WO2014162128A1

WO2014162128A1 - Apparatus and method for recovering casing

Info

Publication number: WO2014162128A1
Application number: PCT/GB2014/051029
Authority: WO
Inventors: Bruce CARDNO; Paul Ray; John Foubister
Original assignee: WEST OIL TOOLS AS
Current assignee: WEST OIL TOOLS AS
Priority date: 2013-04-02
Filing date: 2014-04-02
Publication date: 2014-10-09
Anticipated expiration: 2015-10-02
Also published as: GB201305942D0

Abstract

Apparatus and a method of recovering oil well casing from a well during decommissioning comprises lifting the casing, supporting the casing using a support device, cutting a section of casing (C) extending above the support device while supporting the casing below it from the support device, and moving the cut section of casing to storage (4) using two gantry cranes (10, 30). One of the gantry cranes (30) lifts the string, and typically the other moves away from the other in the x-y plane while still supporting the cut section from one of the cranes thereby tilting the cut section relative to the rig floor. Optionally the cut section is moved over a yoke adjacent to the well, and supported by the yoke while pivoting around it thereby changing the orientation of the cut section, and moving it towards a parallel orientation with the deck.

Description

Title: APPARATUS AND METHOD FOR RECOVERING CASING

The present invention relates to a method of recovering oil well components, optionally casing and conductor components, from an oil well during

decommissioning. The invention also relates to apparatus for performing the method.

Background to the Invention

The lifespan of a typical oil well is generally 20 to 30 years. At or near the end of life of a well, when the reservoir has been substantially depleted of oil and other valuable production fluids, the well must be plugged and abandoned in a safe manner to prevent leakage of environmentally damaging fluids from the well into the surrounding area. Typically, a depleted well is plugged and then monitored for approximately 12 months to ensure that any residual production fluids or other environmentally damaging fluids left in the well are safely contained by the plug, Typically plugs are set by occluding the bore of the casing that lines the borehole with a bolus of cement, which sets to close off the well, optionally near to the reservoir. The casing above the plug is retained following the cement operation, in case further intervention is required during the monitoring phase, for example, if the plug leaks. Once it is determined through the monitoring phase that the plug is effective, and that the residual fluids in the well are safely contained, the casing above the plug is optionally cut and recovered to the surface in order to return the site of the wellhead to its pre-drilling condition, as far as possible.

Typical offshore well comprise a number of concentric strings of casing extending from below the seabed up to the floor of the production platform. The concentric strings of casing are cut using a cutting tool deployed inside the innermost string below the surface of the seabed, optionally 5 to 10 m below the surface of the seabed, and the concentric strings of casing are then pulled from the well before the well is finally abandoned. The concentric strings of casing that are cut and pulled from the well range from relatively narrow bore inner casing strings to very large bore outer strings of conductor conduit. The concentric strings are generally cemented together during the drilling and completion phases of the well, and so the cut portion that is lifted to the surface is very heavy, and this presents significant challenges during recovery of the conductor and casing to surface during the plugging and abandonment operation. Typically after the initial cutting of the concentric strings of conductor and casing from the well, the entire cut section must be lifted and supported at the rig floor while a manageable section of the concentric strings is cut from the top of the string for disposal. Typically the strings are cut into separate lengths of around 6-10m, and stored on the rig for later recovery via a support vessel to the shore.

Plug and abandonment operations typically require high capacity hoisting systems (up to 300 Te). In addition to the lifting requirements, the 6 -10 m long cut portions require handling at the rig floor in in order to store them safely for later recovery to a support vessel. Therefore, the 6-10 m section must be laid onto the floor of the rig (tailed] and secured in a safe and efficient manner, and then safely and efficiently unloaded onto the support vessel. Summary of the Invention

According to the present invention, there is provided a method of recovering oil well casing during a decommissioning operation, the method comprising lifting the casing, supporting the casing using a support device, cutting a section of casing extending above the support device while supporting the casing below it from the support device, and moving the cut section of casing to a storage area, wherein the cut section of casing is moved vertically and laterally by first and second gantry cranes.

The invention also provides apparatus for recovering oil well casing during a decommissioning operation, the apparatus comprising first and second lifting devices for lifting the casing, a support device for supporting the casing, a cutting device for cutting a section of casing extending above the support device while supporting the casing below it from the support device, wherein the first and second lifting devices comprise first and second gantry cranes which are adapted to move the cut section of casing vertically and laterally to a storage area. The support device optionally comprises at least one or more slip device wedged between the casing and the rig floor, for example, in the hole through which the casing emerges at the rig floor. Optionally the support device can comprise a pair of actuable jaws that move from a disengaged position to an engaged position to grip the conductor between them. Optionally the support device prevents rotation of the conductor.

The top of the casing is optionally supported by a lifting device. Optionally the bottom end of the cut section is supported by a lifting device above the support device. Optionally the lower end of the cut section is moved away from the well before the upper end.

The cutting device can comprise a mechanical cutter such as a grinder or a saw. Typical mechanical cutting devices can comprise guillotine saws, wire saws, e.g. diamond wire saws. Optionally the cutting device can comprise a thermal cutter device such as an oxy-fuel torch, for example, oxy-acetylene, oxy-propylene or oxy- propane etc.

Optionally the storage area is adjacent to the wellbore slot in the platform and is laterally spaced from the same.

Optionally the gantry cranes move the cut section vertically (along a z-axis, e.g. the axis of the well) and horizontally along at least one and optionally both of an x-axis and a y-axis in relation to the well (e.g. in an x-y plane perpendicular to the axis of the well). Optionally at least one of the gantry cranes lifts the string of casing prior to cutting the section that is to be moved to the storage area. Optionally the movement of the cut section of casing to the storage area can be accomplished in one lifting operation, but in some examples, the lifting of the cut section to storage is performed in a number of separate lifting operations. For example, in some cases, the cut section is set down before being lifted again in a second lifting operation. Thus in some examples of the invention, the cut section can be lifted vertically (optionally by one of the cranes) and then subsequently moved laterally by the other of the cranes in a second operation. Optionally the second crane(s) can lift the cut section.

