A MOBILE OFFSHORE DRILLING UNIT, A METHOD OF USING SUCH A UNIT AND A SYSTEM COMPRISING SUCH A UNIT

Abstract

An offshore well-processing system includes a mobile offshore drilling unit and a remote well-processing device configured to be positioned on an offshore platform different from the mobile offshore drilling unit, the mobile offshore drilling unit defining at least one well centre and comprising at least one primary drill rig including at least one drill floor and at least one hoisting system for raising and lowering tubular equipment through the at least one well centre from/into a well in the seafloor. The mobile offshore drilling unit and the remote well-processing device are configured to be operationally coupled to each other; and the mobile offshore drilling unit is configured to assist in performing concurrent well-processing tasks on respective wells, including the first well processing task performed by the remote well-processing device on a first well and a second well-processing task concurrently performed by the offshore well-processing system on a second well.

Claims

1. An offshore well-processing system for performing one or more well-processing tasks on one or more wells of an off-shore oil or gas reservoir, the system comprising a mobile offshore drilling unit and a remote well-processing device configured to be positioned on an offshore platform different from the mobile offshore drilling unit, the mobile offshore drilling unit defining at least one well centre and comprising at least one primary drill rig comprising at least one drill floor and at least one hoisting system for raising and lowering tubular equipment through the at least one well centre from/into a well in the seafloor; and wherein the remote well-processing device is configured to perform at least a first well-processing task when positioned on said offshore platform at a position displaced from the at least one well centre defined by the mobile offshore drilling unit; and wherein the mobile offshore drilling unit and the remote well-processing device are configured to be operationally coupled to each other when the remote well-processing device is positioned on said offshore platform; and wherein the mobile offshore drilling unit is configured to assist in two or more concurrent well-processing tasks performed concurrently on respective wells, including the first well processing task performed by the remote well-processing device on a first well and a second well-processing task concurrently performed by the offshore well-processing system on a second well.

2. An offshore well-processing system according to claim 1, wherein the operational coupling comprises at least one connection chosen from: a utility line for transferring power from the mobile offshore drilling unit to the remote well-processing device, a communication line for transferring communications signals between the remote well-processing device and the mobile offshore drilling unit, and a flow line for transferring well fluids between the remote well-processing device and the mobile offshore drilling unit.

3. An offshore well-processing system according to claim 1, wherein the system comprises a pipe transfer apparatus configured to transport tubulars between the mobile offshore drilling unit and the remote well-processing device when said remote well-processing device is positioned on said offshore platform.

4. An offshore well-processing system according to claim 1, wherein the primary drill rig is configured to perform said second well-processing task on said second well concurrently with the remote well-processing device performing the first well-processing task on said first well.

5. An offshore well-processing system according to claim 1, wherein the mobile offshore drilling unit comprises a pump for transferring fluids between the mobile offshore drilling unit and a well; wherein the remote well-processing device is connectable to said pump via a flow line.

6. An offshore well-processing system according to claim 5, wherein the mobile offshore drilling unit comprises a pump configured to selectively or concurrently transfer fluids between the mobile offshore drilling unit and the first well via the remote well-processing device and between the mobile offshore drilling unit and the second well via the primary rig.

7. An offshore well-processing system according to claim 1, wherein the primary drill rig comprises a top drive or another device for imparting torque on a tubular string extending from the mobile offshore drilling unit into a well.

8. An offshore well-processing system according to claim 1, wherein the offshore platform is a production platform.

9. An offshore well-processing system according to claim 1, wherein the mobile offshore drilling unit and/or the offshore platform is/are a bottom-supported platform.

10. An offshore well-processing system according to claim 1, wherein the mobile offshore drilling unit is a jack-up unit or a semi-submersible unit or a drillship.

11. An offshore well-processing system according to claim 10; wherein the mobile offshore drilling unit is a jack-up platform comprising a cantilever.

12. An offshore well-processing system according to claim 11; wherein the mobile offshore drilling unit is configured to extend the cantilever above the offshore platform.

13. An offshore well-processing system according to claim 11, wherein the mobile offshore drilling unit is configured to attach at least a part of the remote well-processing device to the cantilever and to position at least the part of the remote well-processing device onto the offshore platform.

