Downhole Intervention

Abstract

The present invention is directed to novel methods and apparatus for the design, installation, use, recovery, and reuse of a Self Supporting Riser (SSR) for wells that are not under a platform. The SSR of the present invention uses standardized joints that can be recovered, potentially warehoused, and recombined in different configurations for different purposes or locations. Emphasis is on methods and apparatus that use relatively small vessels subject to high motions in the use and recovery of the SSR, especially the methods, apparatus and vessel for downhole intervention and work over through a SSR.

1 . A stabilizer system for a vessel subject to high vessel motions of heave, pitch and roll comprising:
 two or more cylinders supporting a heave platform between said cylinders, said heave cylinders adapted for attachment to said vessel,   a pitch and roll frame;   two or more pitch and roll compensation cylinders attached to said frame, each said cylinder having a compliant coupling on each end of said cylinder, one coupling attached to said frame and the coupling at the other end of said cylinder attached to said platform.   
     
     
         2 . A hydraulic circuit for the heave cylinders of a stabilizer system according to  claim 1  comprising:
 means, including a pump/valve assembly, to maintain constant pressure in load bearing chambers of said heave cylinders connected to said heave platform. 
 
     
     
         3 . A stabilizer system according to  claim 1  wherein the load chamber of each pitch and roll compensation cylinder is attached to said frame. 
     
     
         4 . A hydraulic circuit for said pitch and roll compensation cylinders of a stabilizer system according to  claim 3  comprising:
 a pump in said circuit for adding a fixed volume of fluid to the trapped fixed volume of fluid shared by the load bearing chambers of said cylinders; and 
 isolation means to maintain said fixed volume of fluid between said load bearing chambers of said cylinders, wherein when increased pressure occurs in one or more of said cylinder chambers, fluid flows to the other cylinder chambers. 
 
     
     
         5 . A small sea vessel subject to high vessel motions of heave, pitch and roll and having a moon pool comprising:
 a stabilizer system attached to said vessel comprising:   two or more cylinders supporting a platform between said cylinders, said cylinders attached to said vessel placing said platform over said moon pool, said platform moving perpendicular to the deck of said vessel in response to heave of said vessel;   a pitch and roll stabilized frame;   two or more pitch and roll compensation cylinders attached to said frame, each cylinder having a compliant coupling on each end of said cylinder, one coupling attached to said frame and the coupling at the other end of cylinder attached to said platform.   
     
     
         6 . A small sea vessel according to  claim 5  wherein the load bearing chambers of said heave cylinders are attached to said vessel. 
     
     
         7 . A small sea vessel according to  claim 5  wherein the load bearing chambers of said pitch and roll compensation cylinders are attached to said frame. 
     
     
         8 . A small sea vessel according to  claim 6  wherein the rod end of said heave cylinders support said platform, to move said platform perpendicular to the deck in response to the heave of said vessel. 
     
     
         9 . A small sea vessel according to  claim 5  wherein there are at least four heave cylinders supporting said platform and at least four pitch and roll compensation cylinders attached to said frame. 
     
     
         10 . A small sea vessel according to  claim 5  wherein said pitch and roll frame is stabilized over and in said moon pool. 
     
     
         11 . A small sea vessel according to  claim 9  further comprising:
 a hydraulic circuit for said heave cylinders comprising 
 a pump/valve assembly connected to the said load bearing chambers of the heave cylinders to extend/ retract the cylinder rods together by maintaining essentially the same pressure in said load bearing chambers; 
 said pump responding to vessel downward heave causes the pump to deliver additional fluid to said load bearing chambers extending the cylinder rods, and any upward heave of the vessel causes the pump/ valve assembly to remove fluid from said load bearing chambers retracting the cylinder rods. 
 
     
     
         12 . A small sea vessel according to  claim 9  further comprising:
 a passive hydraulic circuit for said pitch and roll compensation cylinders comprising a fixed volume of fluid in the cylinder circuit, such that the pitch/roll of the vessel changes the load on one or more cylinder chambers causing fluid to flow to the other cylinder chambers changing the length of the cylinder rods in each cylinder chambers in response to the change of load. 
 
     
     
         13 . A method for assembling a riser extension from a vessel subject to high vessel motions of heave, pitch and roll and having a porch extending beyond the deck and having:
 a stabilizer system attached to said vessel including:   two or more cylinders supporting a platform between said cylinders, said cylinders attached to said vessel placing said platform over said porch, said platform moving perpendicular to the deck of said vessel in response to heave of said vessel;   a pitch and roll stabilized frame;   two or more pitch and roll compensation cylinders attached to said frame, each cylinder having a compliant coupling on each end of said cylinder, one coupling attached to said frame and the coupling at the other end of cylinder attached to said platform; and   movable joint connecting tools on said heave platform to assemble a riser extension comprising:   joining selected specialty joints;   lifting said selected joints and lowering said joints through an opening in the heave platform and an opening in said pitch and roll frame;   moving said joint connecting tools to their closed position to support the assembled riser extension joints; and   sequentially lifting an additional joint, connecting the additional joint to the assembled riser extension joints, lifting said assembled joints and additional joint; moving said connecting tools to their open position, lowering said joints assembled through said opening in the heave platform and the opening in said pitch and roll frame until the engagement on the end of said additional joint is above said heave platform, moving said joint connecting tools to their closed position to support the assembled riser extension joints at said engagement, until the desired length of riser extension is obtained.   
     
     
         14 . A method according to  claim 13  further comprising:
 aligning and attaching said riser extension wherein the lowermost joint is a connector to a SSR. 
 
     
     
         15 . A method for attaching a riser extension to a SSR according to  claim 14  wherein an ROV assists in aligning and attaching said riser extension to said SSR. 
     
     
         16 . A method for assembling a riser extension from a vessel subject to high vessel motions of heave, pitch and roll and having:
 a stabilizer system attached to said vessel including:   two or more cylinders supporting a platform between said cylinders, said cylinders attached to said vessel placing said platform over sea water, said platform moving perpendicular to the deck of said vessel in response to heave of said vessel;   a pitch and roll stabilized frame;   two or more pitch and roll compensation cylinders attached to said frame, each cylinder having a compliant coupling on each end of said cylinder, one coupling attached to said frame and the coupling at the other end of said cylinder attached to said platform; and   movable joint connecting tools on said heave platform to assemble a riser extension comprising:   joining selected specialty joints;   lifting said selected joints and lowering said joints through an opening in the heave platform and an opening in said pitch and roll frame;   moving said joint connecting tools to their closed position to support the assembled riser extension joints; and   sequentially lifting an additional joint, connecting the additional joint to the assembled riser extension joints, lifting said assembled joints and additional joint;   moving said connecting tools to their open position, lowering said joints assembled through said opening in the heave platform and the opening in said pitch and roll frame until the engagement on the end of said additional joint is above said heave platform, moving said joint connecting tools to their closed position to support the assembled riser extension joints at said engagement, until the desired length of riser extension is obtained.   
     
     
         17 . A method for according to  claim 16  further comprising:
 aligning and attaching said riser extension wherein the lowermost joint is a connector to said SSR. 
 
     
     
         18 . A method for attaching a riser extension to a SSR according to  claim 17  wherein an ROV assists in aligning and attaching said riser extension to said SSR.