Gas Migration in the Geosphere: the "Geogas" Theory

Abstract

Gas migration in the geosphere is a widespread process, that occurs in numerous geological environments. The most important gases taken into account are CO2, generally present in volcanic and geothermal areas, ans CH4, mainly related to hydrocarbon-prone areas. Diffusion and groundwater flow were traditionally considered as the main mechanisms responsible for the gas migration. However, this approach failed to explain the behaviour of gases in particular situations, such as the long distance transport of radon, or the rapid variations of hydrocarbon anomalies in soil. The "geogas" integrative theory represents a contribution of the last decades, proposing a re-evaluation of several concepts of gas migration in the Earth's crust. Various mechanism of gas migration are described in the present article. The importance of rapid advection and the capabilities of microbubble transport are highlighted.