Molecular study on the behavior of methane hydrate decomposition induced by ions electrophoresis

Abstract

Strong static electric fields can accelerate hydrate decomposition in pure water and induce the migration of ions (Na+ and Cl-) in salty water. The impact of Na+ and Cl- migration on hydrate decomposition under static electric fields deserve to be evaluated. Toward this goal, molecular dynamics (MD) simulations were conducted to investigate the effects of the migration of Na+ and Cl- induced by static electric fields on the decomposition behavior of methane hydrate. We find that the hydrate cages can be pierced and destroyed by the migration of Na+ and Cl- under static electric fields at least 0.9 V/nm at our conditions, thus causing hydrate decomposition. With increasing static electric field strength, the destructive ability of ions to hydrate becomes stronger and hydrate decomposition becomes faster. Moreover, detailed analysis shows that Na+ and Cl- can penetrate and pass through the hydrate block, and some ions concentrate on the surface of the hydrate block and cause hydrate decomposition. This work provides a new method for natural gas hydrate extraction and inhibition of hydrate formation in gas-oil pipelines. The hydrate is worth examining as a new ion exchange membrane material in the future due to the difference of ions migration velocity in hydrate.