Technical Field

Described examples relate to systems and methods for use in decommissioning wells, and in particular for use with tubing from wells being decommissioned.

Background

Often the final stage in the lifecycle of an oil and gas well is decommissioning. Typically, at such times, production wells will be plugged and appropriate well infrastructure will be removed. In particular, there may be a desire to remove well tubings, such as casings, conductors, cement sheaths, or the like.

However, there is a desire to minimise the time taken and cost to decommission. Further, while there may be residual value in metal infrastructure, or the like, any benefits associated with the recovery of such infrastructure may be offset if the costs of removal are too high.

This background serves only to set a scene to allow a skilled reader to better appreciate the following description. Therefore, none of the above discussion should necessarily be taken as an acknowledgement that that discussion is part of the state of the art or is common general knowledge. One or more aspects/embodiments of the invention may or may not address one or more of the background issues. Summary In described examples there are systems and methods for use decommissioning a well. The systems and methods may minimise the time taken and cost to decommission. In some examples, the system may comprise a tubing drill. The tubing drill may comprise a drill section, a drill head and a drive unit. The drill head may be provided at a first end of the drill section so as to drill through tubing of a well being decommissioned. The drive unit may be removably attached at a second end of the drill section. The system may be configured such that, subsequent to drilling, the drive unit is detachable so that at least the drill section can remain in place (e.g. installed in place). The drill section may then be used to assist with lifting of the tubing.

The system may be configured such that the drill head is removably attached at the first end of the drill section. In such a way, the system may be configured such that subsequent to drilling tubing, the drill head is also detachable leaving the drill section (e.g. only the drill section) in place to assist with lifting.

The drill section may be cylindrically formed. The drill section may allow passage of a lifting member therethrough, when installed in tubing. Such a lifting member may be configured to connect the tubing to a hoist, or the like. In similar words, the drill section may be configured, when installed, to permit insertion of a lifting member for use with a hoist, or the like. To that extent, the drill section may be considered to be hollow. When left in place, the hollow drill section may define a lifting aperture through tubing. The drill head may be configured as a hole saw, or the like.

The tubing drill, and in particular the drill head, may be configured to drill through casing, conductor, concrete, etc. In some examples, the system also comprises one or more lifting members configured for insertion through the drill section (e.g. hollow drill section). The or each lifting member may comprise one or more lifting connectors, configured to connect the lifting member (and so any associated tubing) to a hoist, or the like. The/each lifting connector may be defined by one or more apertures extending through the lifting member.

The drill section may be configured to be removable from tubing, subsequent to use with a hoist or the like. The drill section may be re-usable, or indeed may be configured to be used only once.

The system may be configured such that the drive unit is removably attachable to the drill section using a connecting sub. The system may be configured such that the connecting sub is detachable from the drill section so as to remove the drive unit from the drill section.

The system may comprise a tubing jack. The tubing jack may be configured to advance tubing to a hoist (e.g. from a well, seabed or the like, to a hoist). The tubing jack may be configured to advance tubing to a hoist in interval advancements (e.g. defined intervals of tubing being advanced). The system may be configured to drill and install drill sections through tubing at some or all interval advancements.

The tubing jack may comprise an upper restraint and a lower restraint. Both the upper and lower restraint may be configured to selectively retain (e.g. grip) tubing being advanced from a well to a hoist. The upper and/or lower restraint may comprise slips, or the like, in order to provide selective retention of tubing. The upper and lower restraint may be movable relative to one another. One or more actuators may be used to move the upper and lower restraints relative to one another. The actuators may comprise hydraulic piston/cylinder arrangements.

In some examples the tubing drill, and in particular the drill section, may comprise one or more transport connectors. The/each transport connector may be defined by one or more apertures extending through an outer wall of the drill section. The transport connectors, and the drill section may be configured such that, in use, and when positioned relative to tubing, the transport connectors are positioned outside of the tubing for connection to a tubing end cap, or the like.

The system may comprise one or more separation devices, configured to separate one section of tubing from the remainder of the tubing being advanced from a well to a hoist. The separation device may be positioned relative to the tubing jack so as to separate tubing as it is advanced from a well to a hoist. The or each separation device may comprise a saw, such as a band saw.

