Offshore drilling unit

Abstract

The present invention relates in some embodiments to a bottom supported drilling unit having two drilling stations for independently drilling (or otherwise working on) two wells simultaneously from a cantilever.

Claims

1. An offshore drilling unit adapted for performing well-processing tasks on an off-shore hydrocarbon reservoir located below a seabed; wherein the drilling unit comprising a bottom-supported hull and a cantilever movable relatively to the bottom-supported hull, the cantilever supporting a first drilling station defining a first well center, and a second drilling station defining a second well center; wherein the drilling unit is configured to displace the cantilever to align the first drilling station and the second drilling station with a wellhead below the cantilever; wherein at least the first drilling station is arranged displaceable in a horizontal plane relatively to the second drilling station; and wherein the drilling unit is configured to perform drilling and/or well control of a first well by the first drilling station while performing drilling and/or well control of a second well by the second drilling station, the first and the second drilling station comprises respective well control systems for preventing unintentional flow of well bore fluids between an open formation exposed to a well bore and the well bore.

2. The offshore drilling unit according to claim 1, wherein cantilever is provided with skids for being movable relatively to the bottom-supported hull.

3. The offshore drilling unit according to claim 1, wherein the first drilling station defining the first well center is provided with skids for being movable relatively to the cantilever.

4. The offshore drilling unit according to claim 3, wherein the second drilling station defining the second well center is provided with skids for being movable relatively to the cantilever.

5. The offshore drilling unit according to claim 1, wherein the first drilling station and the second drilling station each are adapted for performing one or more well-processing tasks on a plurality of surface-wells of one or more off-shore hydrocarbon reservoirs located below a seabed.

6. The offshore drilling unit according to claim 1, wherein the drilling operations the first and the second well are performed simultaneously.

7. The offshore drilling unit according to claim 1, wherein the wellhead below the cantilever is provided by a bottom-supported wellhead platform comprising a support structure supporting a platform disposed between the cantilever and the sea surface.

8. The offshore drilling unit according to claim 1, wherein the cantilever is for positioning the first well center and the second well center outside of the horizontal contour of the bottom-supported hull.

9. The offshore drilling unit according to claim 1, wherein the first drilling station and second drilling station are arranged to operate substantially independently from each other.

10. The offshore drilling unit according to claim 1, wherein the first drilling station comprises a first well control system, and wherein the second drilling station comprises a second well control system.

11. The offshore drilling unit according to claim 10, wherein the first and/or the second well control system is arranged to provide well control via a blowout preventer (BOP).

12. The offshore drilling unit according to claim 10, wherein the first and second drilling stations each comprises a BOP.

13. The offshore drilling unit according to claim 1, wherein the offshore drilling unit comprises a pipe storage for tubulars for running through the well center and towards the seabed and into the well, and wherein the offshore drilling unit is arranged to provide first and second paths for feeding tubulars to the first and second well centers, wherein each of the first and second paths comprise separate sections.

14. The offshore drilling unit according to claim 13, wherein the first and second paths comprises separate sections each running from a pipe storage outside of the drilling stations and to the respective first and second drilling stations.

15. The offshore drilling unit according to claim 14, comprising one or more machines for tubular handling; wherein the one or more machines for tubular handling form part of said separate sections of the first and second path; and wherein the one or more machines for tubular handling are selected from the group of a catwalk machine, a V-door machine, a tugger and an overhead crane.

16. The offshore drilling unit according to claim 13, wherein the cantilever further comprises two catwalks, each aligned with one of the separate sections of the first and second paths and the catwalks are part of a pipe deck of the cantilever.

17. The offshore drilling unit according to claim 1, wherein the offshore drilling unit comprises respective driller's cabins or operating stations for each of the two of drilling stations.

18. The offshore drilling unit according to claim 1 and being a jack-up drilling unit.

19. The offshore drilling unit according to claim 1, wherein the respective well-control systems utilize separate components that are dedicated to respective ones of the drilling stations.

20. The offshore drilling unit according to claim 19, wherein the separate components of the respective well-control systems comprise separate BOPs, separate diverters, separate choke-and-kill manifolds.

21. The offshore drilling unit according to claim 20, wherein the BOPs are arranged on a wellhead platform above sea surface.

22. A method for performing well-processing tasks on an off-shore hydrocarbon reservoir located below a seabed by applying a drilling unit comprising a bottom-supported hull and a cantilever movable relatively to the bottom-supported hull, the cantilever supporting a first drilling station defining a first well center, and a second drilling station defining a second well center; the method comprising: displacing the cantilever to align the first drilling station and the second drilling station with a wellhead below the cantilever; and displacing the first drilling in a horizontal plane relatively to the second drilling station, wherein the drilling unit is configured to perform drilling and/or well control of a first well by the first drilling station while performing drilling and/or well control of a second well by the second drilling station, the first and the second drilling station comprises respective well control systems for preventing unintentional flow of well bore fluids between an open formation exposed to a well bore and the well bore.

