Siderca has set up field test strings for the development of double-walled tubes to enhance operation of wells in which steam injection is needed. Field tests were conducted in El Guadal, Santa Cruz, USA, through an agreement with Repsol-YPF in order to monitor development and performance of a special double-walled pipeline. Double-walled tubes are used in steam-injected high-viscosity oil recovery applications in order to maintain fluid temperature from bottom to mouth, which is especially important for pumping in cold climates and low temperatures. The tubes are specifically designed to operate with high-temperature steam injections (350°C) and high working pressure (3000psi), to support casing compression and pull stress, to reduce tubing sag, and to withstand cyclic stress. The coupling between the tubes must withstand thermal or mechanical stress. A special welding technique was thus developed in order to achieve a good coupling between the external tube and the liner; likewise, an insulated nipple is placed between both pins and the collar in order to reproduce insulation conditions. Laboratory tests conducted with Siderca’s double-walled tube showed that its design minimizes temperature loss and allowed steam to reach the required depth at values close to surface injected values, though with less loss through annular space.
