Oil-based drilling fluids – still a working environment challenge

“It is almost forty years since oil-based drilling fluids were introduced on the Norwegian Continental Shelf.  From a technical perspective, it is difficult to understand why more robust design solutions have not been established," says Vivian Sagvaag, Principal Engineer in the working environment domain at the PSA.

Oil or water

Drilling fluids have a number of functions, including cleaning the borehole of particles (cuttings) during drilling and controlling downhole pressure to avoid an uncontrolled blowout.

The industry mainly uses two types of drilling fluids: oil-based and water-based. Water-based drilling fluids are preferred, due to the sake of working- and external environments. Oil-based drilling fluids are also used, since they have better technical properties than water-based fluids in various cases.

Working environment risk

Challenges for the working environment is that oil-based drilling fluids form oil vapour and oil mist at high temperatures when the fluid is circulated in the mud handling system.

Inhalation of such emissions can lead to serious health damage.

In addition, workers involved in handling drilling fluids are subject to high noise levels, vibration, adverse ergonomic loads and skin exposure.

The results of the RNNP questionnaire-based survey show that the chemical working environment is reported to be more problematic in drilling than in other areas.

More drilling from mobile facilities

Vivian Sagvaag, who works extensively in monitoring [VS1] mobile facilities, explains that the PSA is now registering an increasing share of drilling from mobile facilities on the Norwegian Continental Shelf. At the same time, more mobile facilities have arrived on the Shelf in recent years that have sub-standard technical solutions for handling drilling mud.

Measurements of oil vapour and oil mist have also revealed examples of failure to comply with the occupational limit values. Studies conducted by the University of Bergen on behalf of the PSA show an adverse trend in the concentrations of oil vapour and oil mist on mobile facilities in recent years.

A decision for the operators

“It is the operating companies that decide on the type of drilling fluids to be used. If they choose to use an oil-based drilling fluid, they must also ensure that the mobile facility  can handle it safely", says Sagvaag.

“What is most important is the design and the technical solutions. For drilling facilities, especially mobile ones, there is a good way to go”, she asserts.

Sagvaag emphasises that there is great uncertainty associated with the use of personal protective equipment, and that this must be a last resort, when other measures are not feasible.

New knowledge

In recent years, the PSA has conducted studies to acquire new and updated knowledge about working environment issues relating to the handling of drilling fluids. Specialist webinars have also been held with the industry to elucidate and discuss this topic.

The Safety Forum, the key tripartite arena for health, safety and the environment in the petroleum activities, has recently reviewed what it is that promotes or inhibits improvements to the working environment and safety. One of the examples concerns the technology for handling drilling fluids.

Safety Forum

“The challenges associated with the use of oil-based drilling fluids fall naturally onto the agenda of the Safety Forum”, says Anne Myhrvold, Director General of the PSA.

“On the PSA's side, we have a good basis for further follow-up in our audit activities. But it is important for the issue to be raised and discussed at industry level.

Systematic work has been put into this problem and the companies have made solid contributions to the studies that have been carried out, but it is important to follow this up, so that we move from good intentions to actual improvements," says Myhrvold.

She points out that the companies can rely on a variety of mechanisms to ameliorate the situation.

“This is a complex problem where progress seems to be locked into various intertwined concerns and interests. It is the companies that are responsible for ensuring that the working environment is safe and, furthermore, in this case, moving forward depends on the different participants looking beyond their own narrow interests and finding means of cooperation to create better solutions. The participants largely agree about the problem as apparent in studies and the webinars, which should promise a good outcome for the working environment of drilling personnel," says Myhrvold.