23. An offshore drilling system comprising: an offshore drilling unit adapted for performing at least one well-processing task on a surface-well of an off-shore hydrocarbon reservoir located below a seabed; and a bottom-supported wellhead platform comprising a support structure supporting the wellhead; wherein the drilling unit comprising a bottom-supported hull and a cantilever movable relatively to the bottom-supported hull, the cantilever supporting: a first drilling station defining a first well center, and a second drilling station defining a second well center; wherein the drilling unit is configured to displace the cantilever to align the first drilling station and the second drilling station with a wellhead on the bottom-supported wellhead platform below the cantilever; wherein at least the first drilling station is arranged displaceable in a horizontal plane relatively to the second drilling station; and wherein the drilling unit is configured to perform drilling and/or well control of a first well by the first drilling station while performing drilling and/or well control of a second well by the second drilling station, the first and the second drilling station comprises respective well control systems for preventing unintentional flow of well bore fluids between an open formation exposed to a well bore and the well bore.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 (a-d) schematically illustrates an exemplary embodiment of an offshore drilling unit and an offshore well-head platform. FIG. 1a shows a front view, FIG. 1b is a side view, FIG. 1c is a top view, and FIG. 1d is an enlarged top view of the cantilever shown in FIG. 1c;

(2) FIG. 2 schematically illustrates a top view of the two drilling stations of the embodiment of FIG. 1;

(3) FIG. 3-6 schematically illustrates a top view of an alternative layout of the two drilling stations of the embodiment of FIG. 1; and

(4) FIGS. 7 and 8 schematically illustrate embodiments of a configurable support structure as described in co-pending patent applications PA201500668, GB1522856.2, GB1607101.1, GB1607180.5, GB1607182.1 and GB1522857.0.

DETAILED DESCRIPTION

(5) Various aspects and embodiments of offshore drilling units and methods of their use as disclosed herein will now be described with reference to the figures.

(6) When in the following relative expressions, such as “upper” and “lower”, “right” and “left”, “horizontal” and “vertical”, “clockwise” and “counter clockwise” or similar are used, these refer to the appended figures and not necessarily to an actual situation of use. The shown figures are schematic representations for which reason the configuration of the different structures as well as their relative dimensions are intended to serve illustrative purposes only.

(7) Some of the different components are only explicitly disclosed in relation to a single embodiment of the invention, but they are meant to be included in the other embodiments without further explanation.

(8) FIG. 1(a-d) shows parts of an offshore drilling unit 400 and parts of a well-head platform 100 comprising a configurable support structure 200, e.g. as explained in the above mentioned patent applications and in relation to FIG. 7. In particular, the configurable support structure supports the conductors and allows each conductor to be moved between a first position and a second position. The configurable support structure (or at least a part thereof) may at least in part be formed by, or even coincide with, a well-head deck.

(9) Shown are also a number of conductors 210 of a number of surface wells 300 where a production tree 420 or the like is located on a well-head of each of the wells.

(10) In some embodiments, at least one suitable mechanism is provided on the offshore well-head platform 100 and/or on the offshore drilling unit 400 for moving a conductor 210 between a first position and a second position.

(11) A cantilever 430 of the offshore drilling unit 400 supports two drilling stations 410 with two adjacent derricks 513. The derricks are formed as two separate structure each carrying the load of one of the hoisting systems. Tubulars are stored horizontally on a pipe deck 514 provided on the cantilever towards the proximal end of the cantilever while the drilling stations are arranged towards the distal end of the cantilever, with respect to the main body of the drilling unit. As mentioned above, the drilling stations 410 may work fully independently but in some embodiments may be able to cooperate for one or more functions. In this context, collaboration is taken to mean that equipment of one drilling station is applied as part of the process that is performed at the other drilling station. Each drilling station comprises a well center 430 and each drilling station comprises a hoisting system and a well control system.

(12) The port and the starboard side drilling stations are each connected to one of the surface wells through their respective BOPs 512 and via respective high pressure risers 519, also referred to as conductors. The well head platform 100 with a configurable support structure 200 (discussed in relation to FIG. 7 below) supports the conductors 210 of the surface wells.

(13) FIG. 1a schematically illustrates a front view of the (aft) of a three legged jack-up drilling unit 400 and of a well-head platform positioned in from of the aft end of the jack-up drilling unit. FIG. 1b schematically illustrates the corresponding side view of FIG. 1a, FIG. 1c schematically illustrates a top view while FIG. 1d is an expanded top-view of the cantilever 405. The jack-up drilling unit 400 comprises a main body in the form of a hull 500 that is elevated above the water level 110 and supported by legs 510 which in turn are supported by the bottom 120.