The system may comprise a hoist for lifting tubing sections. The tubing jack may be rated to support a certain tonnage. The hoist may be rated to support a different tonnage to the tubing jack (e.g. lower tonnage). The system may be configured for use with an offshore platform.

In some examples, there is described a system for use decommissioning a well, comprising:

a tubing drill having a drill section, a drill head and a drive unit, the drill head being provided at a first end of the drill section so as to drill through tubing of a well being decommissioned; and

the drive unit being removably attached at a second end of the drill section, the system being configured such that, subsequent to drilling, the drive unit is detachable so that at least the drill section can remain in place to assist with lifting of the tubing.

In some examples, there is described a system for use decommissioning a well, comprising:

a tubing drill having a hollow drill section, a drill head and a drive unit, the drill head being provided at a first end of the drill section so as to drill a lifting aperture through tubing of a well being decommissioned; and

the drive unit being removably attached at a second end of the drill section, the system being configured such that, subsequent to drilling a lifting aperture, the drive unit is detachable so that at least the drill section can remain in place to assist with lifting of the tubing.

In some examples, there is provided a drill section, connectable at a first end to a drill head, and connectable at a second end to a drive unit; the drill section being configured, for example when decommissioning a well, to remain in place to assist with lifting of the tubing.

In some examples, there is provided a drill section, connectable at a first end to a drill head, and connectable at a second end to a drive unit; the drill section being configured, for example when decommissioning a well, to remain in place to define in the tubing a lifting aperture for a lifting member through the drill section. In some examples, there is described a tubing section having been separated from well tubing, the tubing section comprising one or more installed drill sections. The drill section may have remained in place, after drilling, to assist with lifting of the tubing section. In some examples, the drill section may define in the tubing a lifting aperture for a lifting member through the drill section (e.g. hollow drill section). Alternatively, the drill section may instead define or serve as the lifting member itself.

The drill section may comprise one or more transport connectors. The transport connector may be defined by one or more apertures extending through a wall of the drill section. The transport connectors, and the drill section may be configured such that, in use, and when positioned relative to tubing, the transport connectors are positioned outside of the tubing for connection to a tubing end cap, or the like.

The tubing section may comprise one or more tubing caps, closing or otherwise sealing an end of the tubing.

In some examples, there is described a method for decommissioning a well.

The method may comprise drilling through a tubing using a tubing drill, the tubing drill having a drill section, a drill head and a drive unit. The drill head may be provided at a first end of the drill section and the drive unit may be provided at a second end of the drill section.

The method may comprise subsequently detaching at least the drive unit such that at least the drill section remains in place to assist with lifting of the tubing. The method may comprise detaching the drill head such that the drill section (e.g. only the drill section) remains in place to assist with lifting of the tubing.

The method may comprise drilling through one or more of casing, conductor, concrete, etc.

The method may comprise detaching a connecting sub from the drill section so as to remove the drive unit from the drill section. The method may comprise advancing the tubing towards a hoist in interval advancements (e.g. from a well to a hoist in interval advancements).

The method may comprise drilling through the tubing and installing or otherwise leaving the drill section in place when the tubing is at a first advancement position. The method may comprise advancing the tubing to a second interval advancement. The method may comprise drilling through the tubing and leaving a drill section (e.g. further drill section) in place when the tubing is at the second interval advancement.

The method may comprise advancing the tubing to a third interval advancement. The method may comprise drilling though the tubing, leaving a drill section in place, when the tubing is at a third advancement position.

The method may comprise, while retaining the tubing, separating the tubing between installed drill sections so as to provide a tubing section. That tubing section may comprise only a single installed drill section. The method may comprise hoisting the tubing section using the installed drill section (e.g. using directly, or using a lifting member or the like). At one, some or all interval advancements, the method may comprise drilling through the tubing and installing drill sections that define lifting apertures (e.g. defined through hollow drill sections). The method may comprise inserting lifting members through each lifting aperture. The method may comprise attaching the lifting members to a hoist, or the like.

