Abstract: Natural gas is reinjected into an earth formation for storage and/or stimulating the recovery of hydrocarbon liquids by mixing the gas with water at a pressure sufficient to maintain bubble flow of gas dispersed in a water flowstream in a range of volumetric gas fraction up to about twenty percent of total flow. A water and gas distribution system includes static flow mixers for maintaining uniform distribution of gas bubbles in the water flow stream through the distribution conduits. The mixers may comprise multi-stage bladed mixing elements of the same or opposite pitch and extending across the intersection of branch conduits with the main conduit of the distribution system. The water and gas may be mixed in an injection well having a tubing string extending within the well and having a distal end below the point of injection into an earth formation so that a uniform gas and water mixture enters the formation through the well perforations.