GAS-SURVEY

The aim of the as-laid survey is to undertake a complete visual and instrumental ROV inspection along the pipeline as soon as the pipeline has been laid. The as-laid survey will define: the accurate position of the pipeline, the pipe-seabed configuration (visual and instrumental) and the external status of the pipe.
The as-laid results will be used to confirm/finalise the design of post-lay intervention works.
The aim of the as-built survey is to undertake a visual and instrumental ROV inspection in correspondence of the post lay intervention works areas just after their completion. The as-built survey will define the final status of the pipeline and of the post lay intervention works.

The as-built documentation will then be prepared by properly merging the results of the as-laid and as-built surveys.

During the as laid survey a complete visual and instrumental ROV inspection will be performed to gather the following information:
- Absolute position of the pipeline.
- Longitudinal vertical profile of pipeline lower generatrix as well as seabed.
- Transversal profile of seabed and pipeline.
- Condition of seabed in the vicinity of the pipeline.
- Configuration of pipeline relative to seabed.
- Height, length and position of any pipeline span.
- External condition of the anodes.
- External condition of the pipeline itself, including status of field joints, concrete coating, buckle arrestors, etc.
- Pipeline/cable crossings areas, if any.
- Any remarkable obstacle, object or other structure encountered in proximity of the pipeline.
- Location and dimension of any areas of damage, if any.
Like the as laid survey also the as built survey will be a complete visual and instrumental ROV inspection and the list of information to be gathered is the same as per the as laid survey.
GAS vessel DP1 Odin Finder can be easily mobilized with all the equipment required for a as-laid asbuilt pipeline survey: DGPS, hull mounted USBL, and R.O.V.

The R.O.V. can be equipped with Bathymetric Unit, Modular Scanning Profiler, Panoramic Sonar, Motion sensor & Gyrocompass, Center and Boom Color video cameras, Integral Comprehensive Video Overlay with video eventing

The vessel is provided of an adeguate area for data processing and interpretation, equipped with PCs, A0 plotters and digitizers. Charting and reporting of interpreted data are carried out onboard Odin Finder on a continuous basis throughout the duration of the survey.

In the last 5 years GAS has developped an internal Software named PIPEVIEWER, used for analize the MBES data. After the DTM creation the numeric analysis of the MBES data referred to natural seabed, pipeline TOP and trench will be elaborated by PipeViewer. The software provides TOP, BOP, BOT, OOS and NSB detection and the requested cartography for as-laid and as trenched surveys.
GAS has been successfully employing this software for almost 5 years in the Caspian Sea for the Trunkline Contract with SAIPEM.