The use of supercritical CO2 in deep geothermal reservoirs as a working fluid: Insights from coupled THMC modeling

A two‐phase flow extended finite element technology modeling CO2 in fractured porous media

“…The XFEM approximations of the pressure equation can be obtained according to Eqns (26)(27)(28)(29). (31) where p i is the pressure of each phase's degrees of freedom for standard nodes; N s (x) and N d (x) are shape functions; p j is the additional degrees of freedom for the pressure of each phase.…”

“…These simulations obtained by software simulators are mainly based on the continuum model 26 and the equivalent continuum model, 27 which regard the natural crack or fault system as a continuum part linked to the porous matrix. However, using the difference of porosity and permeability to distinguish matrix and fracture grid cannot reflect the discontinuity between fracture and matrix, making it difficult to accurately predict parameters such as temperature, pressure, and velocity 28–30 . These parameters affect the saturation state that governs CO 2 distribution and migration through capillary pressure and relative permeability effects 31–34 .…”

“…However, using the difference of porosity and permeability to distinguish matrix and fracture grid cannot reflect the discontinuity between fracture and matrix, making it difficult to accurately predict parameters such as temperature, pressure, and velocity. [28][29][30] These parameters affect the saturation state that governs CO 2 distribution and migration through capillary pressure and relative permeability effects. [31][32][33][34] For this reason, the application of the equivalent medium model in modeling CO 2 geological sequestration in fractured porous media is limited.…”

Numerical Simulation of Thermo‐Hydro‐Mechanical‐Chemical Response Caused by CO2 Injection into Saline Geological Formations: A Case Study from the Ordos Project, China

“…On the basis of the aforementioned simulation methods and simulators, some THMC coupling models have been developed. In most models, chemical and mechanical fields are indirectly linked through hydraulic processes, rather than directly interacting (Xiong et al, 2013;Zhang et al, 2015;Zhang et al, 2016;Tao et al, 2019;Gan et al, 2021). These models show that chemical reactions, mechanical expansion and thermal expansion can lead to significant changes in matrix porosity (or the hydraulic aperture of fractures) and permeability in areas in which fluid and heat are exchanged intensely, such as the zone around CO 2 injection wells or CO 2 -Enhanced Geothermal System (CO 2 -EGS) production wells.…”

Dynamic Response of Gas Recovery Enhancement Efficiency in Coalbed Methane Displacement by Hot Flue Gas: From the Perspective of Thermo–Hydro–Mechanical–Chemical Coupling

“…o o o o o o o o n o o o o o o o o o o o (40) where r cj is the reaction rate of the chemical reaction j in the chemical reaction equation; k c is the effective rate constant of the positive chemical reaction; and k c 1 is the effective rate constant of the reverse chemical reaction.Additionally, both the ionization rate constant and the effective rate constant of the chemical reaction comply with the modified Arrhenius equation and can be described as follows53 …”