(14) The jack-up drilling unit comprises a cantilever 405 that can be moved outwards relative to the hull towards the rear of the jack-up drilling unit. In some embodiments the cantilever may also be displaced in a transverse direction, thus providing a so-called x-y cantilever. The jack-up drilling unit comprises two drilling stations 410 positioned at a distal end of the cantilever. To this end, the jack-up drilling unit comprises a support structure formed by a single derrick 513 supporting two crown blocks 511 suspending respective topdrives 509 over respective well centers 430, i.e. the jack-up drilling unit comprises two hoisting systems. Each hosting system further comprises drawworks (not shown in FIG. 1a); it will appreciated, however, that another type of hoisting system may be used, e.g. a hydraulic hoisting system. In general the support structures of the first and second drilling stations may be formed by any suitable support structure suitable for supporting the part of the hoisting system needed over the well center as well as the necessary loads of equipment raised in and out of the well. Suitable support structures may be a joint derrick, two adjacent derricks, two separate derricks, a joint mast such as with well centers on the same side of the mast or with the well centers placed on opposite sides, two masts, a derrick and one mast, one or two towers, or a combination thereof. A joint or adjacent derrick or mast may have the advantage that a more compact total layout may be obtained, that equipment may more readily be shared between the drilling stations, that the total steel structure or mast may be reduced relative to two separate structures and that controls may be closer together providing easier oversight of operations in both drilling stations. On the other hand two separate derricks or masts may facilitate easier separation with reduced risk of interference between the drilling stations and reduces the impact of vibrations induced by one drilling station to be propagated and potentially interfere with drilling operations at the other drilling station. Such interference could include limitations of what can be performed at one drilling station due to the operation being performed at the other drilling station e.g. when there is a risk of dropped objects or hydrocarbons on deck. As noted above, some embodiments comprise one or more partitions to separate the drilling stations.

(15) Each of the two drilling stations is operable to operate independently on high pressure sections of a well (i.e. at depths where well control is required to ensure that drilling fluid is not pushed into the formation or well fluids enter the well bore). Hence, generally, well control of a well involves well control of at controlling at least a high pressure part of the well. To this end, each of the two drilling stations comprises an independently operable well control system, typically via blow-out preventers (BOP) 512 which may, in their operational position, be located inside the cantilever under the respective well centers. As shown in FIG. 1a, the drilling stations of this embodiment are equipped with surface BOPs 512 and FIG. 1d shows (typically high-pressure) manifolds 518, e.g. for a standpipe and for a kill and choke system for the BOP which are typical parts of a mud-based well-control system well known in the art. Typically, further components of such a well control system, such as mud pumps, mixers, shakers and/or mud cubes, are placed inside the cantilever or on/within the main body of the drilling unit.

(16) In FIG. 1a, one of the drilling stations is shown connected to one of the surface wells through the corresponding BOP 512 and via a corresponding high pressure riser 519. The well head platform 100 with a configurable support structure 200 (discussed in relation to FIG. 7 below) supports the conductors 210 of the surface wells.

(17) Typically an extensive number of tubulars are required to efficiently drill wells into offshore hydrocarbon reservoirs, such as drill pipe, drill collars and casings. Before assembly with the string to enter the hole (i.e. the well under construction) or into stands of two or more tubulars (typically stored vertically in a setback 503 ready to enter the hole), such tubulars are typically stored in one or more or pipe storages 515 which may hold horizontal and/or vertical pipes. In the present embodiment, horizontal pipe storages 515 are laid out on the cantilever, e.g. in the form of one or more storage areas for horizontal storage 515 on the pipe deck 514 of the cantilever 405. In FIG. 1c-d the pipe storages are indicated by horizontally stored pipes 515. In some embodiments, the two drilling stations have assigned respective, separate pipe storages at least for some type of pipe e.g. drill pipe or casing. Separate pipe storage (e.g. storage on starboard side of the cantilever stores tubulars for the starboard side drilling station and vice versa) may be preferable as it may provide for less interference between the operations at each drilling station. In order to bring the tubulars to the well center from a pipe storage some embodiments of the offshore drilling unit are arranged to provide first and second paths for providing tubulars from the respective pipe storage to the first and second well centers from one or more pipe storage, wherein one or more sections of said first path are separate from the sections of the second path. In many embodiments, separate paths between the pipe storage to the respective drilling station increase the likelihood that operation in one drilling station prompting the transport of tubulars to this drilling station will not be interrupted due to tubulars being transported to and from the other drilling station. In some embodiments, the one or more sections of separate paths comprises paths from pipe storage external from said drilling stations and into the first and second drilling stations respectively. For example, in the present embodiment in FIG. 1a-d the drill floors of the drilling stations 410 are located on the drill floor deck 522 raised relative to the pipe deck 514. Two catwalks 521 are each aligned with a well center 430 (note that the FIG. 2 provides an expanded view of the drill floor deck). To this end, pipe deck cranes 516 are arranged to service the catwalk machines 508 by taking horizontally stored pipes 515 to and from the catwalk machines which can travel along their respective catwalks and present the pipe to a respective pipe racker 504. The pipe racker raises the pipe to vertical for further transport within the drilling station 410 (indicated by the dashed squares in FIG. 2). For example, pipe rackers 504 may be operable to receive pipe sections, assemble them into stands of two or more pipe sections (e.g. using a foxhole 506) and store them in an associated setback area 503. The same or a different pipe racker may subsequently pick up stands of pipes from the setback 503 and present it to the hoisting system at the well center 430. Accordingly, the paths marked by the dotted lines 517 along each catwalk machine 508 and onto the drill floor of each drilling station are separate from each other. Several machines may be applied to provide this pipe path which may be similar to the machines applied to bring tubulars from the pipe storage to the drill floor on a conventional cantilever. Accordingly, in some embodiments, the separate paths from pipe storage to drilling station may comprise one of more of the group of: a pipe feeding/transport machines, e.g. a catwalk machine or a conveyor, a pick-up/lay-down system (PLS) or pipe racking system (PRS), such as a V-door machine, a tugger, a pipe deck pipe handler (PDPH), such as a pipe deck crane, e.g. a knuckle-boom crane or an overhead crane.