Optionally the gantry cranes are connected to the cut section of casing at spaced apart locations on the cut section, optionally at or near opposite ends of the cut section of casing. Optionally the cut section of casing can be provided with pins that are attached to the cut section to facilitate connection of the cut section to the gantry cranes. Optionally the pins are attached by drilling holes in the cut section into which the pins are inserted and optionally fixed, for example, by fixings such as bolts or slips. Optionally the pins are attached by dogs or nuts, or other fixings that prevent passage of the head of the pin through a hole in the conductor, but which allow rotational movement of the pin relative to the conductor, for example, within the hole cut into the conductor for placement of the pin. The pins can optionally be attached to the cut section before cutting. In one example, the pins connected to the lower end of the cut section are not connected to a crane until after the cutting step, although they may optionally be connected to the casing before the cutting step.

Optionally each gantry crane comprises a frame having two upright pillars (or other upright supporting structures] and a beam supported on the pillars. Optionally the pillars are extendable and retractable to raise and lower the beam, but in certain circumstances, the frame can be fixed in place, and the beam can translate vertically relative to the frame to raise the load. Optionally in examples with movable pillars, the pillars can comprise hydraulic cylinders. Optionally a hoist trolley is movably mounted on the beam to support and lift the load (along a vertical axis, e.g. a z- axis, which can optionally be the axis of the well), and to translate horizontally between the pillars along a horizontal axis e.g. an x- axis. Optionally the pillars are mounted on a frame above the well on the drill floor of a platform. The frame is typically in the x-y plane, and optionally the pillars are movable in a horizontal direction (along a horizontal axis, e.g. a y- axis) that is perpendicular to the movement of the hoist trolley along the beam, thereby allowing the hoist trolley to move along x, y and z axes in relation to the well. However, it is sufficient that the beam is able to move relative to the well along the z axis, perpendicular to the x-y plane. Optionally the two gantry cranes are movable relative to one another along the y- axis of the rig floor, and for this purpose the pillars are optionally mounted on tracks that permit and optionally guide movement of the cranes along the y- axis of the rig floor.

Optionally the cranes can have wheels, tracks or skids or other conveying devices to facilitate movement of the pillars along the y-axis. Optionally the pillars can also move along the x-axis as well as the y-axis, and the rig floor can be provided with tracks for guiding and supporting the pillars during such movement. Optionally one of the cranes can be fixed in the x-y plane above the well.

Optionally the gantry cranes are of unequal lifting capacity, and optionally one is of higher lifting capacity than the other. Optionally the higher capacity crane is used for vertical lifting of the casing from the well. Optionally the higher capacity crane is connected to an upper portion of the cut section. Optionally the lower capacity crane is connected to a lower portion of the cut section of casing. Optionally at least some parts of the cranes can overlap along the z-axis, for example, in some cases, the lower capacity crane can fit inside the higher capacity crane, but in other cases, the bases of the pillars can optionally overlap with the pillar bases of one crane overlapping the pillar bases of the other, so that the beams of the cranes can optionally at least partially overlap or be close to the z-axis. Optionally the lifting devices are attached symmetrically on the casing, for example, to diametrically opposed points on the circumference of the casing, to pins that are attached at opposite sides at the middle of the casing. Optionally one crane is wider than the other, for example, at its pillar bases. Optionally the lower capacity crane is wider than the higher capacity crane. Optionally the two cranes move along parallel tracks and optionally one crane (optionally the narrower crane] can be retracted while the other crane (optionally the wider crane) is extended to allow the one crane to pass under or over the other. Optionally the tracks carrying respective cranes can be non-parallel. Optionally both cranes are connected to the casing via pins or other fixings, and can cooperate to lift the casing vertically, but optionally the higher capacity crane performs the primary vertical lifting operation. Optionally during the vertical lifting operation, the beams of the two cranes are aligned on the z-axis, e.g. above the well, or are close to alignment, and in certain examples, the lower capacity crane can be disposed underneath or partially underneath the larger crane, Optionally when the section to be cut is lifted and supported by the support device, the cranes move apart while still supporting the cut section, to tilt the cut section away from the vertical z-axis above the well, and to move the lower end out of line with the z-axis while the upper end remains above the well. Optionally the lower capacity crane moves along the y-axis away from the larger crane, which optionally remains stationary, or moves more slowly than the lower capacity crane, whereby the cut section tilts by the lifting of the lower end while the upper end remains above the well, but pivots as the angle of the cut section changes relative to the rig floor.

Optionally the lower capacity crane moves along the y-axis while the lower end of the cut section swings out from the z-axis above the well.

Optionally both cranes translate along at least the y-axis to move the cut section to a storage area away from the well, and the cut section is optionally manipulated entirely by the cranes during the process, from pulling out of the hole, through cutting, and lifting, tilting and storing, by manipulation of the cranes. Optionally the hoist trollies on the beams of the cranes from which the load is suspended translate along the x-axis to move the cut section to the required storage area, but x-axis movement can optionally be achieved more safely by movement of the two cranes in concert along the x-axis (optionally along tracks or rails etc on the rig floor].

