HEAT-INSULATED STRING Russian patent published in 2007 - IPC E21B17/00 F16L59/15 

FIELD: oil industry, particularly construction of heat-insulated injection well strings adapted to inject heat-carrier into productive bed.

SUBSTANCE: string comprises inner tube with multilayer screen insulation, centering ring and gas absorbing means. The string also has outer tube compressed along tube axis before outer tube installation and provided with tapered buttress thread at ends thereof. Inner and outer pipe ends are welded with each other to create vacuum-tight welds and inner space is evacuated. The string comprises coupling with grooves and sealing bushes. The coupling is screwed on outer tubes. Sealing ring of polytetrafluoroethylene is installed in hole annuity near inner and outer tube connection at the second tube ends to be connected after the first tube ends connection. The sealing ring is press-fitted between tubes with at least 10 tons/cm² pressure so that it may slide in the annulus under pressure exceeding that of press-fit.

EFFECT: simplified tube space evacuation and vacuum retention during string operation.

2 dwg