Safely connected

In all, Geosel operates 26 caverns for fuels, such as heating oil, diesel, naphtha, super gasoline and kerosene with a total storage capacity of about 11 million m³. Another seven are connected to the methane gas terminal in Fos-sur-Mer and serve for the storage of some 2.5 million m³ natural gas. In addition, there are two sole caverns and about 320 km of pipelines which interconnect the local refineries and petrochemical complexes and link them with the national and international pipeline network. The fuels to be stored are transmitted at an operating pressure of 70 bar from Fos/Lavera to the pump station in Rognac, before being fed into the respective Geosel caverns situated at depths of up to 1,000 m.

Almost 50 years in continuous operation

Routine checks revealed that a pipeline that had been in continuous operation for almost 50 years in the Étang de Berre lagoon at a water depth of 8 m, was showing initial signs of corrosion. To eliminate the risk of this developing into an environmental disaster, it was decided to replace a 1.3 km pipeline section as quickly as possible. However, it was anything but easy to contract a pipe-laying company for such a short offshore section. The challenge was the disparity between the enormous technical effort and the short length of the section to be replaced. In addition, the space available for the storage of the pipes delivered and for welding the pipe string was rather limited.

A tight schedule for production, processing and delivery

Eventually, Geostock as the pipeline operator managed to contract SPIE CAPAG, a VINCI company, for the pipe-laying operations. The project was meticulously planned in close coordination between the two companies and Salzgitter Mannesmann Line Pipe. Vincent Bertolone, who was responsible for the project at Salzgitter Mannesmann Line Pipe: "Given our successful cooperation with Geostock since 2002, we went along with the admittedly extremely tight schedule for the production, processing and delivery of the pipes required." The pipes manufactured by Salzgitter Mannesmann Line were provided with a 3 mm HDPE coating, which was specially roughened as a preparation for the top coat of heavy concrete applied by Conline in the Netherlands to a thickness of 60 mm. From there, they were delivered by truck to the construction site in the south of France just in time. SPIE CAPAG thus had enough time to make four pipe strings of the 116 HFI-welded DN 500 steel pipes with wall thicknesses of 10 and 11 mm. These had to be stored in parallel for the time being, due to the restricted space conditions.

Keeping the fingers crossed for good weather

The next thing was to keep fingers crossed for favorable weather conditions, so as to find a time window for pipe-laying. When stable conditions were on the horizon, the pipe string was welded together, and all welds were field coated with cement mortar.

Vincent Bertolone had especially traveled to the site from Germany. "Given the tightly coordinated planning and the complex offshore pipe-laying operations, it went without saying that we would be there to watch over the progress on site," was the comment of the sales region manager.

After careful preparations, the 500-ton pipe string fitted with special buoys was laid from a pipe-laying vessel with the aid of cranes within three days.

Commissioning and a new order

This done, the new string was connected to the existing Geosel pipeline in Marignane with the aid of a special coupling. During the ceremony to mark the start-up of the new pipeline section, Geostock project manager Pierre Roux expressed his satisfaction: "The planning and completion of the work went without a hitch. Our long-standing close cooperation with Salzgitter Mannesmann Line Pipe has once again paid off."

But there was more in store. Vincent Bertolone managed to acquire a similar project in the Brittany region. "Who knows, this may be the beginning of a beautiful relationship as with Geostock in the south of France?!"