GB2573035A

GB2573035A - Apparatus and method

Info

Publication number: GB2573035A
Application number: GB1901408.3A
Authority: GB
Inventors: Edward Anderson Cameron
Original assignee: Subsea Tooling Services Uk Ltd
Current assignee: Subsea Tooling Services Uk Ltd
Priority date: 2018-02-02
Filing date: 2019-02-01
Publication date: 2019-10-23
Anticipated expiration: 2039-02-01
Also published as: GB201901408D0; GB201801744D0; GB2573035B

Abstract

A pipeline decommissioning apparatus 1 comprises a longitudinally-extending boom 5 upon which are mounted several tools, including a dredger 10, at least two gripping tools 20, at least two cutting tools 30, and at least one propulsion device 50. The gripping tools and cutting tools are axially spaced along the boom, with the cutting tools located on the outside of the gripping tools relative to the centre of the boom. The propulsion device provides propulsion to the apparatus for subsea positioning. A method of using the apparatus is also described, where the cutting and removal of a section (79, figure 9) of pipeline (78) may be carried out in a single step by the apparatus.

Description

APPARATUS AND METHOD

This invention relates to tools for use in a subsea environment. More particularly, this invention relates to a grabbing and cutting tool for use in a subsea environment and a method of using the same.

BACKGROUND TO THE INVENTION

When a pipeline, for example an oil and/or gas pipeline, is to be decommissioned but is assessed as not being suitable for in situ abandonment, the pipeline must be removed from the bottom of the waterway or sea bed on which it was installed. As pipelines may be in place for many years, it is possible that the pipeline will have sunk some way into the sediment or other material forming the sea bed. In order to extract the pipeline, a dredger is commonly used to clear a trench on either side of the pipe, with the dredger being guided and manipulated by an ROV or a diver. Once the dredger has dredged the next section of sea bed, the dredger is pulled away from the pipeline and this clears a path for cutting apparatus which may then be deployed separately from e.g. a nearby vessel.

The pipe can then be cut into sections by the cutting apparatus, for example saws or very high pressure (HP) water jets. Once the pipe is cut, the cutting apparatus is pulled away from the cut section of pipe which can then be lifted onto a transportation vessel by lifting equipment, which may be in the form of e.g. lifting apparatus deployed from the transportation vessel.

Decommissioning of pipelines is therefore currently a multi-step process, requiring changeover of equipment at different stages of the process and can take some time to complete. Improving efficiency of the decommissioning process would lead to reductions in the length of time the process takes and thereby reduce environmental disturbance while decreasing decommissioning costs.

SUMMARY OF THE INVENTION

According to the present invention there is provided a pipeline decommissioning apparatus in accordance with claim 1.

Optionally the pipeline decommissioning apparatus comprises a beam, hull or frame, on which the dredger may be mounted. The beam, hull, or frame is typically any generally longitudinally extending and suitably shaped structural member capable of bearing sufficient load for the task of lifting cut sections of pipeline. For ease of reference, this structural member will be referred to as a beam in this description but with the caveat that the preceding definition applies.

Preferably at least two guiding devices are mounted on the beam, optionally axially spaced apart along the beam, for example optionally at substantially opposing ends of the beam.

Optionally the guiding device or devices are propulsive devices which, when actuated, provide propulsion to the beam. Preferably the propulsive devices are controllable such that an operator can control the quantity, duration and/or direction of propulsion afforded by the one or more propulsive devices. More preferably, the propulsive devices are thrusters. Optionally the at least two guiding devices are positioned such that one guiding device applies a force to the apparatus in one direction and the other guiding device applies a force to the apparatus in an opposing direction. The guiding devices allow lateral manoeuvrability of the beam around the bed of the sea or other waterway, for example to reposition the dredger during dredging operations. Alternatively, one reversible and/or directionally controllable guiding device can be used to also allow manoeuvrability of the beam around the bed of the sea or other waterway. The guiding devices, in use, provide lateral, in other words horizontal, propulsion to the beam. Vertical (lifting/lowering) movement of the beam is carried out by, for example, a crane, winch, or other lifting equipment, optionally located on a vessel. The beam can comprise one or more connection points for connecting a crane rope or wire to the beam for lowering and lifting operations. The crane may provide continued vertical support to the apparatus during pipeline decommissioning operations, for example as the apparatus carries out dredging, gripping, cutting and so forth. The propulsion devices, e.g. thrusters, can permit finer movements of the apparatus typically on the horizontal plane once the apparatus is roughly in position at the pipeline, for example, to provide small rotational/lateral movements to align the longitudinal axis of the beam with the longitudinal axis of the pipe.

Optionally the beam may further comprise lighting equipment, optionally together with cameras, e.g. video camera equipment, to permit an operator to visually inspect the pipeline and optionally the decommissioning apparatus as the gripping device of the apparatus grips the pipeline and/or the cutting tool cuts the pipeline. Optionally the beam may further comprise sonar equipment to map the seabed around the pipeline and/or the pipeline itself. Optionally the beam may comprise additional detection and monitoring equipment as required.

Optionally the beam further comprises a control unit, with which an ROV can interface, for example to plug in at least one control line. Optionally the at least one control line supplies hydraulic power, or optionally the control line supplies electrical power to the control unit of the beam. Optionally there are at least two control lines and optionally at least one control line supplies hydraulic power and at least one other control line may supply electrical power. Alternatively, both lines supply hydraulic power. Optionally when the at least one control line is securely plugged into the control unit of the beam, the pipeline decommissioning apparatus may be controlled remotely, typically by an operator on the vessel at the surface via the ROV.

Preferably there are 3 control lines, 2 of which are hydraulic lines and one electrical control line leading from the ROV to the control unit ofthe beam. The electrical line is preferably an umbilical line providing power data, data and/or communications.

Optionally the ROV comprises an intelligent valve pack which is preferably controlled from a computer typically located on the vessel at the surface such as a laptop via the ROV umbilical. The valve pack provided on the ROV is preferably an Intelligent Dredging System™ (IDS) valve pack offered by Subsea Tooling Services UK Limited of Oldmeldrum, Aberdeenshire, AB51 OBZ, United Kingdom. Optionally the hydraulic and/or electrical power supply is provided by the ROV. Optionally the hydraulic and/or electrical power supply is provided from a suitable supply located on a vessel at the surface.

