US Patent 9052054 Foldable composite tubular structure

Foldable pipe-in-pipe composite tubular structure having between pipes after rounding and hardening a filling material associating the layers to enhance the structure mechanical performance mostly in collapse resistance. Improvements are related to increase foldability by having at least one of the pipe made of two layers and in case of transportation on a reel in continuous length the capability of circulating most of the hardenable filling material when the pipe is still on the reel and in case of wellbore casing application the capability of connecting sealingly successive strings of casing