WO2015108746A1

WO2015108746A1 - Underwater drilling rig assembly and method of operating the underwater drilling rig assembly

Info

Publication number: WO2015108746A1
Application number: PCT/US2015/010586
Authority: WO
Inventors: Randall Scott SHAFER; Peter George NOBLE
Original assignee: Conocophillips Company
Priority date: 2014-01-16
Filing date: 2015-01-08
Publication date: 2015-07-23
Also published as: US20150197989A1

Abstract

An underwater drilling rig assembly includes a hull anchored to a sea floor with at least one anchoring component. Also included is a rig assembly disposed on the hull. Further included is a mast unit of the rig assembly. Yet further included is a pipe handling unit configured to maneuver a drill pipe into operative communication with the mast unit. Also included is a drill bit assembly operatively coupled to the mast unit. Further included is a control unit positioned proximate the sea floor and in operative communication with a plurality of components of the underwater drilling rig assembly, the control unit operatively coupled to at least one surface vessel for remote control of the underwater drilling rig assembly.

Description

UNDERWATER DRILLING RIG ASSEMBLY AND METHOD OF OPERATING THE UNDERWATER DRILLING RIG ASSEMBLY

FIELD OF THE INVENTION

[0001] This invention relates generally to offshore or underwater drilling systems and, more particularly, to an underwater drilling rig assembly, as well as a method of installing and operating the underwater drilling rig assembly.

BACKGROUND OF THE INVENTION

[0002] Drilling for hydrocarbons (e.g., oil and gas) offshore poses a number of challenges that are not a consideration during onshore drilling operations. Typically, floating or fixed platforms that are equipped with drilling equipment are employed to facilitate the offshore drilling operation. A riser connection between the platform and the sea floor is used to circulate a drilling fluid (e.g., drilling mud) during drilling. Such a structure becomes more challenging to maintain during deepwater operations. Furthermore, structural features must be included on the platform to accommodate the wave motion of the platform relative to the sea floor. Often, the drilling operations must be interrupted during extreme weather conditions, which involve hazardous operations and high costs.

[0003] Severe weather environments and deepwater sites require large drilling vessels with substantial marine support. For example, in the Arctic ice forces can be high and conventional drilling vessels cannot resist ice forces and therefore cannot drill in areas with heavy ice or require a high level of ice management support that is often not feasible. Large vessels for severe environment operations require a high level of personnel to support the operations.

[0004] In view of the foregoing challenges, efforts have been made to overcome the challenges by using a seabed rig that is partially or fully submerged. The prior efforts use large structures that are typically supported by the well and often require a surface vessel to be positioned directly over the seabed rig. Maintaining precise position over the seabed rig with the surface vessel includes several challenges due to harsh environment conditions described above and does not fully overcome the disadvantages associated with drilling platforms in such environments. SUMMARY OF THE INVENTION

[0005] In one embodiment, a method of operating an underwater drilling rig assembly is provided. The method includes lowering a hull with a rig assembly disposed thereon to a water depth proximate the sea floor. The method also includes leveling the hull with a plurality of legs extending from the hull and supported by the sea floor. The method further includes operatively coupling a control unit of the rig assembly to a surface vessel, the control unit in operative communication with a plurality of components of the underwater drilling rig assembly, the control unit configured to facilitate remote control of the underwater drilling rig assembly with the surface vessel.

[0006] In another embodiment, an underwater drilling rig assembly includes a hull anchored to a sea floor with at least one anchoring component. Also included is a rig assembly disposed on the hull. Further included is a mast unit of the rig assembly. Yet further included is a pipe handling unit configured to maneuver a drill pipe into operative communication with the mast unit. Also included is a drill bit assembly operatively coupled to the mast unit. Further included is a control unit positioned proximate the sea floor and in operative communication with a plurality of components of the underwater drilling rig assembly, the control unit operatively coupled to at least one surface vessel for remote control of the underwater drilling rig assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying figures by way of example and not by way of limitation, in which:

[0008] FIG. 1 is a schematic illustration of an underwater drilling rig assembly located on a seabed;