The method may comprise continually advancing the tubing in intervals, drilling through the tubing and leaving drill sections installed in place, and separating the tubing into tubing sections for lifting. The method may comprise using a saw, such as a band saw, to separate tubing sections.

The method may comprise attaching a transport cap or transport caps to the tubing sections for subsequent transport. The method may comprise attaching the transport cap or transport caps to transport connector(s) of the drill section.

The method may comprise using a tubing jack to advance tubing from a well, or the like, to a hoist, such a tubing jack having upper restraint and lower restraints. The method may comprise selectively restraining tubing using one or both of the upper and lower restraint in order to advance tubing to a hoist. The method may comprise using slips, or the like, to selectively restrain tubing.

The method may comprise moving the upper and lower restraint relative to one another in order to advance tubing (e.g. in order to advance in intervals).

The method may comprise decommission or removing tubing at an offshore platform. In some examples, there is described a method for decommissioning a well, comprising:

drilling through tubing using a tubing drill, the tubing drill having a drill section, a drill head and a drive unit; the drill head being provided at a first end of the drill section and the drive unit being provided at a second end of the drill section,

subsequently, detaching at least the drive unit such that at least the drill section remains in place to assist with lifting of the tubing.

In some examples, there is described a method for decommissioning a well, comprising:

lifting a tubing section using an installed drill section, the drill section having remained in place subsequent to drilling though the tubing.

The invention includes one or more corresponding aspects, embodiments or features in isolation or in various combinations whether or not specifically stated (including claimed) in that combination or in isolation. As will be appreciated, features associated with particular recited embodiments relating to systems may be equally appropriate as features of embodiments relating specifically to methods of operation or use, and vice versa.

It will be appreciated that one or more embodiments/aspects may be useful in minimising the cost and time taken to decommission.

The above summary is intended to be merely exemplary and non-limiting.

Brief Description of the Figures A description is now given, by way of example only, with reference to the accompanying drawings, in which:-

Figure 1 shows a perspective representation of an offshore production platform. Figure 2 is a cross sectional view of a tubing drill.

Figures 3a to 3d show cross sectional views showing the process of drilling through the tubing with the tubing drill of Figure 2, leaving the drill section in place.

Figure 4 is a system comprising the tubing drill together with a tubing jack as used on a platform.

Figures 5a and 5b are line drawings showing a lifting member being inserted through a drill section.

Figure 6 is a system comprising tubing drill and tubing jack on a platform, showing tubing comprising a lifting member connected to a hoist.

Figure 7 shows a section of tubing with an upper restraint engaged and being advanced from a first interval advancement to a second interval advancement.

Figure 8 shows a section of tubing in a second interval advancement with a lower restraint engaged.

Figure 9 shows the tubing drill being used for drilling the tubing. Figure 10 shows a top section of the tubing being removed.

Figure 11 shows a transport cap affixed to the end of a section of tubing. Description of Specific Embodiments

Figure 1 shows a perspective representation of an offshore production platform 10. Some of the following examples have been described specifically in relation to decommissioning at such offshore platforms 10. However, a skilled reader will appreciate that, in other examples, the systems and methods described herein may also be used onshore, at seabed, or the like.

Here, tubing 50 extends from a well 20, below a mudline 30, to the platform 10. In this case, a wellhead 40 is positioned at the platform 10. During decommissioning, the well 20 is typically sealed at certain positions within the well 20. The wellhead 40, etc. can be removed, and it can be advantageous to remove as much of the tubing 50 as possible. It will be appreciated here that the tubing 50 may comprise single or multiple casing strings, conductors, or the like, which may have cemented annuli. Consider now Figure 2 which shows an example of a tubing drill 100 for use when decommissioning tubing 50 of Figure 1 , and in particular when drilling through tubing of a well being decommissioned, as will be explained.

