Drylands are considered a net sink for atmospheric methane and a main component of global inventories for greenhouse gas budgets. However, a significant portion of drylands occur over sedimentary basins hosting natural gas and oil reservoirs, with gas migration to the surface (named “microseepage”) producing positive atmospheric CH4 fluxes. In this overview, we summarize the outcomes of microseepage surveys performed in different petroleum basins, describe how the microseepage area is estimated and what are the emission factors that can be used for a preliminary global emission estimate. Microseepage frequently overcomes methanotrophic consumption occurring in dry soil throughout large areas, and it is enhanced by faults and fractures [...]