Optionally one crane lifts the cut section vertically, and optionally the cut section is then tailed to tilt it until it can be safely laid horizontally on the floor of the rig. The tailing operation to change the orientation of the cut section from vertical towards the horizontal can be performed while the two cranes are supporting and optionally lifting and moving the cut section, but optionally the tailing operation can be performed with a yoke device to secure the lower end to the deck, and a single gantry crane to swing the cut section pivotally around the yoke device. Optionally the higher capacity crane is used to lift the cut section from the hole, and to move the cut section over a yoke device adjacent to the well, for example, by translation of the hoist trolley of the crane along the beam, or by translation of the crane along rails as a whole. Once over the yoke, the cut section can be lowered onto the yoke and the pins on the lower end of the cut section can optionally engage in U-shaped recesses in the sides of the yoke, allowing the yoke to hold the lower end of the cut section steady while the upper end is pivoted around the lower pins, and lowered by the crane towards the deck, to optionally land the upper section pins in a second yoke, The crane can then move off to repeat the operation with a second cut section, while the first cut section, now supported stably by the yokes in a horizontal configuration, can be lifted by the second crane to a storage location. Optionally the rig can be provided with more than one storage location for cut sections, each optionally with its own lower capacity crane for handling of the cut sections. Thus in certain examples, more than two gantry cranes can optionally be provided and used in concurrent storage lifting operations. Optionally the well is an offshore well, and the apparatus is supported on a platform above the well, for example, a drilling or production platform.

The various aspects of the present invention can be practiced alone or in combination with one or more of the other aspects, as will be appreciated by those skilled in the relevant arts. The various aspects of the invention can optionally be provided in combination with one or more of the optional features of the other aspects of the invention. Also, optional features described in relation to one example can optionally be combined alone or together with other features in different examples of the invention.

Various examples and aspects of the invention will now be described in detail with reference to the accompanying figures. Still other aspects, features, and advantages of the present invention are readily apparent from the entire description thereof, including the figures, which illustrate a number of exemplary aspects and implementations. The invention is also capable of other and different aspects and implementations, and its several details can be modified in various respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, is intended to be broad and to encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers or steps or groups of integers or steps. Likewise, the term "comprising" is considered synonymous with the terms "including" or "containing" for applicable legal purposes.

Any discussion of documents, acts, materials, devices, articles and the like is included in the specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention.

In this disclosure, whenever a composition, an element or a group of elements is preceded with the transitional phrase "comprising", it is understood that we also contemplate the same composition, element or group of elements with transitional phrases "consisting essentially of", "consisting", "selected from the group of consisting of, "including", or "is" preceding the recitation of the composition, element or group of elements and vice versa.

All numerical values in this disclosure are understood as being modified by "about". All singular forms of elements, or any other components described herein are understood to include plural forms thereof and vice versa. References to positional descriptions such as upper and lower and directions such as "up", "down" etc in relation to the well are to be interpreted by a skilled reader in the context of the examples described and are not to be interpreted as limiting the invention to the literal interpretation of the term, but instead should be as understood by the skilled addressee, particularly noting that "up" with reference to a well refers to a direction towards the surface, and "down" refers to a direction deeper into the well, and includes the typical situation where a rig is above a wellhead, and the well extends down from the wellhead into the formation, but also horizontal wells where the formation may not necessarily be below the wellhead.

Brief description of the drawings

In the accompanying drawings:

Figure 1 is a perspective view of a production platform above an offshore well; Figure 2 is a close-up view of the production platform of figure 1, showing apparatus for decommissioning casing;

Figure 3 is a perspective view of the apparatus shown in figure 2 in a first configuration;

Figure 4a and b are further perspective views of the figure 3 apparatus in a second configuration;

Figure 5 is a perspective view of the figure 3 apparatus in a third configuration;

Figure 6 shows three alternative and sequential positions of operation of the figure of the apparatus accessing different slots (conductors) in a rig floor, spaced from one another along a y-axis;

Figure 7 shows four alternative and sequential positions of operation of the figure of the apparatus accessing different slots (wells) in a rig floor, spaced from one another along an x-axis;

Figure 8 shows four sequential configurations of operation of a further example of decommissioning apparatus;

Figures 9 to 13 show sequential configurations of a further example of

decommissioning apparatus;

Figure 14 shows a further example of decommissioning apparatus; Figures 15 and 16 show perspective views of a further example of decommissioning apparatus;

Figures 17-25 show sequential views of the Fig 15 apparatus pulling a conductor section from a well;

Fig 26 shows a perspective view of the Fig 15 apparatus after the Fig 25 position, transitioning to a different well slot;

Figure 27 shows a perspective view of a cutting device for use with any of the examples of decommissioning apparatus herein;

Figure 28 shows a perspective view of conductor clamping apparatus for use with any of the examples of decommissioning apparatus herein; and

Figure 29 shows a perspective view of cutting and pin handling devices for use with any of the examples of decommissioning apparatus herein.

Detailed description of one or more examples of the invention

Referring now to the drawings, the production platform shown in figure 1 is disposed above a mature offshore oil field having numerous wells tied back to the platform. The platform infrastructure is near the end of its serviceable life. The platform is typical of many in mature oil fields. In the example of figure 1, the drilling derrick was removed following the drilling of the well, and the only available and serviceable lifting mechanism is the platform crane.

The conductors from the wells extend from the seabed to the rig floor on the platform, and support the concentric strings of casing and tubing within each well. As is known to those skilled in the art, the outer conductor and the concentric strings inside are cemented together in order to support the concentric strings of casing in each well. The wells before below the platform in figure 1 are near the end of life and are being decommissioned. The wells have been plugged, the plugs has been monitored and found satisfactory, and the last remaining job for the platform is to remove the concentric strings of the conductor and casing by cutting it into sections C and removing the cut sections from the platform for disposal. The conductors emerge from the rig floor in a regular array of slots, best seen in figures 3 and 4. The rig floor is surrounded on opposite sides by platform skid rails 1 which extend horizontally along a y-axis, The rails 1 underlie and support a sub- frame 2 extending horizontally and perpendicularly across the skid rails 1 along an x-axis. The sub frame 2 is clamped to the skid rails 1, resisting vertical movement of the frame 2 vertically away from the rails along the z-axis, but is slidably movable longitudinally along the skid rails 1 along the y-axis by means of jacks lc, which are secured by clamps to the skid rails 1. The frame 2 supports a crane deck 3 having a storage area 4 for storage of cut sections of conductor after they have been cut from the string. The crane deck has a series of crane rails 5, 6, which are parallel to one another and to the skid rails 1, extending along a y-axis relative to the well. The crane rails 5, 6 are clamped to the frame 2 but are movable transversely across the frame 2 along the x-axis by means of jacks 2c. The two sets of crane rails 5, 6 support a pair of gantry cranes 10, 30 above the slots in the rig floor. The crane rails 5, 6 are spaced apart to underlie the pillar bases 11, 31 of the cranes 10, 30. The bases 11, 31 optionally have motorised gears that run on tracks provided on the rails, to move the gantry cranes on the rails 5, 6, along the y-axis of the rig floor. Optionally the cranes have hydraulic cylinders forming vertically extendable pillars 12, 32, which expand and retract to raise and lower beams 13, 33 on the respective cranes 10, 30. The beams 13, 33 support hoist trollies 14, 34, which support the casing by means of tie rods 15, 35 that connect to pins set in the ends of the conductor sections C, for example by, bolting or swaging etc.

