Enhancing Geothermal Performance of Lithuanian Reservoir Using CO2: A Pore-Scale Study

Renewable energy sources have been recognized over the past years as a key solution for mitigating emissions of CO₂ gas into the atmosphere. Meanwhile, the rapid expansion of the artificial intelligence (AI) industry and the growing demand for large-scale data centers have placed unprecedented pressure on the energy sectors and making a significant contribution to greenhouse gas emissions [1]. Consequently, attention is directed toward geothermal energy due to its ability to operate continuously and efficiently, providing a reliable source of energy for both electricity and heat generation [2].Western Lithuania has many subsurface reservoirs with temperatures suitable for geothermal applications. Previous studies have analyzed the heat and electricity generation potential of these reservoirs, highlighting promising opportunities for geothermal development in the region [3, 4]. Consequently, the implementation of enhanced geothermal methods could significantly improve the feasibility and efficiency of these geothermal reservoirs.The Baltic Basin reaches its maximum depths beneath Lithuania, where the subsurface reservoirs in western Lithuania exhibit favorable temperature and pressure conditions and rock properties for CO₂ storage [5]. Several past studies have demonstrated significant storage potential in these subsurface reservoirs of Lithuania [5]. Therefore, opportunity exists to utilize CO₂  , as a fluid for geothermal applications, such as brine displacement for heat extraction. Additionally, CO₂ exhibits advantageous thermophysical properties compared to brine which can enhance heat extraction, electricity generation, and geothermal energy storage efficiency.This research aims to investigate pore-scale CO₂–brine physical interactions under Lithuanian geothermal reservoir conditions (e.g., temperature, pressure, and salinity). The objective is to evaluate the influence of CO₂ on brine displacement and local temperature distribution. In addition, pore-scale scenarios of CO₂ storage for geothermal energy storage are analytically examined to assess CO₂–brine–rock interactions, identify suitable operating conditions, and estimate viable storage durations. Numerical simulations of flow dynamics and heat transfer are conducted using reservoir simulation tools. A homogeneous and a heterogeneous pore-network models are developed for the simulations.  References[1]R. Jha, R. Jha and M. Islam, "Forecasting US data center CO2 emissions using AI models: emissions reduction strategies and policy recommendations," Frontiers in Sustainability, 2025.[2]G. J. N. J. J. P. Ashok A. Kaniyal, "The potential role of data-centres in enabling investment in geothermal energy," Applied Energy, pp. 458-466, 2012.[3]M. Pijus, I. Kaminskaite-Baranauskiene, A. Rashid Abdul Nabi Memon and M. Pal, "Assessing Geothermal Energy Production Potential of Cambrian Geothermal Complexes in Lithuania," Energy, 2024.[4]A. Rashid Memon, P. Makauskas, I. Kaminskaitė-Baranauskienė and M. Pal, "Repurposing depleted hydrocarbon reservoirs for geothermal energy: A case study of the Vilkyčiai Cambrian sandstone in Lithuania," Energy Reports, pp. 243-253, 2025.[5]S. Malik, P. Makauskas, R. Sharma and M. Pal, "Evaluating Petrophysical Properties Using Digital Rock Physics Analysis: A CO2 Storage Feasibility Study of Lithuanian Reservoirs," Applied Sciences, 2024.