14. An offshore well-processing system according to claim 1, wherein the remote well-processing device is arranged moveable/skiddable on the offshore platform.

15. An offshore well-processing system according to claim 1, wherein the remote well-processing device comprises one or more of a connector or manifold for connecting a flow line extending from a pump of the mobile offshore drilling unit to a conductor extending from the offshore platform to the seafloor; a working platform; hang-off device for hanging off tubulars; a device for wireline operations into the first well; a device for coiled tubing operation into the first well; a blow-out-preventer; a drilling support structure; a hoisting system; break-out tongs and/or shearing devices; a control system and cabin for controlling a well-processing task in the second well; a top drive.

16. An offshore well-processing system according to claim 1, wherein the remote well-processing device has a lower rated lift capacity and/or a lower rated torque capacity and/or a lower pipe handling throughput capacity as the primary drill rig.

17. An offshore well-processing system according to claim 1, wherein the mobile offshore drilling unit comprises a pipe setback and/or other off-drill-floor pipe handling apparatus.

18. An offshore well-processing system according to claim 1, comprising a first remote well-processing device and a second remote well-processing device, each configured to perform one or more well-processing tasks when positioned on said offshore platform at a respective position displaced from the at least one well centre defined by the mobile offshore drilling unit; and wherein the mobile offshore drilling unit is configured to be operationally coupled to each of the first and second remote well-processing devices when the first and second remote well-processing devices are positioned on said offshore platform; and wherein the mobile offshore drilling unit is configured to assist in concurrent well-processing tasks performed concurrently on respective wells, including the first well-processing task performed by the first remote well-processing device on a first well and a second well-processing task concurrently performed by the second remote well-processing device on a second well.

19. A method of performing a well-processing task on a plurality of wells of an offshore oil or gas reservoir, the method comprising: positioning a mobile offshore drilling unit in a proximity of an offshore platform different from the mobile offshore drilling unit and located above a plurality of wells, the mobile offshore drilling unit comprising a primary drill rig comprising a drill floor and a hoisting system for raising and lowering tubular equipment from/into a well in the seafloor; performing, at a position on the offshore platform and displaced from a well centre defined by the mobile offshore drilling unit a first well-processing task on a first well, assisted by the mobile offshore drilling unit via an operational coupling extending between the mobile offshore drilling unit and said position on the offshore platform; and concurrently performing a second well-processing task on a second well, wherein the second well-processing task is performed by the mobile offshore drilling unit or is assisted by the mobile offshore drilling unit via an operational coupling extending between the mobile offshore drilling unit and a position of the second well on the offshore platform.

20. A method according to claim 19; comprising: providing a remote well-processing device positioned on said offshore platform different from the mobile offshore drilling unit at a position displaced from a well centre defined by the mobile offshore drilling unit; operationally coupling the remote well-processing device to the mobile offshore drilling unit; performing, by the remote well-processing device positioned on the offshore platform, a first well-processing task on a first well, assisted by the mobile offshore drilling unit via said operational coupling; and concurrently performing a second well-processing task on a second well, wherein the second well-processing task is performed by the mobile offshore drilling unit or is assisted by the mobile offshore drilling unit via an operational coupling extending between the mobile offshore drilling unit and a position of the second well on the offshore platform.

21. A method according to claim 20; wherein the second well-processing task is performed by the primary drilling rig or by a second remote well-processing device positioned on the off-shore platform and operationally coupled to the mobile offshore drilling unit.

22. A method according to claim 19, wherein some or all mud handling and/or some or all off-drill-floor pipe handling associated with the first and second well-processing tasks is handled and/or facilitated/assisted by the mobile offshore drilling unit.

23. A method according to claim 19, wherein the well-processing tasks are sub-tasks of a decommissioning task and wherein the first well-processing task comprises one or more of: killing a well, cementing, logging, testing and/or monitoring tasks in the well; and wherein the second well-processing task comprises one or more of: pulling production tubing from the well, removing casing from the well, milling and logging.

