Visualization of CH4 Hydrate Dissociation Under Permafrost Temperature Conditions Using High-Pressure Micromodel

Description

In this study, we demonstrate the ineffectiveness of depressurizing CH4 gas hydrates under permafrost conditions without thermal stimulation. CH4 gas hydrate phase transitions were visualized using a high-pressure, water-wet, silicon-wafer micromodel with pore network of actual sandstone rock. A set of eight experiments were performed in which CH4 gas hydrate was formed at a constant pressure between 60 – 85 bar and constant temperature between 0 °C – 4°C. CH4 gas hydrate was then dissociated at constant system temperature between -3 °C - 2 °C by pressure depletion to study the effect of hydrate and fluid saturation on dissociation rate, self-preservation, and risk of hydrate reformation. The dissociation rate was heavily affected by the initial hydrate distribution in the pore space. Additionally, the amount of produced CH4 gas was limited below 0 °C due to the rapid formation of ice from the liquid water that was liberated from the initial hydrate dissociation. The liberated CH4 gas was therefore immobilized and trapped by the formed ice and could not be produced without thermal stimulation. The results highlight the importance of morphology and the amount of initial hydrate/ice/free gas saturation for predicting hydrate dissociation patterns and on the selection of effective production techniques.

Period	28 Aug 2020
Event title	InterPore2020 : 12th Annual Meeting & Short Courses
Event type	Conference
Location	Qingdao, ChinaShow on map
Degree of Recognition	International