The conductor sections C are optionally cut into lengths using a grinding device, or a band or a wire saw after the conductor has been supported in a slot by wedging at least one slip into the annular space between the slot and the conductor. After the conductor has been supported in the vertical plane (the z-axis) by the insertion of the slip between the slot and the conductor, an upper section of the conductor and concentric rings of casing with it, is cut from the supported conductor, above the slip, by means of the wire saw or other cutting device. During the cutting operation, the weight of the conductor section C is supported from above by the larger of the two cranes 30, which has a higher lifting capacity, e.g. 300 tonnes. The conductor section C is attached to the crane 30 by virtue of pins that are inserted into holes drilled through the sidewalls of the conductor, to facilitate the attachment of the tie rods 35 to the conductor section C. Therefore, the conductor section C above the slip is supported by the extension of the hydraulic cylinders forming the pillars 32, and by the tie rods 35 linking the pins to the beam 33 via the hoist trolley 34.

Once the upper section of the conductor C has been cut from the supported mass of the conductor below it, the hydraulic cylinders on the pillars 32 are extended to lift the cut section C of the conductor away from the rig floor for subsequent handling of the cut section C. At this point, the smaller crane 10 (which has a lower lifting capacity, e.g. 30-60 tonnes) is moved along the y-axis, on the tracks provided by the crane rails 6 so that the smaller crane 10 approaches the larger crane 30 along the y-axis. Optionally, the pillar bases 11 of the smaller crane 10 are set further apart than the pillar bases 31 of the larger crane 30, and so as the two cranes approach one another, the pillar bases 11 on the smaller wider crane 10 overlap with the pillar bases 31 on the narrower larger crane, allowing the beam 13 of the smaller crane 10 to approach very close to the plane of the beam 33 of the larger crane 30. In some examples, the smaller crane 10 can fit underneath the beam of the larger crane 30.

When the beams of the cranes 10, 30 are as close together as possible, the tie rods 15 of the smaller crane 10 are attached to the lower end of the cut section of conductor C as shown in figure 4. The cut section of conductor C is therefore supported at its opposite ends by the tie rods connecting the pins to the cranes 10, 30. As the large crane 30 remains in place above the well, the smaller crane 10 optionally moves along the tracks in the direction of the y-axis as shown in figure 4. This raises the lower end of the cut section of conductor C, so that the conductor C pivots around the pins and moves out of the vertical orientation into an orientation that is closer to horizontal, as shown in figure 3. Further movement of the small crane 10 along the rails as shown in figure 5, away from the larger crane 30, and optionally simultaneous lowering of the larger crane 30, moves the cut section of conductor C closer to the horizontal plane. After or during the tilting (or "tailing") of the conductor section C, the cranes 10, 30 translate along the y-axis on the tracks of the rails 5, 6 to move the cut section of conductor C along the y-axis to the storage area 4, where the cut section C is placed in a pair of yokes 7 set into the crane deck 3, so that the conductor section is supported off the deck in a horizontal configuration, suitable for combining into a bundle of conductor sections C, in preparation for lifting from the storage area 3 onto a supply vessel. Once stably mounted in the yokes 7 the conductor sections C can be handled more easily and more safely, by less capable equipment, and by personnel who are at reduced risk from the dangers of working underneath heavily laden cranes. Optionally, the entire process can be controlled by a single operator, who can control the two cranes using a remote device, which can be connected to the hydraulic system of the cranes to control the movement by means of a wired connection, or advantageously by a radio controlled connection. Wireless operation of the cranes from the same controller (which can optionally be a portable controller - e.g. a hand-held device) can allow the sole operator to observe and control the operation from any point on the rig floor, but at the same time the operator can be spaced away from the cranes with increased safety and operational benefits.

Once the conductor sections C have been manipulated into the storage area 4 by the pair of cranes 10, 30, they can be manually connected together in preparation for offloading from the platform in a conventional and safe manner. As is shown in fig 6, the frame F can translate laterally along the x-axis by virtue of jacks 2c adapted to push the entire crane deck 3 sideways in order to access different slots on the rig floor. As shown in fig 7, the same operation can be carried out along the y-axis, using jacks lc provided on the skid rails 1, which act on the crane deck 3, to drive it along the y-axis in order to access different slots on the rig floor. Optionally the beam of the smaller crane 10 can be extended to move over the beam of the narrower crane 30, to access the different slots at extreme ends of the crane deck, or the crane deck can be de-rigged and moved to a position in which the larger crane 30 is able to access the top of the slots on the right hand end of the rig floor, as shown in Fig 7 bottom right.

Optionally the cranes 10, 30 can comprise clamp devices at their bases to clamp the bases to the rails on which the cranes are mounted, which in turn are optionally secured by clamps to the skid rails 1, to prevent any upward movement in the event of recoil resulting from a failure of a conductor during initial hoisting. Optionally crane 30 has a hoisting speed of around 2-5m/min, e.g. 3 m/min. Optionally the hoist trollies 15, 35 can incorporate a swivel mechanism to enable rotation of the cut sections C under load.

