Abstract
This paper outlines the technology and benefits of the continuous motion rig concept. This step change in drilling facilities technology is achieved through automation allowing any type of tubular to be pulled or run into the well without frequent intermittent stop in movement.
The continuous movement is enabled by mounting two lift systems in the derrick. The two systems work together in sequence comparable to pulling or lowering a rope continuously with both hands instead of working with only one hand. To be able to work a string with threaded joints in a continuous fashion up or down in the well the joints must be disconnected or connected while in continuous vertical movement. This implies that slips and tong must be mounted on each of the lift systems, taking string weight while connecting or disconnecting the coupling.
The basics and challenges of this system are outlined in the paper. When working in a continuous manner it is shown that even a slow continuous speed results in significant efficiency increases. A continuous slow drill pipe pulling speed of 0,5 m/sec results in tripping 1800 m/hr or app. 64 stands of 28m (app.90 ft) stands per hour. Doubling the speed to 1 m/sec, corresponding to app.peak pulling speed of today's drawworks in low gear, results in tripping speed of 3600m/hr.
One challenge of the system is to have technology in the vertical moving tongs to break connection and spin out in short enough intervals to avoid excessive height in the derrick.
Since string load is taken by the lift system off well center bending loads will be transferred to guide beams which must be given proper strength.
Other benefits of the continuous movement is minimizing problems normally connected with surge and swab effects due to lifting drill pipe out of slips and increasing pulling or lowering speed to peak and then brake down and stop. Further the problem of stuck pipe or casing caused by stop for connection is eliminated.