24. (canceled)

25. A mobile offshore drilling unit comprising a primary drill rig comprising a drill floor and a hoisting system for raising and lowering tubular equipment from/into a well in the seafloor through a well centre defined by the mobile offshore drilling unit; and wherein the mobile offshore drilling unit is configured to establish an operational coupling with a remote well-processing device positioned on an offshore platform different from the mobile offshore drilling unit and at a position different from the well centre defined by the mobile offshore drilling unit; and to assist in performing two or more concurrent well-processing tasks performed on respective wells of an offshore oil or gas reservoir; wherein at least a first one of said well-processing tasks is performed by said remote well-processing device.

26. A mobile offshore drilling unit according to claim 25; comprising: a hull and one or more legs extending from the hull downward towards the sea floor; a cantilever comprising a primary drilling rig; wherein the cantilever comprises an attachment mechanism to which at least a part of the remote well-processing device may be attached and where the cantilever is configured to position at least said part of the remote well-processing device on said offshore platform.

27. A mobile offshore drilling unit according to claim 25, comprising a pump system for transferring fluids between a well and the mobile offshore drilling unit; a first manifold connected to the pump system and a second manifold connected to the pump system; wherein the second manifold is operable to facilitate pumping fluids into or out of a first well through a flow line between the pump system and the remote well-processing device and through a conductor extending from the offshore platform to the first well; and wherein the first manifold is operable to facilitate pumping fluids into our out of a second well through a conductor extending from the mobile offshore drilling unit to the second well.

28. A method of performing a well-processing task on a plurality of wells of an offshore oil or gas reservoir, the method comprising: positioning a mobile offshore drilling unit in a proximity of an offshore platform different from the mobile offshore drilling unit and located above a plurality of wells, the mobile offshore drilling unit comprising a primary drill rig comprising a drill floor and a hoisting system for raising and lowering tubular equipment from/into a well in the seafloor; performing, at a position on the offshore platform and displaced from a well centre defined by the mobile offshore drilling unit a first well-processing task on a first well, assisted by the mobile offshore drilling unit via an operational coupling extending between the mobile offshore drilling unit and said position on the offshore platform; and concurrently performing a second well-processing task on a second well, wherein the second well-processing task is performed by the mobile offshore drilling unit or is assisted by the mobile offshore drilling unit via an operational coupling extending between the mobile offshore drilling unit and a position of the second well on the offshore platform, wherein the method further comprises the use of the system according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0085] The above and/or additional objects, features and advantages of embodiments and aspects of the present invention, will be further elucidated by the following illustrative and non-limiting detailed description with reference to the appended drawings, wherein:

[0086] FIG. 1 schematically illustrates a example of an off-shore well-processing system.

[0087] FIG. 2 schematically illustrates another example of an off-shore well-processing system.

[0088] FIG. 3 schematically illustrates another example of an off-shore well-processing system.

[0089] FIG. 4 schematically illustrates another example of an off-shore well-processing system.

DETAILED DESCRIPTION

[0090] In the following description, reference is made to the accompanying figures, which show by way of illustration how the invention may be practiced.

[0091] FIG. 1 schematically illustrates example of an off-shore well-processing system. In particular shows mobile offshore jack-up drilling unit 114 positioned adjacent an oil production platform 101. The jack-up unit includes a floatable platform having a hull 115, a number of legs 116 and a cantilever 117 which allows a drill rig 132 to be skidded so that the position of the well centre can be moved horizontally. In particular, the cantilever 117 can be skidded such that it extends horizontally outside the periphery of the hull. The legs 116 are in this embodiment placed substantially in each corner of the unit and extend through the hull. The drill rig comprises the drill floor 135 from which drilling operations are conducted. A hole in the drill floor, e.g. in the form of a rotary table, defines the well centre though which drilling operations can be performed. Typically, a diverter system is installed below the rotary table for closing the vertical passage through the pipes and for directing the flow of well fluids away from the drill floor. The drilling rig further comprises a drilling support structure 118, such as a mast or derrick, which extends upwardly from the cantilever and which supports a hoisting system. The hoisting system comprises a hook or similar device from which a string of tubulars 121 may be suspended and lowered and raised through the well centre. To this end, the hoisting system may comprise a top drive to which an upper end of the drill string may be connected and which may impart torque on the drill string.

