Method And Device For Connecting A Riser To A Target Structure

Abstract

The present invention relates to a method for connecting a free end of an at least partially submerged riser to a target structure, the method comprising: (a) connecting the riser by the free end thereof to a riser support assembly; (b) positioning the target structure near the riser support assembly; (c) connecting a lifting assembly, with the free end ( 24 ) of the riser; (d) moving the riser by the free end thereof from the riser support assembly toward the target structure by the lifting assembly; and (e) connecting the riser with the target structure. The present invention also relates to a riser support assembly for connecting a riser by a free end thereof with a target structure.

1 . A method for connecting a free end of an at least partially submerged riser to a target structure, the method comprising: 
 (a) connecting the riser by the free end thereof to a riser support assembly;    (b) positioning the target structure near the riser support assembly;    (c) connecting a lifting assembly with the free end ( 24 ) of the riser;    (d) moving the riser by the free end thereof from the riser support assembly toward the target structure by the lifting assembly; and    (e) connecting the riser with the target structure.    
     
     
         2 . The method of  claim 1 , wherein the target structure and the riser support assembly are maintained in their respective positions independently from one another.  
     
     
         3 . The method of  claim 1  or  2 , wherein the target structure comprises the lifting assembly.  
     
     
         4 . The method of  claim 1 , wherein the riser support assembly is anchored to the seabed by a first anchoring device.  
     
     
         5 . The method of  claim 4 , wherein the target structure is anchored to the seabed by a second anchoring device which is an independent device from the first anchoring device.  
     
     
         6 . The method of  claim 1 , wherein the riser support assembly is directly connected to the first anchoring device throughout steps (a), (b), (c), (d) and (e).  
     
     
         7 . The method of  claim 1 , wherein during step (b) the target structure and the riser support assembly are connected by a connecting means.  
     
     
         8 . The method of  claim 7 , wherein during step (b) the target structure and the riser support assembly are moved towards one another by reducing a length of the connection means.  
     
     
         9 . The method of  claim 1 , wherein the riser support assembly is positioned at a predetermined depth under the water surface when the riser is suspended from the riser support assembly.  
     
     
         10 . The method of  claim 9 , wherein the riser support assembly is positioned at a depth at which the riser support assembly is substantially free from influences from wind and waves at the water surface.  
     
     
         11 . The method of  claim 1 , wherein in step (b) the target structure is at least temporarily positioned substantially above the riser support assembly.  
     
     
         12 . The method of  claim 1 , comprising a further step (f) of removing the riser support assembly.  
     
     
         13 . The method of  claim 1 , wherein prior to step (a) the riser is suspended by the free end thereof from a pipe-laying vessel and in step (a), the riser is transferred from the pipe-laying vessel to the riser support assembly.  
     
     
         14 . The method of  claim 13 , wherein in step (a) the riser support assembly is moved towards the pipe-laying vessel, for transferring the riser from the pipe-laying vessel to the riser support assembly.  
     
     
         15 . The method of  claim 1 , wherein the target structure is chosen from a group of floating structures, comprising: a TLP, a Spar, a Semi-submersible, an FPSO, an FPDSO, an FPWSO, a storage barge, an FSO, an FSU.  
     
     
         16 . The method of  claim 1 , wherein the riser is chosen from a group of risers, comprising: a steel catenary riser, a lazy wave riser with buoyancy elements, a steep wave riser, and a flexible riser.  
     
     
         17 . The method of  claim 1 , wherein the riser is manufactured from a material, chosen from a group of materials, comprising: steel, titanium, a synthetic material, and a composite of a metal and a synthetic material.  
     
     
         18 . The method of  claim 1 , wherein the riser comprises flexible pipe sections.  
     
     
         19 . The method of  claim 1 , wherein at least two risers are connected to the target structure.  
     
     
         20 . The method of  claim 19 , wherein in step (a) at least two risers are connected to a single riser support assembly.  
     
     
         21 . The method of  claim 19  or  20 , wherein a first riser support assembly and a second riser support assembly are provided, and wherein the first riser support assembly and second riser support assembly are connected by a mooring connecting means for maintaining a predetermined distance between the first and second riser support assembly.  
     
     
         22 . The method of  claim 21 , wherein the mooring connecting means are selected from a group of mooring connecting means, comprising: a flexible mooring connecting means and a rigid mooring connecting means.  
     
     
         23 . The method of  claim 1 , wherein the lifting assembly is chosen from a group of lifting assemblies, comprising: a pull-in device with chain jacks, a winch, a crane and a drill tower.  
     
     
         24 . The method of  claim 1 , wherein the target structure is anchored to the seabed using a second anchoring device.  
     
     
         25 . The method of  claim 1 , wherein the lifting assembly is connected to the riser by a remotely operated device.  
     
     
         26 . A riser support assembly for connecting a riser by a free end thereof with a target structure, the riser support assembly comprising: 
 a buoyancy device for providing a predetermined buoyancy to the riser support assembly;    a suspending device configured for suspending the riser by the free end thereof from the riser support assembly;    a first anchoring device for anchoring the riser support assembly to the seabed.    
     
     
         27 . The riser support assembly of  claim 26 , wherein the suspending device is constructed for allowing an upwards movement of the riser relative to the riser support assembly.  
     
     
         28 . The riser support assembly of  claim 26  or  27 , wherein the riser support assembly comprises a recess configured for receiving the riser therein.  
     
     
         29 . The riser support assembly according to  claim 28 , wherein the recess is a channel which, in use, extends substantially through the buoyancy device, preferably in a substantially vertical direction.  
     
     
         30 . The riser support assembly according to  claim 26 , wherein the riser support assembly has a substantially elongated form.  
     
     
         31 . The riser support assembly according to  claim 30 , wherein the substantially elongated form extends in a substantially horizontal direction.  
     
     
         32 . The riser support assembly according to  claim 26 , wherein the buoyancy device comprises a first buoyancy means and a second buoyancy means, wherein the first and second buoyancy means are connected with one another by means of a bridging body.  
     
     
         33 . The riser support assembly according to  claim 26 , wherein the bridging body comprises the suspending device.  
     
     
         34 . The riser support assembly according to  claim 26 , wherein the suspending device is configured for suspending a number of risers therefrom.  
     
     
         35 . The riser support assembly according to  claim 26 , wherein the first anchoring device comprises an mooring line and an anchoring means, the anchoring means being chosen from a group of anchoring means, comprising: a piled foundation, a suction pile and a gravity foundation.  
     
     
         36 . The riser support assembly according to  claim 35 , wherein the anchoring means are configured for bearing a substantially upwardly directed force which is exerted on the anchoring means by the mooring line.  
     
     
         37 . The riser support assembly according to  claim 26 , wherein the first anchoring device comprises a mooring line, the mooring line being chosen from a group of mooring lines, comprising: a tendon, a polyester line, a steel wire and a chain.  
     
     
         38 . The riser support assembly according to  claim 26 , having at least one riser suspended therefrom.