Volume 56

Study on Phase Changes and Migration Characteristics of CO2 during Leakage in Deep Saline Aquifers for Carbon Sequestration Li Wang, Shuyang Liu, Hangyu Li, Zhiqiang Wang, Qizhi Tan, Junrong Liu, Genglin Liu

Abstract

In response to global climate change, carbon capture and storage (CCS) has become a key strategy, opening a new chapter in the use of deep underground space. Deep saline aquifers, with their extensive distribution and substantial storage potential, are ideal for CO2 storage. However, the risks of geological storage, including CO2 leakage and potential environmental impacts, cannot be ignored. This study aims to investigate the migration behavior, distribution patterns, and phase changes of CO2 in saline aquifers and their cap rocks through reservoir numerical simulation. A two-dimensional reservoir model was constructed, incorporating a highly permeable pathway to simulate a fault as a leakage channel, in order to study the phase change and longitudinal migration characteristics of CO2 during the leakage process. The simulation results indicate that during the upward leakage process along the fault, CO2, under the influence of buoyancy, tends to enter the upper strata. As it migrates upward, some of the CO2 is affected by rock adsorption and becomes trapped at the interface between the fault and the overlying dense rock of the saline aquifer, distributing stably. It is noteworthy that during the leakage process, CO2 primarily migrates in a supercritical state; however, when it reaches a critical depth, it transitions to a liquid phase. This phase change from supercritical state to liquid state can impact the storage capacity and pressure, thereby affecting the stability of the formations.

Keywords CO2 storage, Saline aquifer; Phase change; Migration; Leakage