Embodiments of the invention described herein relate to methods and apparatus for recovery of viscous hydrocarbons from subterranean reservoirs. In one embodiment, a completion string for an enhanced oil recovery system is provided. The completion string includes an umbilical device having a plurality of conduits disposed therein, a downhole steam generator coupled to the umbilical device by a connect/disconnect device, and a conduit extending from the downhole steam generator through a packer.