Hydrate-Based CO2 Sequestration with Different Water Saturation and Injection Pressure

Abstract

CO₂ geological sequestration technology based on hydrates offers significant advantages over traditional sequestration methods, making it a research hotspot in recent years. In this experimental study, the heat transfer characteristics and sequestration efficiency of the hydrate formation process upon injection of CO₂ into depleted gas reservoirs were investigated. The experiments were carried out under constant volume, constant gas injection temperature, and constant reservoir temperature conditions. The effects of different gas injection pressures (2.9, 3.6, and 4.3 MPa) and initial water saturations (10%, 20%, and 30%) on the hydrate formation kinetics, as well as heat transfer laws, were analyzed. The results showed that the sequestration amount was highest under 4.3 MPa, and the instantaneous rate in the rapid formation stage was optimal at 3.6 MPa. The initial water saturation (S_Wo) had a double-edged effect. When S_Wo = 20%, the formation of a continuous water phase led to a hydrate saturation of 21.86%, while at S_Wo = 30%, pore clogging restricted mass transfer and reduced the sequestration efficiency. Three-dimensional temperature and pressure fields analysis revealed the spatiotemporal distribution law during the hydrate formation process. The phenomena of local temperature oscillation and pressure accumulation indicated dynamic regulation of the formation kinetics by heat transfer lag and the shell effect. Overall, a gas injection pressure of 4.3 MPa and an initial water saturation of 20% served as the optimal sequestration conditions, providing a theoretical basis for the engineering application of CO₂ hydrate sequestration technology within depleted gas reservoirs.