METHOD OF INSTALLATION OF DOUBLE-WALLED ISOLATED FLOW STRING AND DOUBLE-WALLED ISOLATED FLOW STRING Russian patent published in 2000 - IPC

FIELD: drilling of geothermal and oil wells; methods of installation and designs of double-walled isolated flow strings suspended by supporting means. SUBSTANCE: double-walled flow string has internal pipe string formed by many internal pipes and radial external pipe string consisting of many external pipes. Both strings are independent and located at some distance from each other except for axial connection of strings with each other at upper end of flow string, although fastening of strings in axial direction may be in the lower end of string, as well, if required. Annular isolating space between internal and external strings is sealed on both opposite ends with its possible vacuum treatment. Internal and external strings may be lowered into well using known technology of oil well drilling. In this case, mechanical connection between internal and external strings is absent, especially in points of joint of respective internal and external lengths of pipe. To prevent fluid from getting into inside of external string, plug is installed before lowering of internal string into well and its sealing with respect to external string, on its lower end. Plug closes first lower end of external string. Then plug is removed before fluid may pass through heat-insulated double-walled string. EFFECT: higher reliability of use, ensured simplicity in assembling of double-walled strings. 19 cl, 11 dwg