Mike Rice discusses the threat of dropped objects in decommissioning – and explores various strategies to minimise such events
Decommissioning is a significant phase in the lifecycle of every rig – and one that requires particularly careful management to maintain the hard-won high standards in health and safety that prevail in the oil and gas industry.
This poses challenges for offshore business in the region, but also presents considerable opportunities. There are 600 oil and gas platforms in the North Sea, of which 470 are scheduled to be decommissioned over the next 30 years. The UK will be the largest global decommissioning market over the next decade, with approximately 880,000 tonnes of topside forecast for removal.
Oil & Gas UK estimates that over £15 billion will be spent on decommissioning around the UK in that time – with the result that decommissioning now accounts for 10% of the overall expenditure of the UK industry.
Decommissioning provides a great opportunity to leverage the existing knowledge base within oil and gas, and this should extend to the hard-earned health and safety culture seen within the industry, with self-regulation increasingly becoming the norm.
What are the hazards of oil decommissioning?
Many of the specific risks from decommissioning oil infrastructure stem from the practice of ‘cold stacking’ rigs. This is because the time between shutting down operations on the rig and the beginning of the decommissioning process can be anywhere from five to 15 years.
Often, this involves minimal maintenance. Humidity, saltwater and adverse weather can cause corrosion during time periods of this extent, undermining the structural integrity of the rig and leading to fixtures becoming compromised. With even small objects able to cause serious injury or damage when dropped from considerable heights, the risks to personnel and assets are too great to ignore.
Dropped object (drops) incidents occur when an object comes loose from its fitting and falls. These can be ‘static’ drops, where the object falls without the application of external force, or ‘dynamic’ drops, where objects fall as a result of external force.
Examples of static drops are floodlights, cameras, speakers and pipes coming away from their securing points due to corrosion or lack of maintenance, and falling. Dynamic drops could involve vibration, jarring impacts and cranes hitting equipment, dislodging objects and causing them to fall. Dynamic drops can also happen when personnel drop or knock tools over the edge of walkways, stairs and raised working platforms.
When the process of decommissioning has started, the latent risks entailed by unsafe and unsecure equipment can quickly manifest – posing risks to personnel, assets, finances and the reputations of companies that allow drops to occur.
During the removal and dismantling of topside infrastructure, there will inevitably be raised levels of vibration, with high potential for heavy jolting impacts. Reduced structural strength may lead to more severe consequences if a drops incident does occur – even the collapse of critical areas.
Additionally, the labour-intensive nature of decommissioning means that personnel will work on and around the ageing structure in large numbers – including at height, across multiple levels and using cranes or heavy lifting equipment. Often, cranes will be temporary and used with greater frequency, which means a higher risk profile. Lifting large equipment and sub-structures when removing them from the main rig is also associated with a higher risk due to uncertainty regarding the integrity of structures.
Drops during decommissioning can also be large enough to pose risks to shipping and subsea infrastructure. A particular risk is to fishing vessels, as objects on the seafloor can lead to snags for trawlers.
Finally, drops during decommissioning can have grave environmental consequences. Increasingly high levels of scrutiny on environmentally sound practices in oil and gas make the adoption of robust drops prevention programmes throughout the industry essential. Damage to pipelines and other infrastructure could be expensive to rectify and could lead to hydrocarbon release – which is almost certain to make national news, causing irreparable harm to both the environment and company reputations.
Offshore assets often harbour fragile marine ecosystems, supporting rare species of fish, plant and bird. Preventing drops from falling into the sea and causing environmental damage is essential to ensure that the long-term reputation of the decommissioning is upheld.
Drops prevention solutions for oil and gas decommissioning
A cornerstone of drops prevention in decommissioning is the use of secondary securing solutions. These wrap around vulnerable objects and fix to an attachment point. Best practice is to use a high-quality steel wire mesh net to completely enclose an object. Nets will arrest the fall of objects such as lights, pipes and cameras should the object become loose due to corrosion or impact. A worrying trend with secondary securing solutions is the use of makeshift solutions such as wire slings – a false economy due to increased maintenance and replacement costs. These solutions are not compliant with the same high standards of safety that are increasingly the norm in the industry. The DROPS Reliable Securing Handbook sets out a best practice approach to secondary securing.
Robust secondary securing solutions can also reduce need for more regular ‘check ups’, where HSE professionals will enter the rig while it is ‘cold stacked’ to make basic checks on structural integrity of equipment. Less frequent deployments mean less potential for drops, as well as saving on crew transfer vessel hire and labour costs.
Another key solution is the installation of barriers on walkways, stairs and raised working platforms. This will stop tools and other equipment from being knocked through gaps and becoming drops. It is vital to choose a durable product with a long service life, negating the need for risky replacements.
Companies may seek to use products with smaller upfront costs – but during the long periods at sea, UV exposure, humidity and temperature changes will cause many products to become ineffective and require replacement, leading to greater expense over the long-term.
Ease of installation is another important consideration for the overall cost-effectiveness of a drops prevention solution. With both barrier and secondary securing solutions, keeping downtime and labour costs low is key to ensuring that costs are kept to a minimum.
With many personnel working across different levels, it is essential that workers are trained and equipped with personal tethering solutions. Steel wire mesh pouches can secure and tether tools to personnel and prevent handheld equipment such as two-way radios and wrenches from becoming drops.
If the decommissioning industry is viewed as unresponsive to HSE issues and environmental concerns, years of progress in building up a reputation for safety could be lost. As the increasing prevalence of aging assets provides impetus for growth, continuing proactive drops prevention throughout the entire lifetime of rigs is crucial if the industry is to sustain its success in the next decade.
Mike Rice is with Dropsafe