Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
  • E21B17/01—Risers
  • E21B17/012—Risers with buoyancy elements

Definitions

• the present invention relates generally to self-standing riser assemblies utilized during oil and gas exploration and production operations, and in a particular though non- limiting embodiment, to a self-standing riser system equipped with multiple buoyancy chambers suitable for deployment in a variety of water depths and sea conditions.
• SSR Self-standing risers
• Known SSR can be used to facilitate standard "shallow-water” (e.g., between 0 feet and around 600 feet of water) drilling units and cost effective production facilities by placing blow-out preventers and production trees on top of a buoyancy chamber.
• a self-standing riser system suitable for deepwater oil and gas exploration and production including a lower riser assembly disposed in communication with a primary well-drilling fixture; one or more intermediate buoyancy chambers disposed in communication with the lower riser assembly and one or more portions of intermediate riser assembly, wherein one or more of the buoyancy chambers further includes an open-bottomed lower surface portion; and an upper riser assembly disposed in communication with one or more upper buoyancy chambers, wherein one or more of the upper buoyancy chambers further includes a fully enclosed portion.
• Fig. IA is a schematic diagram of a self-standing riser system equipped with an open-bottom buoyancy chamber in calm waters, according to an example embodiment known in the prior art.
• Fig. IB is a schematic diagram of a self-standing riser system equipped with an open-bottomed buoyancy chamber that is nearing its spill point.
• Fig. 1C is a schematic diagram of a self-standing riser equipped with an open- bottomed buoyancy chamber that has tilted beyond its spill point.
• Fig. 2 is a schematic diagram depicting the effects of pressure, temperature and depth on a closed-bottom buoyancy chamber.
• FIG. 3 is a schematic diagram of a self-standing riser system comprising multiple buoyancy chambers, according to example embodiments of the present invention.
• FIG. 4 is a schematic diagram depicting the installation of a self-standing riser system comprising multiple buoyancy chambers, according to example embodiments of the invention.
• the closed container design is similar in some respects to a submarine, in that there are typically one or more ballast chambers used to house a fluid, such as a light gas, seawater, etc. Once a desired ratio of fluids is achieved, the chamber is closed off by valves or other means known in the art.
• a fluid such as a light gas, seawater, etc.
• An open-bottomed buoyancy chamber includes many design functions similar to those of the closed container design. However, once desired buoyancy characteristics are achieved, fluid disposed within the chamber is simply trapped by the sides and top thereof.
• Figure IA illustrates a known, open-bottomed, buoyancy chamber disposed in communication with an SSR and filled with a fluid, for example, a pressurized gas.
• a fluid for example, a pressurized gas.
• Figure IB illustrates how the fluid contained within the chamber has shifted relative to the system's tilt away from its vertical axis.
• the chamber can accommodate a tilt of up to a certain critical angle (which depends largely on its design dimensions) before the critical spill point angle is reached, and fluid begins to escape from the chamber.
• Figure 1C further illustrates how the spill rate of the gas contained within an open-bottomed buoyancy chamber will increase as the critical tilt angle is reached and exceeded.
• spillage will result in even greater loss of buoyancy, and therefore a proportionately increasing tilt angle, which will cause more and more gas to escape from the chamber.
• enough gas escapes that the buoyant force is reduced to the point where the chamber can no longer support the riser, thereby causing the system to fail.
• open-bottomed chambers can operate at extreme water depths with a reduced concern of structural collapse than a closed system, since the open design allows fluid pressures within the chamber to equalize with surrounding pressures at even great depths. Furthermore, the open-bottomed design has less overall system weight due to a reduction in required construction materials, since there is no bottom, and the remainder of the shell will require less thickness and reinforcement in order to withstand deep water fluid pressures.
• Closed container buoyancy chambers must also be robust enough to offset external forces such as deepwater fluid pressure. As illustrated in Figure 2, such chambers must, as a threshold matter, have sufficient structural integrity and wall thickness to resist expected pressures that might cause a collapse of the chamber's outer shell. Moreover, when deploying a closed buoyancy chamber filled with a gas, the internal gas pressures and temperatures should be sufficiently proportional to the external water pressures and temperatures that an associated pressure or temperature gradient will not induce an effective change in gas volume within the chamber which could cause the chamber's outer shell to crack or collapse.
• an SSR system 14 comprising a plurality of subordinate buoyancy chambers configured to admit to installation in deeper water depths than any previously known SSR systems.
• SSR 14 can be stacked with multiple buoyancy chambers as illustrated in Figures 4A, 4B, 4C and 4D.
• Figure 3 illustrates in Figure 3 as a combination of lower SSR assembly 10 and upper SSR assembly 12, embodiments of the overall SSR system 14 can comprise any number of individual SSR assemblies.
• lower SSR assembly 10 is first deployed.
• a specially designed vessel equipped specifically to deploy buoyancy chambers and SSR assemblies is used.
• lower SSR assembly 10 is joined in mechanical communication with a casing wellhead established near the mud-line.
• the casing wellhead has been preset into a well hole bored into an associated seafloor surface.
• one or more intermediate buoyancy chambers 16 is attached to lower SSR assembly 10, thereby providing increased stability in deep or turbulent waters.
• intermediate buoyancy chamber 16 can comprise a closed-container design, but in most instances will comprise the open- bottomed design for the reasons described above, with the only firm requirement being that intermediate chamber 16 must in any event be capable of providing the support required to control lower SSR assembly 10 and upper SSR assembly 14.
• intermediate buoyancy chamber 16 is disposed in mechanical communication with either previously known or custom-designed drilling, production and exploration equipment.
