Hydrate equilibrium conditions in aqueous electrolyte solutions: mixtures of methane and carbon dioxide

Abstract

Gas hydrates play an important role in the exploitation, transportation, and processing of natural gas. There is risk of hydrate formation at all the stages of natural gas handling due to the operating conditions of pressure and temperature that favor hydrate formation. Large reserves of natural gas also exist as hydrates. In addition, natural gas may have to be drilled through a zone of hydrates. Carbon dioxide is normally present along with these hydrocarbons. CO[sub 2] emission from the various combustion processes is identified to be the major reason for the greenhouse effect, and it is suggested that it be extracted and stored in deep sea waters as hydrates. Hydrate phase equilibrium data on CO[sub 2] and its mixtures with hydrocarbons are, therefore, essential. Three-phase equilibrium conditions (aqueous solution-vapor-hydrate) of methane + carbon dioxide mixtures in electrolyte solutions containing NaCl, KCl, CaCl[sub 2], and their mixtures were measured in the temperature range of 262--285 K and in the pressure range of 1.5--10.6 MPa a using a pressure search'' method. The ionic strengths of the solutions ranged from 0.7 to 6.76 m.