Optionally the beam comprises at least two gripping devices spaced apart from one another along the axis of the beam. Optionally the gripping devices are mounted to the underside of the beam and are optionally connected to the control unit. Optionally each gripping device comprises at least two curved arm sections which are configured to grip and retain a portion of a pipe between them. Optionally the arm sections are connected at a single point such that the arm sections may pivot around an axis, for example around a hinged connection. Optionally each arm section is actuated by a hydraulic cylinder or similar device. Optionally the arm sections comprise tapered or bladed ends that enhance the penetration of the arm sections into the sediment or other matter around the pipeline during gripping operations.

Optionally the gripping devices are connected to the beam by pivotable connections that permit the gripping devices to rotate around an axis. Optionally the axis, i.e. the pivot axis, of the gripping devices, is an axis that is perpendicular to the longitudinal axis of the beam, and in use, the longitudinal axis of the beam is typically arranged to substantially lie on the horizontal plane, and the pivot axis of the gripping devices is typically arranged in use to lie on a substantially vertical axis. Optionally the pivot axis of the gripping devices extends longitudinally through the centre of the gripping device. For example, if the longitudinal axis of the beam is horizontal, the pivot axis of the gripping device is vertical. This allows the gripping devices to change angles if required during the initial gripping process, for example to enhance penetration of the arm sections into the seabed. This also allows the gripping devices to be positioned in a particular way for transportation if desirable, for example the gripping devices may be positioned in a parallel alignment with the longitudinal axis of the beam during transportation and, in use, the gripping devices may be rotated to be perpendicularly aligned with the longitudinal axis of the beam.

Optionally the, or each, gripping device may be a mechanical grab, an orange peel grab, a grapple or another gripping device as required.

Optionally each cutting tool is positioned closer to the edge of the beam than each of the gripping devices. That is, the cutting tools are preferably the most external tools relative to the centre of the beam, and are preferably positioned on the outside of the gripping devices relative to the centre of the beam.

Optionally each cutting tool comprises a body having a frame and a plate. Optionally the plate of the cutting tool comprises a drive wheel and further guide wheels, rollers or similar rotating components, around which a wire may be looped. Optionally the cutting tool may be a wire saw and the wire saw may comprise diamond wire. Optionally an alternative wire type may be used according to the material to be cut.

Optionally the drive wheel comprises a motor, for example a hydraulic motor, and is adapted to feed the wire around the plate. Optionally the wire is held in tension between the drive wheel and the guide wheels. Optionally the plate is substantially C-shaped, with an open end into which a pipeline may be received. Optionally the guide wheels are arranged so that a portion of the wire is held in a straight line across the open end of the plate, thereby providing an abrasive cutting surface. Optionally at least a portion of the plate or body of the cutting tool is movable relative to the gripping devices. Optionally as the gripping device grips a portion of a pipeline, at least a portion of the plate or body of the cutting tool may move in the direction of the pipeline and continue to move in the same direction until the pipeline has been at least partially or fully severed.

Optionally the frame of the cutting tool comprises at least one clamp that clamps the section of pipeline or pipe to be cut and thereby further stabilise the pipe during cutting operations. Optionally the frame comprises a substantially C-shaped portion at a lower end of the frame, having an open end into which a pipe may be received, and then optionally clamped. Optionally the clamp comprises at least two jaws, optionally arranged such that there is one jaw at one side of the open end of the frame and one jaw at the other side of the open end of the frame. Optionally each jaw pivots around a connection point from a first configuration, where the jaws are open and a pipe may be received, to a second configuration, where the jaws have pivoted, optionally towards a central axis of the frame, to clamp a pipe. Optionally the jaws are hydraulically powered.

Optionally the frame of the cutting tool comprises at least one contact pad and preferably comprises two contact pads. Optionally the contact pad is configured to contact the pipe when the pipe is clamped within the frame. Optionally the contact pad enhances the stability of the pipe when clamped and optionally during cutting operations. Optionally the contact pad contacts an upper surface of the pipe while the jaws contact a lower surface of the pipe. Optionally there are two contact pads in a V-shaped configuration along the frame. Optionally the contact pads resist rotation of the pipe during cutting.

Optionally the frame of the cutting tool comprises a shaft along which the plate may move. Optionally the frame comprises a feed motor that drives the movement of the plate, which is optionally restricted to move linearly. Optionally the feed motor drives the plate towards the pipeline during cutting operations. Optionally the cutting tool is capable of tilting to enhance cutting, for example +/- 5° around the central axis of the cutting tool.

Alternatively, the at least one cutting tool may comprise a band saw, guillotine saw or other suitable cutting device.

Optionally the at least one cutting tool is mounted on an end of the beam. Preferably, there are two cutting tools and the cutting tools are preferably each mounted on an end of the beam such that they are on opposing ends of the beam.

Optionally the beam may be extended such that it is extendable on one or both sides. Optionally the beam may be extended from, for example, 10 metres in length to 20 metres in length. Optionally the beam may have flanged portions axially spaced apart, located at each end of the beam. Optionally the flanged portions comprise apertures that are suitable for receiving fasteners. Optionally, when the beam is to be extended, an extension bar (for example, 5 metres in length, but any suitable length may be used for the beam and for the extension bar) may be connected to an end of the beam. Optionally the extension bar is also flanged at either end. Optionally the flange of the extension bar is connected to the flange of the beam and fastened thereto. Optionally the beam and bar are connected via removable threaded fasteners, for example bolts. Optionally the fasteners pass through apertures formed in both of the flanges to be connected. Optionally there is at least one shear puck provided at the interface between the flanges.

Optionally additional gripping devices may be mounted according to the length of the beam and optionally according to the properties of the pipeline to be cut. The addition of one or more gripping devices permits larger payloads to be handled and therefore longer sections of pipe to be cut and manipulated. By extending the beam and increasing the payloads that may be handled, a pipeline may be decommissioned even more efficiently.

