Hybrid reverse transfer system

Abstract

The present invention relates to a system to transport petroleum fluids using a riser, capable of operating with aggressive fluids, in regions of irregular sub-sea terrain, yet using low-complexity and low-cost components and connections. The hybrid reverse transfer system, comprises: a first, top, rigid riser section, a second, bottom, flexible riser section, connected to a bottom end of the rigid riser section, and a series of support buoys connected to the rigid riser section, wherein the lower end of the bottom, flexible, riser section connects to a bottom connector on the seabed.

1 . Hybrid reverse transfer system, comprising:
 a first, top, rigid riser section,   a second, bottom, flexible riser section, connected to a bottom end of the rigid riser section, and   a series of support buoys connected to the rigid riser section,   wherein the lower end of the bottom, flexible, riser section connects to a bottom connector on the seabed.   
     
     
         2 . Hybrid reverse transfer system according to  claim 1 , wherein the buoys cause a portion of the rigid riser section to assume a wave configuration. 
     
     
         3 . Hybrid reverse transfer system according to  claim 1 , wherein the assembly of the first and second riser sections takes on a steep-wave configuration. 
     
     
         4 . Hybrid reverse transfer system according to  claim 1 , characterised in that the bottom riser section connects to a Vertical Connection Module type of bottom connector. 
     
     
         5 . Hybrid reverse transfer system according to  claim 1 , wherein the thrust provided by the support buoys is such that the flexible riser has a large angle of elevation with respect to the seabed, at the point it connects to the connector at the seabed. 
     
     
         6 . Hybrid reverse transfer system according to  claim 4 , wherein the angle of elevation of the flexible riser at the point it connects to the seabed is from 35° to 90°, optionally from 45° to 90° and further optionally from 60° to 90°. 
     
     
         7 . Hybrid reverse transfer system according to  claim 1 , characterised in that the lower end of the top riser section is fitted with a mechanical connector, such as a flange, for connecting to the bottom riser section. 
     
     
         8 . Hybrid reverse transfer system according to  claim 1 , wherein the rigid riser section is made of steel pipe. 
     
     
         9 . Hybrid reverse transfer system according to  claim 1 , wherein the rigid riser section comprises up to 94% of the total length of the hybrid reverse transfer system. 
     
     
         10 . Hybrid reverse transfer system according to  claim 1 , wherein the flexible riser section is made of flexible tubing. 
     
     
         11 . Hybrid reverse transfer system according to  claim 1 , wherein the flexible riser section comprises at least 6% of the total length of the hybrid reverse transfer system. 
     
     
         12 . Hybrid reverse transfer system according to  claim 1 , wherein the support buoys are attached to a bottom portion of the top riser. 
     
     
         13 . Hybrid reverse transfer system according to  claim 1 , wherein the top end of the hybrid reverse transfer system is connected to a floating structure. 
     
     
         14 . A steep-wave riser system, comprising:
 a rigid riser section,   a flexible riser section connected to a bottom end of the rigid riser section, and   wherein the lower end of the flexible riser section connects to a bottom connector on the seabed.   
     
     
         15 . A method of providing a transfer system, comprising:
 providing a first, top, rigid riser section,   providing a second, bottom, flexible riser section, connected to a bottom end of the rigid riser section,   providing a series of support buoys connected to the rigid riser section, and   connecting the lower end of the bottom, flexible, riser section to a bottom connector on the seabed.