[0092] The drill rig 132 is configured to perform drilling of other well-processing operations, e.g. through a BOP stack installed below or inside the cantilever and through a conductor pipe extending from the BOP stack downwards towards the seabed.

[0093] The offshore production platform 101 is configured for production of oil or gas offshore. The offshore platform 101 of FIG. 1 is a fixed platform and comprises a superstructure supported by a jacket 102. The jacket comprises tubular members interconnected together to form a 3-dimensional frame including a number of jacket legs. The jacket is anchored to the seabed to provide stability against overturning moment caused by waves or extreme weather conditions. The superstructure normally includes a few levels and includes a skid deck 136. The offshore platform also includes conductor pipes 137 set in the seabed to provide foundations for a wellhead. The conductor pipes are configured to provide passage for drilling fluid and drill string to be lowered down into the wells and the fluid and cuttings to flow back to the rig as well as to prevent formations near the well from caving into the wellbore.

[0094] For example, an offshore platform may have a grid of several well slots 103. These well slots may be located between skid beams 104.

[0095] The offshore well-processing system of FIG. 1 further comprises a remote well-processing device 106 that is movable positioned on offshore platform so as to be repositioned above respective well slots 103. In order to cover the whole well slot area, the remote well-processing device 106 may be equipped with skidding jacks 105. These skidding jacks are latched onto the skid beams and enable the remote well-processing device to skid from one well slot to the other well slots. In the example of FIG. 1, the remote well-processing device is currently positioned over one of the well slots 103b. Alternatively, the remote well-processing device 10 may e moved between well slots in a different manner, e.g. by an on-deck crane of the jack-up unit or the offshore platform 101.

[0096] The offshore jack-up rig 114 is positioned adjacent the existing fixed offshore platform which serves as a grid, over which the cantilever 117 of the jack-unit is extended. The offshore platform remains at some distance from the jack-up unit such that a gap exists between the two structures. While the jack-up unit is positioned next to the existing offshore platform, no weight is transferred between the jack-up unit and the offshore platform, other than placement of the remote well-processing device 106 on the offshore platform.

[0097] The cantilever is extended above the existing platform 101 such that the well centre defined by the drill floor 135 of the drill rig is positioned above one of the well slots 103a and such that the drill rig can raise or lower a string of tubulars 121 from or into the well 103a, e.g. so as to pull production tubing or casings from a well. The pipes or other tubulars may then be efficiently handled by pipe handling apparatus of the jack-up unit (not explicitly shown in FIG. 1) and stored on pipe storage areas of the jack-up unit. Concurrently with the operation performed on well 103a by the drill rig of the jack-up unit, the remote well-processing device 106 can perform another well-processing operation on another well 103b. In the example of FIG. 1, the remote well-processing device 106 comprises a skiddable platform having a hole through which coiled tubing 109 may be run into the well 103b. To this end, the remote well-processing device comprises a coiled-tubing injector 107. The coiled tubing injector may include one or more of the following: a gooseneck or guide-arch 108, and injector drive motor, a stripper assembly, a coiled-tubing BOP, an injector-head break system, an injector-head chain assembly.

[0098] The jack-up unit 114 assists the remote well-processing device 106 in performing the coiled tube operation. In particular, in the example of FIG. 1, a coiled tubing reel 111 is positioned on a deck 112 attached to and extending from the hull 115 of the jack-op unit. And from a power-supply and control unit 120 placed on the main deck of the jack-up unit. The control and power-supply unit 120 is connected to the reel 111 by power and control fines 119 and the coiled-tubing injector 107 is connected to the power and control unit 120 via power and control lines 110, in this example via the reel. The coiled tubing extends from the reel 111 to the gooseneck 108 of the injector 107 and from there downwards through the injector into the well 103b.

[0099] It will be appreciated that, in alternative embodiments, the reel and/or other parts of the coiled tubing equipment may be placed in the production platform and/or on other parts of the jack-up unit. Moreover, alternative embodiments of a system may include one or more further remote well-processing devices which may each be positioned above respective well centres 103 and which may each perform respective tasks.

