METHOD FOR MANUFACTURING OF HEAT-INSULATED STRING SECTION Russian patent published in 2013 - IPC E21B17/00 

FIELD: oil and gas industry.

SUBSTANCE: method includes coaxial placement of inner tube with insulation, gas absorbers and centring skids in outer tube. Outer tube is equipped with fluid-tight valve that provides vacuum 10^-4-10^-3 mm Hg in tubular annulus. Outer and inner tubes are connected through steel linings by means of their welding to pipes by vacuum-tight seams. To outer tube linings are welded at the point of male screw placements at ends within area under the section from the first turn till base plane of thread. Thermal treatment of vacuum-tight seams provides improvement of their plasticity. Heating of inner and outer tube is made stage by stage up to final temperature of 350-450°C. At each stage of heating in tubular annulus vacuum of 10^-4-10^-3 mm Hg is created. Male screws are made at the ends of outer tube after mechanical treatment of vacuum-tight seams.

EFFECT: reducing heat losses at heat carrier passage through tube string, increasing operational reliability of string and efficiency of string section assembly.

2 cl, 2 dwg