For drilling high pressure wells in the North Sea Central Area, it became necessary to develop a complete 15,000 working pressure B.O.P. System that could be used on any available rig without any major modification. The choke and kill line system had therefore to be quickly adaptable to any existing 10,000 psi W.P. marine riser.
This system comprises:
A double drum pneumatic winch.
Two long continuous flexible kill and choke lines spooled onto this winch and clamped onto the existing riser whilst running it.
Two tension clamps set at mid barrel of the telescopic joint.
Two davit roller guide assemblies attached to the riser retainer ring.
A certain number of guide clamps easily attached to the riser joint flanges, which keep the flexible choke and kill lines running parallel to the marine riser.
Used on board the Sedco 709, this system brought the following advantages:
Total flexibility.
Pick and simple installation onto the existing riser.
Suppression of the great separating forces due to the high pressure on the riser corrector known as the "pin pump out effect" therefore increased safety.
The interest of such a system is further enhanced as it is well suited for floating production systems and for quick intervention to kill wild subsea wells as it has been done for DITOC I blowout.
In recent years offshore drilling has been performed in ever deeper water and to greater depths thus increasing the complexity of the process Specifically, higher pressure has been encountered making necessary roared effective teleology and equipment.
On floating offshore drilling vessels there exists the requirement for numerous flexible junctions to aid the continuous flow of the various fluids in the system. Of utmost importance are the flexible lines utilized in correcting the subsea blowout prevented stack and the choke and kill Mani folding at the surface. Currently these lines are primarily utilized in relatively short lengths around the subsea ball joint to offset the lateral movement of the drilling vessel and in the moon pool at the telescopic joint to compensate for vertical Movement due to heave.
Flexible pipes, such as those manufactured by Coflexip since 1972, have been designed to meet a variety of drilling and production applications. Their application has gained acceptance by the major oil companies and drilling contractors worldwide. The utilization of a continuous 500 foot length flexible 15,000 psi working pressure choke and kill system from blowout prevented stack to deck by Shell U.K. Exploration & Production on the Sedco 709 has extended this application to its fullest potential. Shell U.K. and Coflexip have thus initiated a .revolutionary method of installing and upgrading drilling riser choke and kill systems. This technique system allows increased safety, reduced riser maintenance, and rapid upgrading of existing equipment.
