Oil and gas decommissioning – as complex as it can get

Here is an insight into some of the biggest safety challenges in oil and gas decommissioning and, most importantly, how to mitigate them.

It has not been an easy time for the oil and gas sector in recent years. Difficult trading conditions – as well as a shift in demand for ‘cleaner’ energy – have gradually made it uneconomically viable for many firms to remain operational.

Several facilities are also reaching the end of their natural design life, which is another factor necessitating plant closure. Over the past decade, the number of hydrocarbon processing sites, petrochemical plants, refineries, storage and terminal depots that have closed, in Europe alone, has increased remarkably.

The UK has seen the closure of the Coryton refinery in Essex, the Murco refinery in Milford Haven and Petroplus’ plant in Teesside, for example, to name just a few. There have been offshore announcements too, with Shell’s recent divestment of multiple North Sea assets.

In the face of such challenges, operators soon face a difficult decision – what to do with their redundant assets. Mothballed, rationalised or permanently closed sites all require frequent inspections and maintenance, not least to ensure legislative compliance. But EHS (environmental, health and safety) concerns also naturally mount as these plants deteriorate.

Decommissioning – a specialist skill

Mindful of their corporate social responsibilities, many operators naturally seek to decommission their facilities. Often, this is the precursor to clearing the entire site for regeneration, some elements may remain operational, and it is even possible, on occasions, to carefully dismantle assets for resale and re-erection elsewhere.

But irrespective of the project schedule, decommissioning is not a straightforward exercise. It is a scientific discipline that requires a defined and experienced skill set, if projects are to be executed safely, cost-effectively and with maximum respect for the environment.

It should not be viewed merely as an extension of normal operations or the reverse of commissioning and construction, nor should it be rushed to achieve an accelerated exit. The client’s perception of risk is therefore one of the first safety challenges to navigate.

Recognising that decommissioning represents a great step into the unknown for most organisations, specialist external guidance is usually required. Of course, this expertise encounters a cost and when money is tight some companies are tempted to take shortcuts.

But economic pressures do not mean that risks are any less onerous or that legislation can be flouted. Armed with an experienced, independent skill set, on the other hand, oil and gas operators can instead make safe, environmentally sound and commercially robust decisions about their site – secure in the knowledge that personnel, the surrounding community and even the company’s reputation, will not be exposed to undue risk.

Rigorous documentation and a competent supply chain

Regardless of the selected project model, all methodologies and risks must be rigorously documented, with detailed specifications of work created for the preparatory decommissioning exercise, as well as any hazardous material surveys, demolition contractor tenders and so on. A suitably skilled project team should also be assembled and a time-specific programme of works drawn up. This is a very different process to preparing a plant for an overhaul.

The assembly of the project team is, in itself, becoming increasingly difficult. The number of decommissioning projects coming to the fore is unmistakeable, and for one of the first times in the history of the profession, there is the risk of demand outstripping supply.

This issue is being experienced on a global scale, especially when it comes to more specialist areas of demolition such as explosives engineering. The number of such competent professionals, worldwide, is very small – certainly in comparison to the thousands of projects to be carried out.

Savvy decommissioning firms are of course willing to travel, but the challenge for the client is knowing how to locate them in the first place.

Bringing assets to a known state

On many redundant sites, the assets that need to be decommissioned were mothballed many years ago. This poses a number of difficulties – some structures will have only been partially cleaned, drawings may be non-existent, and it is almost inevitable that the knowledge of site personnel will have long been lost. This means that it is extremely difficult to establish the ‘known state’ of such plants and understand the potential pitfalls that lie ahead.

When first arriving on site, the level of residual product, any loss of containment and the structural integrity of the assets that remain, should therefore be rigorously assessed.

Technology such as drones or unmanned aerial vehicles (UAVs) can, in many cases, provide a helpful aid before people have to enter any vessels or work at height themselves. In fact, they can collect vast amounts of data during the surveying stage of a project, with virtually no risk to personnel whatsoever.

If drones are flown over and/or within an even partially-operational site, added precautions will undoubtedly be required. Potentially explosive atmospheres must be clearly zoned, as it is likely that flights will only be permitted within predefined distances. Limitations may also be placed on whether the drone can fly inside a structure, if it could represent a possible source of ignition.

Geographical safety variances

It could be argued that safety concerns are even greater when undertaking works in a location with differing standards or cultural acceptance of what is ‘safe enough’. However, there should be no sliding scale – it is either safe, or not.

RVA has previously declined to take on a project, when a somewhat dismissive attitude to on-site actions could have put people in danger. And during a project in Southeast Asia, the team had to regularly demonstrate not only why harnesses should be worn, but also why they must be tethered to something immovable when working at height.

But, unfortunately, geography isn’t the only factor influencing operators’ mindsets.

Admittedly, cultural differences, language barriers and the availability of local fit-for-purpose equipment can add to the challenge. However, all of these challenges are navigable with the right attitude and adequate preparation time.

Almost 10 years ago, RVA was called out to the desert of Turkmenbashi to provide specialist assistance on a demolition assignment that would enable the commissioning of a new Delayed Coker Unit (DCU).

First, there was a 10-hectare refinery to clear. EPC contractor Lotus Enerji had committed to a three-month schedule during which time a number of structures had to be taken down, including three distillation columns up to 50 metres tall, three reinforced concrete storage silos weighing 2,000 tonnes, a 1,300-tonne reaction structure with four coke drums sitting on a 1,000-tonne reinforced concrete bed, and a 62 metres tall flue stack.

The complexity of these structures plus the absence of modern demolition machinery meant that the project posed too large a challenge for Lotus to manage single-handedly.

RVA therefore rectified the programme’s sequencing issues, delivered a much-needed insight into state-of-the-art demolition techniques and practices, imparted health and safety guidance, and project managed the scheme of works thereafter. This was certainly a very different undertaking, in an environment with highly contrasting standards, but the programme came to a safe, efficient and timely conclusion due to the input of specialist demolition expertise.

In truth, the safety challenges associated with decommissioning assignments are vast and varied. But as could be said for virtually every profession – if competent people are appointed for the job, and given the respect to do their job with appropriate resource, the highest standards of excellence can be ensured irrespective of the inherent hazards.

Richard Vann is managing director, engineering consultancy RVA Group and Past president of the Institute of Demolition Engineers and Institute of Explosives Engineers