Impact due to loss of containment on offshore production assets through degradation of minor infrastructure is a growing concern for operators looking to extend the life of their assets.
Such infrastructure includes small-bore tubing (SBT), in many cases installed decades ago, which has until now largely gone without the level of exhaustive inspection, maintenance and/or replacement investment afforded to larger engineering infrastructure.
This is a cause for concern since continued production from aged assets invariably means sweating of assets connected to mature wells and further recovery via older infrastructure. With many assets dating from the 1970s and 1980s, which are far beyond their original design life, this could in itself contribute to the potential for hydrocarbon release.
Hydrocarbon releases originating from SBT failures have been a focus for industry regulators and all North Sea operators, and much has been done to reduce the number of minor/significant hydrocarbon releases. Failures to date have primarily been gas- or diesel-system-related and, while limited in scale—the largest reported being around 1 tonne of produced gas—in a zero-incident-target environment, any unmitigated risk is unacceptable.
Major hydrocarbon releases are still unpredictable. Depending on the size and pressure, an SBT system failure could lead to a major classification hydrocarbon release. Additionally, pressurized containment loss poses a significant risk of injury since the force of a fluid escape from degraded SBT could propel objects that then strike personnel, though incidences of this are comparably low.
To address SBT integrity, the U.K.’s Health and Safety Executive (HSE) has introduced new requirements which, if properly applied, will help eliminate the risk inherent in mature assets worldwide, protect the integrity of new assets as they age and enhance process safety.
Generally, asset integrity is the focus for inspection works. However, this is not necessarily defined as the primary means to ensure that process safety is achieved. Process safety is in turn crucial to maintaining operational integrity—protecting people, the environment and longterm production status of the asset as a consequence.
In many cases, operators—particularly those acquiring aged assets—might find that the standard of SBT is not what they expected. Finding losses of containment or identifying potential weaknesses involves a mass of permutations, with multiple root causes requiring evaluation after initial inspection and analysis has been carried out.
The age of some components and the widespread issue of SBT having been improperly installed to the specific standard required are key causes in exterior degradation, with a number of environmental corrosion mechanisms then taking hold. In the 1970s when a significant volume of SBT was installed, stainless steel was meant to last forever. However, it is starting to fail and at a rate higher than expected from more modern construction materials.
Identifying the risk, managing the spread of potentially containment-compromising corrosion, reducing the number of hydrocarbon releases and ensuring that the HSE’s requirements are being met is the absolute focus for operators, inspectors and maintenance providers. This requires a management system specifically targeted to the inspection and maintenance of SBT.
The HSE has called for an asset registry of all SBT assemblies to be maintained, with likely failure mechanisms being identified and assessed.
At present, the strategy used is generally “find and report.” This strategy should change to allow the problem to be arrested and where possible fixed since there are limitations on what can be fixed, so this must be carefully considered.
Most SBT inspection is carried out “hands-off.” There is no physical intervention of any kind due to the risk that high pressures within the tubing could result in a fracture and cause a leak. All hands-on work in a high-pressure scenario needs to be carried out on a depressurized line. However, that isn’t necessarily confined to a shutdown.
CAN Group is introducing tablet reporting designed to significantly improve the speed, quality and accessibility of data collation being achieved during SBT inspection.
Tablet reporting, which has moved forward rapidly through the availability of Zone 1-approved devices in production environments, enables real-time data transfer, allowing faster detection and notification of potential weaknesses. It also streamlines the reporting process, enhancing productivity and efficiency and allowing technicians more time to conduct actual inspections—ultimately providing the cost savings sought in the continued low oil price environment.
With regard to competence, the HSE has stated that installation operators and duty holders must have arrangements in place to ensure personnel required to work with SBT are competent where, at present, no standard exists for inspection workscopes.
It also lists a program of SBT inspection as a requirement for scheduling on the basis of risk using visual methods combined with gauge checks for joint tightness, with a follow-up intrusive inspection or maintenance campaign where faults are identified or suspected. The initial focus is to ensure technicians have SBT inspection competence.
CAN Group has developed the industry’s first route to achieving competence specifically designed for SBT inspection through the delivery of a comprehensive in-house training program, which is delivered to the company’s experienced inspection and maintenance personnel.
It includes general and close visual inspection, options for remedial action in terms of replacing weaknesses in the system and replacement of minor components using Energy Institute-approved methods.
The accepted route to competence involves maintenance contractors gaining industry certification for SBT installation. This program works well for installation workscopes; however, it does not cover in-service SBT inspection, which is necessary to ensure safe operation of SBT is maintained.
CAN’s SBT inspector competence is supported with certification in visual inspection. This course is CSWIPendorsed and delivered. CSWIP is the internationally recognized certification arm of The Welding Institute.
The holistic approach brings together services from three of the company’s business streams. The initial inspection is delivered by qualified technicians who have completed CAN’s SBT-specific training program.
ENGTEQ, the company’s integrity management and engineering business stream, will then provide corrosion management and engineering guidance for the appropriate replacement of old systems determined by the asset’s life cycle.
CAN’s trades business stream would then carry out any required maintenance, repairs or replacement of affected infrastructure, including managing common failure points such as SBT clamps.
Additionally, since CAN is a rope access contractor, all field personnel are rope access-qualified, enabling CAN to carry out SBT inspection and maintenance in difficult-to-access locations safely and efficiently.
The industry needs to assure all stakeholders that the inspection approach is applied appropriately and that its efficiency and efficacy move forward to meet the technological achievements seen in other engineering disciplines to allow remedial action in line with the Energy Institute’s guidelines for SBT to be taken expediently and not wait another 30-plus years before collectively addressing the elephant in the room.
To meet the HSE’s requirements, operators and the supply chain will need to agree on supporting action that will significantly increase the attention given to SBT, investment in training and technology used to improve inspection and mitigation works, all of which will reduce the risk of an escalating problem within the upstream and downstream sectors.
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