Evaluation of CH4 gas permeation rates through silicone membranes and its possible use as CH4-extractor in gas hydrate deposits

Abstract

This preliminary study discusses the option of using silicone (PDMS) tubes for the extraction and monitoring of CH4 gas from hydrate deposits during decomposition. For this, the gas flow of gaseous and dissolved CH4 through hand-manufactured silicone tube membranes has been tested on a small lab scale. The permeability of pure CH4 gas at ambient pressure and 295K is in good agreement with literature reports. The permeability rate of CH4 derived from dissolved methane is expectedly lower and decreases by more than half. Theoretical assumptions and lab results are not in straightforward correlation. This leads to the conclusion that experimental constraints influence the permeability. These are mainly an increase of the gas stream resistivity due to the membrane-filling and membrane-sediment contact points as well as the effect of degassing dissolved CH4 on the tube surface due to pressure gradients. Therefore, the use as a monitoring tool needs to be individually tested before the respective application. Due to the robust nature of the membranes, their application as a tool for capturing gaseous CH4 during hydrate decomposition is a feasible goal.