(18) In some embodiments (such as those shown in FIGS. 2-5 and some embodiments of FIG. 6), the pipe transport machine, such as a catwalk machine 508, may traverse to present tubulars at the well center such as via the rails 507.

(19) Each drilling station further comprises a respective iron roughneck machine 502.

(20) FIG. 2 is an expanded view of the drilling stations and drill deck of the embodiment of FIG. 1a-d. FIGS. 3-6 are alternative layouts for the drilling stations.

(21) The layout of FIG. 2 is designed with a joint driller's cabin 501 for controlling the first and second drilling stations 410. Typically, each drilling station will have a designated operating station including a dedicated operator's seat and man-machine-interface to the respective control system of the corresponding drilling station. In some embodiments, the operating stations are separated by a dividing wall so as to reduce the risk for miscommunication with the respective operator teams. However, in some embodiments a single operating station may be switched between drilling stations. In some embodiments the drilling station is remotely operatable such as from onshore. As noted in relation to the support structure, it may be preferable to have the controls close to one another although it may also be preferable to enhance independence e.g. by shielding the operation from each other (e.g. by a wall). Separating the driller's cabin for the first and second drilling station as in FIGS. 3 and 4 reduces the risk of interference between the operations at the two drilling stations.

(22) The driller's cabin(s) may be placed forward (closer to the main body of the drilling unit) of the well centers as in FIGS. 2-4 and 6 or aft of the well center as in FIG. 5. Placement aft of the well center has the advantage of good overview of tubulars entering the drilling stations as well as in relation to the well center but a drawback may be that the well center may need to be closer to the hull and thus may limit the reach of the cantilever. The reach of the cantilever is typically limited by the length of the cantilever and/or by the maximum deck load at the well center which typically decreases as the cantilever is extended.

(23) In some embodiments, it may be preferable to raise some parts of the drilling station from the drill deck e.g. to provide a more compact layout and/or more deck space available for equipment. In the embodiments of FIG. 2-6 the driller's cabin 501 and drawworks 505 have been elevated. This may e.g. provide additional for an iron roughneck machine 502 (for making and breaking connections at the well center) below the drawworks and below the driller's cabin. In some embodiments, each drilling station 410 comprises a setback area 503 typically for storing stands vertically but horizontal storage is feasible. With separate setbacks the risk of interference between the operations at the two drilling stations is reduced.

(24) In some embodiments, the setback area of the first and second drilling stations is a joint setback or adjacent and connected setback area. In this way stands and/or bottom-hole assemblies made up at one drilling station may be used by the other drilling station.

(25) In some embodiments, the first and second drilling stations comprise multiple setback areas such as a separate setback area as well as a joint setback area.

(26) In some embodiments, each of the first and second drilling stations comprises a pipe racker, such as the rackers 504. In some embodiments, each of the first and second drilling stations comprises two pipe rackers, e.g. as illustrated in FIGS. 2-6.

(27) In some embodiments, the drilling station comprises one or more standbuilding stations. In the embodiments of FIGS. 2-6 the standbuilding station comprises a standbuilding center 506, such as a fox-hole, a pipe racker 504 (adjacent to the corresponding standbuilding center 506) and an iron roughneck 502 (adjacent to the corresponding standbuilding center 506). In some embodiments, the catwalk machine 508 can present tubulars to the pipe racker 504 which raises horizontal pipe to vertical and proceeds to make the connection between the pipe and a second pipe thus building a stand via the iron roughneck and the fox hole. The pipe racker may proceed to rack the finished stand made from two, three or more pipes back into the setback area 503 or present it at the well center. Offline (i.e. away from the well center) stand building e.g. via a fox hole is well known in the art. In some embodiments (such as in FIGS. 2-5), the offline stand building center is along the path for providing tubulars to the well center from outside of the drilling station. This is convenient in that a catwalk machine 508 will often provide most pipes for standbuilding but can conveniently progress to the well center 430 to present pipes here as well.

(28) FIGS. 3-6 illustrate alternative embodiments of a drill floor layout of a drilling unit having two drilling stations on a single cantilever. The embodiments of FIGS. 3-6 comprise the components already described in connection with the embodiment of FIG. 2, but arranged in different layouts relative to each other. In particular, the embodiments of FIGS. 3-6 each comprise two drilling stations 410 arranged on a cantilever. The drilling stations comprise respective drawworks 505, well centers 430, setbacks 503, pipe rackers 504, iron roughnecks 502, standbuilding centers 506, rails 507, all as described above. The drilling units further comprise one or more driller's cabins 501, and catwalk machines 508, also all as described above.