[0100] Hence, FIG. 1 illustrates an example of a system where a well-processing task—in this example a coiled tubing operation—is in progress at a remote well-processing device defining a secondary well centre 103b, but where the mobile offshore drilling unit, or equipment positioned on-board the mobile offshore drilling unit, assists the remote well-processing device in performing the well operation task. In particular, in the example of FIG. 1, the coiled tubing reel, controls and power are all provided by the mobile offshore drilling unit or by equipment positioned on-board the mobile offshore drilling unit. Hence a primary operation is performed on one well entirely by the drilling rig 132 of the mobile offshore drilling unit, while a parallel, secondary operation is performed by the remote well-processing device on the platform which provides structural support to the remote well-processing device, but where the secondary operation is otherwise assisted/facilitated by equipment on-board the mobile offshore drilling unit.

[0101] It will be appreciated that, in addition or alternative to coiled tubing operation, a remote well-processing device may be configured to perform another type of secondary process, such as logging operation, a wireline operation, a pumping operation, e.g. for killing a well, and/or the like.

[0102] FIG. 2 schematically illustrates another example of an off-shore well-processing system. In particular, shows a top view of a mobile offshore jack-up drilling unit 114 positioned adjacent an oil production platform 101 as described above. The features of the jack-up unit that have already been described in detail in connection with FIG. 1 will not be described in detail again, but they are referred to by the same reference numerals as in FIG. 1.

[0103] As in the example of FIG. 1, the drill rig of the jack-up unit comprises the drill floor from which drilling operations are conducted. A hole in the drill floor, e.g. in the form of a rotary table, defines the well centre 221 through which drilling operations can be performed.

[0104] FIG. 2 further shows an example of a pipe handling apparatus 222, such as a catwalk machine for transferring pipes or other tubulars between a pipe storage area 223 and the drill floor of the drill rig 132. The jack-up unit may provide additional pipe storage areas, e.g. a pipe storage area 224 and/or at other locations of the unit. Hence, some or even all pipe handling may be performed by pipe handling equipment of the jack-up unit.

[0105] As in the example of FIG. 1, the system of FIG. 2 also comprises a remote well-processing device 206 which is shown positioned on the offshore platform 101 above a well slot 103b but which may be repositioned to other well slots 103, e.g. as described in connection with FIG. 1. In the example of FIG. 2, the remote well processing device 206 comprise a work platform and a fluid interface 238 which can be coupled to a conductor pipe and through which mud or cement can be pumped into or out of a well. The fluid interface may further comprise a blow-out preventer. The fluid interface 238 is connected by flow lines 210, to a pump station 220 located on the jack-up unit e.g. a mud pump or a cement pump station.

[0106] Hence, as in the previous example, a primary operation is performed on one well entirely by the drilling rig 132 of the mobile offshore drilling unit, while a parallel, secondary operation is performed by the remote well-processing device on the platform which provides structural support to the remote well-processing device, but where the secondary operation is otherwise facilitated by equipment on-board the mobile offshore drilling unit.

[0107] FIG. 3 schematically illustrates another example of an of an off-shore well-processing system. In particular, shows a top view of a mobile offshore jack-up drilling unit 114 positioned adjacent an oil production platform 101 as described above. The features of the jack-up unit that have already been described in detail in connection with FIGS. 1 and 2 will not be described in detail again, but they are referred to by the same reference numerals as in FIGS. 1 and 2.

[0108] The system of FIG. 3 comprises two remote well-processing devices 306 and 329, respectively. Remote well-processing device 329 is shown positioned on the offshore platform 101 above a well slot 103a while remote well-processing device 306 is shown positioned on the offshore platform 101 above a well slot 103b. However, both remote well-processing devices may be repositioned to other well slots 103, e.g. as described in connection with FIG. 1. In the example of FIG. 3, the remote well-processing device 206 comprise a work platform and a fluid interface 238, e.g. as described in connection with FIG. 2. The fluid interface 238 is connected by flow lines 319b to a manifold 320 located on the jack-up unit. The manifold may in turn be connected to a pump station, e.g. a mud pump (not shown in FIG. 3), of the jack-up unit. The manifold 320 may be the same manifold which also services the primary drill rig 132 of the jack-up unit, or it may be an additional manifold in addition to the manifold which also services the primary drill rig 132 of the jack-up unit.

