Molecular Study on the Mechanism of Methane Hydrate Formation in Formate Solution

Abstract

AbstractThe formation of gas hydrate can block wellbore and drilling equipment during deep sea oil and gas exploitation and transportation, causing high flow pressure and bringing serious threat to the safe production and transportation. Therefore, it is urgent to develop efficient natural gas hydrate inhibitors. In this paper, the formation detail process of methane hydrate in three formate solution was studied by molecular simulation technology, and the micro mechanism of formate in the formation of methane hydrate was revealed. The results show that formate can significantly inhibit the formation of methane hydrate. The order of inhibition ability of three formates is HCOONa > HCOOK > HCOOCs. The detailed analysis shows that the inhibition mechanism of formate on the formation of methane hydrate mainly includes: (1) inhibiting the dissolution of methane gas and weaken the nucleation and growth power of methane hydrate, (2) affecting the water molecular structure of methane hydration, reducing the tetrahedral water substructure in methane hydration, and inhibiting the transformation of water molecular orientation to the direction conducive to the formation of methane hydrate, and (3) delaying the mutual transformation between multicomponent rings of water molecules in solution. In addition, (4) The ions can replace the water molecules in the hydrate cage at the methane hydrate growth interface to form an unstable hydrate cage structure and slow down the hydrate growth. This study explores the mechanism of formate inhibiting the formation of methane hydrate from the micro level, which can provide theoretical support for the evaluation and research and development of methane hydrate salt inhibitors.KeywordsMethane hydrateMolecular dynamicsFormate solutionInhibitor