Autonomous Underwater Vehicle (AUV) to be Used for Engineering Surveys on the Undersea Section of “South Stream” Pipeline

September 24, 2011 - via Oil and Gas Eurasia

Interview with Alexander Arkhipov, First Deputy General Director for engineering
By This article was supplied courtesy of Piter Gaz Company

– Alexander, you control the implementation of comprehensive engineering surveys and project design directions within the company. What are the key projects you work on now?

Currently, our priority project is the complex engineering survey for undersea segment of “South Stream” gas pipeline. 
The pipeline route is long, about 900 kilometers across the Black Sea, passing through the territorial waters and exclusive economic zones of the Russian Federation, the Republic of Bulgaria and the Republic of Turkey. As you know, the pipeline will pump Russian natural gas to South and Central Europe. Gas exports (including fuel gas) are estimated at 63.0 billion cubic meters per year.

– What are the challenges you face in implementing the project?
The “South Stream” project is extremely challenging from technical viewpoint. At the engineering survey stage, the main difficulty is a considerable (over 2,100 meters) sea depth of the pipeline route. At the subsequent design and construction stages the key challenges will be the special conditions of the sea bed, the steep (up to 27 degrees) slopes, geological hazards, high seismic activity at the route. Of particular note is the high hydrogen sulfide content in water and soil – the component is particularly damaging for concrete and metal pipeline structures.
Such environmental conditions require the most detailed information on seabed properties, the structure and properties of the foundation bed.

– What engineering surveys have been conducted so far, what methods were used?

Engineering surveys for pipeline design and construction began in 2009 and continued in late 2010 and into 2011.
The work was run from the research vessels using multibeam sonar and surface analyzer. In shallow waters (up to 200 meters) we also used appendages – side-scan sonar and magnetometer.

In 2009 the company completed reconnaissance survey topography for sea bed and foundation bed. Obtained data confirmed the technical feasibility of the project. 
2010–2011 surveys provided the information for optimization of the pipeline route in shelf waters up to 200 meters deep. The collected data are sufficient for selecting the final route of the pipeline. 
Available data on the sites of intersection of the underwater slopes and abyssal plains provide only general details for pipeline route selection.

The level of detalization is insufficient for making fine-tuned project decisions.
–  As you just pointed out, the detail level is insufficient for selecting the final route of the pipeline. How do you plan to run detailed engineering survey on these segments?
–  Indeed, much of the projected pipeline route runs over the sea at a considerable depth (from 200 meters up to over 2,100 meters); the end shelf to deep sea slopes are steep with highly dissected topography. Considering the above, as well as little knowledge of the studied region, we plan to use AUUV (autonomous unmanned underwater vehicle) for hydrographic and geophysical surveys.

The AUUV carries the following hydrographic and geophysical equipment:
– Multibeam sonar for seabed topography data and digital elevation modeling;
– Side-scan sonar for detection of seabed man-made and natural objects that encumber the safe pipeline placement;
– Profiler for collecting data on quality parameters of the layers forming the seabed.
Moving in close proximity to the sea floor, some 50 meters above, the AUUV enables detailed deep sea exploration (up to 3,000 meters).

Also, AUUV’s high-resolution data are useful for detailed inspection of deep-sea pipelines. 
AUUV underwater navigation is fully autonomous, calculated by the data coming from the onboard inertial navigation system. Simultaneously, the research ship, while moving above the device, monitors its coordinates using ultrafine acoustic underwater positioning system. There is also an acoustic communication channel between the device and the operator at the vessel, for controlling power, recording, propulsion and other AUUV systems. The operator can use the channel for issuing verbal commands to the device. The AUUV is propelled by an electric motor fed by on-board batteries; single charge runs the device for up to 24 hours at a speed of about 7 kilometers per hour.

– What are the advantages of using the AUUVs?

There is no better option than AUUV for detailed engineering surveys at significant depths. 
Alternatively, the following underwater research equipment may be used:
– Remotely operated vehicle (ROV);
– Deep-sea tow system (Tow Fish).

However, these options lose the game compared to the AUUV. 
For example, ROV surveys will take much longer due to the limited speed of the underwater device, below 4 kilometers per hour. 
Tow Fish is also impractical because at the depths of about 2,000 meters, the length of the tow cable will exceed 10 kilometers, requiring additional vessel for positioning and leading to huge time losses during the switchover from one survey traverse to another.

The first AUUV development began in the 1980s; production prototypes appeared already in 1990s. AUUVs are designed and manufactured in different countries – US, Canada, Norway, France, Japan. Built devices successfully operate at various sites, being used for complex engineering surveys, construction and subsequent operation of the deep-sea underwater structures around the world.

– What other equipment do you use in the project?

On this project we also plan to use the HUGIN 1000 for the 3,000 meters. The device was built by Kongsberg Maritime AS, a market leader in marine research and navigation equipment. 
We plan to equip this device with multibeam sonar Kongsberg EM 2040, which is a fundamentally new and the most modern model of multibeam sonar.

It is worth noting the compactness and mobility of the system as a whole. The required for project work equipment – the apparatus, the energy complex maintenance system, computers and operator workstations are installed in a mobile container for easy transportation, installation and operation on any vessel.

External link: http://www.oilandgaseurasia.com/articles/p/146/article/1619/

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