Laying oil and gas pipelines through middle eastern desert terrain throws up a plethora of challenges
Acombination of searing midday heat and near freezing overnight lows, gale force winds, abrasive sandstorms, shifting sand dunes and high chloride levels found in the sand all contribute to making the Middle East’s deserts amongst the most challenging environments in the world in which to
lay pipework.
Having completed numerous large scale pipeline projects here in the Middle East, Dolphin Energy have a wealth of experience when it comes to laying pipelines in the Middle East, including Dolphin Energy’s Taweelah-Fujairah Pipeline (TFP), its Al Ain-Fujairah Pipeline (AFP) and the company’s UAE Gas Network.
Senior vice president, Dolphin Energy, Anwar Zuarub says that the key to a successful pipeline project is choosing an optimum route.
“For the Taweelah-Fujairah Pipeline, we conducted a comprehensive environmental and social impact assessment study to determine the final route and obtain approvals from the relevant authorities before any pipework was laid,” he explains.
Once the optimum route has been established, the appointed contractor needs to consider the environmental and topographical conditions of the pipeline route.
“The TFP pipeline was unique in that it crossed Sabkah, sand dunes, wadis and mountain terrain. This required high levels of skill among the engineering team and an ability to optimise the route by reducing mountain heights and the length of wadi and road crossings,” he adds.
Establishing an effective right of way is also critical to the successful execution of the pipeline project, as it will determine your ability to service the entire pipeline route effectively.
“An effective right of way is crucial in terms of getting manpower, equipment and construction materials to and from the site efficiently, effectively and safely,” he says.
This can impact dramatically on the costs associated with laying pipeline through the desert. Building construction camps, warehouses and marshalling yards close to the pipeline itself helps to reduce the time taken to reach the site, which in turn helps to improve site efficiency.
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“In the case of TFP where the mountain section of the pipeline route measured 44kms and harsh desert section 85kms, the need for a proper construction road within the Right Of Way was required, as well as various access points to the nearest black top roads,” he explains.
“This helped us to move materials, equipment and manpower to and from the site in a timely, safe, efficient and reliable manner,” he adds.
During the construction of the TFP pipeline, Dolphin Energy transported more than 116,000 metric tonnes of pipe line from the port at Abu Dhabi to a specialised storage area 100km from the city.
“Handling line pipe on mountain slopes was hugely challenging and 4×4 trailer trucks were used where possible.
Where it wasn’t possible pipe transportation skids with winches were used,” he adds.
While physical challenges in terms of laying the pipe are abundant, the make up of the sand itself also causes huge problems.
Contractors need to consider that much of the sand here in the Middle East contains chlorides. These Chlorides in the sand react with the steel pipework and create an osmotic cell, which in turn results in the pipeline being corroded.
One relatively low tech solution to this problem is to run the pipeline on sleepers, elevating it above ground level and preventing contact between the steel of the pipeline and the chloride rich sand. However, this is far from a complete solution.
With the shifting desert terrain, pipeline that has been elevated above ground level can still find itself buried after just a single, heavy sandstorm.
Elevating pipelines on sleepers may be a viable solution for relatively short sections of pipe where maintenance crews can be employed to patrol the entire length, keeping it free from the encroaching sand. For longer sections of pipeline, however, more advanced systems are required.
In instances such as this, pipeline layers can opt for cathodic protection (CP) systems, which use electrical current to shield the pipeline from corrosion. CP systems work by making the steel of the pipeline act as the cathode in an electrochemical cell. The anode is made of a sacrificial metal, for example silicone iron.
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By connecting the cathode and anode by electrical current, the sacrificial anode corrodes instead of the steel pipeline. For long stretches of pipework, an external DC power source is used to generate adequate amounts of current.
Relying on externally generated electrical current in the desert can present challenges of its own, particularly in regions with a high water table. Rain water has the ability to seriously disrupt the CP systems prevention against pipeline corrosion.
In the event of heavy rainfall, CP systems can experience power-outages. In this case, silver / silver chloride reference cells buried beneath the sands surface communicate with the CP system’s power transformer and relay the extent of the power outage caused by the rainfall. The system then adjusts itself to increase or decrease the power as it is required, automatically adjusting the power output.
In addition to the damage done to pipeline’s by the sand itself, contractors also have to consider other environmental elements. Whether that be sun, wind or rain, desert pipelines need to be able to withstand some blisteringly harsh conditions, as regional NOC’s are discovering to their dismay.
As new technology evolves, many pipeline designers are now issuing a 25 year to first maintenance guarantee on their pipework. This is largely due to the 3 layer technique, which has been a revelation in pipeline maintenance since it came onto the market.
The three layer system involves a pipeline’s carbon steel exterior being blasted. It is then heated and the manufacturer deposits a powder onto the pipeline using electrostatic flocking, to act as a primer.
The third and final layer is a polypropylene and polyethylene coating that is applied in a continuous strip. This trinity of anti-corrosive technology had been thought to be almost indestructible when first manufactured.
However, the challenging desert environments of the Middle East are taking their toll on even these three layer pipelines.
Polyurethane coated pipes could offer greater protection against the desert environment than either polypropylene or polyethylene. However, contractors are often put off by the high cost of polyurethane, compared to other coatings, despite the superior performance.
