Investigating the influence of Joule-Thomson cooling on hydrate reformation near the wellbore

Abstract

Hydrate reformation, caused by the Joule-Thomson effect (JTE) during depressurization, poses a major obstacle to efficient gas production. This study examines the impact of the JTE on hydrate reformation near the wellbore during depressurization, focusing on the influences of gas-to-water ratio, depressurization range, and permeability. The results indicate that JTE significantly contributes to a gradual temperature decrease, leading to hydrate reformation. Reformed hydrates, potentially saturating up to 80%, initially appear near the wellbore then move away due to intense depressurization that eroded their inner surface, creating a moving low-permeability barrier that obstructs fluid flow and reduces gas-water production rates. Formations with higher permeability and gas saturation experience intensified JTE, leading to faster temperature drops, shorter hydrate reformation times, and quicker expansion of secondary hydrate bands. The study also evaluates the effectiveness of wellbore heating to mitigate hydrate reformation. Wellbore heating is found to be more effective in low-permeability formations, but only within a 0.5 m radius near the wellbore in high-permeability formations. This research suggests narrower depressurization ranges to prevent hydrate reformation and indicates the limited impact of wellbore heating on enhancing gas production. The findings have significant implications for preventing hydrate reformation near the wellbore and improving hydrate production efficiency.