A Method of Laying a Pipeline on a Seafloor, Monitoring Surrounding Zones of the Installed Pipeline for Approaching Vessels and Warning Vessels Considered to be Able to Cause Harm to the Pipeline

Abstract

It is described a method of laying a pipeline (1) on a seafloor (2), wherein the method comprises the steps of: —bringing the pipeline to an offshore location using a vessel, —laying the pipeline on the seafloor using the vessel, —defining a first zone (10) surrounding at least a first part length (1′) of the pipeline when laid subsea, wherein the first part length is uncovered, —defining a second zone (20) extending from the first zone, —monitoring the second zone for vessels approaching the first zone, —analysing vessels detected during said monitoring of the second zone, for the purpose of determining whether the vessels can cause harm to the first part length of the pipeline, —for each vessel monitored in the second zone and considered to be able to cause harm to the first part length of the pipeline, informing the vessel about the first zone and/or requesting the vessel not to enter into the first zone.

Claims

1. A method of laying a pipeline on a seafloor and protecting the pipeline with at least two types of protection, comprising: bringing the pipeline to an offshore location using a vessel; laying the pipeline on the seafloor using the vessel; defining a first zone surrounding at least a first part length of the pipeline when laid subsea, wherein the first part length is uncovered; covering at least a second part length of the pipeline when laid subsea with a physical protection barrier; defining a second zone extending from the first zone; leaving the second part length unmonitored; monitoring by use of satellites and/or other tools activities in the second zone for vessels approaching the first zone; analysing vessels detected during said monitoring of the second zone for the purpose of determining whether the vessels can cause harm to the first part length of the pipeline; and for each vessel monitored in the second zone and considered to be able to cause harm to the first part length of the pipeline, informing the vessel about the first zone and/or requesting the vessel not to enter into the first zone.

2. The method according to claim 1, wherein said second zone encircles the first zone.

3. The method according to claim 1, wherein said physical protection barrier comprises rocks.

4. The method according to claim 1, wherein said second part length of the pipeline is laid at or close to an offshore installation and/or at or close to shore.

5. The method according to claim 1, wherein the subsea pipeline is a fluid pipeline.

6. The method according to claim 1, wherein the subsea pipeline is a cable.

7. The method according to claim 1, wherein the subsea pipeline is a combination of a fluid pipeline and a cable.

8. The method according to claim 1, wherein the method comprises laying the pipeline between an offshore installation and a satellite well.

9. The method according to claim 1, wherein the method comprises laying the pipeline between an offshore installation and shore.

10. The method according to claim 1, wherein the method comprises laying the pipeline between an offshore installation and another offshore installation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] FIG. 1A is a side view of a vessel laying a subsea pipeline laying on a seafloor;

[0068] FIG. 1B is a top view of a pipeline on a seafloor, where a first part length of the pipeline corresponds to a first zone, and where a second zone extends from the first zone;

[0069] FIG. 1C is a top view of an uncovered first part length of a pipeline on a seafloor, where there are arranged six real AIS ATONs along the first part length of a pipeline and virtual AIS ATONs in between the real AIS ATONs, where the circles indicate a coverage area of the real AIS ATONs which coverage area represents the second zone;

[0070] FIG. 2A is a top view of a subsea laid pipeline extending from a subsea location to a position on shore, where the pipeline is divided in an uncovered first part length of pipeline protected by real AIS ATONs and virtual AIS ATONs at a part of the pipeline farthest away from shore and a covered second part length of the pipeline closest to shore, where the cover is formed by rocks;

[0071] FIG. 2B is a top view of a subsea laid pipeline extending from a subsea location to a subsea installation, where the pipeline is divided in an uncovered first part length of pipeline at a part of the pipeline farthest away from the subsea installation and a covered second part length of the pipeline closest to the subsea installation, where the cover is formed by a protective structure;

[0072] FIG. 2C is a top view of a subsea laid pipeline extending between two offshore installations, where the pipeline is divided in an uncovered first part length of pipeline between two covered part lengths of the pipeline closest to the offshore installations, where the covers are formed by a protective structure;

[0073] FIG. 3 shows a sequence of laying a pipeline on a seafloor according to the present invention;

DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF EMBODIMENT

[0074] In the following, embodiments of the invention will be discussed in more detail with reference to the appended drawings. It should be understood, however, that the drawings are not intended to limit the invention to the subject-matter depicted in the drawings.

[0075] FIG. 1A is a side view of a vessel 3 laying a subsea pipeline 1 on a seafloor 2. The vessel 3 moves on a surface 4 of water. The vessel 3 can be any pipe-laying vessel 3. Such pipe-laying vessels 3 are known to the skilled person and will not be further described herein.