Referring now to figure 8, a further example of a conductor decommissioning apparatus and method is shown, with features the same or similar to those described previously, comprising a large crane 30, essentially as previously described, and a pair of smaller cranes 10, as previously described. In the figure 8 example, the large crane 30 is optionally positioned above the slot being decommissioned, and is used to pull the conductor vertically from the slot and support the cut section of conductor C after the cutting process, as previously described. One of the smaller cranes 10a, is moved close to the larger crane 30 as previously described, and is hooked up to the lower end of the cut section of conductor C, as described in relation to the previous example. The larger crane 30 is then retracted as the smaller crane 10a moves laterally away, along the y-axis, in the same manner as previously described, and the cut section of conductor C tilts closer to the horizontal plane as a result. Between stages 3 and 4, as shown in figure 8, the cut section of conductor C is laid in a horizontal configuration in a temporary holding area, optionally adjacent to the well, while the cranes 10a, 30 are unhooked from the pins, to allow the smaller cranes 10a, 10b to be connected to the opposed ends of the conductor section C, which can then be manipulated into a storage area for onward handling. In this example, the provision of two smaller cranes allows the larger crane to return more quickly to the lifting and cutting process, leaving the smaller cranes to deal with the manipulation of the cut sections of conductor C. Greater efficiencies can thereby be achieved. Referring now to figures 9 to 13, in a further example, the cranes 10, 30 are essentially as described previously, and these operate in conjunction with a set of yokes 7 to lift and tail the cut section C using [in this example) only the higher capacity crane 30. As indicated in fig 9, the crane 30 supports the cut section C during the cutting operation, in a position vertically above the slot of the well, and then the crane 30 carries the cut section C laterally along the y-axis away from the well slot, and deposits the lower end of the cut section C in a first yoke 7, with the cut section C still in a vertical orientation as shown in figure 10. Once the pins at the lower end of the cut section C are firmly located in the recesses on the sidewalls of the yoke 7, as shown in figure 10, the crane 30 translates back along the y-axis towards the well slot, thereby tailing the cut section C, and changing its orientation to move from the vertical orientation in fig 10 towards the horizontal configuration shown in stage 6 of figure 11. Once the cut section C is firmly supported on a horizontal axis in the yokes 7, the crane 30 moves back towards the well slot, along the y-axis.

In this example the second smaller capacity crane 10 is mounted on a different set of rails from those supporting the crane 30, and in particular, the lower capacity crane 10 is arranged on rails that are perpendicular to and intersect with those supporting the larger capacity crane 30. Once the crane 30 is moved laterally, and is clear of the rails supporting the crane 10, the smaller crane 10 moves along the x-axis towards the cut section C that is supported by the yokes 7. When the crane 10 is directly above the cut section C supported by the yokes 7, their hydraulic cylinders on the pillars of the smaller crane 10 are retracted to lower the beam, and the tie rods are connected to the pins protruding from the U-shaped recesses on the yokes 7. The cut section C is then in the configuration shown in stage 8 of figure 12.

The cut section C can then be moved off the yokes 7, to a storage area 4 on either side of the initial parking area at the yokes 7. Thus, the present example separates the lifting and storing operations, performing these by separate independent cranes, thereby freeing up the first crane 30 to do additional work while the second crane 10 is storing the cut section C.

Figure 14 shows a modification of the previous example, having a large capacity crane 130 operating above a well slot, and two smaller cranes 110a and 110b, operating on either side of the larger capacity crane 130. The operation of the figure 14 example is similar to that described for the figure 9 to 13 example, and like features are given the same reference number but increased by 100. The figure 14 example uses a central large capacity crane 130 to perform the lifting and tailing operation, moving along the Z and Y axes, and employs two separate smaller cranes 110a, and 110b on opposite sides of the slotto lift and move cut sections of conductor C from the initial parking area at the yokes 107 to storage areas that are spaced along the x-axis. The figure 14 arrangement allows greater efficiencies, because the central large capacity crane 130 can be continuously operating delivering a cut section of conductor C to one side to be picked up by one of the smaller capacity cranes 110a while on the other side, the other smaller capacity crane 110b is moving a previously-cut section C from the parking area the storage area 104. While the central crane 130 is lifting, both of the side cranes 110a, b, can be working.

Referring now to figs 15-25, a further example of a production platform is shown, similar to that shown in previous examples, having a large capacity crane 230 operating above a well slot S, and two smaller cranes 210a and 210b, operating on one side of the larger capacity crane 230. The configuration of the present example is similar to that described for the figure 5 example, and like features are given the same reference number but increased by 200. The present example uses a central large capacity crane 230 to perform the lifting and tailing operation, moving along the Z and Y axes, and employs two separate smaller cranes 210a, and 210b on the same side of the slot S to lift and move cut sections of conductor C from the initial parking area at the yokes 207 to storage areas 204 that are spaced along the x-axis. The arrangement allows greater efficiencies, because the central large capacity crane 230 can be continuously operating at the same time as each of the handling cranes 210a, b.