• the top and bottom portions of an intermediate buoyancy chamber may comprise one or more of a blowout preventer, a production tree, or a wellhead that functions in a manner similar to the casing wellhead placed near mud-line of the ocean floor.
• Attachment of the drilling, production and exploration equipment can be achieved using either known or custom connection and fastening members, e.g., hydraulic couplers, various nut and bolt assemblies, welded joints, pressure fittings (either with or without gaskets), swaging, etc., without departing from the scope of the invention.
• an upper SSR assembly 12 is deployed and disposed in mechanical communication with a wellhead, blowout preventer, or production tree (or another, custom-designed device combining elements of one or more of such devices) installed atop an upper surface of the intermediate chamber 16 or a connecting member associated therewith. According to other example embodiments, the installation process continues until the desired number of such assemblies are installed in serial communication with one another in order to achieve a stable and efficient SSR system 14, as depicted in Figures 4A - 4D.
• example embodiments can utilize stress joints 22, as depicted in Figure 3.
• Stress joints 22 can comprise any known material, for example, a plastic, rubber, or metal material, but should in any event be capable of maintaining the SSR 14 system's structural integrity and overall stability.
• a plurality of upper buoyancy chambers 18, 20 includes an open-bottomed chamber 18 and a closed- container type chamber 20.
• at least one of said upper chambers - generally the topmost - will comprise a closed design, while others in the system, including intermediate chamber 16, will comprise an open-bottomed design.
• all of the chambers in the system are either open or closed, and in still further embodiments, combinations of open and closed chambers are employed across the system.
• the multiple open-bottomed design buoyancy chambers are utilized to facilitate deployment in deeper waters in which surrounding fluid pressures are greatest.
• Other embodiments utilize a plurality of closed-container type chambers disposed near the top of the SSR system 14, thereby improving the system's overall stability and balance. Such configurations can also help avoid the system's tendency to tilt away from its vertical axis as a result of external lateral forces, such as a forceful cross-current.
• a plurality of buoyancy chambers disposed in mechanical communication with upper SSR assembly 12 allows for the overall SSR system 14 to maintain required functionality and stability in varying water depths and conditions, thereby improving its efficiency and operability.
• FIG. 1033 Further example embodiments comprise a plurality of upper buoyancy chambers disposed in mechanical communication with commonly known drilling, production and exploration equipment.
• the top and bottom portions of an upper buoyancy chamber may comprise one or more of a blowout preventer, a production tree, or a wellhead designed to function in a manner similar to the casing wellhead placed near mud- line of the ocean floor.
• the buoyancy chambers utilized throughout the system further comprise auxiliary buoyancy materials, such as syntactic foam or air filled glass micro-spheres that lend buoyancy to the system. Injecting one or more of these materials within an open-bottomed chamber will assist in prevention of buoyancy fluid (e.g., gas, liquid, etc.) loss should tilting occur, or if there is a breach or failure of tubing, valves, or other equipment utilized in connection with the buoyancy chamber.
• auxiliary buoyancy materials such as syntactic foam or air filled glass micro-spheres that lend buoyancy to the system. Injecting one or more of these materials within an open-bottomed chamber will assist in prevention of buoyancy fluid (e.g., gas, liquid, etc.) loss should tilting occur, or if there is a breach or failure of tubing, valves, or other equipment utilized in connection with the buoyancy chamber.
• a deployment vessel deploys a lower SSR assembly 40 to the ocean floor where it is mechanically disposed in communication with a casing wellhead near the mud-line.
• Figure 4A further depicts an intermediate buoyancy chamber 41 installed atop the SSR assembly 40.
• the intermediate buoyancy chamber 41 further comprise one or more previously known or custom-fit attachment mechanisms, such as a combined blowout preventer and production tree, so that the intermediate chamber 41 is useful during operations for purposes other than mere connection with an upper SSR assembly 42.
• a plurality of intermediate buoyancy chambers 41 are deployed and mechanically disposed in communication with a previously installed SSR assembly or another intermediate buoyancy chamber (see, for example, Figures 4B - 4D).
• intermediate SSR assemblies 42 and 44 are deployed and disposed in mechanical communication with a well-head affixed atop intermediate buoyancy chamber 41.
• additional intermediate buoyancy chambers 41, 43, 45 serve as additional support and connection components for the intermediate SSR assemblies.
• Such redundant embodiments can achieve heretofore unknown SSR system depths of more than 15,000 ft. with the addition of multiple intermediate SSR assemblies.
• FIG. 4D a final SSR assembly 46 is deployed to complete the SSR system 50.
• Figure 4D further depicts an embodiment employing a plurality of buoyancy chambers 47 atop SSR assembly 46 in order to complete the overall SSR system 50.
• embodiments of the plurality of buoyancy chambers 47 can comprise a mixture of open-bottomed and closed-container designs, or any other configuration made desirable by operating conditions, including of course the installation of only a single such chamber.

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• Engineering & Computer Science (AREA)
• Geology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Mining & Mineral Resources (AREA)
• Physics & Mathematics (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Earth Drilling (AREA)
• Filling Or Discharging Of Gas Storage Vessels (AREA)
• Revetment (AREA)
• Other Liquid Machine Or Engine Such As Wave Power Use (AREA)

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• 2008
  • 2008-11-19 AU AU2008326408A patent/AU2008326408B2/en not_active Ceased
  • 2008-11-19 MX MX2010005485A patent/MX2010005485A/es not_active Application Discontinuation
  • 2008-11-19 US US12/274,124 patent/US20090126937A1/en not_active Abandoned
  • 2008-11-19 WO PCT/US2008/084057 patent/WO2009067532A1/en active Application Filing
  • 2008-11-19 AP AP2010005290A patent/AP2010005290A0/en unknown
  • 2008-11-19 CN CN200880117681.2A patent/CN101939491B/zh not_active Expired - Fee Related
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• 2011
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• 2013
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