Volume 65

Experimental Investigation of Pore Water Migration in COâ‚‚ Hydrate-Bearing Sediments under Thermal Gradients Yuan Zhou, Pan Chen, Yanlong Li, Nengyou Wu

Abstract

A promising method for geological COâ‚‚ storage is through the formation of COâ‚‚ hydrates in sediment pores. However, the uniform distribution of hydrates is essential to ensure storage stability and representative experimental properties. In this study, we investigated pore water redistribution during COâ‚‚ hydrate formation, with a comparative analysis of ice crystallization to elucidate underlying phase transition mechanisms. Experimental results revealed that under temperature gradients, phase change induces local water migration, resulting in heterogeneous water distribution. Key factors include the type of phase transition, temperature gradient, and salt concentration. Increased salinity reduced heterogeneity in water distribution, and at 0.5 mol/L NaCl, migration was largely inhibited, maintaining initial uniformity. A migration model incorporating these parameters effectively captured the behavior. A physical model incorporating these parameters effectively predicted the migration behavior. These findings highlight that similar heterogeneity in COâ‚‚ hydrate distribution may occur in field-scale storage sites, potentially affecting the sealing integrity and long-term stability of the reservoir.

Keywords Pore water redistribution; hydrate-bearing soil; temperature gradient; phase transition; migration model