The skid rails 1 as previously described support a crane deck 203 having a storage area 204 for storage of cut sections of conductor after they have been cut from the string. The crane deck has a series of crane rails 205, 206, which are parallel to one another and to the skid rails 1, extending along a y-axis relative to the well. The crane rails 205, 206 are clamped to the frame but are movable transversely across the frame 202 along the x-axis by means of jacks 2c. The two sets of crane rails 205, 206 support the pair of gantry cranes 210, 230 above the slots S in the rig floor, and the cranes move on the rails 205, 206, along the y-axis of the rig floor. As well as crane rails, the crane deck 203 has a set of yoke rails 207r, which support a set of yokes 207. The conductor sections C are optionally cut into lengths using a guillotine saw mounted on the crane deck 203 (see fig 27] after the conductor has been supported in a slot S closing a pair of jaws on the underside of the crane deck (see fig 28]. After the conductor has been supported in the vertical plane (the z-axis] by the closing of the jaws, an upper section of the conductor and concentric rings of casing within it is cut from the supported conductor, above the jaws, by means of the guillotine saw or by another cutting device. During the cutting operation, the weight of the conductor section C is supported from above by the crane 230, and from below by the jaws. The conductor section C is attached to the crane 30 by virtue of pins that are inserted into holes drilled through the sidewalls of the conductor (see Fig 27].

Once the upper section of the conductor C has been cut from the supported mass of the conductor below it, the crane 230 lifts the cut section C of the conductor away from the rig floor for subsequent handling of the cut section C by the smaller handling cranes 210 a, b and the yokes 207.

The cranes 210, 230 are essentially as described previously, and these operate in conjunction with a set of yokes 207 to lift and tail the cut section C using (in this example) only the higher capacity crane 230. In a similar manner to the example of fig 9, the crane 230 supports the cut section C during the cutting operation, in a position vertically above the slot S of the well, as shown in Fig 19 and then a yoke 207 that is mounted on a set of wheels to run on yoke rails 207r is moved underneath the suspended conductor section C, as shown in Figure 20. The crane 230 lowers the cut section C vertically and deposits the lower end of the cut section C in the yoke 207 above the well slot, with the cut section C still in a vertical orientation as shown in figure 21. Once the pins at the lower end of the cut section C are firmly located in the recesses on the sidewalls of the yoke 207, as shown in figure 21, the yoke 207 translates passively along the yoke rails 207r along the y- axis away from the well slot, thereby tailing the cut section C, and changing its orientation to move from the vertical orientation in fig 21 towards the horizontal configuration shown in figure 22. During the translation of the lower end of the cut section C along the y-axis, the crane 230 optionally lowers the upper end of the cut section, and optionally the whole operation of tailing can be conducted under the power of the crane 230, with the movement of the yoke 207 supporting the lower end of the cut section C being passive. Once the cut section C is firmly supported on a horizontal axis in the pair of yokes 207, as shown in Fig 23, the cut section C can be detached from the crane 230, which is now optionally fully retracted as shown in Fig 24.

The cut section C can then be moved laterally off the yokes 207, to a storage area 204 on one or each side of the initial parking area above the yoke rails 207r as shown in Fig 25, which is accomplished by the smaller cranes 210a, b, which pick up the cut section C at each end, and move the cut section by translation of their hoist trolleys along the x-axes of the beams of the smaller cranes 210a, b. Thus, the present example separates the lifting and storing operations, performing these by separate independent cranes, thereby freeing up the first crane 230 to do additional work while the second cranes 210 are storing the cut section C.

The smaller cranes 210 move along the y-axis, on wider tracks provided by the crane rails 206 so that the smaller cranes 210 approach the larger crane 230 along the y-axis. The pillar bases of the smaller cranes 210 are set further apart than the pillar bases of the larger crane 230, and so as the two cranes approach one another, the smaller wider cranes 210 can pass over the narrower larger crane when its beam is retracted as shown in Fig 25.

The deck 203 can translate laterally along the x-axis by virtue of jacks 2c adapted to push the entire crane deck 203 sideways in order to access different slots S on the rig floor. The same translation operation can be carried out along the y-axis, using jacks lc provided on the skid rails 1, which act on the crane deck 203, to drive it along the y-axis in order to access different slots S on the rig floor. The ability to translate the main crane within the x-y plane allows different well slots to be serviced without the need to rig down and back up in a different location.

Optionally the smaller cranes 210 can be extended to pass over the narrower crane 230 as shown in the transition between figures 24 and 26, to access the different slots S at extreme ends of the crane deck 203, or the crane deck can be de-rigged and moved to a different position. The cutting and pin insertion devices can also be skidded on the yoke rails 207r to work on a different well slot in a similar manner. Optionally at least one of the yokes of any of the previous examples can be motorised, and can be driven along the rails, optionally away from the well slot, when supporting the lower end of the cut section. The motorised yoke could be driven away from the crane pulling the bottom of the cut section away with it. As the crane continued to lower the upper end of the cut section, that end could then be laid off in a second trolley, which may be motorised or passive.

In this example, the hoist trollies on the two smaller cranes can be used to transfer the cut section C along the x-axis, and manoeuvre the cut section C into the storage areas without translation or movement of the bases of the cranes 210, which reduces further the number of movements of the cranes between lifting and handing, and allows the larger crane 230 to return more quickly to the lifting and cutting process, leaving the smaller cranes to deal with the manipulation of the cut sections of conductor C. Operator safety is also improved as a result. The Fig 25 example can be provided with a pair of storage areas, each with a pair of smaller cranes 210, on each side of the main well being worked on, in a similar manner to the example of Fig 14, Greater efficiencies can thereby be achieved.

Optionally, in any of the examples described, the system can be electronically controlled from a control box, not shown, which integrates the movement of the individual cranes. This permits removal of personnel from the working area, with increased benefits for safety.

In certain examples of the invention the cranes are hydraulic telescopic gantry cranes. In certain examples, the canes can move freely along the x & y axes, allowing the cranes to adopt optimal lifting and handling positions in relation to the well slots at the rig floor. In typical examples, the cranes can be equipped with backup overturning mechanisms to enable tracking along the x and y axes.

Optionally at the end of life of an oil well, the platform servicing the well no longer has the high capacity hoisting structure that it had during the drilling phase 30 years previously; these may have been removed for use elsewhere, or may have decayed beyond the limits of safe use Aspects of the invention allow modular systems such as the cranes 10, 30 to be used during plug and abandonment operations on such facilities where the high-capacity lifting equipment necessary for safely conducting the operations is not available on the original production platform.

