| 摘要 |
<p>OPEN BOTTOM FLOAT TENSION RISER A marine riser, which is hung from a drilling platform floating on a body of water and connected at its lower end to a wellhead, is buoyantly tensioned by one or more float cans with open bottoms. These float cans are connected at their upper end to the riser to which air under pressure is controllably supplied. The pressurized air blows out the water in each can to achieve the desired buoyancy. The float can may have an air dump valve interconnected with similar valves in the other cans. The function of these valves is to release the pressurized air in the can if the riser parts. At the upper end of the riser is a slip joint, which may include safety water-dampening gear to further reduce upward motion of a parted riser. The optional dampening gear comprises an annular piston formed by the upper section of the slip joint that forces water through ports in the exterior of the lower section of the slip joint as the riser below the slip joint moves upward. A method of running this riser includes the steps of lowering the riser with or without: the air under pressure flowing into the float cans, a ballast weight at the bottom end of the riser, and supplementary tensioning or motion compensating equipment. The riser's descent may be stopped at a point above a water bottom connector at which time motion compensating equipment may be engaged and then gradually lowered to make the connection. The foregoing is reversed when removing the riser from the water bottom connection.</p> |
