APPARATUS AND METHOD FOR REMOVING SOIL FROM A CONDUIT

Abstract

An apparatus for removing soil from a conduit for a subsea well that is forced or placed into a seabed is provided. The apparatus comprises a soil disturbance device to displace soil within the conduit before drilling is performed. A method of removing soil from a conduit for a subsea well that is forced or placed into a seabed is also provided. The method comprises using a soil disturbance device to displace soil within the conduit before drilling is performed.

Claims

1. An apparatus for removing soil from a conduit for a subsea well that is forced or placed into a seabed, wherein the conduit has a first free end that is above or approximately level with the seabed and a second buried end that is embedded in the seabed, and the apparatus comprises a closure means for closing the free end of the conduit and a soil disturbance device to displace soil within the conduit before drilling is performed.

2. An apparatus according to claim 1, wherein the closure means comprises a lid, cap or plug suitable for closing the free end of the conduit.

3. An apparatus according to claim 1, wherein the soil disturbance device comprises a mechanical soil disturbance device.

4. An apparatus according to claim 3, wherein the apparatus comprises a lance along which the mechanical soil disturbance device is arranged to travel.

5. An apparatus according to claim 4, wherein the apparatus is arranged such that the mechanical soil disturbance device travels along the lance when the lance is rotated.

6. An apparatus according to claim 1, wherein the soil disturbance device comprises a liquid flow soil disturbance device.

7. An apparatus according to claim 6, wherein the apparatus comprises a plurality of apertures, through which liquid can flow into the conduit, thereby forming the liquid flow soil disturbance device.

8. An apparatus according to claim 7, wherein the apparatus comprises a lance along which the mechanical soil disturbance device is arranged to travel, and wherein the apertures are located on the lance.

9. An apparatus according to claim 1, wherein the apparatus comprises a conduit protector for covering a portion of the internal surface of the conduit.

10. An apparatus according to claim 1, wherein the apparatus comprises a centraliser located at or towards the end of the apparatus remote from the closure means.

11. An apparatus according to claim 1, wherein the conduit is a conductor.

12. An apparatus according to claim 1, wherein the conduit is a centre pipe of a suction anchor.

13. An apparatus according to claim 1, wherein the closure means comprises at least one outlet passage, and at least one outlet passage is for the flow of liquid and entrained or suspended soil out of the conduit.

14. As apparatus according to claim 13 wherein one or more outlet passage of the closure means is provided with an outlet port, and at least one outlet port is suitable for engaging with an underpressure source.

15. An apparatus according to claim 1, wherein the closure means comprises at least one inlet passage, and at least one inlet passage is for the flow of liquid into the conduit.

16. An apparatus according to claim 15 wherein one or more of the inlet passages of the closure means is provided with an inlet port, and at least one of the inlet ports is suitable for engaging with a pressurised liquid source.

17. A system for removing soil from a conduit comprising an apparatus according to claim 14 and an underpresssure source, wherein the under pressure source is an outlet pump, and the outlet pump is configured to cause an underpressure in the or each outlet passage with which it is in liquid communication.

18. A system according to claim 17 in which the outlet pump is part of or mounted on a remote operating vehicle.

19. A system for removing soil from a conduit comprising an apparatus according to claim 16 and a pressurised liquid source, wherein the pressurised liquid source is an inlet pump, the inlet pump is configured to pump liquid into the or each inlet passage with which it is in liquid communication.

20. A system according to claim 19 in which the inlet pump is part of or mounted on a remote operating vehicle.

21. A method of removing soil from a conduit for a subsea well that is forced or placed into a seabed, wherein the conduit has a first free end that is above or approximately level with the seabed and a second buried end that is embedded in the seabed, the method comprises closing the free end of the conduit with a closure means, and using a soil disturbance device to displace soil within the conduit before drilling is performed.

22. A method according to claim 21, wherein the method comprises forcing liquid into the conduit and/or forcing liquid with soil suspended therein from the conduit via one or more outlet passages in the closure means so as to also remove soil from the conduit.

23. (canceled)

Description

[0093] Certain preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0094] FIG. 1 shows an apparatus for removing soil from a conduit or conductor for a subsea well that is forced or placed into a seabed; and

[0095] FIG. 2 shows the apparatus mounted in a conduit for a subsea well.

[0096] FIG. 1 shows a soil removing apparatus 1 for removing soil from a conduit for a subsea well that is forced into a seabed.

[0097] The apparatus 1 comprises a soil disturbance device 2 that comprises a mechanical soil disturbance device 4 and a liquid flow soil disturbance device 6.

[0098] The mechanical soil disturbance device 4 comprises a plurality of blades. The blades are connected to an internally threaded nut 8 that is mounted on an externally threaded lance 10. The lance 10 is connected at its top end to an ROV interface 12.

[0099] Located along the length of the lance 10 are a plurality of apertures 14 (for clarity only one of the twelve sets of apertures 14 is labelled with a reference numeral in the figure). The apertures 14 provide the liquid flow soil disturbance device 6.

