Investigating the Mechanism of Hydrate-Based CO Sequestration in Marine Sediments: A Large-Scale Experimental Simulation Approach

Abstract

Hydrate-based marine CO sequestration has attracted attention because of its high storage density and geological security. In this study, a large-scale experimental system was independently developed, featuring a high-pressure reactor with an effective volume of 1178 L. Utilizing this system, CO was injected into water-saturated quartz sand under low-temperature (3) and high-pressure (3.5 MPa) conditions to replicate marine hydrate-based CO sequestration and to evaluate the evolution of hydrate formation and stratigraphic responses. Multidimensional monitoring, including temperature, pressure, electrical resistivity, and overburden displacement, was employed to track thermalhydraulicmechanical (THM) coupling processes. The results indicate that gasliquidsolid coupling and its spatial distribution were significantly influenced by stratigraphic heterogeneity, with variations in gas migration patterns, hydrate formation, and solid matrix interactions across different layers. Hydrate formation began rapidly in the upper layers, extended downwards, and displayed an outside-in growth pattern because of efficient peripheral heat dissipation during vertical CO2 migration. Under the experimental conditions, a total of 4320.83 L of CO was sequestered, with the hydrate saturation reaching 0.248. Furthermore, hydrate formation resulted in significant volumetric expansion, characterized by a maximum vertical deformation of 88.2 mm and a total volume increase of 6.24%. This expansion markedly increased the overburden pressure (exceeding 5.1 MPa), highlighting the strong coupling between hydrate-induced deformation and reservoir mechanics. These findings provide critical experimental evidence for understanding the kinetics and multiphysics interactions in hydrate-based marine CO sequestration.

Keywords: Large-scale physical experiment, Marine CO₂ sequestration, Hydrate-based CO2, Multiphase flow, Phase transition