Optionally if the beam is extended, one or more additional guiding device(s) may be mounted on the extended beam. Similarly, additional lights, cameras or sonic devices may be added to the extended beam if required.

Optionally the apparatus is lowered to its deployment location by a vessel crane or hoist. Optionally the crane or hoist is connected to the beam by a wire, line or chain, optionally by at least one connection point that may be located on a surface of the beam which is preferably an upper surface of the beam and preferably by at least two connection points spaced apart along the longitudinal axis of the beam. Optionally the connection points are padeyes, but any suitable connection type may be used.

Optionally the beam comprises forklift pockets that allow a forklift to manipulate the apparatus when onshore.

Optionally the apparatus may be used in combination with a cradle or frame, for example a subsea basket. Optionally where the cradle is a subsea basket, the basket may be modified, for example to remove floor gratings and/or to add additional strengthening braces.

Optionally the cradle may act as a support for the apparatus during transportation. Optionally the cradle comprises a frame onto which mounts for the apparatus may be placed. Optionally the beam comprises protrusions that facilitate docking of the beam to the mounts or the cradle, thereby securing the beam in position during transportation. Optionally the mounts are provided at a sufficient height within the cradle such that, when the apparatus is docked onto the mounts, the gripping devices are not in contact with the cradle, for example, the ends of the arm sections of the gripping devices do not make contact with a base of the cradle or with the ground or deck if the cradle does not have a base.

Optionally the mounts may be in a substantially A-frame configuration. Optionally the A-frame is reinforced with at least one supporting strut, preferably more than one supporting strut. Optionally the docking sites on the mounts may be located at the apex of the A-frame. Optionally the docking sites comprise further extensions that extend either side of the beam when the beam is docked on the mounts. These extensions provide further support and resistance to movement of the beam during transportation of the apparatus.

Optionally the cradle comprises a platform on which personnel may move around to, for example, connect a vessel crane to the beam for deployment. Optionally the platform comprises an access ladder and safety railings.

Optionally the pipeline decommissioning apparatus can be deployed from the deck of a vessel by lifting the apparatus from the cradle mounts and lowering it to the deployment location.

Optionally the apparatus may be deployed in combination with the cradle. Optionally the cradle comprises connection points for a crane or hoist, for example padeyes. Optionally the crane or hoist is connected to the cradle and the cradle may then be lifted and moved by the crane or hoist. Optionally the cradle is connected to a vessel crane which may then move the cradle and the apparatus from the deck of the vessel and lower the cradle and apparatus to a deployment location on the seabed. Optionally the crane may be connected to the connection points on the beam of the apparatus to lift the apparatus from the cradle as the cradle rests on the seabed.

Optionally the cradle and the apparatus may be wet stored subsea in that the cradle and the apparatus may be left at the deployment location on the seabed for collection. For example, a first vessel may transport the apparatus and cradle to the deployment location before being loaded with pipe sections as decommissioning operations progress and the first vessel may then lower the cradle with the apparatus mounted and secured thereon to the subsea surface (i.e. the sea bed) to wet store the same. The first vessel may then depart to take the pipe sections to be reused or scrapped. A further vessel may then collect the apparatus and the cradle from the deployment location and move it to e.g. a further decommissioning site or back to shore.

Optionally one or more separate subsea basket(s) or the like are deployed from the vessel and optionally lowered to the seabed and preferably, the correct required number of basket(s) are deployed to the deployment location before pipeline cutting operations are commenced, typically so that the crane does not need to let go of the apparatus once cutting operations have commenced preferably until cutting operations have been completed. Optionally the separate basket is located adjacent to the pipeline being decommissioned. Optionally the separate basket is used as a pipeline storage basket to collect cut sections of pipeline, allowing several sections to be cut by the apparatus without requiring the apparatus to be returned to the vessel to dispose of the pipe section after each cut. Optionally the apparatus cuts the section of pipe and then is manoeuvred to sit over the pipeline storage basket, into which the apparatus may drop the pipe section. Optionally once the one or more pipeline storage basket(s) is/are full, the basket(s) may be returned to the vessel. Typically where the decommissioning operation is not yet complete, one or more further pipeline storage basket(s) may be deployed to the seabed for additional collection of sections of pipe, if required, preferably by a second crane provided on the vessel at the surface.

Also according to the present invention there is provided a method of decommissioning a pipelinein accordance with claim 20.

Optionally the method includes manipulating a dredger to clear a channel or trench around the pipeline and thereby provide a path for one or more gripping devices to grip the pipe. Optionally the method includes manipulating the dredger using a diver or an ROV. Optionally the method includes gripping the pipeline with a grab, a grapple or another suitable gripping device.

Optionally the method includes clamping a portion of the pipe within the, or each, cutting tool. Optionally the method includes cutting the pipe with a wire saw, optionally a diamond wire saw and optionally includes moving at least a part of the cutting tool during cutting of the pipe. Optionally the method includes transferring the cut section of pipe to another location, optionally by holding the section of pipe in the gripping device or devices of the pipeline decommissioning apparatus and steering said apparatus to another location where the pipeline may be deposited for subsequent collection, or optionally by retaining the section of pipe within the gripping device or devices as the apparatus is lifted back to the vessel.

Optionally the method includes the steps of deploying the pipeline decommissioning apparatus, optionally from the deck of a vessel, by connecting a crane or hoist to the apparatus.

Optionally the method includes supporting the apparatus during transportation by mounting said apparatus onto a cradle. Optionally the method includes deploying the apparatus together with the cradle, optionally from the deck of a vessel, optionally by connecting a crane or hoist to the cradle. Optionally the method includes mounting the apparatus onto the cradle on mounts that are sufficiently sized such that the or each gripping device does not make contact with e.g. the base of the cradle, the deck of the vessel or the ground during transportation and/or storage.

