The solubility of methane in sodium chloride brines

Abstract

The solubility of methane in pure water and in solutions of 5%, 10% 15%, and 20% (by weight) sodium chloride was determined experimentally at various temperatures and pressures. Methane solubility in sodium chloride solutions is significantly less than it is in pure water because of the salting-out effect. For example, in a solution of 20 weight % NaCl, the solubility of methane is only 28% of that in pure water under the same temperature and pressure conditions. We report here an experimentally determined value of 0.129 0.03 for the salting-out (Setschenow) constant for methane. Also presented is a set of equations for calculating the solubility of methane under conditions of pressure, temperature and salinity as great as 137.9 MPa (20,000 psi), 350C (662F) and 25 weight % sodium chloride, respectively when only the salting-out constant and the solubility of methane in pure water at the temperature and pressure of interest are known.