(29) In the embodiment of FIG. 2, the setback areas are positioned on the lateral side of the well centers that face away from the other well center. A common driller's cabin (accommodating two separate operator stations) is positioned centrally on the cantilever between the well centers. In the embodiment, the positions of the setback 503 and the driller's cabin are interchanged: The drilling unit of FIG. 3 comprises a shared setback area 503 positioned centrally between the well centers and two separate driller's cabins 501 that are positioned laterally outwards. It will be appreciated that, in this embodiment, the shared setback area 503 may still be large enough to provide separate, dedicated setback parts for the respective drilling stations.

(30) In the embodiments of FIGS. 2 and 3, the layouts of the drilling stations are substantially mirrored relative to a center line dividing the drilling stations from each other. FIG. 4 shows a different embodiment where the drilling stations have substantially the same layout but translated transversely relative to each other. In particular, the embodiment of FIG. 4 comprises two separate driller's cabins 501 and two separate setback areas 503. While one setback area is positioned centrally on the cantilever, the other setback is positioned laterally outwards. Similarly, one of the driller's cabins is positioned central and the other laterally outwards.

(31) The embodiment of FIG. 5 is similar to the embodiment of FIG. 2 with separate setback areas 503 positioned laterally outwards on respective sides of the drilling stations and with a shared driller's cabin. In this embodiment, the driller's cabin is positioned further rearwards on the cantilever (i.e. longitudinally displaced from the well centers further away from the main body of the drilling unit, but still substantially aligned with a longitudinal axis of the cantilever.) This placement of the driller's cabin allows the well centers 430 to be moved even more closely together, as illustrated in FIG. 5.

(32) In the embodiment of FIG. 6, the setback areas are positioned at the most rearward end of the cantilever (on the side away from the main body of the drilling unit. The drawworks 505 and the elevated driller's cabin are positioned towards the front side of the drill floor, i.e. towards the main body of the drilling unit. This layout also allows a particularly small distance between the well centers.

(33) As discussed above, it may be preferable to shield the operation at one drilling station from the operation at the other drilling station. Accordingly, in some embodiments, the offshore drilling unit comprises one or more partitions separating and/or shielding the plurality of drilling stations from each other. Such partitions may be placed where equipment of the two drilling stations are in proximity of each other and pose a risk of interference (such as dropped objects, well liquids or other hazardous items may transit between drilling stations). A partition may be movable or fixed and placed inside or on the cantilever. In one embodiment, a partition is placed to shield the drill floors of the drilling stations from each other. In the embodiments of FIGS. 2-6, the extent of the respective drilling stations 410 is indicated by respective dashed rectangles where one side of each rectangle faces an adjacent side of the corresponding other, neighbouring rectangle. A partition is preferably placed at least part of the way between the adjacent rectangles, along the sides of the rectangle that face the other rectangle.

(34) Typically the distance between the well centers of the first and second (or even third or fourth) drilling stations is fixed. However, in some embodiments one or more of the well centers may be displaceable. Displaceable well centers are known from the PCT application WO14140369A2. In some embodiments one or more of the well centers (such as both or all) are displaceable over 50 cm, such as over 1 meter, such as over 2 meters, such as over 3 meters, such as over 4 meters, such as over 5 meters, such as over 6 meters, such as over 7 meters, such as over 8 meters, such as over 9 meters, such as over 10 meters, such as over 11 meters, such as over 12 meters. In some embodiments the well center may be displaceable to allow adjustment to match the location of the drilling centers on a well head platform. In some embodiments the drilling unit is arranged so that the first well center may be displaced to the second drilling station so that drilling can be performed through the first well center by the second drilling station. In this way the unit may provide redundancy and/or the ability to perform specialized operations at one of the stations and then skidding the well center of the other to have such operation performed.

(35) As noted above, the offshore drilling unit of the invention is in particular advantageous for well-operations on surface wells supported by a platform with a configurable support structure as described in co-pending patent applications PA201500668, GB1607101.1, GB1607180.5, GB1607182.1, GB1522856.2 and GB1522857.0.

(36) With reference to FIG. 7 and continued reference to FIG. 1, the following is a summary of various aspects of the configurable support structure (and its collaboration with the offshore drilling unit of the invention.

(37) Traditionally, conductors may e.g. be arranged in a matrix type layout at their upper end. Once a well is completed it will typically have installed a production tree (also referred to as Christmas or x-mas tree) or similar on the well head making it ready for e.g. hydrocarbon extraction or production, injection, or other.

(38) By surface-well is to be understood that the well-head of the well is located above the water level 110. Surface-wells are opposed to sub-sea wells, subsea trees, wet trees, etc.

(39) In some embodiments, the offshore well-head platform 100 may be part of, or used in connection with, such an offshore facility, e.g. with facilities to extract and process hydrocarbons or other liquids and/or gasses, inject liquid(s) or gas(es) in one or more wells, and e.g. to temporarily store products somewhere until it can be brought to shore for refining, etc.

(40) The offshore well-head platform 100 may be supported by resting on the seabed directly or indirectly, by being connected or attached to another structure, e.g. a drilling unit, jack-up drilling unit, etc., that is supported by resting on the seabed. The offshore well-head platform 100 may also be supported by or integrated into other types of units. In some embodiments a drilling unit as described herein may comprise a well head platform as described herein or at least parts thereof, e.g. a configurable support structure as described herein. For example, the support and optional manipulation of the conductors may be done utilizing the drive pipe support deck (also referred to as the Texas Deck) or similar.

