Recent trends in offshore field development have been toward subsea completions, especially in the North Sea. It is estimated that the number of subsea wells in the North Sea will double by 1994. Since subsea wells are often completed in the same formations as conventional offshore wells and completion designs are the same, downhole service requirements for subsea wells are generally the same. Semi-submersible rigs using tensioned risers have offered the only practical means of performing vertical intervention services such as wireline and reeled (coil) tubing.
A subsea reeled tubing system (SRTS) has been designed and manufactured that offers a more economical means of performing a range of reeled tubing services on subsea wells. The SRTS is operated from a diver support vessel (DSV) or other relatively small vessels in lieu of a rig which effects a considerable savings in cost and time. A tensioned riser is not required with the SRTS.
This paper describes the SRTS in detail and discusses the reeled tubing services offered by the unit. Safety features and operational procedures are also discussed.