Page 96: of Offshore Engineer Magazine (May/Jun 2013)

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Subsea grouting solves

Pipelines many seabed problems seabed via: installed when seabed scour has

Subsea damage and support n Foundation grouting eroded previously supportive sedi- problems can often be solved n Pipeline and J-tube grouted fabric ment, and in some instances, can using injection grouting. formwork supports actually help reinstate the seabed.

n Member inflling to strengthen FoundOcean recently completed

James Bell of FoundOcean fooded or degraded jacket members a project in the Bay of Bengal to tells us how its accomplished.

Grouting repair clamps around install formwork supports for a n

Extending the life of an asset means damaged pipelines and jacket new 32in. export pipeline and 14in. that the structure can still generate members intra-feld pipeline. Engineers used n revenue, whereas removing it can be Other highly customized projects. computer modelling software to a highly complex operation, often identify tens of potential freespans more so than the original instal- Fabric formworks that would need addressing along

Fabric formworks are used to prevent lation. There are many options to the pipelines’ paths. But, it was not or cure pipeline freespans. They can rehabilitate structures. The state of possible to confrm whether the also be used to raise a pipeline or the asset will have a bearing on the spans were acceptable until the structure by jacking it up. The fexible, likely success and available restora- pipeline had been laid.

high-strength synthetic woven fabric tion options: for example, upgrade Fifty-one custom grout bags were bags are cost effective to make and are works due to regulation changes are designed and manufactured to easy to deploy by ROV or diver. likely to be relatively straightfor- suit the terrain and height of the ward, whereas vessel damage repairs freespans. The large-base grout will be more technically challenging. Freespan rectifcation bags had anti-scour protection skirt

Grout is the essential element It is recommended practice for pipe- sleeves built into them, which slows securing jackets, monopiles, gravity- line engineers to adhere to specifc down the local current and causes base structures, and tripods to the design codes like DNV-RP-F105, suspended particulate matter to or similar codes, for freespans. settle. Over time, the skirts become

Surveying the seabed topography engorged with sediment, reinstating and local currents can help engineers the seabed.

to plan whether freespans or scour The grout bags required flling in may occur during the installation of two or more stages due to their vol- a new pipeline. This can infuence ume. This was achieved by inject- the design and path of the asset and ing grout into the lower section enable operational teams to plan of the bag and allowing it to cure scour rectifcation measures into the to provide a stable support for the installation schedule, or incorporate grout injected in the upper sections closer inspection regimes during the later. The formworks were installed asset’s operational lifetime. in water depths up to 186m over a

Fabric bags are flled with grout as

Grout bags can be installed in 90-day campaign.

seabed supports.

both preventative and curative instances. Where the sea foor is Deepwater pipeline separation particularly undulating, new pipe- There are other subsea applications line installations will require some for fabric formworks, such as jack- form of support to ensure freespans ing or separating crossing pipelines. fall within the regulatory param- This year, the company was con- eters, preventing unacceptable tracted to work in the Gulf of Mexico freespans from occurring. to separate two subsea pipelines

Current velocity increases locally that crossed at a depth of 1,370m around a mass that lies on or pro- (4,500ft). The solution chosen pro- trudes from the seabed. This causes tects the lower pipeline and provides

Where the sea foor undulates, Grout localized seabed erosion adjacent support to the upper pipeline.

bags can be installed to form support to the structure and is known as The two pipelines will be sepa- across freespans.

scour. Curative formworks can be rated by jacking the upper pipeline

OE | May 2013 oedigital.com 98 0513OE_pipelines2_found ocean.indd 98 4/22/13 6:12 PM