NOVELTY - The process involves collecting native brine obtained by flowing or pumping to a surface from a set of wells made by drilling, digging, driving and boring at a first location in an aquifer or a reservoir. Methane is extracted from gas phase comprising the methane in the native brine, where the extraction is done by contacting the native brine with carbon dioxide under pressure or by reducing pressure at a surface of the native brine and the carbon dioxide displaces the gas phase comprising methane from the native brine.    USE - Process for producing methane from an aquifer e.g. non-geopressured-geothermal aquifer and geopressured-geothermal aquifer, and a reservoir or a combination of aquifer and reservoir.    ADVANTAGE - The process enables reducing cost and increasing acceptance and feasibility for mitigating greenhouse gas emissions. The process enables injecting the carbon dioxide in saline aquifers, so that pressure restricts injection rate since the pressure is kept below a certain maximum value to avoid unacceptable risks associated such as fracturing of the aquifer's seal. The process enables closing extracted brine reinjected, while deriving revenue from the methane and thermal energy removed from the brine and injecting the carbon dioxide dissolved in the brine into deep geopressured formations without large injection pressures, so that better safety is achieved. The process enables providing smaller injection pressures due to greater density of the brine compared to the carbon dioxide that gives larger bottom-hole pressure in the formations, so that the brine in the formations is hot and used as a source of geothermal energy in an efficient manner.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a process for producing methane and geothermal energy from an aquifer, a geopressured formation and a reservoir or combination of aquifer, geopressured formation and the reservoir    (2) a method for producing methane from carbon capture and sequestration in a deep saline aquifer    (3) a closed-loop system for producing methane and geothermal energy from carbon capture and sequestration in a geothermal aquifer.