[0100] The apparatus 1 comprises a liquid inlet 16. The liquid inlet passage 16 is in liquid communication with the apertures 14.

[0101] The apparatus 1 comprises an outlet passage 18 through which liquid and soil can pass out of the conduit. The inlet passage 16 and outlet passage 18 extend through a lid 20. The lid 20 may be for sealing to the conduit when the apparatus 1 is installed.

[0102] The apparatus 1 comprises a conduit protector 22. The conduit protector 22 is connected to the lid 20. When the apparatus 1 is installed in a conduit the conduit protector 22 covers, and optionally contacts, an uppermost portion thereof.

[0103] Towards the bottom of the lance 10 is a centraliser 24. The centraliser 24 is for guiding and supporting the lance 10 within the conduit. The centraliser 24 also acts as a stop to prevent the nut 8 moving off the bottom of the lance 10 when the lance is rotated.

[0104] FIG. 2 shows the apparatus 1 of FIG. 1 mounted in a conduit 26. In this case the conduit 26 is the centre pipe of a suction anchor 28. Although the apparatus 1 is shown in a centre pipe 26 of a suction anchor, the conduit for a subsea well cleaned by the apparatus 1 does not need to be part of a suction anchor. The apparatus can equally be used to displace soil from a conduit that is not part of a suction anchor. Such a conduit may have been forced into the seabed by a means other than suction, such as by piling or placed in a drilled hole.

[0105] At the top of the conduit 26 is a conductor housing 30. Once the conduit 26 has been forced into the seabed at least the conductor housing 30 may protrude from the top of the seabed. Thus there may be no soil within the conductor housing 30 after the conduit 26 has been forced into the seabed.

[0106] The apparatus 1 is installed in the conduit 26 as shown in FIG. 2. The bottom end of the lance 10 and centraliser 24 are first inserted into the top end of the conduit 26. The apparatus 1 is supported and guided down within the conduit 26 by the centraliser 24. The apparatus 1 is inserted further into the apparatus 1 until the conduit protector 22 is within the conductor housing 30 and the lid 20 is in contact with the top of the conduit 26 (i.e. the top of the conductor housing 30). The apparatus 1 may then seal with the top end of the conduit 26 via the lid 20 and/or the conduit protector 22. At this point a closed volume may be formed within the conduit 26. The closed volume is formed within the conduit 26 by the top end being sealed by at least the lid 20 and the bottom end being sealed by soil.

[0107] The apparatus 1 may be installed within the conduit 26 before the conduit is forced into the seabed. Alternatively the apparatus 1 may be installed within the conduit 26 after the conduit 26 has been forced into the seabed. In either case the apparatus 1 will be forced through soil within the conduit 26. The soil disturbance device 2 (e.g. the mechanical soil disturbance device 4 and/or fluid flow soil disturbance device 6) may be operated as the apparatus is forced through soil within the conduit 26. This may ease the installation of the apparatus 1.

[0108] The mechanical soil disturbance device 4 may be operated by rotating the lance 10. The lance 10 may be rotated using the ROV interface tool 12.

[0109] Rotation of the lance 10 causes the nut 8 to move along the lance 10. This causes the blades of the mechanical soil disturbance device 4 connected to the nut 8 to also move along the lance 10 such that they can act to displace soil.

[0110] Upon continued rotation of the lance 10 the nut 8 moves down along the lance 10 until it reaches the stop at the end of the lance 10 (in this case the centraliser 24). At that point, upon continued rotation, the nut 8, together with the blades 4, moves back up the lance 10 until it reaches the top.

[0111] Movement of the blades 4 up and down along the lance 10 within the conduit displaces soil within the conduit and moves fluid such that soil may be removed from the conduit 26.

[0112] The fluid flow soil disturbance device 6 may be operated by forcing fluid in through the inlet 16, through the lance 10, through the apertures 14 into the conduit and then out of the conduit 26 via the outlet 18. The fluid may be forced through this fluid path by means of one or more pumps (not shown) connected to the fluid inlet 16 and/or outlet 18.

[0113] The fluid flow from the apertures 14 to the outlet 18 may displace soil within the conduit 26 and remove it therefrom via soil being in suspension within the fluid.

[0114] The apertures 14 may be constrictions such that fluid flowing therethrough forms jets that act to dislodge surrounding soil.

[0115] The mechanical soil disturbance device 4 and/or the fluid flow soil disturbance device 6 may displace soil and cause it to go into suspension in the fluid within the conduit and/or may cause fluid (e.g. with soil in suspension) to flow out of the conduit 26, e.g. via outlet 18. Thus the mechanical soil disturbance device 4 and/or the fluid flow soil disturbance device 6 may act to remove soil from the conduit 26.

[0116] Once the soil has been removed from the conduit 26, the apparatus 1 may be removed from the conduit 26. After the apparatus 1 has been removed, a drill and drill string may be passed through the cleaned conduit so that drilling may be performed to create a borehole below the conduit 26.