Acceleration mechanism of methane hydrate dissociation in inorganic salt solutions: Experimental and molecular dynamics study

Abstract

In the exploration and exploitation of methane hydrates, the influence of inorganic salt environments on hydrate behavior is particularly pronounced. This study employs experimental methodologies to evaluate the dissociation performance of hydrates in common inorganic salt solutions, coupled with molecular dynamics simulations to investigate the dissociation mechanisms under varying types of inorganic salts (MgCl₂, CaCl₂, KCl, and NaCl), mass concentrations, and multi-salt coexistence systems. The findings reveal that the efficacy of inorganic salt solutions in promoting hydrate dissociation follows the order: MgCl₂ > CaCl₂ > KCl > NaCl. The smaller ionic radius of Mg²⁺ and its stronger adsorption capacity for water molecules facilitate ion intrusion and the disruption of the hydrate's cage-like structure. In systems where multiple inorganic salts coexist, the higher potential energy and adsorption capacity result in the dissociation-promoting ability being predominantly determined by higher-valent metal cations. This research provides valuable macro and micro perspectives on the dissociation mechanisms of methane hydrates in inorganic salt environments, holding significant implications for the development of high-performance hydrate drilling fluid systems.