Offshore drilling rig assembly and method

Abstract

Well centre assembly for an offshore drilling rig and associated method. There is described a well centre assembly 10 for an offshore drilling rig. The well centre assembly 10 comprises a diverter assembly 16 and a movement control system 18. The movement control system 18 is operable between the diverter assembly 16 and a supporting structure 12 of the rig. In use, the movement control system 18 controls or permits relative movement between the diverter assembly 16 and the supporting structure 12. A connector such as a riser 34 connected to the diverter assembly 16 during deployment, while deployed or during retrieval of the riser 34 may experience external forces such as from tidal, wind and/or wave movement at a water surface 50, which may cause the positioning and/or orientation of the riser 34 to vary. The movement control system 18 may control the movement of the diverter assembly 16 so as to compensate for movement of the riser 34.

Claims

1. A well centre assembly for an offshore drilling rig, comprising: a movement control system, a supporting structure of the offshore drilling rig, and a diverter assembly, wherein the diverter assembly is connectible to at least one diverter connector for receiving fluid diverted by the diverter assembly, wherein the diverter connector is configured to permit movement of the diverter assembly while maintaining fluid communication with the diverter assembly, a riser connected to the diverter assembly, wherein the movement control system is operable between the diverter assembly and the supporting structure of the offshore drilling rig, and wherein the movement control system is configured to control movement of the diverter assembly to compensate for movement of the riser.

2. The well centre assembly according to claim 1, wherein the movement control system comprises at least one actuator for controlling movement of the diverter assembly, and wherein the actuator is configurable between an extended configuration and a retracted configuration to control movement of the diverter assembly relative to the supporting structure.

3. The well centre assembly according to claim 2, wherein the movement control system comprises a plurality of actuators, and each of the plurality of actuators is fixable to define a fixed spacing between at least part of the diverter assembly and the supporting structure.

4. The well centre assembly according to claim 1, wherein the movement control system is configured to compensate for movement of the diverter assembly out of a plane defined by the supporting structure.

5. The well centre assembly according to claim 1, wherein the movement control system is configured to compensate for an angular variation in an orientation or inclination of the diverter assembly relative to the supporting structure.

6. The well centre assembly according to claim 1, wherein the diverter assembly defines a throughbore configured to permit passage of a riser joint of the riser therethrough during deployment or retrieval thereof.

7. The well centre assembly according to claim 1, wherein the diverter assembly comprises at least one of a rotary table and a spider.

8. An offshore drilling rig, comprising: a movement control system; a supporting structure; and a diverter assembly, wherein the diverter assembly is connectible to at least one diverter connector for receiving fluid diverted by the diverter assembly, wherein the diverter connector is configured to permit movement of the diverter assembly while maintaining fluid communication with the diverter assembly; a riser connected to the diverter assembly; wherein the movement control system being operable between the diverter assembly and the supporting structure of the offshore drilling rig; and the movement control system configured to control movement of the diverter assembly to compensate for movement of the riser.

9. The offshore drilling rig according to claim 8, further comprising a tensioner system for controlling a tension applied to the riser.

10. The offshore drilling rig according to claim 8, wherein the diverter assembly comprises at least one of a rotary table and a spider.

11. A method of controlling a diverter assembly for an offshore drilling rig comprising a riser connected to the diverter assembly, wherein the diverter assembly is connectible to at least one diverter connector for receiving fluid diverted by the diverter assembly, wherein the diverter connector is configured to permit movement of the diverter assembly while maintaining fluid communication with the diverter assembly, the method comprises steps of: controlling movement of the diverter assembly relative to a supporting structure of the offshore drilling rig by operating a movement control system between the diverter assembly and the supporting structure to compensate for movement of the riser.

12. The method according to claim 11, wherein the controlling of movement of the diverter assembly includes at least one of: limiting, preventing, restricting or stopping movement of the diverter assembly relative to the supporting structure.

13. The method according to claim 11, wherein the controlling of movement of the diverter assembly includes at least one of: permitting, allowing, varying the rate of, or dampening movement of the diverter assembly relative to the supporting structure.

14. The method according to claim 11, wherein the controlling of movement of the diverter assembly includes at least one of: controlling a position, orientation or inclination of the diverter assembly relative to the supporting structure.

15. The method according to claim 11 and comprising compensating for movement of the riser during deployment or retrieval of the riser between the offshore drilling rig and a wellhead, and/or during a hang-off scenario in which the riser is disconnected from the wellhead.

16. The method according to claim 11 and comprising determining a movement parameter of the diverter assembly and controlling movement of the diverter assembly based on the movement parameter.

17. The method according to claim 11 and comprising determining a further movement parameter upon compensating for movement of the diverter assembly to define a feedback loop for compensating for movement of the diverter assembly relative to the supporting structure.

