Numerical Simulation of Secondary Hydrate Formation Characteristics and Effectiveness of Prevention Methods

Xian Li, Hongfeng Lu (), Panpan Zhang, Lu Yu, Changwen Xiao and Yan Li ()
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Xian Li: Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou 511458, China
Hongfeng Lu: Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou 511458, China
Panpan Zhang: Institute of Petroleum Engineering, China University of Petroleum-Beijing at Karamay, Karamay 834000, China
Lu Yu: Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou 511458, China
Changwen Xiao: Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou 511458, China
Yan Li: Institute for Ocean Engineering, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China

Energies, 2024, vol. 17, issue 20, 1-18

Abstract: The exploitation of natural gas hydrates by the pressure reduction method is affected by the decomposition heat absorption effect, and the range of the formation temperature reduction area is expanding. At the same time, the temperature reduction phenomenon is more significant around the production wells under the influence of gas throttling and expansion effects, and hydrate formation will occur under certain temperature and pressure conditions, leading to blockage of effective seepage channels in the reservoir in the region and elevation of seepage resistance, which may affect the output of hydrate decomposition gas. A numerical simulation model is constructed for the purpose of studying the secondary hydrate generation pattern around the well, analyzing the impact of secondary hydrates around wells on the production capacity, and assessing the effectiveness of prevention methods to inform the actual production of hydrates. The results demonstrate that secondary hydrate is typically formed in the near-well area of the upper part of the production well, and the secondary hydrate around the upper part of the production well is the first to be formed, exhibiting the highest saturation peak and the latest decomposition. The formation of the secondary hydrate can be predicted based on the observed change in temperature and pressure, and the rate of secondary hydrate formation is markedly rapid, whereas the decomposition rate, approximately 0.285 mole/d, is relatively slow. Additionally, the impact of secondary hydrates on cumulative gas production is insignificant, and the effect of secondary hydrates on capacity can be ignored. Hot water injection, wellbore heating, and reservoir reconstruction can effectively eliminate secondary hydrates around the well. Reservoir reconstruction represents a superior approach to the elimination of secondary hydrates, which can effectively enhance production capacity while preventing the generation of secondary hydrates.

Keywords: natural gas hydrate; throttling expansion; secondary hydrate formation; numerical 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: 2024
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