[0076] FIG. 1B is a top view of a pipeline 1 on a seafloor. The pipeline 1 is divided in a first part length of the pipeline 1′ and a second part length of pipeline 1″. The first part length of the pipeline 1′ corresponds to a first zone 10. I.e. the first zone is the vertical projection of the first part length of the pipeline 1′ on the water surface. The first part length of pipeline 1′ is at a depth were protection is required in order to avoid trawls and or anchors from vessels which can damage the pipeline. However, the first part length of pipeline 1′ is uncovered and is rather protected by monitoring vessels entering a second zone, which second zone 20 extends from the first zone 10. In the example of FIG. 1B, the second zone 20 encloses the first zone 10. The second zone 20 is monitored 20 for vessels approaching the first zone 10, the vessels detected during said monitoring of the second zone 20 are analysed for the purpose of determining whether the vessels 20 can cause harm to the first part length of the pipeline 1′. Each vessel monitored in the second zone 20 and considered to be able to cause harm to the first part length of the pipeline 1′ are informed about the first zone 1′ and/or it is requested that the vessel does not to enter into the first zone 1′.

[0077] FIG. 1C is a top view of an uncovered first part length of a pipeline 1′ on a seafloor. This first part length of pipeline 1′ is, similar to the first part length of pipeline 1′ in FIG. 1B at a depth were protection is required in order to avoid trawls and or anchors from vessels which can damage the pipeline. In the example of FIG. 1C, it is arranged six real AIS ATONs 30 along the first part length of a pipeline 1′ and virtual AIS ATONs 31 in between the real AIS ATONs 30. The circles indicate a coverage area of the real AIS ATONs 30, which coverage area represents the monitored second zone 20.

[0078] The real AIS ATONS 30 may be positioned on a spar buoy placed in the field, with several virtual AIS ATONs 31 marking the first part length of the pipeline 1′ at the seafloor. Such a buoy would be the size of a typical navigational marker. This buoy could also be equipped with a radar reflector, marking it for vessels who for some reason have turned off their AIS transponder. Additionally, with the position messages being broadcast, naval ships may also receive information about the ongoing operation even though their AIS is in turned to receiving mode only, and not transmitting mode.

[0079] FIG. 2A is a top view of a subsea laid pipeline 1 extending from a subsea location to a position on shore 40. The pipeline 1 is divided in an uncovered first part length of pipeline 1′ virtually protected by real AIS ATONs 30 and virtual AIS ATONs 31 at a part of the pipeline 1 farthest away from shore 40 and a covered second part length of the pipeline 1″ closest to shore 40. The cover is formed by rocks 5.

[0080] FIG. 2B is a top view of a subsea laid pipeline 1 extending from a subsea location to a subsea installation 50. The pipeline 1 is divided in an uncovered first part length of pipeline 1′ at a part of the pipeline farthest away from the subsea installation 50 and a covered second part length of the pipeline 1″ closest to the subsea installation 50. The cover is formed by a protective structure 6.

[0081] FIG. 2C is a top view of a subsea laid pipeline 1 extending between two offshore installations 60. The pipeline 1 is divided in a first part length of pipeline 1′, a second part length of pipeline 1″ and a third part length of pipeline 1′″. The second and third part lengths of pipeline are closest to the offshore installations 60 and are both covered by a protective structure 6. The first part length of pipeline 1′ which is arranged between the second and third part lengths of pipeline 1″, 1′″ is uncovered.

[0082] FIG. 3 shows a possible sequence of a method of laying a pipeline on a seafloor according to the present invention (reference 100), defined by the steps of: [0083] 100. bringing the pipeline to an offshore location using a vessel, [0084] 101. laying the pipeline on the seafloor using the vessel, [0085] 102. defining a first zone surrounding at least a first part length of the pipeline when laid subsea, wherein the first part length is uncovered, [0086] 103. defining a second zone extending from the first zone, [0087] 104. monitoring the second zone for vessels approaching the first zone, [0088] 105. analysing vessels detected during said monitoring of the second zone, for the purpose of determining whether the vessels can cause harm to the first part length of the pipeline, [0089] 106. for each vessel monitored in the second zone and considered to be able to cause harm to the first part length of the pipeline, informing the vessel about the first zone and/or requesting the vessel not to enter into the first zone.

[0090] Common for all of the examples in the Figures is the first part length of pipeline 1′ which is at a depth were protection is required in order to avoid trawls and or anchors from vessels which can damage the pipeline. However, instead of protecting the laid first part length of pipeline 1′, the first part length of pipeline 1′ is uncovered and is rather protected by monitoring vessels entering the second zone 20. Each vessel monitored in the second zone 20 and considered to be able to cause harm to the first part length of the pipeline 1′ is informed about the first zone 10 and/or requested not to enter into the first zone 10. The means of monitoring and informing may vary dependent on the requirements in the specific projects, and may include but are not limited to the examples above: real and virtual AIS ATONS, S-AIS, AIS message, radar, visual inspection (camera), satellite phone, GMDSS, MF DSC, VHF and ECDIS etc.

[0091] The invention is now explained with reference to non-limiting embodiments. However, a skilled person will understand that there may be made alterations and modifications to the embodiment that are within the scope of the invention as defined in the attached claims.

LIST OF REFERENCES

[0092]

TABLE-US-00001  1 Pipeline  1′ First part length of pipeline  1″ Second part length of pipeline  1″′ Third part length of pipeline  2 Seafloor  3 Vessel  4 Surface of water  5 Rocks  6 Protective structure 10 First zone 20 Second zone 30 Real AIS 31 Virtual AIS 40 Shore 50 Subsea installation 60 Offshore installation