Optionally the method includes deploying the apparatus and cradle from a first vessel and collecting the apparatus and cradle using a second vessel or optionally the first vessel during a separate trip. For example, the apparatus may be deployed and left on the seabed for collection after the decommissioning process has taken place. The decommissioned sections of pipeline may be lifted to the first vessel and that first vessel may return to port to offload the pipeline. The apparatus and cradle may be left on the seabed until a second vessel arrives to collect the apparatus and cradle or alternatively until the first vessel has completed offloading of the pipeline and returns to collect the apparatus and cradle.

Optionally the method includes deploying a subsea basket to locate the subsea basket adjacent to the pipeline being decommissioned. Optionally the subsea basket is configured to act as a pipeline storage basket. Optionally the method includes storing cut sections of pipe within the pipeline storage basket. Optionally the method includes collecting sections of pipe within the pipeline storage basket and optionally returning the pipeline storage basket to the surface, for example to a vessel, when the pipeline storage basket is full and/or decommissioning operations are complete. Optionally the method includes deploying further pipeline storage baskets, optionally such that several are located on the seabed for collection of cut sections of pipe or optionally sequentially after a full pipeline storage basket is returned to the surface and/or vessel.

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 aspect can typically be combined alone or together with other features in different aspects of the invention. Any subject matter described in this specification can be combined with any other subject matter in the specification to form a novel combination.

Various 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 illustrates a number of exemplary aspects and implementations. The invention is also capable of other and different examples and aspects, and its several details can be modified in various respects, all without departing from the scope of the present invention. Accordingly, each example herein should be understood to have broad application and is meant to illustrate one possible way of carrying out the invention, without intending to suggest that the scope of this disclosure, including the claims, is limited to that example. 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 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. Likewise, the term comprising is considered synonymous with the terms including or containing for applicable legal purposes. Thus, throughout the specification and claims unless the context requires otherwise, the word “comprise” or variations thereof such as “comprises” or “comprising” will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

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. In this disclosure, the words “typically” or “optionally” are to be understood as being intended to indicate optional or nonessential features of the invention which are present in certain examples but which can be omitted in others without departing from the scope of the invention.

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 directional and positional descriptions such as upper and lower and directions e.g. “up”, “down” etc. are to be interpreted by a skilled reader in the context of the examples described to refer to the orientation of features shown in the drawings 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. In particular, positional references in relation to the seabed such as “up” and similar terms will be interpreted to refer to a direction toward the surface and “down” and similar terms will be interpreted to refer to a direction towards the seabed. Furthermore, references to “seabed” may be understood as a general term for the bottom of water bodies and waterways including other underwater surfaces such as subsea surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a perspective view of a pipeline decommissioning apparatus in accordance with the present invention;

Figure 2 shows a plan view of the apparatus of Figure 1;

Figure 3 shows a side view of the apparatus of Figure 1;

Figure 4 shows an end view of the apparatus of Figure 1;

Figure 5 shows a perspective view of an example of the apparatus of Figure 1 having been extended, with close-up views of the extension interface and end flange;

Figure 6(a) shows a side view of the apparatus of Figure 1 docked onto a first exemplary cradle;

Figure 6(b) shows an end view of the docked apparatus and cradle of Figure 6(a);

Figure 6(c) shows a side view of the cradle of Figure 6(a) (without the apparatus of Figure 1);

Figure 6(d) shows an end view of the cradle of Figure 6(c);

Figure 7 shows the first stage of a first embodiment of a method of deployment of the apparatus of Figure 1 from the back deck of a vessel, where the apparatus is docked onto the cradle of Figures 6(a) to 6(d) and where a lifting crane is connected to the apparatus;

Figure 8 shows a further (i.e. the second) stage of deployment of the apparatus of Figure 1 (following on from the first stage of Figure 7), where the apparatus has been lifted from the cradle by the crane;

Figure 9 shows end views of the next four stages (following on from the second stage of Figure 8) of deployment of the apparatus of Figure 1 and in particular shows the subsea operation of the apparatus of Figure 1 as it grips and cuts a pipeline and subsequently lifts the cut section of pipeline from the sea bed;

Figure 10 shows the next stage (the seventh stage following on from the sixth stage shown at the bottom of Figure 9) of deployment of the apparatus of Figure 1 and in particular shows a side view of the vessel crane lifting the apparatus from the sea bed with the cut section of pipeline;

Figure 11 shows the next stage (the eighth stage following on from the seventh stage of Figure 10) of deployment of the apparatus of Figure 1 and in particular shows the apparatus and cut section of pipeline being returned to the deck of the vessel, where there are several pipeline storage baskets located;

Figure 12 shows a first stage of an alternative deployment sequence (i.e. a second embodiment of a method of deployment) of the apparatus of Figure 1, where one or preferably a plurality of pipeline storage basket(s) is/are deployed prior to deployment of the apparatus;

Figure 13 shows a side view of the second stage of the alternative deployment sequence following on from the first stage shown in Figure 12, with the apparatus of Figure 1 being deployed to a subsea pipeline, with the prior deployed pipeline storage basket(s) of Figure 12 being shown adjacent to the pipeline being decommissioned;

Figure 14 shows end views of the next four stages following on from the second stage of the alternative deployment sequence of Figure 13, showing the steps of subsea operation of the apparatus as it grips and cuts a pipeline and subsequently transfers the cut section of pipeline to one of the prior deployed pipeline storage basket(s) of Figure 12; and

Figure 15 shows the next stage (i.e. the seventh stage following on from the four stages shown in Figure 14) of the alternative deployment sequence, with the filled pipeline storage basket(s) being returned to the deck of the vessel.

DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION

Referring now to the drawings, Figure 1 shows an example of a pipeline decommissioning apparatus 1 for decommissioning subsea pipeline 78 or pipe (particularly oil and/or gas pipeline 78) or other suitable subsea structures (not shown) which require decommissioning in a subsea environment. The apparatus 1 as shown in Figure 1 comprises a beam 5 on which a dredger 10 is mounted; two cutting tools in the form of diamond wire saws 30; three gripping devices in the form of grabs 20 axially spaced apart along the beam 5; and two guiding devices capable of providing controlled directional on-board propulsion to the apparatus 1 in the form of thrusters 50.

