Presence of NaCl as Strategy for Improving the CO2 Replacement Process in Natural Gas Hydrate Reservoirs

Natural gas hydrates represent a valid opportunity in terms of energy supplying, carbon dioxide permanent storage and climate change contrast. Research is more and more involved in performing CO2—replacement competitive strategies. In this context, the inhibitor effect on the hydrate formation process of sodium chloride needs to be investigated in depth. The present work shows the inhibitor effect produced by salt, dissolved in pure demineralized water with a concentration of 37 g/l, on the carbon dioxide hydrate formation process. Results proved how the formation trend is very similar between tests realized with salt and tests realized without it; the only difference stays in the equilibrium curve that, in case of salt presence, is shifted to higher pressure and/or lower temperature. The distance between equilibrium curves obtained in the absence of salt and in its presence is strongly dependent on its concentration. The present paper represents the first step of a wider scientific investigation, where the main goal consists in verifying if the inhibitor effect of sodium chloride might have a selective behaviour in function of the ‘guest’ species and if that phenomenon is related to its concentration. A comparison between CO2 and CH4 equilibrium curves, realized both in the presence and in absence of salt, has been provided. The feasibility of a carbon dioxide replacement process is directly related to the respective equilibrium curves distance. Thus, the influence of salt on their behaviour (and so on their distance) might determine the replacement process efficiency. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.