Abstract: In order to prevent freezing of the input lift gas in an oilwell in which gas under pressure is used to lift the well fluids, a heat exchanger is provided which serves to heat the input gas from the warm well fluids. The heat exchanger includes an outer casing and a coaxial tubing which is in line with the well fluid flow. The casing is sealed, and the tubing within the casing is provided with openings which permit the circulation of well fluids in the space between the casing inner wall and the tubing. Relatively small stainless steel tubing is spirally wrapped, in two spaced apart sections, around the tubing within the casing, and access parts are provided to permit the passage of input lift gas through the wrapped tubing prior to its injection into the well. The two wrapped tubing sections are coupled by a gas flow control valve external to the casing.