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

Abstract

Thermo‐hydro‐mechanical‐chemical (THMC) interactions are prevalent during CO2 geological sequestration (CGS). In this study, a sequential coupling THMC numerical simulation program was constructed, which can be used to explore the following issues of CGS: fluid and heat flow, solute transport; stresses, displacements and rock failures related to geo‐mechanical effects; equilibrium and kinetic chemical reactions; chemical damage to mechanical properties of the rock. Then, the coupling program was applied to the Ordos CGS Project to study the formation response under the multi‐field interaction caused by CO2 injection. The simulation results show that the mechanical process dominates the short CO2 injection period. Specifically, the formation's permeability near the injection well increases by 43%, due to the reduction of effective stress, which significantly promotes the lateral migration of CO2. When the injection rate exceeds 0.15 million tons per year, the cohesion of the reservoir rock is not enough to resist the shear force inside the rock and rock failure may occur. During the subsequent long‐term sequestration period (200 years), the influence of mineral reactions gradually increases. Due to calcite dissolution, the shear modulus of caprock is predicted to decrease by 7.6%, which will to some extent increase the risk of rock failure.

Long‐term CO2 sequestration mechanisms and influence of injection mode in Zhujiang Formation of Pearl River Mouth Basin

“…The reaction equation of minerals can be viewed in the GEM manual. The parameters for the reactive‐surface area and kinetic rate law were obtained from previous studies, 25,46,48,49 which have been widely used and proved to be suitable. The porosity and permeability would be changed by mineral dissolution and precipitation, which were calculated as follows: $$$$\begin{equation}{\hat{\phi }}^* = {\phi }^*\ - \mathop \sum \limits_{j\ = \ 1}^{{n}_m} \left( {\frac{{{N}_j}}{{{\rho }_j}} - \frac{{N_j^0}}{{{\rho }_j}}} \right)\end{equation}$$$$ $$$$\begin{equation}\phi \ = {\hat{\phi }}^*\ \left[ {1 + {c}_\emptyset \left( {p - {p}^*} \right)} \right]\end{equation}$$$$ $$$$\begin{equation}\frac{k}{{{k}_0}} = {\left( {\frac{\phi }{{{\phi }^*}}} \right)}^3\ \cdot {\left( {\frac{{1 - {\phi }^*}}{{1 - \phi }}} \right)}^2\end{equation}$$$$where $$\phi $$ is the porosity, $${\phi }^*$$ is the reference porosity without mineral precipitation/dissolution, $${\hat{\phi }}^*$$ is the reference porosity including mineral precipitation/dissolution, $${N}_j$$ is the total moles of mineral …”

Hydrogeochemical characteristics, driving factors, and health risk assessment of karst groundwater in Southwest Hubei Province, China

“…Indeed, karst underground rivers are the main water source for industrial and agricultural purposes in southern karst areas. Compared with surface water, both the development and exploitation of karst underground river resources are relatively convenient because of their high water flow rates and frequent exchange with surface water bodies (Fan et al, 2023; Wang et al, 2023; Yu et al, 2023). However, groundwater resources are more susceptible to anthropogenic activities and associated pollutant emissions (Jiang et al, 2019; Jiang, Liu, et al, 2022).…”