Ab-Initio Molecular Dynamics investigation of gas adsorption on α-quartz (001) for CO2 enhanced natural gas recovery

Abstract

In this work, the interaction of methane and carbon dioxide on α-quartz with surface 001, with a siloxane termination (dense) surface was investigated by means of Ab-Initio Molecular Dynamics. Different temperatures were addressed, ranging from 298 to 423 K. For completeness, pure and mixed compositions were considered, to replicate the conditions present during Enhanced Gas Recovery processes by CO 2 injection. When considering pure compositions, both gases stick to the surface, except for the highest temperature (423 K), where most of CH 4 tend to desorb. When mixed compositions are addressed, carbon dioxide generally hinders the interaction of methane, except for high temperature, where both gases are equally distributed both close and far from the surface. To the goal of improving EGR processes on sandstone reservoirs, this work shows that a temperature of 323 K offers the best efficiency by increasing the interaction of carbon dioxide and pushing methane out of the surface. At the same time, this study would not recommend the use of very high temperatures (T > 373 K) and excessive concentration of CO 2 , as the majority of this gas would desorb, without improving methane extraction in a meaningful way. • With pure compositions, CH 4 possesses high mobility on α-quartz compared to CO 2 , though both gases are characterized by the same interaction. • At room temperature and mixed composition, both gases interact strongly with the surface, so the extraction of methane is usually inefficient. • A temperature of 323 K offers the best EGR efficiency, improving carbon dioxide interaction with the surface and pushing methane out. • Very high temperatures and excessive concentration of CO 2 could reduce gas recovery and sequestration.