Licence to Remote Well Kill

Flexlife recently performed what is thought to be the world's first remote well kill, using flexible pipe to pump concrete into an over-pressured producer on the Didon field off Tunisia. Darius Snieckus hears more from the Aberdeen-based consultancy's projects director, John Marsden.

The trend toward 'rigless' offshore remedial work diversified into emergency well control recently with a remote well kill assignment carried out by Aberdeen-based flexible pipe consultancy Flexlife on a PA Resourcesoperated producer on the Zarat permit off Tunisia. Handled by Flexlife's three-man project team in the space of four months, the £2 million job involved pumping zonal isolation concrete from the deck of an anchor handling vessel speciallyequipped with a pair of pumping stations, cement blender and pipe chute, into the Didon 3 well, in answer to downhole pressure concerns.

Flexlife was approached in April to join forces with Norway's AGR, already contracted by PA Resources for a 270-day well management campaign, to take on the pioneering assignment, the workscope of which encompassed manning the AHTS Team Sallalah, overseeing flexible pipe installation and concrete pumping, and designing and installing a purposebuilt mooring system for added vessel stability during the operation.

'Normally this sort of job would use a semi or a jackup to kill the well but there were issues surrounding the well's integrity,' explains Flexlife projects director John Marsden. 'So killing it remotely was what needed to be done, and this entailed injecting water to bullhead the fluids all the way down the well and then pumping in the concrete to kill it. The pressures were in the region of 2000psi.'

As devising a method with existing technology to kill the well was 'proving quite difficult', the consultancy opted to use a length of standard flexible pipe, engineered up for a short term dynamic application to perform the operation. Though located in less than 80m of water in a relatively benign environment, Flexlife took a belt-and-braces approach to station-keeping and designed and outfitted the DP AHV with a full mooring spread, with the vessel picking up pre-laid anchors as it sailed on to the field.

Pumping began on 3 August.With the 150m long NKT flexible pipe in a free-hanging catenary configuration, some 40m³ of Schlumberger's 'self-healing' Futur active-set cement was pumped down into the Didon well to a total depth of around 3000m.

'Given the success of this operation, it may well be that it raises a few eyebrows as another way of doing this sort of thing,' notes Marsden, 'but for the time being I think the remote well kill is likely to remain a method used only in emergency situations. This work was carried out in short order and safely so it is certainly a reference point for the industry going forward.'

Last month, meanwhile, Flexlife and AGR announced they had formed a partnership to develop a patented in situ scanner that detects annulus flooding at any point along a flexible riser's length. Flexlife devised the solution and AGR is putting up the ROV-deployable Neptune subsea inspection systems.

According to Flexlife, the application has had 'a 100% success rate' and will help prevent the failure of flexible risers and flexible flow lines, meaning minimised lost production and associated environmental impact from the leak. The cost of lost production resulting from a riser failure has been estimated at between Euro1-3 million/d.

'This is the first time it has been possible to scan any flexible pipe in situ without access to the end-fitting meaning any potential failures can be identified and dealt with more quickly than was possible previously,' states Marsden. 'Neptune is fast, reliable and can go down to 6000m so the technology can go anywhere in any environment meaning the potential cost savings and environmental benefits are immense.'

Ultrasonic boom

The first technology capable of scanning unbonded flexible pipe, the companies believe the as-yet-unnamed modular system, adapted from ultrasonic testing technology, will make the conventional approach of vacuum testing obsolete.

'One of the things that we did when we formed Flexlife in 2007 was to look at what were the most common failure modes in flexibles,' he offers. 'And one of the first patents we applied for was for an annulus scanning technology we wanted to develop. AGR had an ultrasonic technology that they didn't think they could apply to flexible pipe. Our partnership is very complementary.' The scanning technology is to be further developed to identify corrosion in flexibles armour wires, Marsden notes.

Plans are already well-advanced at Flexlife to evolve the system to handle repair work on flexibles as well. Partnered up with Aberdeen's Brinker Technology, specialist in 'unplanned flow events', the two companies are looking to commercialise a technology that would see Brinker's 'platelets' (OE March) ? free floating, discrete particles that travel through well fluids and are entrained to seal leaks ? injected into Flexlife's device that will both repair the outer sheath of a flexible while also sealing the tool itself. The system is on track to come on to the market by the end of 1Q 2009.

'Flooded annuluses are a well-known problem in the industry ? not least because once an annulus has been flooded for some time the line may have to be shut down and that is a serious matter.With this technology we can scan a flexible and tell the operator exactly where the problem lies, what the corrosion state of the armour wires is, and then repair the problem.We can see this technology fitting well within the realm of production optimisation,' Marsden concludes.