Researchers aim to crack costly issue of asphaltenes build-up
Scientists seek breakthrough to tackle the 'cholesterol' of the oil industry
The story of mankind's relationship with asphalt goes back millennia.
Discoveries in the Syrian desert have shown Neanderthals may have used the naturally occurring material to attach flint blades to handles some 40,000 years ago.
And more recently, around 5,000 years ago, a civilisation in southern Mesopotamia known as the Sumer people are believed to have used it to build homes.
Today, centuries on, the material is no less valuable. It is seen it in the construction of vast super highways to the distinctly more ordinary waterproofing of flat roofs.
But while asphalt has proved hugely useful for thousands of years, the components of crude oil used to manufacture it today – substances called asphaltenes – have long created problems in the petroleum industry.
The tiny molecules, even though larger than is typical for oil, can clog up well heads and pipelines, restricting flow and causing huge financial losses.
“Asphaltenes can cause massive problems and cost a lot of money,” said Professor Spencer Taylor, director of the Centre of Petroleum and Surface Chemistry at the University of Surrey in the UK.
“During production they can deposit on surfaces they come into contact with – usually pipelines and valves – and clog them up.
"The worst-case scenario is that they shut wells down so production has to be stopped. Every day the field is not producing costs an awful lot of money.
"Apart from cleaning the wells, which can be an issue, they're not getting the revenue from selling the oil. It's a lose-lose situation."
Asphaltenes are sometimes compared by those in the oil industry with cholesterol, the fatty substance which can cling to human artery walls and reduce blood flow.
Fortunately, chemicals do exist which can combat the problem, although injecting solvents into pipelines can be dangerous and in some cases even make the problem worse.
Now, research carried out in collaboration with scientists at The Petroleum Institute, part of the Khalifa University of Science and Technology in Abu Dhabi, aims to shed new light on the issue.
Researchers have used their own technology – known as a microfluidic system – to observe how liquids behave at a microscopic level.
Previously, the oil industry has typically relied on looking at the large-scale results of dispersants use. But the remarkable microfluidic devices give a much better idea of why things are happening, offering clues as to how practices can be improved.
“The biggest advantage of using these systems is the insight we gain on what's happening on a microscopic scale,” said Dr Sibani Lisa Biswal, associate professor of chemical and biomolecular engineering at Rice University in Houston, Texas.
“Being able to understand what it is the dispersants are doing is critical for developing a process which can assure users of clear oil flow.
“There's lots of new things in terms of digital imaging, but still these transparent microfluidic devices offer new insight that we cannot obtain by using rock samples.”
The microfluidic devices used by researchers contain tiny posts or pillars with a diameter of just 0.125 millimetres.
Small amounts of crude oil is allowed to flow through the structures.
In a remarkable time-lapse video produced by the team, the microfluidic devices show the build up of asphaltenes on the tiny columns and then, in some cases, break away and follow the flow of crude oil as it passes through the system.
What scientists have so far found surprising in the study, is that when dispersants are used initially, deposits actually grow faster in size.
On the upside, however, they were found to be softer and more easily broken up, making it easier for them to be washed away.
Published in the journal Energy and Fuels produced by the American Chemical Society, Dr Biswal's research was funded by organisations including the Abu Dhabi National Oil Company (Adnoc) and The Petroleum Institute.
“It's always much appreciated when the actual end user, which is going to be Adnoc, shows interest in understanding what's happening at a fundamental level. They can be able to make better decisions about what processes to use on a field scale,” said Dr Biswal.
The ties between her team and The Petroleum Institute date back five years to when she visited a research and development conference. She said the researchers at The Petroleum Institute are able to help her team at Rice University understand better what the practical needs of the petroleum industry are.
“Our collaborators are complementary to us,” she said. “They're doing experiments that complement what we're doing with microfluidic devices – they're doing it on a larger scale or simulations. It creates a nice cohesive team.”