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Engineering Subsea Pipelines
In the oil and gas industry, the term subsea relates to the exploration, drilling and development of oil and gas fields in locations that are underwater, usually the sea bed. The oil and gas is extracted from reservoirs under the sea bed and partly processed on production platforms which make use of highly specialized equipment. The equipment must safeguard the environment and enable economic feasibility of the exploration of subsea hydrocarbons.
Once processed, the oil and gas is exported ashore through subsea pipelines that are buried beneath the sand and sediment under the sea bed. These pipelines are prone to acid attack from the oil and gas internally and corrosion from the sea water externally. This raises the need for corrosion protection for the pipes.
A rigorous system of anti-corrosion is thus employed which each pipeline that is laid is subject to. To efficiently preclude corrosion, measures taken must be in accordance with the environment under which the pipeline is located. Let us look at some measures currently taken to subsea pipelines in the hostile environment.
Before we can successfully describe anticorrosion measures, we must first of all understand the procedure for laying pipelines. Foremost,[link widoczny dla zalogowanych], a geotechnical engineering survey is conducted along the path which the pipeline is to be buried. The engineer will excavate the sand and sediment to a depth suiting the pipeline being laid so as to obtain an image of the undulating ridges and hollows.
A ROV (Remote operated vehicle) - Robotic equipment operated from afar to perform tasks on the sea floor, is used to excavate trenches and strives to follow a straight line from production platform to the shore. Ideally a specialized barge may also be used. An excavating barge moves ahead of the pipe laying barge which unreels the pipe and then covers it with sand,[link widoczny dla zalogowanych], sediment and ballast.
The pipes are treated against corrosion ashore at a specialist coating facility depending on the nature of the oil and gas passing through it. Unlike before where the pipe was normally blasted to remove loose particles,[link widoczny dla zalogowanych], the pipes are now treated using a spraying device that efficiently applies a two part polyurethane primer followed by another coat of primer to make the internal surface heat and acid resistant. The external part is treated the same way with only a slightly modified polyurethane topcoat of anti-impact design followed by a coat of concrete or aluminium spray.
Special care must be taken to repair any damage since the corrosion will attack the weakest point. Ideally this is the reason why an experienced contractor should do the work.
Once the pipeline is finished,[link widoczny dla zalogowanych], cathode protection is then done. For information on geotechnical engeering or engineering geology go to Fugro Geoconsulting.Topics related articles：

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