In this particular example, the tubing drill 100 comprises a hollow drill section 110 which, at a first end 120, there is provided a drill head 130. At a second end 140 there is provided drive unit 150 (e.g. for rotating the drill section 1 10 and drill head 130). The drill head 130 here may be considered to be configured similar to a hole saw, or the like. Similarly, the drill section 110 may be considered to be broadly cylindrical. Also, the drill section 1 10 may be considered to be of a similar - or indeed the same - diameter to that of the drill head 130. Here, the drive unit 150 is removably attached at the second end of the drill section 110 using an intermediate connecting sub 160. In other examples, the drive unit 150 may be directly connected and disconnected to the drill section 110.

Figure 3a shows a cross section of tubing 50 that comprises multiple casing strings, cementing, etc., as may be expected. Here, the tubing drill 100 has been used to drill through the tubing 50 from one side of the tubing 50 to the other. Put in other similar words, the tubing drill 100 has been used to cut roughly diametrically across the tubing 50. Subsequent to drilling, and as is shown in Figure 3b, the drill head 130 and drive unit 150 are detached. In the example provided both the drill head 130 and the drive unit 150 are connected to the drill section 110 using threaded connections.

Once the tubing drill 100 has passed through the tubing 50, both the drill head 130 and drive unit 150 can be removed. Once removed, this leaves in place the drill section 110, which extends across and beyond the tubing 50. As mentioned, in the example described, the drill section 1 10 broadly speaking has the same cross section as the drill head 130. As such, when left in place, the drill section 110 will be in close proximity, if not touching, the cut tubing 50.

In this particular example - and given that the drill section is hollow - when the drill head 130 and drive unit 150 have been removed, the drill section 1 10 remains in place to define, through the hollow drill section 110, a lifting aperture 170 for a lifting member, or the like. As is evident in Figure 3b, the drill section 1 10 extends beyond the edge of the tubing 50. Figure 3c and Figure 3d show two different side views of the tubing 50 in which the drill section 1 10 remains installed, and in this case defines the lifting aperture 170. Figure 4 shows an example of a system comprising the tubing drill 100 together with a tubing jack 200, which may be used at the platform 10 (show in Figure 1). Here, tubing 50 is positioned and restrained relative to the jack 200, as will be described.

The jack 200 comprises an upper restraint 210 and lower restraint 220. In the example described, both are configured as constraint tables through which the tubing 50 may be secured. The upper and lower restraints 210, 220 comprise upper slips 230 and lower slips 235 respectively, which allow for selective retention of the tubing 50 so as to advance the tubing 50 from the well 20 (shown in Figure 1) to a hoist (not shown in Figure 4). Of course other means, rather than tables/slips, may be used.

Here, the upper and lower restraints 210, 220 are movable relative to one another using one or more actuators 240, which in this case are provided by hydraulic piston/cylinder arrangements. While the lower restraint 220 may remain stationary, the upper restraint 210 can raise and lower relative the lower restraint 220 by means of the actuators 240.

When the tubing 50 has been restrained, as is shown in Figure 4, an initial lifting aperture 170 may be provided using the tubing drill 100, by leaving the drill section 1 10 installed, after drilling through the tubing 50. The lifting aperture 170 may be provided at an upper end of the tubing 50, above the upper restraint 210, for connection to a hoist. Subsequently, and as is shown in Figure 5a and 5b, a lifting member 180 can be inserted through the lifting aperture 170. Here, the lifting member 180 extends beyond the drill section 110, and comprises lifting connectors 185 at each end region of the lifting member 180, configured to connect the lifting member 180 (and so any associated tubing 50) to a hoist 300, or the like, as is shown in Figure 6. It will be appreciated that without leaving the drill section 110 in situ, and otherwise withdrawing the tubing drill 100 subsequent to drilling the tubing 50, that one or more of the casings, or the like, may displace within the overall tubing 50, thus causing problems when locating lifting member 180 through the formed aperture. In such cases, the time taken to locate lifting members 180 may be increased, or indeed the tubing 50 may require re-drilling.

