泥岩に対するメタンおよび二酸化炭素の吸着挙動実験と考察

抄録

In the development of reservoirs of natural gas dissolved in water and shale gas, knowledge of the adsorption behavior of natural gas on reservoir rock is crucial. Furthermore, it is reported that carbon dioxide, rather than methane, is selectively adsorbed on the clay minerals, which suggests a possible enhanced gas recovery by injection of carbon dioxide. This paper provides a technical discussion on the adsorption behavior of methane and carbon dioxide on mudstone samples.

The adsorption tests of methane showed that the amount of adsorbed gas increases with increasing clay mineral contents in mudstone. The adsorption test of carbon dioxide showed that the amount of carbon dioxide adsorbed is five times larger than that of methane. The amount of methane and carbon dioxide adsorbed to mudstone was well predicted by Langmuir's adsorption isotherm. The adsorption tests of a mixture of methane and carbon dioxide showed that the amount of adsorbed methane and carbon dioxide depends on the partial pressure of each gas. As the partial pressure of carbon dioxide increased, the concentration of carbon dioxide in the absorption phase increased and that of methane decreased. Meanwhile, the amount of absorbed methane and carbon dioxide was also observed to be affected by the gas phase composition. As the concentration of carbon dioxide in the gas phase increased, the amount of methane adsorbed increased to a value more than that obtained in the ideal state. When the concentration of carbon dioxide in the gas phase decreased, the amount of carbon dioxide adsorbed decreased greatly from the value obtained in the ideal state.