Each grab 20 is mounted on and connected to the underside of the beam 5 via rotatable connection 21 and comprise interleaving symmetrically curved arms 23. One arm 23 comprises two identically shaped parts 23a, 23c that are spaced apart from each other in such a way that the opposing arm 23b fits between the parts 23a, 23c in an interleaving arrangement when in a resting configuration. Each arm 23 further comprises a tapered end 24, which may be reinforced by use of a coating or insert made from particularly high-strength or erosion-resistant material, for example titanium or similar. Use of the coating or insert is optional and dependent on the type of substrate that the grabs 20 may be required to penetrate during grabbing operations.

The rotatable connection 21 permits changing of the angle of the grab 20, for example to rotate the grab 20 by 90° around a vertical axis, i.e. an axis perpendicular to the in use substantially horizontal beam 5, when changing between a transportation configuration (where the grabs 20 are parallel to the longitudinal axis of the beam 5) to an operational configuration (where the grabs 20 are perpendicular to the longitudinal axis of the beam 5). The connection 21 also allows smaller changes in angle of the grabs 20, for example to enhance penetration of the grab arms 23 into the seabed and to better align the grabs 20 with the pipeline 78. The grabs 20 would be rotated if for example the pipeline 78 was curved or horseshoe shaped.

The grabs shown in the illustrations are exemplary and may instead take the form of, for example, orange peel grabs, grapples or other suitable grabs.

The arms 23 in each grab 20 are configured to pivot around an axis. In this example, the arms 23 are connected by a hinge 25 around which the arms 23 may pivot. Each arm 23 is actuated by a hydraulic cylinder 22 which retracts and extends to pivot the arms 23 around the hinge 25. In use, the cylinder 22 actuates the arms 23 from the resting configuration into a first configuration where the arms 23 are open and ready to grip a section of pipeline 78. Once the grab 20 is positioned with an arm 23 on either side of the pipeline 78 that is to be gripped, the cylinder 22 then applies force to the arms 23 to penetrate the substrate S around the pipeline 78 and continues applying force until the arms 23 have securely gripped the pipeline 78 between them.

The hydraulic power required by the hydraulic cylinders 22 is supplied via a control unit, in this example an ROV interface panel 40 that is disposed on the beam 5. The ROV interface panel 40 is adapted to receive hydraulic and/or electrical power supplied by either a remotely operated vehicle (ROV - not shown) or from the surface, for example from a vessel 70. The ROV can insert e.g. a hot stab (not shown) into ports 42LF, 42HF within the ROV interface panel 40 to supply fluid into said ports 42LF, 42HF and plug electrical power cables into an electrical socket (not shown) within the panel 40. In operations where the ROV (not shown) is a work class ROV with, for example, its own on board high pressure hydraulic supply controlled by, for example, an intelligent valve pack such as an Intelligent Dredging Systern^tm (IDS) valve pack offered by Subsea Tooling Services UK Limited of Oldmeldrum, Aberdeenshire, AB51 0ΒΖ, United Kingdom, the workclass ROV will be provided with its own electrical power supply from the vessel at the surface by an ROV umbilical, such that the workclass ROV can supply High Flow (HF) hydraulic fluid to the High Flow (HF) hydraulic port 42HF via a first hydraulic fluid hose (not shown). In addition, the ROV can also provide Low Flow (LF) hydraulic fluid to the Low Flow (LF) hydraulic fluid port 42LF via a second hydraulic fluid hose (not shown) and the ROV can also provide electrical power via an electrical cable (not shown) to an electrical socket (not shown) provided in the ROV interface panel 40, controlled by an operator using a computer such as a laptop. Alternatively, hydraulic and/or electrical power may be supplied from the surface, for example from a vessel 70, typically via an ROV with no on-board HP or LP hydraulic supply but controlled by an operator using a computer such as a laptop. Either way, the operator can control and operate the ROV and at this point will instruct the ROV’s manipulator arm to engage, rotate and thus open the required valve 41 to operate the required associated equipment on board the beam 5 such as the thrusters 50, grabs 20, saws 30 or dredger 10 or other equipment that is powered by the hydraulic fluid supply. The electrically operated equipment mounted on the beam 5 such as the cameras, lights or sensors etc. are supplied the electric power by the electric line from the surface via the ROV. Overall, once the apparatus 1 is powered by or via the ROV, it may be remotely operated from the surface.

The diamond wire saws 30 are mounted at each end of the beam 5, further spaced apart from the centre of the beam 5 than each grab 20, i.e. the saws 30 are the outermost devices on the beam 5. Each diamond wire saw 30 comprises a body having a frame 30f and a plate 30p. The plate 30p comprises a drive wheel 37, with guide wheels 39 around which the diamond wire 38 is looped. The drive wheel 37 comprises a motor and feeds the wire 38 around the guide wheels 39. The wire 38 is held in tension around the guide wheels 39 and the drive wheel 37 so that there is no slack in the loop that may risk the wire 38 detaching from the guide wheels 39.

As can be seen from e.g. Figure 4, each plate 30p is substantially C-shaped. In this example, the guide wheels 39 are arranged so that a portion of the wire 38 is held in a straight line across the open end of the plates 30p, thereby providing an abrasive cutting surface when the drive wheel 37 feeds the wire 38 around the guide wheels 39. The plates 30p are movable so that as the grabs 20 grip a portion of a pipeline 78, the plates 30p move towards the section of pipe 79 to be cut. The wire 38 is driven around each plate 30p by the drive wheel 37 and thereby cuts through the pipeline 78 to create the section of cut pipe 79. As the wire 38 cuts through the pipeline 78, each plate 30p continues to move in a direction away from the beam 5 until the section of pipe 79 (see e.g. Figure 9) is severed at two ends. The plate 30p then retracts to its initial position and the section of pipe 79 (that was cut from the pipeline 78) can be recovered.

