Efficient heat exploitation strategies from geothermal systems demand for accurate and efficient simulation of coupled flow-heat equations on large-scale heterogeneous fractured formations. While the accuracy depends on honouring high-resolution discrete fractures and rock heterogeneities, specially avoiding excessive upscaled quantities, the efficiency can be maintained if scalable model-reduction computational frameworks are developed. Addressing both aspects, this work presents a multiscale formulation for geothermal reservoirs. To this end, the nonlinear time-dependent (transient) multiscale coarse-scale system is obtained, for both pressure and temperature unknowns, based on elliptic locally solved basis functions. These basis functions account for fine-scale heterogeneity and discrete fractures, leading to accurate and efficient simulation strategies. The flow-heat coupling is treated in a sequential implicit loop, where in each stage, the multiscale stage is complemented by an ILU(0) smoother stage to guarantee convergence to any desired accuracy. Numerical results are presented in 2D to systematically analyze the multiscale approximate solutions compared with the fine scale ones for many challenging cases, including the outcrop-based geological fractured field. These results show that the developed multiscale formulation casts a promising framework for the real-field enhanced geothermal formations.@en

A multi-physics framework for compositional and non-isothermal two-phase flow in a porous medium is presented which adapts locally the model complexity depending on the physical state. It is based on a sequential (IMPET) solution scheme. As a second adaptive strategy, the simulation grid can be refined locally. This may lead to a mesh with hanging nodes, which is treated by a multi-point flux approximation (MPFA) for improved flux representation. The two adaptivity concepts are employed to simulate a combined subsurface CO2 injection and geothermal application in an existing reservoir, the Tensleep formation.@en

A multi-physics framework for compositional and non-isothermal two-phase flow in a porous medium is presented which adapts locally the model complexity depending on the physical state. It is based on a sequential (IMPET) solution scheme. As a second adaptive strategy, the simulation grid can be refined locally. This may lead to a mesh with hanging nodes, which is treated by a multi-point flux approximation (MPFA) for improved flux representation. The two adaptivity concepts are employed to simulate a combined subsurface CO2 injection and geothermal application in an existing reservoir, the Tensleep formation.@en

A multi-physics framework for compositional and non-isothermal two-phase flow in a porous medium is presented which adapts locally the model complexity depending on the physical state. It is based on a sequential (IMPET) solution scheme. As a second adaptive strategy, the simulation grid can be refined locally. This may lead to a mesh with hanging nodes, which is treated by a multi-point flux approximation (MPFA) for improved flux representation. The two adaptivity concepts are employed to simulate a combined subsurface CO2 injection and geothermal application in an existing reservoir, the Tensleep formation.@en

Discrete-fracture modeling and simulation of two-phase flow in realistic representations of fractured reservoirs can now be used for the design of IOR and EOR strategies. Thus far, however, discrete fracture simulators fail to include a third compressible gaseous phase. This hinders the investigation of the performance of gas-gravity drainage, water alternating gas injection, and blow-down in fractured reservoirs. Here we present a new numerical method that expands the capabilities of existing Black-Oil models for threecomponent - three-phase flow in three ways: i) It utilizes a finite element - finite volume discretization generalized to unstructured hybrid element meshes, ii) It employs higher-order accurate representations of the flux terms, iii) Flash calculations are carried out with an improved equation of state allowing for a more realistic treatment of phase behavior. We illustrate the robustness of this numerical method in .several applications. First, quasi-ID simulations are used to demonstrate grid convergence. Then, 2D discrete fracture models are employed to illustrate the impact of mesh quality on predicted production rates in discrete fracture models. Finally, the proposed method is used to simulate three-component - three-phase flow in a realistic 2D model of fractured limestone mapped in the Bristol Channel, U.K. and a 3D stochastically generated discrete fracture model.@en

Discrete-fracture modeling and simulation of two-phase flow in realistic representations of fractured reservoirs can now be used for the design of improved-oil-recovery (IOR) and enhanced-oilrecovery (EOR) strategies. Thus far, however, discrete-fracture simulators usually do not include a third compressible gaseous phase. This hinders the investigation of the performance of gas gravity drainage, water alternating gas injection, and blowdown in fractured reservoirs. We present a new numerical method that expands the capabilities of existing black-oil models for three-component, three-phase flow in three ways: (a) It uses a finite-element/finite-volume discretization generalized to unstructured hybrid element meshes, (b) It employs higher-order accurate representations of the flux terms, (c) Flash calculations are carried out with an improved equation of state allowing for a more realistic treatment of phase behavior. We illustrate the robustness of this numerical method in several applications. First, quasi-lD simulations are used to demonstrate grid convergence. Then, 2D discrete-fracture models are used to illustrate the effect of mesh quality on predicted production rates in discrete-fracture models. Finally, the proposed method is used to simulate three-component, three-phase flow in a realistic 2D model of fractured limestone mapped in the Bristol Channel, UK, and create a 3D stochastically generated discretefracture model.@en

Discrete-fracture modeling and simulation of two-phase flow in realistic representations of fractured reservoirs can now be used for the design of improved-oil-recovery (IOR) and enhanced-oilrecovery (EOR) strategies. Thus far, however, discrete-fracture simulators usually do not include a third compressible gaseous phase. This hinders the investigation of the performance of gas gravity drainage, water alternating gas injection, and blowdown in fractured reservoirs. We present a new numerical method that expands the capabilities of existing black-oil models for three-component, three-phase flow in three ways: (a) It uses a finite-element/finite-volume discretization generalized to unstructured hybrid element meshes, (b) It employs higher-order accurate representations of the flux terms, (c) Flash calculations are carried out with an improved equation of state allowing for a more realistic treatment of phase behavior. We illustrate the robustness of this numerical method in several applications. First, quasi-lD simulations are used to demonstrate grid convergence. Then, 2D discrete-fracture models are used to illustrate the effect of mesh quality on predicted production rates in discrete-fracture models. Finally, the proposed method is used to simulate three-component, three-phase flow in a realistic 2D model of fractured limestone mapped in the Bristol Channel, UK, and create a 3D stochastically generated discretefracture model.@en