(41) The surface-wells 300 are connected to one or more offshore reservoirs (not shown) located below a seabed 120.

(42) The offshore well-head platform 100 comprises a configurable support structure 200 for supporting upper parts of plurality of conductors 210 through which one or more well-processing tasks can be performed. Each conductor 210 forms part of a surface-well 300.

(43) Even for embodiments, where the conductors 210 are considered relatively rigid, e.g. such as steel pipe or the like, they are sufficiently flexible to allow for some movement or deflection of its upper part or end—even when in place for extraction or production or injection—especially given their typical length (that typically will depend on the total depth of the well, i.e. the length from the well-head at the well head platform 100 to its location in the seabed near the relevant reservoir). Generally, the longer the conductors are above the seabed, the lesser angular deviation between its first positions at its shared second position is generally needed.

(44) The time saving may be applicable to processing multiple wells both in a more traditional manner (completing one well at a time) and as batch-drilling (completing the same task(s) and/or sub-task(s) for all or at least some or several wells at a time).

(45) Furthermore, as specialized equipment like skids, rails, cantilever are not needed or needed less they may be omitted or be of simpler design or used for other purposes.

(46) Additionally, when the wells are completed and used for extraction or production or injection or other operations they may simply be ‘parked’ at an individual first position.

(47) Once maintenance, work-over, etc. or other intervention is needed, the conductor 210 and its associated well may simply be moved to the shared second position again to carry out the maintenance or work-over process(es).

(48) The angular deviation typically needed will depend on the specific design of the well head platform 100 or the configurable support structure 200 (e.g. the maximum distance that a conductor 210 should be designed to maximally move between a first and a shared second position, e.g. taking into account certain tolerances) and the length of the conductors 210, the material of the conductors 210 (and e.g. the number, dimensions, etc. of the smaller conduits being located inside the conductor 210), and so on.

(49) Here and in the following, reference to a distance between respective positions (e.g. between a first and a shared second position) is intended to refer to the distance between the upper ends of conductors positioned at said positions. Purely as examples of a design of a well head platform 100 or the configurable support structure 200 e.g. comprising one centrally located, shared second position and six adjacent first positions (see e.g. FIG. 7) with a maximum distance (e.g. center-to-center distance) between the second and each individual first position being—purely as an example—about 1.3 meters, the smallest angular deviation needed may e.g. be about 0.8° for a water depth of about 70 meters (or corresponding length of the conductor 210 often being the water depth plus the length from the water level to the location of the well head platform/configurable support structure and plus the length of the conductor in the seabed), e.g. be about 1.0° for a water depth of about 60 meters, e.g. be about 1.1° for a water depth of about 50 meters (with the only varying parameter being the water depth).

(50) In principle, the configurable support structure 200 could comprise one or more (further) conductors without a first and/or a shared second position.

(51) At least one suitable mechanism is provided for moving or deflecting a conductor 210 between its first position and its shared second position. The at least one mechanism for moving the conductors may e.g. be located on the offshore well-head platform 100 or could be located on an offshore drilling unit. The mechanism may be any suitable mechanism capable of moving or deflecting (the upper part) of a conductor 210 e.g. by pulling, pushing, etc.

(52) The well head platform 100 or the configurable support structure 200 may e.g. comprise two (or more) shared second positions for use with two (or more) well centers or drilling stations. They may belong to a single same group or cluster or alternatively to different groups or clusters.

(53) In some embodiments, the conductors 210 are used at water depths e.g. being selected from about 30 meters to about 300 meters or from about 30 meters to about 150 meters. Various aspects and embodiments of a method of processing or drilling one or more offshore surface-wells using a configurable support structure 200 and embodiments thereof will now be described with reference to FIG. 7.

(54) FIG. 7 schematically illustrates a top view of an exemplary embodiment of a part of a configurable support structure.

(55) Shown from above or below is a configurable support structure (or at least a part thereof) such as the ones shown and explained in connection with FIG. 1 and throughout the present description.

(56) The configurable support structure 200 comprises a number, here as an example six, of first positions 150 and a number, here as an example one, of shared second positions 160.

(57) In the example of FIG. 7, the configurable support structure comprises a number of slots that extend radially from a central hole in a star-like arrangement. The central hole defines the shared second position while each slot defines a first position. More generally, in some embodiments, the first positions and the shared second positions are provided according to an arrangement wherein the shared second position(s) is/are provided substantially centrally and the first positions are arranged around the shared second position(s), e.g. in a substantially circular or oval pattern. It will be appreciated, however, that other geometries may be provided.

(58) In each first position or slot 150 is shown one conductor 210. The conductors 210 may each comprise a smaller diameter conduit 215 and an even smaller diameter conduit 220, e.g. the production liner, as generally known. There may be an air-gap or space present at each first position or slot 150 for giving room between the conductors 210 and the configurable support structure 200. Also shown and indicated by ‘A’ is a center-to-center distance between two neighboring conductors 210 each in a first position.