[0009] FIG. 2 is a schematic top plan view of the underwater drilling rig assembly;

[0010] FIG. 3 is a schematic illustration of the underwater drilling rig assembly with a mast raised for drilling into the seabed; and

[0011] FIG. 4 is a schematic view of a rig assembly of the underwater drilling rig assembly with a drilling module coupled thereto for drilling purposes. DETAILED DESCRIPTION OF THE INVENTION

[0012] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not as a limitation of the invention. It will be apparent to those skilled in the art that various modifications and variation can be made in the invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the invention cover such modifications and variations that come within the scope of the appended claims and their equivalents.

[0013] Referring to FIGS. 1 and 2, a portion of an underwater drilling rig assembly 10 is illustrated in a partially installed and assembled condition. The underwater drilling rig assembly 10 is depicted in a submarine environment. This environment, which may be referred to as "undersea" or "subsea," can be any underwater environment in which is there is a sea floor 12 and a water surface 14. Such environments include freshwater seas and lakes, as well as offshore oceanic environments. The underwater drilling rig assembly 10 may be employed at a deepwater drilling location or in a relatively shallow body of water. The underwater drilling rig assembly 10 is particularly beneficial in bodies of water that are prone to ice formation therein and bodies of water that are commonly subjected to harsh environment conditions at the water surface 14. The harsh environment conditions may include severe weather, including the presence of high wind, large waves, precipitation and/or bodies of ice, any of which would pose challenges to a surface vessel 16.

[0014] The underwater drilling rig assembly 10 can be transported to the drilling site by towing or by transport on a lift vessel. Typically, the underwater drilling rig assembly 10 is transported in a fully assembled form, however, transport as a plurality of components with on-site assembly is contemplated. Irrespective of the form of transport, the underwater drilling rig assembly 10 is installed on the sea floor 12 and configured to carry out drilling operations on the sea floor 12, thereby overcoming the issues associated with surface vessel or platform drilling operations in harsh environment conditions.

[0015] The following description pertains to a structure and method to transport, install, and operate the underwater drilling rig assembly 10. The underwater drilling rig assembly 10 includes a hull 18 that is buoyant and configured to float at the water surface 14, if desired. Ultimately, the underwater drilling rig assembly 10 is lowered from the water surface 14 in a controlled descent to a location proximate the sea floor 12 with any suitable mechanism. The underwater drilling rig assembly 10 includes a moonpool 19 that extends through the hull 18 and is positioned over a desired drilling location on the sea floor 12. It is to be appreciated that all aspects of the transport, installation, and operation of the underwater drilling rig assembly 10 may be monitored with an underwater remote operated vehicle (ROV) 20. The ROV 20 typically provides a video feed to a human operator that visually monitors the process.

[0016] The underwater drilling rig assembly 10 also includes a rig assembly 22 operatively coupled to, and disposed on, the hull 18. The rig assembly 22 includes a number of components and structures that are typically associated with drilling operations. In one embodiment, the underwater drilling rig assembly 10 is similar to a jack-up structure, but the entire assembly is configured to be submerged and placed on the sea floor 12, as described in detail herein. The hull 18 is configured to be ballasted proximate the sea floor 12. Extending from the hull is at least one, but typically a plurality of legs 24 extending from the hull 18 toward the sea floor 12. In one embodiment, three such legs are included to provide desired stability, but more or less are contemplated. The legs 24 are lowered to engage the sea floor 12 and the load of the underwater drilling rig assembly 10 is transferred to the legs 24. It is to be appreciated that the plurality of legs 24 bear the overall load of the underwater drilling rig assembly, specifically the hull 18 and the rig assembly 22. This is in contrast to a wellhead supporting a drilling assembly. The legs 24 can be adjusted to compensate for a sea floor region that is not level. The adjustment, if needed, provides an overall leveling of the hull 18, and therefore the underwater drilling rig assembly 10 overall. In one embodiment, a plurality of spud cans 26 are installed proximate ends of the plurality of legs 24 to provide further anchoring and self-leveling of the underwater drilling rig assembly 10, however, this may not be required in certain applications.