The frame 30f of the diamond wire saw 30 comprises a substantially C-shaped portion at a lower end of the frame 30f, having an open end into which the pipe is received. The frame 30f comprises two jaws 32 arranged so that there is one jaw 32 at either side of the open end of the frame 30f. The jaws 32 actuate to clamp the section of pipeline 78 to be cut there between and thereby further stabilise the pipeline 78 during cutting operations. Each jaw 32 pivots around a connection point from a first configuration, where the jaws 32 are open and a pipeline 78 may be received, to a second configuration, where the jaws 32 have pivoted towards the central axis of the frame 30f, to clamp a pipeline 78. Optionally the jaws 32 may be hydraulically powered.

The frame 30f further comprises four contact pads 33, spaced apart in pairs in a Vshaped configuration at the upper end of the C-shaped portion of the frame 30f. Depending on the diameter of the pipeline 78 being clamped, the contact pads 33 may contact the upper surface of the pipeline 78 and further stabilise the pipeline 78 during cutting, for example by restricting rotational movement of the pipeline 78. However, it is not essential that the contact pads 33 contact the pipeline 78 for effective cutting to take place.

The frame 30f further comprises a shaft 34 along which the plate 30p moves. The frame 30f comprises a feed motor (not shown) that drives the movement of the plate 30p, which is restricted to move linearly up and down the frame 30f. The feed motor drives the plate 30p towards the pipeline 78 during cutting operations. Optionally the diamond wire saw 30 is capable of tilting slightly to enhance cutting, for example +/5° around the central axis of the saw 30.

As best seen in Figures 1 and 3, the thrusters 50 are mounted on the underside of the beam 5 towards opposing ends of the beam 5. The thrusters 50 point in different directions; for example, as shown in Figure 1, thruster 50a is directed in the opposite direction to thruster 50b. This allows an operator to steer the apparatus 1 by activating one thruster 50a, 50b at a time, thereby applying a lateral force relative to the beam 5, moving the end of the beam 5 to which the thruster 50a, 50b is mounted. However, the operator could and usually would decide to actuate both thrusters 50a, 50b simultaneously if the operator intends to rotate the longitudinal axis of the beam 5 on the horizontal plane about its midpoint. The thrusters 50 allow an operator to finely manoeuvre the apparatus 1 around the seabed S to e.g. reposition the dredger 10 during dredging operations and/or to assist in manoeuvring the apparatus 1 into the correct position over and into contact with pipeline 78 to be cut and/or to assist in manoeuvring the cut section of pipe 79. Alternatively, the thrusters 50 could be arranged to point in the same direction but one thruster 50 could be provided with its hydraulic power supply in the reverse direction to the other such that it operates its propeller in the reverse direction to that of the other thruster 50. Further alternatively, the fixed thrusters 50 could be replaced or supplemented with controllable variable directional thrusters (not shown) which can be controlled by an operator to allow significantly greater control over the direction of propulsion provided to the beam 5. In any event, embodiments of the present invention allow an operator to move and position the apparatus 1 much more quickly and safely than by just relying on positioning by use of the crane 71 and the ROV alone.

Optionally the beam 5 may further comprise lighting equipment (not shown), optionally together with cameras (not shown), e.g. video camera equipment, to permit an operator to visually inspect the pipeline 78 and optionally the decommissioning apparatus 1 as the apparatus 1 grabs and cuts the pipeline 78. Optionally the beam 5 may further comprise sonar equipment (not shown) to map the seabed S around the pipeline 78 and/or the pipeline 78 itself. Optionally the beam 5 may comprise additional detection and monitoring equipment, for example an altimeter (not shown) and/or a transponder (not shown but commonly known as a bathy which pulses a signal which pings off the seabed to inform the operator how far away the beam 5 is from the sea bed), to measure respectively depth and distance to seabed as required.

Optionally the beam 5 may be extended on one or both sides with beam extensions 5e. Optionally the beam 5 may be extended from, for example, 10 metres in length to 20 metres in length, where each beam extension 5e is 5 metres long. The beam 5 comprises flanges 8 axially spaced apart, located at each end of the beam 5. The flanges 8 comprise apertures that are suitable for receiving fasteners. When the beam 5 is to be extended, the beam extension 5e is connected to an end of the beam 5. Each beam extension 5e also comprises flanges 8e at each end and one flange 8e of the beam extension 5e is connected to a flange 8 of the beam 5 and fastened thereto. Optionally the flanges 8, 8e are connected via removable threaded fasteners, for example bolts, that pass through apertures formed in both of the flanges 8, 8e to be connected.

When the beam 5 is extended using beam extensions 5e, additional grabs 20 may be mounted according to the length of the beam 5 and optionally according to the properties of the pipeline 78 to be cut. In that case, the thruster(s) 50 are mounted on the ends of the extended beam 5, 5e. Similarly, additional lights, cameras or sonic devices may be added to the extended beam 5, 5e if required.

In use, as shown in Figures 7-11, the apparatus 1 is lowered to its deployment location by a vessel crane 71 which is connected to the beam 5 by padeyes 7, which are spaced symmetrically apart on the upper surface of the beam 5.

The beam 5 further comprises forklift pockets 6 on the lower surface of the beam 5 that allow a forklift (not shown) to manipulate the apparatus 1 when onshore.

The apparatus 1 may be used in combination with a cradle 60 having a cradle frame 61, as seen in e.g. Figures 6 and 7. The cradle 60 acts as a support for the apparatus 1 during transportation, reducing the risk of damage to the apparatus 1 and holding the apparatus 1 steady, and in particular its various components such as the beam 5, the grabs 20 and the saws 30. The cradle 60 comprises a frame 61 onto which mounts 65 for the apparatus 1 are secured, for example bolted or welded to the frame 61. The mounts 65 are sufficiently tall that, when the apparatus 1 is lowered into the mouth 65M of the mount 65 and then docked onto the mounts 65, the grabs 20 are not in contact with the cradle frame 61, for example, the lower ends of the arm sections 24 of the grabs 20 do not make contact with the base of the cradle frame 61, or with the ground or deck of the vessel 70 if the cradle frame 61 does not have a base.