Subsequently, the lifting member 180, and so the tubing 50, may be connected to a hoist 300, as is shown in Figure 6. The tubing drill 100 can now be used to provide a further, or indeed second, lifting aperture 170 in the tubing 50 between the upper and lower constraints 210, 220. At this time, the tubing 50 is still being restrained by the jack 200, and in particular using one or both of the upper/lower slips 230, 235 and upper/lower restraints 210, 220, rather than the hoist 300. Indeed, the hoist 300 may be unlikely to have the lifting capacity to restrain the tubing 50.

After the second lifting aperture 170 in the tubing 50 has been drilled (leaving the drill section 1 10 in place), the jack 200 is configured to advance the tubing 50 from this first position to a further interval advancement. To do so, the lower restraint 220 can be released from the tubing 50 (for example by removing the lower slips 235) and the upper restraint 210 which currently engages the tubing 50 can be moved upwards using the actuators 240, thereby advancing the position of the tubing 50 , as is shown in Figure 7. The lower restraint 220 can then reengage the tubing 50 (e.g. by reintroducing the lower slips 235), while the upper restraint 210 can be released from the tubing 50 (e.g. by removing the upper slips 230), and restraint 210 using the actuator 240, as is shown in Figure 7 and Figure 8.

When the second lifting aperture in the tubing 50, defined by the drill section 110, is positioned above the height of the lowered upper restraint 210, relatively speaking, then the upper slips 230 may be reengaged with the upper restraint 210 as is shown in Figure 9. A third lifting aperture 170 comprising lifting member 180 can then be drilled in the tubing 50, again leaving the drill section 1 10 in place. This may be provided after the tubing 50 has been moved to a further interval advancement. In essence, as the tubing is advanced by "walking" the tubing up using the restraints 210/220, further drill sections may be installed in the tubing 50. At some point (e.g. after installing a third drill section 1 10), a upper section of the tubing 50a can be removed, as shown in Figure 10. The top section of the tubing 50a can be removed by means of a separation device 270. Removal may be, for example, by cutting or sawing, for instance with a band saw as shown in Figure 10. The separation device 270 is configured such that it separates top section of the tubing 50a at a point above drill section 1 10b, as shown in Figure 10. The upper section of the tubing 50a, which is attached to the hoist 300 by lifting member 180, can then be removed and, for example, taken to another location on the offshore production platform 10.

Subsequently, the tubing 50 can be advanced and drill sections 1 10 installed in the tubing 50, in the manner described above, or indeed similar to that described above. For example, the drill sections 1 10 may be installed in a different order, or the like. In any event, the process can generally be repeated to remove further sections of the tubing 50.

In some examples, each drill section 100 may also comprise one or more transport connector 290 for use by connection device 280. The transport connectors may be apertures, or the like, defined in the wall of the drill section 1 10. Each removed section of the tubing 50a may then be fitted with a transport cap 260, preventing matter contained within the section of tubing 50a (e.g. dirt, water, sand etc.) from exiting the section of tubing 50a after its removal. The transport cap 260 can be attached to the transport connector 290 by use of a connection device 280, for example pins, ties or screws.

Although exemplary drill section 110 (for example in Figure 2 or 3a-d) has been described as a "hollow" drill section, it will be appreciated that "hollow", in this sense, may be considered to be to the extent that it permits passage of a lifting member, or the like, therethrough - for example a steel rope, rod, tie or the like. Indeed, the drill section 100 may not be limited to a hollow cylinder with a common hollow bore, but indeed the section 1 10 may comprise structure or objects within the bore (e.g. to improve strength), but nevertheless would not inhibit passage or insertion of a lifting member 180. In such cases, the drill section may still be considered hollow.

Further, while in the above described example, the drill section 110 has been described as being configured to permit insertion of a lifting member, it will be appreciated that in other examples the drill section 1 10 may serve as a lifting member, when installed. In that regards, in some example, the drill section may be solid. In addition, while in the above example, the drill head 130 is detached, it will be appreciated that that need not always be the case, and in some examples, the drill head may be formed integrally with the drill section 1 10 - both of which remain installed in the tubing, after drilling.

While it may be advantageous to leave the drill section installed in tubing sections (e.g. so as to inhibit unwanted movement of inner casings, etc., during transport), nevertheless in some examples, the drill section may be configured to be removed and reused.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.