Collapsible buoyancy device for risers on offshore structures

A method for adding upward force to a marine riser supported by a marine structure for counteracting the weight the marine riser in the marine environment, comprising:

• (a) attaching at least one inflatable buoyancy module to a marine riser, said inflatable buoyancy module defining at least one internal inflation chamber and having a deflated condition and a distended inflated condition developing an upwardly directed buoyancy force;
• (b) inflating said inflatable buoyancy module with a buoyant medium to apply an upwardly directed buoyancy force to said marine riser to reduce the effective weight of the marine riser;
• and
• introducing a liquid composition into said inflatable buoyancy module for ballast.

A method for adding upward force to a marine riser supported by a marine structure for counteracting the weight of the marine riser in the marine environment, wherein the marine structure defines an opening having a defined dimension, said method comprising:

• (a) attaching at least one inflatable buoyancy module to the marine riser, said inflatable buoyancy module being of greater external dimension when at said inflated condition as compared to the external dimension thereof at said collapsed condition and defining at least one internal inflation chamber and having a deflated condition and an inflated condition and when at said inflated condition in the marine environment developing an upwardly directed buoyancy force;
• (b) with said inflatable buoyancy module at said deflated condition, moving the marine riser and said inflatable buoyancy module through the marine structure opening;
• and
• (c) after moving the marine riser and said inflatable buoyancy module through the marine structure opening, inflating said inflatable buoyancy module to a dimension greater than the defined dimension of the marine structure opening and when submerged in the marine environment causing said inflatable buoyancy module to apply an upwardly directed force to said marine riser to reduce the effective weight of the marine riser.

A method for adding upward force to a marine riser supported by a marine structure for counteracting the weight of the marine riser in the marine environment, wherein said plurality of inflatable buoyancy modules have an inflation control system interconnected therewith, said method comprising:

• (a) attaching at least one inflatable buoyancy module to a marine riser, said inflatable buoyancy module defining at least one internal inflation chamber and having a deflated condition and a distended inflated condition developing an upwardly directed buoyancy force;
• (b) inflating said inflatable buoyancy module with a buoyant medium to apply an upwardly directed buoyancy force to said marine riser to reduce the effective weight of the marine riser;
• and
• (c) actuating said inflation control system for selectively inflating each of said plurality of inflatable buoyancy modules.

In a marine structure having a riser support and having at least one marine well production riser extending from said riser support downwardly to a subsurface riser well connection, the improvement comprising:

• (a) at least one inflatable buoyancy module defining a flexible inflatable envelope and being secured to the marine well production riser and having a deflated dimension enabling its movement through small deck openings of the marine structure and an inflated condition of greater dimension as compared to the small deck openings and providing buoyancy force to the marine riser to offset the weight thereof;
• (b) at least one access port being defined by said inflatable buoyancy module and having communication with said internal inflation chamber;
• and
• (c) a buoyancy control system having a source of inflation medium for communication with said at least one access port and permitting selective flow of inflation medium from said source through said access port and into said at least one inflation chamber for desired inflation of said inflatable buoyancy module.

In a deepwater production development spar having a riser support and having at least one marine riser extending from said riser support downwardly to a subsurface riser connection, the buoyant deepwater production development spar defining a working opening having a defined diameter, the improvement comprising:

• (a) at least one longitudinal tubular element defining an internal passage receiving the riser therein;
• (b) at least one expandable and contractible pressure tight envelope being fixed to said longitudinal tubular element and defining at least one internal inflation chamber therein, said expandable and contractible pressure tight envelope having a deflated condition defining a diameter less than the defined diameter of the working opening permitting passage thereof through said working opening along with the riser and an inflated condition defining a diameter greater than said defined diameter of the working opening;
• (c) at least one access port being defined by said expandable and contractible pressure tight envelope and having communication with said internal inflation chamber;
• and
• (d) a buoyancy control system having a source of inflation medium for communication with said at least one access port and permitting selective flow of inflation medium from said source of inflation medium through said access port and into said at least one inflation chamber for desired inflation of said expandable and contractible pressure tight envelope.