The mounts 65 can be (see Figure 6) in a substantially U-frame configuration. The docking sites for the apparatus 1 on the mounts 65 are located at the apex of the frame 61 and comprise further extensions 65a that extend on one side of the beam 5 when the beam 5 is docked on the mounts 65. These extensions 65a aid entry of the beam 5 into the mouth 64M and also provide further support and resistance to movement of the beam 5 and thereby the apparatus 1 during transportation of the apparatus 1.

The cradle frame 61 includes a platform 67 on which personnel may move around to, for example, connect a vessel crane to the beam 5 for deployment. The platform 67 comprises an access ladder 68 and safety railings 69.

The cradle 60 may comprise mud mats at the bottom of the frame 61 (not shown) that are adapted to resist the cradle frame 61 sinking into the seabed as the cradle 60 rests on the seabed.

The pipeline decommissioning apparatus 1 can be deployed from the deck of a vessel 70 by attaching the wire 72 of the lifting crane 71 to the padeyes 7 and lifting the apparatus 1 from the cradle mounts 65 such that they separate and lowering the apparatus 1 to the subsea deployment location, leaving the cradle 60 on the deck of the vessel 70 as shown in Figures 6-15.

Figure 7-11 show the various main stages in sequence of a first embodiment of a method of deployment of the apparatus 1 from the back deck of a vessel 70. The apparatus 1 is connected to the wire 72 of a crane 71 (Figure 7) and lifted from the cradle 60 (Figure 8). The apparatus 1 is then deployed over the side of the vessel 70 and lowered (top of Figure 9) to the location of the pipeline 78 on the seabed S that is to be decommissioned. The crane 71 continues to support the apparatus 1 during the various operations of the decommissioning process, providing vertical movement (lifting/lowering) and larger lateral movement where required. Once the apparatus 1 is located in the near vicinity of the pipeline 78, the thrusters 50 can provide further lateral (but much finer) movement to position the apparatus 1 as required over the pipeline 78 under the control of the operator at the surface. Figure 9 shows the further steps of gripping the pipeline 78 with the grabs 20, the wire cutter 30 cutting through the pipeline 78 and the apparatus 1 being lifted away from the seabed S while gripping the cut section of pipe 79 in the grabs 20. The apparatus 1 is then lifted (Figure 10) back to the vessel 70 and the section of pipe 79 may then be placed (Figure 11) into a pipeline storage basket 75 for transportation. These steps may then be repeated as often as required until the pipeline 78 has been removed or the pipeline storage baskets 75 are full and no further sections of pipe 79 may be safely held on the vessel 70.

Figures 12-15 show some of the main steps of an alternative and preferred method of deployment (i.e. a second embodiment) where a pipeline storage basket 75a is connected via wire 72 to the vessel crane 71 and then deployed off the side of the vessel 70 to the seabed S. The pipeline storage basket 75 is lowered to a location that is adjacent to the pipeline 78 that is to be decommissioned. Preferably, a number of additional baskets 75 are then also lowered to the deployment location until as many baskets 75 as will be required to collect the cut sections of pipe 79. As described above for Figures 7-11, the apparatus 1 is then subsequently connected to the same crane 71 (or a separate crane if the vessel has a second crane that can be dedicated just to the apparatus 1) via wire 72 and lowered to the location of the pipeline 78. Figure 14 shows the steps of gripping, cutting and then moving the cut section of pipe 79 from the seabed S to the nearby pipeline storage basket 75a. Several sections of pipe 79 may be cut and lifted to the pipeline storage basket 75a before the basket 75a is filled. The apparatus 1 can thus cut several sections of pipe 79 without having to be lifted back to the vessel 70 after each cut and instead it is the pipeline storage baskets 75 that are changed out. This can save time during the decommissioning operations.

Alternatively, in a third embodiment of a method of deploying the apparatus 1, the apparatus 1 may be deployed from the deck of the vessel 70 to the subsea location in combination with the cradle 60. In this deployment configuration (not shown), the wire 72 of the crane 71 is instead attached to connection points 63 for the wire 72 of the crane 71, for example padeyes 63 secured at suitable locations on the cradle 60 by bolts or welding or the like. The wire 72 of the crane 71 is thus connected to the cradle 60 and the cradle 60 may then be lifted and moved by the crane 71. The vessel crane 71 may then be uncoupled from the padeyes 63 of the cradle 60 and instead then be connected to the connection points 7 on the beam 5 of the apparatus 1 to lift the apparatus 1 from the cradle 60 as the cradle 60 rests on the seabed S.

The cradle 60 and the apparatus 1 may then be left or “wet stored” on the seabed S for subsequent collection, for example, a first vessel may transport the apparatus 1 and cradle 60 to the deployment location before being loaded with pipe sections 79 as decommissioning operations progress. The first vessel may then depart to take the pipe sections 79 to be reused or scrapped. A further vessel may then collect the apparatus 1 and the cradle 60 from the deployment location and move it to e.g. a further decommissioning site or back to shore.

No matter which embodiment of method of deployment is employed, the operator has the great advantage that the on board thrusters 50 can be used to significantly aid the manoeuvrability of the beam 5 and thus the apparatus 1 in addition to the movement caused by the crane 71 via its wire 72.

Modifications and improvements may be made to the embodiments of the present invention substantially as hereinbefore described without departing from the scope of the present invention.

Claims

1. A pipeline decommissioning apparatus, said apparatus comprising a longitudinally-extending beam upon which is mounted:

at least one dredger;

at least two cutting tools axially spaced apart on the beam, at least two gripping devices adapted to grip a portion of a pipeline, the at least two gripping devices being axially spaced apart on the beam;

wherein the axial spacing of the cutting tools is greater than the axial spacing of the gripping devices;

wherein the dredger is capable, in use, of manipulation to clear a channel around the pipeline and thereby provide a path for the at least two gripping devices to grip the pipeline; and at least one powered propulsion device;

wherein the at least one powered propulsion device is adapted to provide propulsion to the apparatus when the at least one powered propulsion device is actuated;

wherein the at least one powered propulsion device is, in use, controllable such that an operator can control the quantity, duration, and/or direction of propulsion afforded by the at least one powered propulsion device.

2. A pipeline decommissioning apparatus as claimed in claim 1, wherein the apparatus further comprises a control unit configured to receive at least one control line, wherein the at least one control line supplies power to the apparatus.

