This invention provides a tubing injection system that contains one injector for moving a tubing from a source thereof to a second injector. The second injector moves the tubing into the wellbore. In an alternative embodiment for subsea operations, the system may contain a first injector placed under water over the wellhead equipment for moving the tubing to and from the wellbore. A second injector at the surface moves the tubing to the first injector and a third injector moves the tubing from the tubing source to the second injector. In each of the tubing injection systems sensors are provided to determine the radial force on the tubing exerted by the injectors, tubing speed, injector speed, and the back tension on the source. A control unit containing a computer continually maintains the tubing speed, tension and radial pressure on the tubing within predetermined limits. The control unit is programmed to automatically control the operation of the tubing injection systems according to programs or models provided to the control unit.