(59) Further shown and indicated by ‘B’ is a center-to-center distance between a center of the shared second position 160 and a center of each of the first positions 150. In some embodiments (and as shown), B will be substantially the same to all first positions or at least have a minimum distance for all associated first positions. However, it may also be different for at least some embodiments.

(60) In some embodiments, A is selected from about 0.25 meters to about 10 meters. In some embodiments, A is selected from about 0.8 meters to about 5 meters. In some embodiments, A is selected from about 1 meter to about 2.5 meters. In some embodiments, A is selected from about 0.8 meters to about 2 meters. In some embodiments, A is selected from about 1.2 meters to about 1.9 meters.

(61) In some embodiments, B is selected from about 0.25 meters to about 25 meters. In some embodiments, B is selected from about 0.5 meters to about 15 meters. In some embodiments, B is selected from about 1.5 meters to about 10 meters. In some embodiments, B is selected from about 1 meter to about 4 meters. In some embodiments, B is a value being larger than about 0.1 meters. In some embodiments, B is a value being larger than about 0.25 meters. In some embodiments, B is a value being larger than about 0.5 meters. In some embodiments, B is a value being larger than about 0.75 meters. In some embodiments, B is a value being larger than about 1 meter. In some embodiments, B is a value being larger than about 1.25 meters. In some embodiments, B is a value being larger than about 1.5 meters. In some embodiments, B is a value being larger than about 2 meters. In some embodiments, B is a value being larger than about 2.5 meters. In some embodiments, B is a value being larger than about 3 meters. In some embodiments, B is a value being larger than about 3.5 meters. In some embodiments, B is a value being larger than about 4 meters. In some embodiments, B is a value being larger than about 5 meters. In some embodiments, B is a value being larger than about 6 meters.

(62) Finally, a working and/or drilling center zone 250 is indicated by a central darker dashed circle. It is noted, that the working and/or drilling center zone 250 does not form part of the configurable support structure 200 but rather is projected thereon to better illustrate its position in relation to the shared second position when used.

(63) The offshore well-head platform comprising the configurable support structure 200 may comprise an opening at its upper structure (e.g. at the weather deck of the offshore well head platform) above the one or more shared second positions 160 that are to more or less coincide or at least overlap with the working and/or drilling center zone 250 defined by a drilling station of the drilling unit during well construction of a well/wells at a shared second position/positions. Also see FIGS. 5, 6a-6b, and 7 of GB 1522856.2 for examples of a configurable support structure together with an appropriate working and/or drilling center zone.

(64) The configurable support structure 200 may e.g. be or comprise parts that are part of a wellhead deck (often also referred to as wellhead platform deck, cellar deck, well-bay area, well slot area, etc.) of an offshore wellhead platform. As a note, production trees of completed wells may be located at a deck (sometimes referred to as the Christmas tree deck) located between the weather deck and the well head deck.

(65) As indicated by double arrows, the respective conductors 210 are movable between the first and shared second positions 150, 160 as explained in connection with FIG. 1 and throughout the present description.

(66) The configurable support structure 200 may be used to carry out aspects of a method of processing or drilling one or more offshore surface-wells using an offshore drilling unit according to the invention. In some embodiments, the method comprises constructing and/or processing multiple offshore surface-wells from a single work or drill center position by moving one or more selected conductors to and from the single work or drill center position.

(67) In some embodiments, the method comprises using at least one offshore well head platform as described elsewhere wherein the single work or drill center position is a shared second position.

(68) In some embodiments, the method comprises progressing a plurality of surface-wells towards completion by moving one of the conductors 210 to a first position 150 from a shared second position 160 subsequent to carrying out one or more well constructing and/or processing tasks (e.g. including sub-tasks) to complete the surface-well of said conductor 210 at the shared second position 160. After the well has been completed (or at least progressed towards completion as desired), said conductor 210 is moved to a first position (e.g. to the position it has previously been positioned at, or to another one of the first positions). Then another one of the conductors 210 may be moved from its current first position to the shared second position for carrying out one or more well constructing and/or processing tasks on the well associated with said another conductor at the shared second position. This process may be repeated until all conductors as desired have been processed. In some embodiments, the conductor may be installed at the shared second position, in some embodiments, at its first, in some embodiment between these two positions and in some embodiments at a third position.

(69) It should be noted that the method and embodiments thereof may be carried out, e.g. overlapping in time, at two (or more) shared second positions. The specific steps, tasks, etc. and their timing carried out at different shared second positions may and often will be different—although they may be the same.

(70) In some alternative embodiments, the method comprises progressing a plurality of surface-wells towards completion by moving a selected conductor 210 from a first position 150, where it is located, to a shared second position 160 and carrying out at least one well constructing and/or processing task and/or sub-task. After the task(s) and/or sub-task(s) has/have been completed, the selected conductor is moved to a first position (original or different). Then a next conductor 210 is moved from its first position to the shared second position and the task(s) and/or sub-task(s) are carried out on or for the next conductor 210 after which it is moved to a first position (original or different). This is repeated until the relevant task(s) and/or sub-task(s) have been carried out on the desired conductors 210. Once that is the case, the next task(s) and/or sub-task(s) is/are carried out on all the desired conductors 210. The next task(s) and/or sub-task(s) need not—but may do so—start with the same conductor as was started with for the previous task and/or sub-task. This is repeated until all desired tasks and/or sub-tasks have been carried out for all desired conductors 210. In some embodiments, the conductor may be installed at the shared second position, in some embodiments at its first, in some embodiment between these two positions and in some embodiments at a third position.

