Excavating a path through Iraq's unexploded ordnance

Marin Subsea was called out recently for an operation central to allowing Iraq – the world's fifth largest holder of crude oil reserves – to properly exploit its estimated 143 billion barrels. David Morgan looks at how the job was planned and painstakingly executed.

Some 75% of Iraq's oil exports are at present handled by the al-Basra oil terminal (ABOT) which, with the neighbouring Khor al-Amaya oil terminal (KAAOT), lies southeast of the Persian Gulf's Al Faw peninsula. Both terminals and the pipelines connecting them with Iraq's southern onshore oilfields are more than 30 years old, have been poorly maintained and have suffered the ravages of two conflicts. As a result, daily exports are limited to 1.8 million of the 2.2-plus million b/d currently available and the 3.5 million b/d projected for 2013.

The Marin Evo 150 STE mass-flow excavator tool from the AOS Constructor.

Now the entire infrastructure is being replaced, and in the first phase of the Iraq Crude Oil Export Expansion Project being led by South Oil Company, two new 40km pipelines will eventually connect the Fao oil depot to four single point mooring systems (SPMs), each with a nameplate capacity of 900,000b/d, allowing the two terminals to between them simultaneously serve 16 tankers up to VLCC class.

Left: One of the pre-1945 phosphorus-cased shells recovered by Marin's excavation team towards the end of the operation. Right: An Imaginex sonar system attached to thte mass flow excavator.

The first two SPMs form part of the project's first phase with the third and fourth — plus a central metering and manifold platform — to follow in later phases.

The transition from the drawing board to the construction phase has however brought myriad challenges, including the need to clear the new pipeline routes and corridors of actual and suspected unexploded ordnance (UXO) and other hazardous debris. Overall responsibility for this operation was awarded to Maritime & Underwater Security Consultants (MUSC), a London-based company specialising in subsea UXO disposal and pipeline security, and Marin Subsea – part of the Marin Group of subsea service companies, based near Aberdeen – was approached in April 2010. MUSC was looking for specialist excavation support for the team of divers tasked with mitigating classified targets. Marin Subsea was awarded the contract in August 2010.

The ABOT and KAAOT zone is hazardous in itself – the British only handed over responsibility for the tight patrol of these waters to joint Iraqi defence forces earlier this year, and both the US and UK still retain a strong military marine presence as the two terminals feature high on any list of major terrorist targets. Exclusion zones are rigorously applied, vessels are tracked night and day, and the scars of war are evident everywhere.

The Diver hand-held Marin Evo Hydrovac tool, used for localised excavation.

Marin Subsea believes it won this challenging contract for three key reasons: first, the company's Evo technology is well suited to this type of high-risk work as mass-flow excavation is a non-contact excavation method exclusively using water to shift subsea soils; second, Marin's reputation as a pioneer of MFE tooling and techniques; and third, the company's 30-plus years track record of working in exceptionally hostile environments (OE March). The team was also able to point to past expertise in using claycutting and MFE tooling to excavate suspected UXO sites, including a three-month project in 1992 for the UK Ministry of Defence in Beaufort's Dyke, and a 2005 project for a client excavating and removing second World War ordnance along a pipeline route in Sicily. Marin's technology and members of the team were also involved in the complex 2001 Kursk submarine excavation and recovery in the Barents Sea.

Excavation tools

A suite of Marin's patented proprietary excavation technology – including the centrepiece Evo 150 STE and HTE mass-flow excavation tools plus a custom-built high-impact pulse water jetting system and a selection of diver hand-held tools – was fast-track transported in late August 2010 to MUSC's operational base in Ras Al Khaimar in the UAE. The spread was then fast-tracked through customs to one of MUSC's three charter dive vessels, the four-point moored barge AOS Constructor. Five days later – now with Iraqi guards on board – the vessel was within the ABOT and KAAOT zone and the Marin team could begin work.

All movable items on the deck of the four-point moored barge AOS constructor had to be lashed down during harsh winter weather.