18. The method according to claim 11 and comprising utilizing the movement control system operable between the diverter assembly and the supporting structure of the offshore drilling rig to control movement of the diverter assembly relative to the supporting structure of the offshore drilling rig, and further comprising actuating the movement control system to permit at least one actuator of the movement control system to be inspected, repaired or replaced.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other examples of the present disclosure will now be explained, by way of example only, with reference to the following drawings, in which:

(2) FIG. 1 is a schematic side view of a well centre assembly according to an example of the present disclosure;

(3) FIG. 2 is a schematic side view of the well centre assembly, the assembly supporting a riser in a vertical inclination;

(4) FIG. 3 is a further schematic side view of the well centre assembly, the assembly supporting the riser, which in this example is inclined relative to the vertical inclination of the riser illustrated by FIG. 2;

(5) FIG. 4a is a cross-sectional view of a movement control system of the well centre assembly of FIGS. 1 to 3;

(6) FIG. 4b is a cross-sectional view of the movement control system across the section A-A in FIG. 4a;

(7) FIG. 5 is a cross-sectional view of the movement control system of FIG. 4a and including further components for operating the movement control system; and

(8) FIG. 6 is a schematic side view of the well centre assembly, with a deployed riser.

DETAILED DESCRIPTION OF THE DRAWINGS

(9) FIGS. 1, 2 and 3 illustrate a well centre assembly 10 according to an example of the present disclosure. The well centre assembly 10 may be concerned with various operations associated with offshore hydrocarbon extraction, for example, drilling operations and the like. The well centre assembly 10 is supported by a supporting structure 12 of an offshore drilling rig (not shown), which in this example is disposed below a drilling floor 14 of the offshore drilling rig.

(10) The well centre assembly 10 includes a diverter assembly 16 mounted on a movement control system 18, which in this example includes a plurality of actuators 20 for controlling movement of the diverter assembly 16 relative to the supporting structure 12. The actuators 20 are supported by the supporting structure 12. An opening 22 in the supporting structure 12 is aligned with a drilling floor opening 24 in the drilling floor 14. The drilling floor opening 24 may be sized or configurable in size to permit the diverter assembly 16 to be provided on, inserted into or removed from supporting structure 12 via the drilling floor opening 24. For example, during installation of the diverter assembly 16 and/or at least part of the movement control system 18, the diverter assembly 16 and/or the movement control system 18 can be installed by being passed through the drilling floor opening 24 and appropriately aligned relative to the opening 22 in the supporting structure 12. The diverter assembly 16 extends partially through the opening 22 once installed. Similarly, when being removed, the diverter assembly 16 and/or at least part of the movement control system 18 can be retrieved via the drilling floor opening 24.

(11) As best illustrated by FIG. 4a, the actuators 20 are disposed circumferentially spaced apart around the opening 22 of the supporting structure 12. The supporting structure 12 also includes a plurality of support members 26 for supporting the diverter assembly 16. The support members 26 are disposed circumferentially spaced apart around the opening 22 and are interposed between adjacent circumferentially spaced-apart actuators 20. The support members 26 provide a back-up support for the diverter assembly 16 in the event of failure of at least one of the actuators 20, if maintenance needs to be carried out, and/or if the actuators 20 are not required for any reason. At least part of the movement control system 18 and/or the diverter assembly is provided within a housing 25. If maintenance is required, at least one access hatch 27 of the housing 25 provides access to at least part of the movement control system 18 and/or the diverter assembly. It will be appreciated that access to the movement control system 18 and/or diverter assembly 16 may be provided in any other appropriate way. FIG. 4b illustrates section A-A of FIG. 4a and includes part of the diverter assembly 16 including an access hatch 27 either side of the housing 25.

(12) The actuators 20 are actuatable so as to control movement of the diverter assembly 16 relative to the supporting structure 12. The actuators 20 include or define a movement system configured for controlling movement of the diverter assembly 16. In this example, the actuators 20 each include a cylinder arrangement 28 forming a compensating cylinder system that is actuatable by pressurised fluid. In use, the compensating cylinder system uses pressurised fluid to extend and/or retract at least part of the cylinder arrangement 28 so as to control movement of the actuator 20, as is described in greater detail herein. The actuator 20 may actively apply a force or respond passively (e.g. by applying a reaction force in response) to an applied force exerted on the actuator 20 by the diverter assembly 16. Each of the actuators 20 may move, permit, prevent, restrict, reduce, dampen or otherwise control movement of the diverter assembly 16 in any appropriate way.