(71) Again, the process and variations thereof may be carried out, e.g. overlapping in time, at two (or more) shared second positions (then by two or more well-processing stations). The specific steps, tasks, etc. and their timing carried out at different shared second positions may and often will be different—although they may be the same.

(72) In this way, efficiency is increased for batch drilling or batch processing a plurality of wells carrying out a group of one or more tasks and/or sub-tasks at a time on all the relevant conductors. The conductors need not necessarily be completed or progressed to the same extent, although they often will be.

(73) After completion (by either method and embodiments thereof), the conductors may be secured at a number of first positions e.g. for production, injection or other operations.

(74) The configurable support structure 200 may comprise one or more locking or securing mechanisms or elements (not shown; forth only referred to as securing elements).

(75) In some embodiments, at least one securing element provides securing of one or more conductors at first positions 150 that, e.g. permanently, may lock at least one conductor in place at respective first positions, e.g. when the conductor is ready for extraction, production, injection, or similar. As examples of such securing elements are e.g. latches, clamps, wedges, or other securing elements.

(76) In some embodiments (e.g. in combination with one or more of the embodiments described above), at least one securing element is provided at each shared second position 160 for temporarily and securely holding a conductor in place at a respective shared second position during well-processing, drilling, etc. Such securing elements may e.g. allow some degree of movement. Examples of such securing elements are e.g. mechanical or hydraulic push or pull, a rack and pinion drive, winch-wire, or any other suitable mechanisms for retaining, moving, shifting, etc. In some embodiments, the shared second position securing element may be combined with at least one mechanism for moving or deflecting a selected conductor between its first position and its shared second position.

(77) In some embodiments (e.g. in combination with one or more of the ones described above), the offshore well head platform or the configurable support structure 200 comprises a number of collision prevention or separation elements 170 e.g. one for each first position 150 where the collision prevention or separation element forms a barrier or similar between the shared second position(s) 160 and the first positions 150 e.g. as indicated by the dashed line 170. Preferably, the collision prevention or separation elements will shield each first position 150 from the shared second position(s) 160, e.g. one collision prevention or separation element for each first position 150 or one collision prevention or separation element covering more or all first positions 150. As examples of such collision prevention elements are e.g. structural elements, beams, cushion or dampening elements, etc. One or more collision prevention or separation elements may e.g. be combined with one or more shared second position securing elements and/or the one securing element(s) providing securing of one or more conductors at first positions.

(78) Such configurable support structures and methods as described above function particularly well together with embodiments of an offshore drilling unit comprising at least two drilling stations, wherein the drilling stations are capable of operating independently of each other although they need not to be or at least not to be all the time. In some embodiments, the drilling stations are each capable of constructing a respective well simultaneously. When operational, the distance between the two drilling stations may be fixed. Each of the at least two drilling stations may comprise their own mud supply, well control system, and mud return systems.

(79) A shared second position (or a zone or area around it) may be used—e.g. after one or more wells have been completed at the shared second position—to complete one or more additional wells, e.g. those additional wells will have first positions located overlapping fully or partly with the shared second position(s) in question or a zone or area around the shared second position(s).

(80) Note, that the shown position of the shared second position(s) is shown idealized in FIG. 7. Due to tolerances the one or more shared second positions will have a position within the working or drilling center zone 250.

(81) In some embodiments, a shared second position and associated first positions is available for two or more drilling stations such as one or more for each drilling station. The position of the shared second positions is designed to match the well centers of the drilling stations of the offshore drilling unit. In some embodiments, two or more sets of shared second positions are provided so that subsequent to completing one set the cantilever can be skidded to the next set.

(82) For example, FIG. 8 shows an example of a configurable support structure that comprises multiple (in this example four) shared second positions 160, each shared second position having a plurality of first positions 150 associated with it so as to form a cluster 600. Such an embodiment may be particularly useful in combination with a drilling unit having two drilling stations as described herein, as each drilling station may operate on a respective one of the clusters. When the processing of two clusters is finished (or at least has proceeded to a desired stage), the cantilever of the drilling unit may be repositioned such that the drilling stations can work on two further clusters.

(83) The various aspects described herein have mainly been disclosed in the context of drilling units, but in some embodiments the various aspects may be used in relation with units specialized to perform other well-processing tasks that a drilling unit is either not suited for or that are more economically performed by a specialized rig. Such well-processing tasks may be one or more of well-completion, well-intervention, work-over and plug and abandonment. For such embodiments the drilling station may be replaced by a well-processing station with the equipment needed for the task and the well-center is replaced by a well-processing center. Hence, a skilled person will recognize that the invention may be applicable to well-processing systems in general including well-processing systems which are not drilling units, such as work-over rigs or rigs specialized for completion of wells.

(84) While the present invention is advantageous for surface wells it may in some embodiment find utility for building subsea wells.