Each of the sites pre-surveyed by MUSC in 2009 as potential UXO clusters had to be investigated and then mitigated. The eight-strong Marin Subsea team worked with MUSC's divers in waters varying in depth from 5m to 35m. The diver would go in first, using hand-held surveying tools and a metal detector to locate a target. If the diver was able to reach and identify the target, that was all that was required. However, the majority of targets were lodged below the seabed, and the Marin Subsea team would move in next, deploying from the Constructor with a 50t SWL crane. A mine-hunting unit was sourced and a Reson SeaBat multi-beam sonar system attached to the Evo 150 STE MFE tool to accurately pinpoint the target before the site was excavated to de-bury whatever was there. This task completed, the MUSC clearance diver would return to identify the target and prepare to mitigate. Throughout the project, the Marin team provided maximum additional support, on occasion stepping in to help recover debris to the surface, rigging equipment, and carrying out safety case audits together with project and site reviews.

Across the site, the first half metre of soil below the seabed was generally loose, light, non-cohesive silt material of around 3-9kPa – ideal for excavating using the Evo 150 STE MFE tool. Where excavation below half a metre was needed, the Evo system was operated in tandem with the impact jet to cut through harder soils of between 10kPa and 15kPa or higher. The Marin team used soil pooling technology (SPT) to apply low pressure so as not to set off potential targets. One site in particular required an excavation measuring 8m in diameter by 4m deep to expose the target.

Throughout the project, every target was treated as a UXO, and the combination of MUSC's highly-trained ex-Navy clearance diving and security specialists plus the Marin Subsea team's operation of the Evo technology and wider support proved highly successful. In the event, the majority of the targets proved harmless, yielding little more than jetsam from ships: anchors, walkways and hatches, tyres, radio communications equipment, gas canisters and chains. Nonetheless, they all had to be cleared as part of the route preparation process.

But towards the end of the project, with the scheduled demobilisation date of May 2011 now in sight, the picture changed when at first a handful of UXO devices was found, then a few hundred, and eventually 4800 shells in six different locations. Against all probability, they were not of recent provenance but found to be white phosphorus-cased shells and tips, manufactured pre-1945 and in all probability dating back to the first World War. The Marin Subsea team played a critical role in ensuring the targets were safely de-buried, identified, and mitigated before they were re-located away from the pipeline route and made ready for disposal.

Marin's MFE Evo technology is capable of use 24/7 and in up to 4 knots of current. However, the MUSC clearance divers could only operate within small tidal windows and in relatively good weather, and as a result the excavation and mitigation operation lasted nearly 12 months. For security reasons, diving could also only take place during the daylight hours, further extending an already onerous project. Temperatures reached the high 40s centigrade in the summer months, and during winter heavy seas and very rough weather made conditions onboard the Constructor particularly challenging and demanding. The durability of all equipment supplied by Marin and MUSC was tested to the limit on the shallow water barge, with all movable items at times having to be lashed to the deck. At one point, the vessel's entire supply of bottled water was washed overboard and in a separate incident the control systems for the anchor winch house were destroyed by impact damage from a large wave, causing survey data and recording problems.

George Stroud, Marin Group CEO, says his team are satisfied with the way they executed their role in this challenging operation.

‘The outcomes were positive for all involved and in particular proved the value of Marin's Evo MFE equipment and the team's specialist expertise in a context where precision, reliability and safety were paramount,' he adds. OE

A taxing project
Marin's Iraq operation was led by group offshore excavation superintendent John (Rocky) Greig, who has seen plenty of challenging action in hazardous locations during his 30 years of drilling and subsea excavation and troubleshooting.

Greig (pictured) says he is very proud of the Marin Subsea team who worked alongside him in Iraq. ‘They were never anything but highly professional and motivated,' he adds. ‘This was a particularly taxing project because of where it was and the job we had to do, and although the job was obviously oil-related, we were working alongside a team coming from a variety of backgrounds with little or – more usually – no oil & gas offshore experience.

‘Operating in the middle of a high-profile security zone was also difficult – and at times nerve-wracking – and the AOS Constructor was not the easiest of vessels to have as an operational base. It was badly affected when the weather turned rough over the winter months, and our accommodation was rudimentary to say the least, and very cramped.

‘However, our biggest challenge lay in matching key elements of the project management and HSE regimes we're accustomed to having in place when working offshore with our client's own systems and procedures. We worked closely with them to introduce some of our best practice processes and in doing so we were able to help speed up the project significantly.'

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