(13) The diverter assembly 16 includes at least one shoulder 30 for mounting the diverter assembly 16 on the actuators 20. Extending at least one of the actuators 20 causes at least part of the diverter assembly 16 to be moved away from the supporting structure 12 so as to increase a vertical spacing between the supporting structure 12 and the shoulder 30. Retracting at least one of actuators 20 causes at least part of the diverter assembly 16 to be moved towards the supporting structure 12 so as to decrease the vertical spacing between the supporting structure 12 and the shoulder 30. Each of the actuators 20 can be independently actuated or the actuators 20 can be actuated in unison, or in any appropriate sequence. Extending and/or retracting the actuators 20 can move the diverter assembly 16 or permit the diverter assembly 16 to move so as to vary at least one of: a position, orientation and inclination of the diverter assembly 16. For example, at least one of the actuators 20 can be actuated to move or to permit movement of the diverter assembly 16 vertically and/or to orient or incline (e.g. tilt, rotate, pivot, angle, or otherwise move) the diverter assembly 16 in any appropriate way. The shoulder 30 includes a moveable connection in the form of a pivot pin 31 connecting the diverter assembly 16 to the actuator 20, the pivot pin 31 being arranged to permit the diverter assembly 16 to move, for example tilt, pivot or the like in response to extension or retraction of the actuators 20.

(14) If the diverter assembly 16 moves, providing the movement control system 18 may permit such movement, and at least one of the actuators 20 may control movement of the diverter assembly 16 in any appropriate way. Such a situation may occur if a component, which in this example is in the form of a riser joint 32 of a riser string 34, is connected to or otherwise has a fixed inclination relative to the diverter assembly 16. FIGS. 2 and 3 illustrate the example of the riser joint 32 passing through or being held within (depending on the stage of the riser deployment/retrieval process) a spider 36, a rotary table 38 and the diverter assembly 16. Each of the spider 36, rotary table 38 and the diverter assembly 16 includes a throughbore or passageway for permitting the passage of a component e.g. the riser joint 32 therethrough. The supporting structure 12 is configured to withstand the weight of the riser string 34 before, during or after applying tension via the spider 36 for supporting the riser string 34. The supporting structure 12 is configured to withstand the weight of the riser string 34 if the spider 36 does not support the riser string 34.

(15) FIG. 2 illustrates an example where the riser 34 is vertically inclined (i.e. the riser 34 is not inclined at an angle to the vertical) relative to the supporting structure 12 and extending below a water surface 50. FIG. 3 illustrates an example where the riser 34 is inclined at an angle relative to the vertical inclination of the riser string 34 illustrated by FIG. 2. Depending on wind, water current, wave and/or tidal conditions or the like, the riser string 34 inclination may vary as illustrated by FIGS. 2 and 3. For example, FIG. 2 shows the water surface 50 as being relatively even with the riser 34 in the vertical inclination. Providing forces on the riser 34 such as caused by water current, wind, waves, and the like do not cause the riser 34 to move from the vertical inclination, the riser 34 may remain substantially in the vertical inclination of FIG. 2. FIG. 3 shows the water surface 50 as being uneven (for example due to wave motion), but it is possible that water current, wind, and the like are also present. In the example of FIG. 3, the riser 34 is inclined at an angle to the vertical due to the movement of the water (e.g. due to water current and/or wave movement) and/or due to wind movement. In some examples, either or both of the riser 34 and the supporting structure 12 may move, for example if the offshore drilling rig is of a floating type, in response to water and/or wind movement. Relative movement between the riser 34 and the supporting structure 12 may be controlled in any appropriate way. It will be appreciated that the riser 34 may be longer than or shorter than the riser 34 illustrated in FIGS. 2-3.

(16) In some examples there may be prevailing current which may cause the riser 34 to adopt a relatively fixed orientation relative to the supporting structure 12. In some examples, such as in poor weather conditions (e.g. in a storm, high winds, or the like), the riser 34 may swing or move continuously or continually so that the inclination of the riser 34 relative to the supporting structure 12 varies. In any of the examples, the diverter assembly 16 may move or be permitted to move by the movement control system 18.

(17) In some examples, a relatively fixed orientation of the diverter assembly 16 relative to the supporting structure 12 may be required, for example if a riser joint 32 connection is being made up above the drilling floor 14. In this situation, the actuators 20 may be configured to prevent movement of the diverter assembly 16 and to force the diverter assembly 16 to adopt a certain orientation, for example, a vertical inclination such as that illustrated by FIG. 2. If the riser joint 32 is not correctly oriented or inclined it may be difficult to make up a connection between two riser joints 32. The same may apply for connecting together any type of connector.

