Method of assembly of a dual-walled pipe

A method for making a double-walled pipe assembly for use in a permafrost zone in a wellbore comprising providing two sections of pipe which fit together concentrically to provide an annulus therebetween, the inside pipe being threaded at both ends on its outside wall, the outside pipe being threaded at both ends on its inside wall, providing first and second annular connecting means which are threaded on their inner and outer walls, threading the first connecting means onto a first of said pipes, threading the second connecting means onto the second pipe, said second pipe having threads of opposite rotational directions at either end so that when said first pipe and said first connector means are assembled with said second pipe said second connector means can be rotated relative to said first pipe thereby moving said second connector means longitudinally toward or away from said first pipe and lining up thread start points on said second connector means and first pipe, rotating said first pipe and first connector means together to thread said first connector means onto said second pipe, rotating said second connector means relative to said first pipe until the thread start points on said first pipe line up with the thread start points on said second connector means, stopping the rotation of said second connector means, and continuing rotation of said first pipe and first connector means so that said second connector means threads onto said first pipe at the same time said first pipe threads onto said second connector means.