[0017] Referring now to FIG. 3, with continued reference to FIGS. 1 and 2, the rig assembly 22 includes a mast and pipe lifting arm module 28. Upon proper securement of the underwater drilling rig assembly 10 to the sea floor 12, a mast 30 of the mast and pipe lifting arm module 28 is raised from the illustrated horizontal position (FIG. 1) to a substantially vertical position (FIG. 3) to facilitate various lifting and drilling operations performed by the underwater drilling rig assembly 10. As shown, the mast 30 is maneuverable between substantially horizontal and vertical orientations. Such a feature may be particularly beneficial in bodies of water having an ice keel that protrudes to depths of the body of water that may interfere with the underwater drilling rig assembly 10. If such a condition is detected, the mast 30 is simply maneuvered to a substantially horizontal position. A pipe handling unit 34 of the mast and pipe lifting arm module 28 is configured to be pivoted from the horizontal position (FIG. 1) to facilitate maneuvering of a drill pipe (not shown) to be operatively coupled to the mast 30. A drill bit assembly (not shown) is lowered into a desired position and operatively coupled to the mast 30.

[0018] A control unit 42 is installed at a location proximate the sea floor 12 and the rig assembly 22. In the illustrated embodiment, the control unit 42 is integrated with the rig assembly 22 on the hull 18. Alternatively, the control unit 42 may be placed directly on the sea floor 12. The control unit 42 includes a plurality of components configured to carry out various tasks associated with overall operation of the underwater drilling rig assembly 10. The specific tasks are numerous and the following are merely illustrative of the contemplated tasks. The control unit 42 includes various lines, such as at least one return line 44 operatively coupled to the surface vessel 16 and the control unit 42. The return line 44 is configured to return fiuids, such as drilling fluid and waste fluid to the surface vessel 16 from the underwater drilling rig assembly 10. Additionally, at least one supply line 46 is operatively coupled to the surface vessel 16, as well as one or more components of the rig assembly 22, including the control unit 42. The supply line(s) 46 comprise a flow line to provide drilling fluid and an electrical line to provide power to the underwater drilling rig assembly 10. To facilitate routing of fluid, the control unit 42 includes a pump configured to direct the fluid in a desired direction. The control unit 42 further includes a plurality of cables (not shown) extending from the control unit 42, each of the cables connected to components of the underwater drilling rig assembly 10. Such a connection between the surface vessel 16, the control unit 42, and various components of the underwater drilling rig assembly 10 allows remote control of various functions of the underwater drilling rig assembly 10. The configuration of the lines extending between the control unit 42 and the surface vessel 16 is such that the surface vessel 16 does not need to remain directly over the underwater drilling rig assembly 10. By providing flexibility regarding the positioning of the surface vessel 16, challenges associated with maintaining precise position of the surface vessel 16 are avoided. This is particularly advantageous in severe weather environments.

[0019] In addition to a physical connection with the above-described lines and cables, a wireless connection may be present between the control unit 42 and the surface vessel 16 and/or the components of the underwater drilling rig assembly 10. By remotely controlling the underwater drilling rig assembly 10 with the surface vessel 16, it is not necessary to have human operators in direct physical contact with the underwater drilling rig assembly 10. In addition to remote control of the assembly, numerous aspects of operation of the underwater drilling rig assembly 10 may be automated, as is the case with onshore drilling assemblies. In particular, an automated drilling mode is enabled with the underwater drilling rig assembly 10. Once the underwater drilling rig assembly 10 is fully installed and operational, the drill bit assembly initiates drilling into the sea floor 12. After reaching a sufficient depth with the drill bit assembly, a casing may be installed within the hole and a blowout preventer (BOP) may be run and installed proximate a wellhead of the hole.

[0020] Referring to FIG. 4, the underwater drilling rig assembly 10 is configured to receive various equipment modules (not shown) from the surface vessel 16 or another vessel specially designed to store, transport and deliver the modules to the underwater drilling rig assembly 10. One such module 50 is generally illustrated and is configured to be disposed on the hull 18 to interact with the mast 30 and pipe handling unit 34 of the mast and pipe lifting arm module 28. The equipment modules are prepared for running and drilling the well and casing that is run in the well when a required well segment is complete.