Claims

1 A method of recovering oil well casing during a well decommissioning operation, the method comprising lifting the casing, supporting the casing using a support device, cutting a section of casing extending above the support device while supporting the casing below it from the support device, and moving the cut section of casing to a storage area, wherein the cut section of casing is moved vertically and laterally by first and second gantry cranes, 2 A method as claimed in claim 1, wherein the support device comprises at least one slip device, and wherein the method includes wedging the slip device between the casing and the rig floor.

3 A method as claimed in claim 1 or claim 2, wherein the support device comprises a pair of jaws, and wherein the method includes moving the jaws from a disengaged position to an engaged position to grip the casing between them.

4 A method as claimed in any one of claims 1 to 3, including resisting rotation of the casing.

5 A method as claimed in any one of claims 1 to 4, including lifting the string of casing prior to cutting the section that is to be moved to the storage area, wherein one of the gantry cranes lifts the string. 6 A method as claimed in any one of claims 1 to 5, wherein the movement of the cut section of casing to the storage area comprises a plurality of separate lifting operations.

7 A method as claimed in any one of claims 1 to 6, including connecting the first and second gantry cranes to the cut section of casing at spaced apart locations on the cut section. 8 A method as claimed in any one of claims 1 to 7, including attaching at least one lifting pin to the section of casing, and connecting at least one gantry crane to the casing via the lifting pin. 9 A method as claimed in claim 8, wherein pairs of pins are rotationally attached to the section of casing allow rotational movement of the pin relative to the casing.

10 A method as claimed in claim 8 or claim 9, wherein the at least one pin is attached to the section of casing before cutting.

11 A method as claimed in any one of claims 1 to 10, including moving the cut section vertically along a z-axis and horizontally along at least one of an x-axis and a y-axis in relation to the well.

12 A method as claimed in claim 11, including moving the cut section horizontally along both of the x-axis and the y-axis in relation to the well.

13 A method as claimed in any one of claims 1 to 12, including moving at least a part at least one gantry crane relative to the other along an x-axis or a y- axis.

14 A method as claimed in any one of claims 1-13, including moving at least a part of at least one gantry crane relative to the other along an axis perpendicular to the x- or y- axis.

15 A method as claimed in any one of claims 1-14, including moving at least a part of one of the gantry cranes underneath at least a part of the other.

16 A method as claimed in any one of claims 1-15, wherein the gantry cranes each comprise a beam supported by two pillars, and wherein the method includes aligning the beams of the gantry cranes during a vertical lifting operation of the casing, such that the beams of the two cranes are substantially aligned close to the z- axis above the well.

17 A method as claimed in any one of claims 1-16, wherein the gantry cranes each comprise a beam supported by two pillars, wherein each of the gantry cranes is connected to the cut section of casing at respective spaced apart locations on the casing, and wherein the method includes moving the two gantry cranes apart along an axis perpendicular to the x- axis or the y-axis while still supporting the cut section from one of the cranes.

18 A method as claimed in claim 17, wherein both cranes move along the y-axis relative to the well.

1 A method as claimed in any one of claims 1-18, including tilting the cut section relative to the rig floor by lifting the lower end of the cut section while the upper end of the cut section remains above the well.

20 A method as claimed in claim 19, including suspending at least a part of an upper end of the cut section from a first gantry crane located above the well, and suspending at least a part of the lower end of the cut section from a second gantry crane, moving the second gantry crane along the y-axis relative to the first crane, and swinging the lower end of the cut section out of a z-axis co-axial with the well.

21 A method as claimed in claim 20, wherein the first crane lifts the cut section vertically, and the second crane lifts the lower end of the cut section to change the orientation of the cut section from substantially vertical in line with the well, towards a horizontal orientation parallel to the floor of the rig.

22 A method as claimed in claim 21, wherein the operation to change the orientation of the cut section from vertical towards the horizontal is performed while the two cranes are supporting the cut section. 23 A method as claimed in any one of claims 1-18, including lifting the cut section in a direction parallel to the z-axis of the well using a first crane, moving the lower end of the cut section off the z-axis and over a yoke device adjacent to the well, engaging a pivot point at the lower end of the cut section with the yoke device to form a pivotal connection between the lower end of the cut section and the yolk device, maintaining the position of the pivot point at the lower end of the cut section while pivotally moving the cut section around the pivot point, thereby changing the orientation of the cut section relative to the z-axis, and moving the cut section towards a parallel orientation with the deck.

24 A method as claimed in claim 23, wherein an upper end of the cut section is moved towards the horizontal orientation and wherein a pivot point near the upper end of the cut section is engaged with a second yoke device. 25 A method as claimed in claim 24, wherein after the upper end of the cut section is engaged with the second yolk device, the first crane detaches from the cut section, and wherein the cut section is moved by the second crane to a storage location after the cut section is detached from the first crane. 26 A method as claimed in any one of claims 23-25, wherein at least one of the yoke devices is motorised, and the method includes driving movement of at least one yoke device by a motor.

27 A method as claimed in any one of claims 1 -26, wherein the well is an offshore well, and the apparatus is supported on a platform above the well.

28 A method as claimed in any one of claims 1 -27, wherein at least a part of each crane translates along at least the y-axis to move the cut section to a storage area away from the well. 29 A method as claimed in any one of claims 1-28, wherein the cut section is manipulated by the cranes during the steps of pulling out of the hole, cutting the section, lifting, tilting and storing of the cut section. 30 A method as claimed in any one of claims 1 -29, wherein the cut section is moved along an x-axis relative to the well by movement of the two cranes in concert parallel to the x-axis.

31 A method as claimed in any one of claims 1 -30, wherein the cranes move along generally horizontal tracks or rails on the rig floor.

32 A method as claimed in any one of claims 1 -31, including moving the lower end of the cut section away from the well before the upper end of the cut section, 33 A method as claimed in any one of claims 1-32, including supporting the top of the casing with a lifting device.

