Different Mechanism Effect between Gas-Solid and Liquid-Solid Interface on the Three-Phase Coexistence Hydrate System Dissociation in Seawater: A Molecular Dynamics Simulation Study

Zhixue Sun, Haoxuan Wang, Jun Yao, Chengwei Yang, Jianlong Kou, Kelvin Bongole, Ying Xin, Weina Li and Xuchen Zhu
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Zhixue Sun: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Haoxuan Wang: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Jun Yao: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Chengwei Yang: Exploration & Development Research Institute, Petro China Changqing Oilfield Company, Xi’an 136201, China
Jianlong Kou: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Kelvin Bongole: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Ying Xin: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Weina Li: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Xuchen Zhu: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China

Energies, 2017, vol. 11, issue 1, 1-16

Abstract: Almost 98% of methane hydrate is stored in the seawater environment, the study of microscopic mechanism for methane hydrate dissociation on the sea floor is of great significance to the development of hydrate production, involving a three-phase coexistence system of seawater (3.5% NaCl) + hydrate + methane gas. The molecular dynamics method is used to simulate the hydrate dissociation process. The dissociation of hydrate system depends on diffusion of methane molecules from partially open cages and a layer by layer breakdown of the closed cages. The presence of liquid or gas phases adjacent to the hydrate has an effect on the rate of hydrate dissociation. At the beginning of dissociation process, hydrate layers that are in contact with liquid phase dissociated faster than layers adjacent to the gas phase. As the dissociation continues, the thickness of water film near the hydrate-liquid interface became larger than the hydrate-gas interface giving more resistance to the hydrate dissociation. Dissociation rate of hydrate layers adjacent to gas phase gradually exceeds the dissociation rate of layers adjacent to the liquid phase. The difficulty of methane diffusion in the hydrate-liquid side also brings about change in dissociation rate.

Keywords: methane hydrate; adjacent phase; dissociation rate; molecular dynamic simulation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2017
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