OREANDA-NEWS. March 31, 2008. Think of a shoelace or a piece of string. If you pull it it will be stronger but if you push it – it will buckle. That’s the analogy Sakhalin Energy Project Engineering and Procurement Manager, William Lindsay uses to describe the properties of Sakhalin’s unique onshore pipelines.

Crossing 19 active seismic faults during the installation of Sakhalin Energy’s onshore pipelines presents extraordinary challenges. Five of the fault crossings have already been completed with complete success.

William Lindsay says that the pipelines were designed to stringent criteria enabling them to withstand a ground rupture caused only by a very significant earthquake. It took three years for specialists to decide where the active faults were on the island and to predict how the faults would move and extend during an earthquake. Optimum pipeline crossing angles for each of the 19 faults were identified and as each crossing is unique in its complexity, innovative engineering solutions for dealing with this were developed.

The pipelines need to be able to move up to 5.5 metres, the maximum identified by seismologists, should a “design” earthquake occur. Trenches dug for the pipelines through the fault crossing areas differ to conventional designs by size, shape and backfill material, which will allow “free movement” of the pipe ensuring the pipe is not over stressed and therefore will not break.

One of the most challenging parts of the fault crossing design is the drainage system. Water in the trenches, which may freeze around the pipelines during winter, would inhibit movement during an earthquake. Beads of expanded clay, the same material that is used to help drainage in pot plants, fills the trenches and surrounds the pipes. Alternatively special backfill sand is used and the trenches are also laid with special waterproof material—geomembrane to prevent the ingress of water.

Safety and reliability are Sakhalin Energy’s watchwords and safety measures taken on the pipelines are exceptional. Block valves are installed on either side of the fault crossings on the pipeline. In the event of an earthquake, sections of the pipeline can be quickly isolated by a signal from the central control rooms. A pan-island seismic monitoring system is being installed which will be able to accurately determine the intensity of any earthquake at the fault crossings.

All fault crossings are provided with compensators, i.e. specially fabricated 90° bent pipe sections. In an earthquake situation these will act as effective shock absorbers almost mimicking the movement of an accordion being played.

Another safety measure is the extra thickness of the pipes. ‘Seismic‘ grade pipes were used for all fault zones and their special steel composition guarantees that the pipes can handle extremely high loads. Each weld seam is given a double inspection to ensure its pressure sealing capability: a complete X-ray inspection and then an automatic ultrasonic inspection. The drainage pipes have also been age-tested to 30 years in Moscow laboratories.

Sakhalin Energy’s onshore pipeline team can be very proud of the designs they have created as an essential part of one of the biggest integrated oil and gas project in the world.