2 discharge along a fault zone; (C) CO2 injection into a layered brine formation; and (D) leakage through an abandoned well. For these applications, ACGSS gives results similar to well-established compositional simulators. Minor discrepancies can be rationalised in terms of the alternative, spatially adaptive discretisation and the treatment of NaCl solubility. While these benchmarks cover issues related to compositional simulation, they do not address the accurate representation of geologically challenging features of CO2 storage sites. An additional 3D application scenario of a complexly faulted storage site demonstrates the advantages of the FEFVM discretisation used in the ACGSS for resolving the geometric complexity of geologic storage sites. This example also highlights the significant computational benefits gained from the use of the asynchronous time marching scheme.
Publications 1 - 10 of 22