(18) The diverter assembly 16 further includes at least one diverter outlet 52, in this example there are two diverter outlets 52 illustrated, for connecting to corresponding diverter connectors 54. The diverter assembly 16 may function to divert fluid away from a work area of the offshore drilling rig, for example, during a gas kick from a formation. The diverter connectors 54 provide fluid communication between the diverter outlets 52 and a diverter conduit 56 for diverting fluid away from the diverter assembly 16 while permitting movement of the diverter assembly 16 relative to the supporting structure 12. The diverter connectors 54 may include a flexible, conformable, deformable, extendible, compressible, or otherwise adaptable component for permitting said relative movement between the diverter assembly 16 and the diverter conduit 56. Providing the diverter connectors 54 may allow the diverter assembly 16 to move as required and may avoid compromising on the safety function of the diverter assembly 16.

(19) FIGS. 4a, 4b and 5 illustrate at least part of the movement control system 18 and diverter assembly 16. FIG. 5 illustrates an example of the movement control system 18. The movement control system includes a hydraulic fluid supply 58 configured to supply fluid to or from a hydraulic control system 60 via supply fluid connectors 62 (which may be in the form of rigid or flexible hoses, or the like). The hydraulic fluid supply 58 and hydraulic control system 60 are connected to a controller 64 which functions to control operation of the hydraulic fluid supply 58 and hydraulic control system 60. The controller 64 can be manually or automatically operated. The controller 64 may be configured to receive data from one or more sensors (not shown, but for example could be provided on any component) configured to collect data such as movement data from the diverter assembly 16 and/or movement control system 18. The hydraulic control system 60 is provided in fluid communication with each of the actuators 20 via actuator fluid connectors 66 (which may be in the form of rigid or flexible hoses, or the like). The supply fluid connectors 62 and/or the actuator fluid connectors 66 can include one or more fluid conduits for passing hydraulic fluid therethrough for actuating one or more of the actuators 20. The hydraulic fluid supply 58, the hydraulic control system 60, the supply fluid connectors 62, the actuator fluid connectors 66 and any other components may comprise any appropriate valve arrangement and/or pump arrangement so as to provide fluid pressure for actuating the actuators 20 as required. Since each actuator 20 can be individually addressed, each actuator 20 can individually, or where appropriate, collectively, control movement of the diverter assembly 16 by either moving, permitting movement, restricting, reducing, dampening, or otherwise controlling movement of the diverter assembly 16.

(20) Reference is now also made to FIG. 6 of the drawings, which illustrates the well centre assembly 10 in combination with an installed riser string 34. The spider 36 used during the deployment of the riser 34 has been removed and a cover 29 has been fitted to the drilling floor 14 to cover the gap between the drilling floor opening 24 and the assembly 10. The riser string 34 includes an upper flex joint 46 and a tensioning ring 42. The tensioning ring 42 is supported from the supporting structure 12 using a tensioner system 44. The tensioner system 44 supports the tensioning ring 42 via a number of support cables 48 so as to control the tension in the riser string 34.

(21) The tensioner system 44 is configured to control or vary tension in the support cables 48, which in turn permits the tensioner system 44 to control the tension in the riser string 34. In this example the tensioner system 44 is in the form of a winch 49 supported by the supporting structure 12 and operable to control or vary tension in the support cables 48. The tension in the riser string 34 may depend on a number of factors, including movement of the riser string 34, buoyancy of the riser string 34, current, tidal movement, or the like. The tensioner system 44 can react to changes in the tension of the riser string 34 and/or control tension of the riser string 34 by applying a force via the cable 48 to either pull the riser string 34 upwards or permit movement of the riser string 34 downwards, so as to vary or control the tension in the riser string 34.

(22) As noted above, the well centre assembly 10 of the disclosure has particular utility when deploying or retrieving a riser string 34. However, the assembly 10 may also be operated in combination with a deployed riser string 34, which may incorporate one or more flex joints 46, as illustrated in FIG. 6. Alternatively, the assembly 10 may be locked in position when the riser string 34 is fully deployed.

(23) It will be appreciated that various modifications or alternative features may be provided where appropriate. Any of the features that are described as being an example may be readily replaced by any other appropriate feature providing the same, similar, equivalent or different function. Various options are described in the summary section of the present disclosure. Further examples of modifications or alternatives are described below.

(24) It will be appreciated that the diverter assembly 16 could include any appropriate component. The diverter assembly 16 may be configured to compensate for movement of the riser 34 or other connector, but may not necessarily include all of the components illustrated by the illustrated example. For example, the diverter assembly 16 may only include the diverter assembly 16, wherein the diverter assembly 16 is the only component of the well centre assembly 10 that is configured for compensating for movement of the riser 34 or other connector. The diverter assembly 16 may include at least one component, including at least one of: a spider 36, a rotary table 38, and the diverter assembly 16, wherein the movement control system 18 compensates for movement of the riser 34 as described herein.