[0021] Advantageously, the underwater drilling rig assembly 10 is a highly automated unit that can be remotely operated by as little as one human operator. The hull 18 rests on the sea floor 12, thereby allowing loading of the other components to be on the base, rather than on the well itself. Furthermore, based on the remote control of the underwater drilling rig assembly 10, the surface vessel(s) supporting the assembly are not required to be positioned directly over the assembly and the well. This is particularly advantageous in harsh weather conditions, including those where ice formation is present at the water surface 14 of the body of water. Conducting the drilling operations on the sea floor 12 overcomes several obstacles with drilling in such environments. In deepwater drilling locations, the above-described embodiments obviate the need for the long length of a drilling riser that would normally extend from the surface vessel 16 to the sea floor 12.

[0022] While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.

Claims

CLAIMS What is claimed is:

1. A method of operating an underwater drilling rig assembly comprising: lowering a hull with a rig assembly disposed thereon to a water depth proximate the sea floor; leveling the hull with a plurality of legs extending from the hull and supported by the sea floor; and operatively coupling a control unit of the rig assembly to a surface vessel, the control unit in operative communication with a plurality of components of the underwater drilling rig assembly, the control unit configured to facilitate remote control of the underwater drilling rig assembly with the surface vessel.

2. The method of claim 1, further comprising anchoring the hull to the sea floor with a plurality of spud cans operatively coupled to an end of the plurality of legs.

3. The method of claim 1, further comprising ballasting the hull at a depth proximate the sea floor.

4. The method of claim 1, further comprising observing installation of the underwater drilling rig assembly with an underwater remote operated vehicle (ROV).

5. The method of claim 1, further comprising pumping fluid to a water surface with a pump of the control unit.

6. The method of claim 1, further comprising providing power and fluid to the underwater drilling rig assembly through at least one line connected to the surface vessel and the control unit.

7. The method of claim 1, further comprising installing a blowout preventer (BOP) proximate a wellhead.

8. The method of claim 1, further comprising drilling a hole in the sea floor with a drill bit assembly of the rig assembly.

9. The method of claim 8, further comprising installing a casing within the hole drilled with the drill bit assembly.

10. An underwater drilling rig assembly comprising: a hull anchored to a sea floor with at least one anchoring component; a rig assembly disposed on the hull; a mast unit of the rig assembly; a pipe handling unit configured to maneuver a drill pipe into operative communication with the mast unit; a drill bit assembly operatively coupled to the mast unit; and a control unit positioned proximate the sea floor and in operative communication with a plurality of components of the underwater drilling rig assembly, the control unit operatively coupled to at least one surface vessel for remote control of the underwater drilling rig assembly.

11. The underwater drilling rig assembly of claim 10, wherein the hull is configured to be ballasted proximate the sea floor.

12. The underwater drilling rig assembly of claim 11, wherein the hull comprises a plurality of legs extending therefrom, each of the legs configured to engage the sea floor to support the load of the underwater drilling rig assembly.

13. The underwater drilling rig assembly of claim 10, wherein the at least one anchoring component comprises a plurality of spud cans configured to be at least partially embedded within the sea floor.

14. The underwater drilling rig assembly of claim 10, wherein the control unit is operatively coupled to the at least one surface vessel with at least one line.

15. The underwater drilling rig assembly of claim 14, wherein the at least one line is a flow line configured to route fluid between the at least one surface vessel and the underwater drilling rig assembly.

16. The underwater drilling rig assembly of claim 14, wherein the at least one line comprises an electrical cable for providing power to the plurality of components of the underwater drilling rig assembly.

17. The underwater drilling rig assembly of claim 10, wherein the underwater drilling rig assembly is configured to operate in an automated drilling mode.

18. The underwater drilling rig assembly of claim 10, wherein the underwater drilling rig assembly is an unmanned assembly.