| 摘要 |
A recoil system and method for supporting a marined riser which is extended from offshore well head equipment to a floating platform are disclosed. The purpose of the recoil system is to prevent a violent collision of the riser with the platform when the riser becomes separated from the well head equipment during a planned or an emergency disconnect operation. Upon disconnection of the riser from the well head equipment, the lifting force applied to the riser is reduced to a predetermined lower level and the riser is retracted to an elevated position above the well head equipment to permit unobstructed excursions of the riser. A variable lifting force is applied to the riser to maintain the riser substantially in equilibrium in the retracted position as the floating platform heaves relative to the riser in response to wave action. The riser is supported by a tensioner assembly which includes a hydraulic cylinder having a housing member attached to the platform, a movable piston dividing the housing member into a high pressure hydraulic chamber and a low pressure hydraulic chamber, and a rod connected to the piston and coupled to the riser for applying a lifting force to the riser in response to pressurization of they hydraulic pressure chamber. Collision of the riser against the floating platform is prevented by apparatus which includes a reservoir of compressed gas and a valve connected intermediate the compressed gas reservoir and the low pressure hydraulic chamber for selectively applying a pneumatic or pneumatic over hydraulic pressure load to the piston in opposition to the hydraulic pressure load when the riser is disconnected from the well head equipment.
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