Patent ID: 7934560
Filing Date: 2011-05-03
Classification: B63B,E21B

Abstract:
1. A free standing riser system connecting a subsea petroleum production wellhead on the seabed and a Floating Production Unit (FPU), that allows the petroleum production to be conveyed to the FPU and to an intervention rig without the need to retrieve the free standing riser and a flexible jumper interconnected to the FPU, said system comprising: a riser formed by interlinked joints with a lower-end being directly connected to the wellhead and enclosed in a buoy assembly installed below a terminal at the upper-end of the riser, the riser being maintained in an erect substantially vertical position by a tension applied by the buoy assembly; a subsea intervention unit, coupled to the terminal at the upper-end of the riser, including a Y-shaped divider with three connections: a first connection to the terminal, a second connection with a valve to the flexible jumper, and a third connection with an intervention valve that provides a vertical direct access from the intervention rig to the wellhead through the interior of the riser; an umbilical for controlling, monitoring and transmitting electrical and hydraulic energy, the umbilical linking the FPU to the wellhead; and wherein the subsea intervention unit includes in sequence: an upper guide funnel, an internal mandrel with the Y-shaped divider, a first connector and a bottom inverted guide funnel linking the internal mandrel to the terminal at the upper-end of the riser via a second connector and an isolation valve.