[0109] The other remote well-processing device 329 comprises a derrick or other support structure and a hoisting system configured to raise or lower tubulars through the well centre 103a. The remote well-processing device may further comprise a blow-out-preventer and further equipment such as break-out tongs and/or shearing devices, and/or a top drive. The remote-well processing device thus provides satellite drill floor in addition to the drill floor 135 of the drill rig of the jack-up unit. It will be appreciated that the drill rig of the remote well-processing device 329 may have the same rating or a different, e.g. a lower, rating compared to the drill rig 136. The remote well device 329 is skiddable mounted e.g. on skid beams 330 traversing the grid of well slots 103. The jack-up unit assists the remote well-processing device 329 e.g. via a flow line connection 319a which may be connected to manifold 320 or to a separate an fold of the jack-up unit. Hence, the remote well-processing device 329 may receive mud, cement and/or other fluids from the jack-up unit. Additionally or alternatively, the remote well-processing device 329 may receive hydraulic and/or electrical power from the jack-up rig. The remote well-processing device 329 may further be controlled from a driller's cabin or other control station of the jack-up unit via suitable communication lines. The remote well-processing device 329 may also utilise pipe storage and pipe handling facilities of the jack-up unit. For example, pipes may be transferred between a storage are 223 of the jack-up unit and a temporary storage area 327 of the offshore platform 101. This transfer may be performed by a crane 325 of the jack-up unit and/or by other pipe handling equipment of the jack-up unit and/or by a pipe handling apparatus extending between the jack-up unit and the platform 101. The pipe may be transferred individually or as stacks of multiple pipes.

[0110] Hence, as in the previous example a primary operation is performed on one well while a secondary operation is performed on another well. However, in this example, both operations are performed by respective remote well-processing devices. It will be appreciated, however, that the drill rig of the jack-up unit may be used to operate on a third well concurrently with the operation of the two remote well-processing devices.

[0111] As in the previous examples, the offshore platform 101 provides structural support to the remote well-processing devices, but where the operations performed by the remote well-operating devices arm assisted/facilitated by equipment on-board the mobile offshore drilling unit.

[0112] FIG. 4 schematically illustrates another example of an shore well-processing system. In particular, shows a side view of a mobile offshore jack-up drilling unit 114 positioned adjacent an oil production platform 101 as described above. The features of the jack-up unit that have already been described in detail in connection with FIGS. 1-3 will not be described in detail again, but they are referred to by the same reference numerals as in FIGS. 1-3. In the example of FIG. 4, the cantilever 117 of the jack-up unit 114 is equipped with connectors 434 to which a remote well-processing device 429 can be detachably connected, such that the cantilever can position and set-off the remote well-processing device onto the platform 101. It will be appreciated that the re-positioning of the well-processing device 429 between well slots may also be performed by the cantilever. Alternatively, the remote well-processing device 429 may be repositioned by other means e.g. by a skidding arrangement as described above. The positioning of the remote well-processing device may be particularly advantageous in embodiments where the remote well-processing device 429 comprises a large structure such as a mast and a hoisting system (e.g. the device 329 described in connection with FIG. 3) and a satellite drill floor, since even large structures may be positioned in one piece. In the example of FIG. 4, the well-processing device comprises a derrick, mast or similar hoisting/drilling support structure and a substructure 433 or ponybase supporting the derrick or similar hoisting/drilling support structure. The substructure provides an interface to the offshore platform, e.g. facilitating skidding etc.

[0113] Although some embodiments have been described and shown in detail, the invention is not restricted to them, but may also be embodied in other ways within the scope of the subject matter defined in the following claims. In particular, it is to be understood that other embodiments may be utilised and structural and functional modifications may be made without departing from the scope of the present invention. For example, embodiments of the invention have mainly been described with reference to a jack-up unit. It will be appreciated, however, that embodiments of the system described herein may also be used in connection with other types of mobile offshore drilling units.

[0114] In device claims enumerating several features, several of these features can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims or described in different embodiments does not indicate that a combination of these measures cannot be used to advantage.

[0115] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.