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Special report: trenchless technologies or open cut method?

Published by , Senior Editor
World Pipelines,

With pipeline infrastructure expanding, trenchless pipelaying technologies are starting to gain traction. Will horizontal directional drilling (HDD), microtunnelling, auger boring and Direct Pipe methods replace the traditional ones? Natalya Kuznetsova, Project Director of the Midstream Oil and Gas Congress 2019 explains what such techniques may offer to the market.

1. Reduced environmental impact

Trenchless pipelaying methods do not require invasive excavations and soil replacement, allowing the preservation of the landscape, the topsoil, and a decrease in the rehabilitation time. For example, HDD method includes one dig down at the beginning and at the end of the route. This means the pipelaying activities do not tear up the soil along the whole length of pipe, interrupt the development of buildings or infrastructure, and involve less equipment. Microtunnelling is often used together with vacuum extraction system and dust collectors. The Direct Pipe method focuses on a significant cut on generated slurry, and Auger Boring is known for its dry installation without the production of slurry.

2. High cost-effectiveness

There is a need for solid investments in trenchless technologies, especially for large diameter pipe installation, but they quickly make up for the investment. Potentially, in comparison with traditional open cut methods, they could allow for a decrease in the expenses by half. They take less time, equipment, and manpower resources for installation; saving the money needed for infrastructure recovery.

3. Installation accuracy

Due to the sophisticated guidance systems, pipeline installation has a deviation of only 5 - 10% from the initial route. This allows pipelaying works to travel through horizontal curves as well as upward and downward slopes. For Microtunnelling the deviation does not exceed 10 mm, making it the most precise trenchless technology at the moment.

4. Durability

With the traditional open cut method used for river crossings, the pipeline usually passes under a bridge. This accelerates its wearing and cuts the lifespan by 50 - 75%. Trenchless pipe-laying methods, like HDD, lay the route under the bed of a river and employ more durable materials. And the accurate installation techniques reduce the risk of damage during the construction.

5. Faster installation

As no trench excavation is needed, trenchless pipeline construction requires less time than the traditional open cut method. When all the preparatory works at the site are finished, the average advance is 120 ft/d (36.6 m). The Direct Pipe method shows the shortest time with its one-step installation of pushing the pipe into the ground. Microtunnelling takes the longest period of time for steel welded pipe construction.

6. Flexible location

Because of the underground execution, trenchless pipelaying can be carried out regardless of the soil type and without the disturbance of existing infrastructure; under roadways and buildings or for river crossings. However, during Auger Boring the stability of the soil structure should be carefully observed.

At the moment trenchless pipelaying methods have only begun to spread because of length limitations, though their advantages are confirmed by the usage in the largest midstream projects. During the Trans Adriatic Pipeline construction in Albania, HDD was employed for the two widest river crossings, Microtunnelling for narrower ones, and Auger Boring for small channels. The Nord Stream 2 (NS2) project also tries the same approach; Mezhregiontruboprovodstroy (MRTS) and Van Oord-Boskalis apply HDD, Microtunnelling, and Direct Pipe methods to preserve the environment at the Russian onshore segment in the Kurgalsky nature reserve.

Representatives from Van Oord-Boskalis, Saipem, Baltic Connector Oy, DESFA, Emerson, and many others will attend the Midstream Oil and Gas Congress in February this year. We will observe new approaches, trends and issues in oil and gas storage, transportation, and trading.

To find out more about the Congress, click here.

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