3. A pipeline decommissioning apparatus as claimed in claims 1 or 2, wherein the control unit comprises an intelligent valve pack, and wherein the intelligent valve pack is configured to supply hydraulic and/or electrical power to the apparatus.

4. A pipeline decommissioning apparatus as claimed in claims 1-3, wherein the at least one gripping device comprises at least two curved arm sections, wherein the arm sections are configured to grip and retain a portion of a pipe between the arm sections; wherein the arm sections are connected at a single point such that the arm sections are pivotable around an axis; and wherein each arm section is actuated by a hydraulic cylinder.

5. A pipeline decommissioning apparatus as claimed in claim 4, wherein the arm sections comprise tapered end portions.

6. A pipeline decommissioning apparatus as claimed in claims 1-5, wherein the at least one gripping device is connected to the apparatus by a pivotable connection, wherein the pivotable connection permits the at least one gripping device to rotate around an axis.

7. A pipeline decommissioning apparatus as claimed in claims 1-6, wherein the at least one cutting tool comprises a body having a frame and a substantially Cshaped plate having an open end into which a pipeline is receivable in use; wherein the plate comprises a drive wheel and guide rollers around which a cutting wire is capable of being looped, and wherein the drive wheel is configured to drive the cutting wire around the guide rollers.

8. A pipeline decommissioning apparatus as claimed in claim 7, wherein the wire is held in tension between the drive wheel and the guide wheels, and wherein the guide wheels are arranged so that a portion of the wire is held in a straight line across the open end of the plate, thereby providing an abrasive cutting surface; wherein at least a portion of the plate or body of the cutting tool is configured to move towards the pipeline as the pipeline is gripped by the at least two gripping devices and thereby cut the pipeline..

9. A pipeline decommissioning apparatus as claimed in claims 7 or 8, wherein the frame of the cutting tool comprises at least one clamp that clamps the section of pipeline or pipe to be cut, wherein the clamp comprises at least two jaws disposed on either side of the frame, wherein each jaw is pivotable around a connection point and wherein each jaw is adapted to pivot from a first, open configuration to a second, clamping configuration.

10. A pipeline decommissioning apparatus as claimed in claims 1-9, wherein the beam is adapted to be extended on at least one side of the beam.

11. A pipeline decommissioning apparatus as claimed in claim 10, wherein the beam comprises flanges located at each end of the beam, wherein the flange of the beam is adapted to be removably connected to a corresponding flange on an extension bar.

12. A pipeline decommissioning apparatus as claimed in claims 10 or 11, wherein additional gripping devices are mounted onto the beam when the beam is extended.

13. A pipeline decommissioning apparatus as claimed in claims 10-12, wherein additional guiding devices are mounted onto the beam when the beam is extended.

14. A pipeline decommissioning apparatus as claimed in claims 1-13, wherein the apparatus comprises at least one connection point suitable for connection to a crane.

15. A pipeline decommissioning apparatus as claimed in claims 1-14, wherein the apparatus comprises protrusions that facilitate docking of the apparatus to a cradle, wherein the cradle further comprises a frame onto which mounts for the apparatus to be docked thereon are placed, thereby securing the beam to the cradle, and wherein the cradle supports the apparatus during transportation.

16. A pipeline decommissioning apparatus as claimed in claim 15, wherein the mounts are in a substantially A-frame configuration, wherein the A-frame is reinforced with at least one supporting strut; wherein the apparatus is docked at the apex of the A-frame.

17. A pipeline decommissioning apparatus as claimed in claim 16, wherein the Aframe comprises extensions that extend either side of the apparatus when the apparatus is docked onto the cradle.

18. A pipeline decommissioning apparatus as claimed in claims 14-17, wherein the pipeline decommissioning apparatus is adapted to be deployed from the deck of a vessel by lifting the apparatus from the cradle and lowering the apparatus to the deployment location.

19. A pipeline decommissioning apparatus as claimed in claims 14-18, wherein the apparatus is deployed in combination with the cradle, wherein the cradle comprises connection points for a crane.

20. A method of decommissioning a pipeline using the pipeline decommissioning apparatus of claim 1-, said method including the steps of:

manipulating the dredger to clear a channel around the pipeline and thereby providing a path for the at least two gripping devices to grip the pipeline;

gripping the pipeline with the at least two gripping devices;

cutting the pipeline with the at least two cutting devices; and guiding the pipeline decommissioning apparatus with the at least one propulsion device;

wherein the method further includes the steps of providing propulsion to the pipeline decommissioning apparatus by actuating the at least one powered propulsion device; and controlling the powered propulsion device and thereby controlling the quantity, duration, and/or direction of propulsion applied to the pipeline decommissioning apparatus by the at least one powered propulsion device.

21. A method as claimed in claim 20, the method including transferring the cut section of pipeline to another location by gripping said section of pipeline with the at least one gripping device until the cut section of pipe can be deposited.

22. A method as claimed in claim 21, the method including steering said apparatus to another location by applying propulsion using the at least one powered propulsion device, where the cut section of pipeline is deposited for subsequent collection.

23. A method as claimed in claim 21, the method including retaining the cut section of pipeline within the at least one gripping device as the apparatus is lifted to a vessel, wherein the cut section of pipeline is deposited.

24. A method as claimed in claims 20-23, the method including the steps of deploying the pipeline decommissioning apparatus from the deck of a vessel by connecting a crane to the apparatus and lifting the apparatus to its desired location.

25. A method as claimed in claims 20-24, the method including supporting the apparatus during transportation by mounting said apparatus onto a cradle, and deploying the apparatus together with the cradle from the deck of a vessel by connecting a crane to the cradle and lifting the cradle and apparatus to their desired location.

26. A method as claimed in claims 20-25, the method including deploying a

5 subsea basket and locating the subsea basket adjacent to the pipeline being decommissioned, wherein the subsea basket acts as a pipeline storage basket; and including storing cut sections of pipeline within the pipeline storage basket and returning the pipeline storage basket to the surface with said cut sections of pipeline.