3 A method as claimed in any one of claims 1-33, including supporting the bottom end of the cut section of casing with a lifting device above the support device.

35 Apparatus for recovering oil well casing during a well decommissioning operation, the apparatus comprising first and second lifting devices for lifting the casing, a support device for supporting the casing, a cutting device for cutting a section of casing extending above the support device while supporting the casing below it from the support device, wherein the first and second lifting devices comprise first and second gantry cranes which are adapted to move the cut section of casing vertically and laterally to a storage area.

36 Apparatus as claimed in claim 35, wherein the support device comprises at least one slip device engaging the casing. 37 Apparatus as claimed in claim 35 or 36, including a pair of actuable jaws that move from a disengaged position to an engaged position to grip the casing between them. 38 Apparatus as claimed in claim 37, wherein the jaws restrict rotation of the casing relative to the drill floor.

39 Apparatus as claimed in any one of claims 35-38, wherein the gantry cranes are pivotally connected to the cut section of casing at spaced apart locations on the cut section.

40 Apparatus as claimed in any one of claims 35-39, wherein the gantry cranes are pivotally connected to the cut section of casing at or near opposite ends of the cut section of casing.

41 Apparatus as claimed in any one of claims 35-40, wherein pins are connected to the cut section of casing to facilitate connection between the cut section and the gantry cranes. 42 Apparatus as claimed in claim 41, wherein the connection between the pin and the casing allows rotational movement of the pin relative to the casing.

43 Apparatus as claimed in any one of claims 35-42, wherein each gantry crane comprises a frame having two upright pillars and a beam supported on the pillars.

44 Apparatus as claimed in any one of claims 35-43, wherein the two gantry cranes are movable relative to one another in an x-y plane that is perpendicular to the axis of the well. 45 Apparatus as claimed in claim 44, wherein the cranes are mounted on tracks that guide movement of the cranes in the x-y plane, and wherein the cranes have wheels, tracks or skids or other conveying devices to facilitate movement of the pillars on the tracks.

46 Apparatus as claimed in claim 45, the tracks comprise x-axis tracks configured to guide the movement of the cranes along the x-axis relative to the axis of the well, and y-axis tracks configured to guide the movement of the cranes along y-axis tracks perpendicular to the x axis and to the axis of the well.

47 Apparatus as claimed in any one of claims 35 to 46 wherein one crane is wider than the other.

48 Apparatus as claimed in any one of claims 35 to 47, wherein the gantry cranes are of unequal lifting capacity, with a first crane being of higher lifting capacity than the second crane.

49 Apparatus as claimed in claim 48, wherein the first higher capacity crane is used for vertical lifting of the casing from the well.

50 Apparatus as claimed in claim 48 or 49, wherein the higher capacity crane is connected to an upper portion of the cut section of casing.

51 Apparatus as claimed in any one of claims 48 to 50, wherein the second lower capacity crane is connected to a lower portion of the cut section of casing. 52 Apparatus as claimed in any one of claims 35-51, wherein at least one of the cranes is moveable in relation to the other into an overlapping configuration in which at least some parts of the second lower capacity crane overlap with at least some parts of the first higher capacity crane along the axis of the well. 53 Apparatus as claimed in claim 52, wherein at least a part of the second lower capacity crane can move into the same plane as at least a part of the first higher capacity crane so that the cranes at least partially overlap in the same plane. 54 Apparatus as claimed in claim 53, wherein the second lower capacity crane can move underneath the first higher capacity crane. 55 Apparatus as claimed in any one of claims 35-54, wherein both cranes are capable of translating along at least the y-axis relative to the well to move the cut section to a storage area away from the well,

56 Apparatus as claimed in any one of claims 35-55, including at least one yoke device configured to engage and support a part of the cut section of casing during a tailing operation to change the orientation of the cut section from vertical towards the horizontal.

57 Apparatus as claimed in claim 56, including first and second yoke devices to engage and support opposite ends of the cut section of casing during a tailing operation to change the orientation of the cut section from vertical towards the horizontal.

58 Apparatus as claimed in any one of claims 56-57, wherein at least one of the yoke devices is motorised.

59 Apparatus as claimed in any one of claims 35-58, wherein the cranes include clamp devices to fix the cranes in position relative to the well during lifting operations.

60 Apparatus as claimed in any one of claims 35-59, wherein one of the lifting devices is fixed in the x-y plane above the well during a lifting operation, and the other is movable in the x-y plane relative to the well. 61 Apparatus as claimed in any one of claims 35-60, incorporating one large capacity crane and two smaller capacity cranes, each crane comprising a pair of support pillars, a beam between the pillars, and at least one hoist trolley connected to the beam, wherein the beams of the two smaller capacity cranes are arranged parallel to the beam of the higher capacity crane, and wherein the apparatus also comprises first and second yoke devices, mounted on rails spaced apart on opposite sides of the well, wherein the first yoke device can be moved over the axis of the well, after cutting of the section of casing, to receive the lower end of the cut section, and wherein the second yoke device can be moved over the axis of the well, to receive the upper end of the cut section of casing after it has been lowered by the higher capacity crane, and wherein the yokes can move the cut section away from the axis of the well, and wherein the smaller capacity cranes are adapted to pick up the cut section from the yokes, and by translation of the hoist trolleys on the beams of the smaller cranes, can move the cut section laterally to the storage area.

63 Apparatus as claimed in claim 62, wherein the cranes can adopt a configuration in which the height of the large capacity crane is less than the height of the lower capacity cranes, and wherein the large capacity crane can translate underneath the smaller capacity cranes to access a different well slot.

64 Apparatus as claimed in claim 62 or 63, wherein at least one of the cranes has a pair of hoist trolleys attached to their beams, and being capable of later movement away from one another on the beam, to accommodate different thicknesses of cut section of casing.