Thermo-Hydro-Mechanical (THM) wellbore analysis under sub-zero CO2 injection

A prototype finite element double porous Thermo-Hydro-Mechanical (THM) model that considers elastoplastic and damage evolution effects, is used to investigate deformability, fluid flow and heat transfer during injection of carbon dioxide (CO₂) injection. The primary objective is to explore the feasibility of injecting CO₂ at temperatures lower than the surrounding formation, including subzero conditions. This is done to enhance the energy efficiency of the CO₂ storage process by eliminating the need to pre-heat the CO₂ prior to injection. The numerical analysis investigates the impact of internal wellbore temperatures and pressures on the surrounding rock, using Stainton Sandstone as the reference material. Various internal wellbore temperatures and pressures are simulated to represent different CO₂ injection scenarios. The results suggest that injecting CO₂ at lower temperatures than the wellhead is feasible. However, the long-term integrity and lifespan of the wellbore may require further investigation. This study provides a novel approach to enhancing energy efficiency in CO₂ storage by exploring subzero injection, potentially reducing operational costs. Additionally, it identifies critical challenges regarding wellbore integrity, which warrant further research to ensure the safety and durability of the storage site.