A Study on the CO2 Jet Erosion Natural Gas Hydrate with the Influence of Temperature and Confining Pressure

ABSTRACT Natural gas hydrate (NGH) has been regarded as important potential energy resource. CO2 jet erosion HBS can be combined with Radial Jet Drilling (RJD) technology to achieve high efficiency and low-cost gas hydrate mining. The replacement of CO2 hydrate and CH4 hydrate can also be used to form a stable cap layer on the hydrate reservoir to achieve CO2 storage. In this study, the Arbitrary Lagrangian Euler (ALE) method is used to establish a heat-liquid-solid coupling model for water/CO2 jet erosion HBS, and the CO2 phase change is considered. The influence of different temperature and pressure on jet erosion effect was studied. The results indicate that confining pressure has an inhibitory effect on jet erosion ability, which gradually weakens as the confining pressure increases from 5-10MPa. At confining pressures ranging from 0.1-2.5MPa, the erosion volume decreases with rising temperature due to the gaseous CO2 in the submerged environment, resulting in reduced resistance. The erosion effect is influenced by the characteristics of the jet. At 2.5-5MPa, the CO2 in the submerged environment undergoes a phase transition from gaseous to liquid. At 5-10MPa, the erosion volume increases with temperature due to the liquid CO2 in the submerged environment, resulting in relatively higher resistance. The erosion effect is affected by the fluid in the submerged environment. Additionally, under equivalent temperature and pressure conditions, CO2 jet exhibits superior erosion effectiveness compared to water jet. This study can provide theoretical basis and technical ideas for using RJD technology to mine hydrate and achieve "carbon peak and carbon neutrality". INTRODUCTION Natural gas hydrate is a kind of clean energy with great potential (Sloan, 2003). It is commonly found in marine sediments and permafrost at continental margins, especially in marine sediments (Chong et al., 2016; Michael et al., 2019). The global amount of organic carbon in NGH is twice that of fossil fuels combined (Yu et al., 2019; P. Zhang et al., 2021). So far, many countries in the world have successively formulated the exploitation plan of gas hydrate (Xiao & Zhang, 2021). It can be predicted that the research and exploitation of NGH will remain the focus of global attention for a long time in the future.