Topic: Integrity


Region: North Sea
Content Types: Report
Date: June, 2021


Speaking at the Virtual Offshore Well Intervention Europe Conference 2021, Bruce Trader, President of MADCON Corporation, guided an audience through his company’s Structural Composite Retrofit (SCR) process, developed to restore the structural integrity of conductors and well casings as well as providing long term corrosion protection.

Trader explained how the process was conceptualised after a major international oil and gas company requested a process to restore the integrity and provide long term corrosion production for their conductors and surface casings as they had been experiencing several years of less than optimal performance. The company had numerous conductors that all were suffering from severe corrosion and required an immediate solution.

For this to be a success, the company issued several key mandates which MADCON had to fulfil including:
-Restore the original design capacity
-Allow future work
-Minimal to zero hot work
-Long term corrosion protection
-Ease of installation in the splash zone
-Meeting regulators compliance
-No cofferdam required
-Fit within the existing conductor guides
-Conduct the work from vessels or the platform and not require a barge or rig
-Eliminate the need for future maintenance.

When the operator hired a third party engineering company to analyse and validate the method MADCON put forward, they assumed that there was no remaining conductor wall or inner string pipe capacity and that the composite section had to be designed to take the full axial and bending load.

Trader explained the basic SCR process which they followed to help the operator, which begins by, if the surface casing is not already grouted, grouting the surface casing annulus to a select elevation (in this case 2-3 metres below the water). This consists of installing a plug to isolate the annulus and putting on epoxy grout before finishing with cement grout all the way up to the wellhead (there is no need to grout to the mud line as the corrosion is not severe a couple of metres below the water). If there is a large length of unsupported casing a reinforcement cage made may be required before, in the final step, a fibreglass jacket is installed to be pumped full of epoxy grout from the bottom up.

As one of the key mandates was to install in splash zone, the materials were all lightweight, composite and easy to install. In more than thirty years of conducting these operations MADCON has recorded zero incidents for the divers involved.

In order to keep hot work (and by extension expense) down, MADCON also took pains to make the repair within the existing conductor guides. The platform had a tight space which posed a challenge but this was able to be overcome and today the company’s repairs only add 1-3 inch in overall diameter meaning they can perform repair work within most existing guides out there saving time, money and eliminating hot work. The company additionally captured more value by performing the work without the use of a rig or large barge as they are able to perform the repairs with relatively small vessels of opportunity or even the platform itself.

Summarising this job, Trader said, “We were able to achieve all the mandates stipulated by the operator including, once the repair was done, eliminating future maintenance so that 27 years (and counting) after the repair everything is still in perfect condition.”

Reliable performance

After gaining a formidable reputation for this kind of work, operators even began commissioning the company for wells that had corroded so much to the point where the surface casing had collapsed. But, as Trader demonstrated with a string of case studies to conclude the session, this was not an issue but something they have now come to specialise in.

For one well, for instance, prior inspection posted no abnormal operational conditions but an inspection from MADCON identified that in fact the well had in fact collapsed and had to be shut in. The company then dissected and removed some of the conductor pipe and identified that the conductor to surface casing was open at a certain elevation and, without anyone knowing, it had been slowly corroding the surface casing to the point that it failed. While supporting the well with casing jacks, the MADCON crew of 8 techicians were able to perform full structure repairs from the platform, from -3 to +20 metres, in just 12 days. Once done the operator was able to get his well back online and producing again.

Trader said, “This process can be modified to restore any capacity that the operator might need and we have been successfully using it to restore original design capacity and provide long term corrosion protection on hundreds of wells.”