Oilfield exploitation

A new method developed in Britain over the past 17 years for extracting oil is now at the forefront of plans to exploit a massive heavy oilfield in Canada.

Duvernay Petroleum is to use the Toe-to-Heel Air Injection (THAI) system developed at Bath University at its site at Peace River in Alberta, Canada.

Unlike conventional light oil, heavy oil is very viscous, like syrup, or even solid in its natural state underground, making it very difficult to extract. But heavy oil reserves that could keep the planet’s oil-dependent economy going for a hundred years lie beneath the surface in many countries, especially in Canada.

Although heavy oil extraction has steadily increased over the last ten years, the processes used are very energy intensive, especially of natural gas and water. But the THAI system is more efficient, and this, and the increasing cost of conventional light oil, could lead to the widespread exploitation of heavy oil.

‘Conventional light oil such as that in the North Sea or Saudi Arabia is running out and getting more expensive to extract. That’s why the pressure is on to find an efficient way of extracting heavy oil,’ said Prof Malcolm Greaves, who developed the THAI process.

THAI uses a system where air is injected into the oil deposit down a vertical well and is ignited. The heat generated in the reservoir reduces the viscosity of the heavy oil, allowing it to drain into a second, horizontal well from where it rises to the surface.

THAI is very efficient, recovering about 70 to 80 per cent of the oil, compared to only 10 to 40 per cent using other technologies.

Duvernay Petroleum’s heavy oil field in Peace River contains 100 million barrels and this will be a first test of THAI on heavy oil, for which it was originally developed. Duvernay Petroleum has signed a contract with the Canadian firm Petrobank, which owns THAI, to use the process.

The THAI process was first used by Petrobank at its Christina Lake site in the Athabasca Oil Sands, Canada, in June 2006 in a pilot operation which is currently producing 3,000 barrels of oil a day. This was on deposits of bitumen – similar to the surface coating of roads – rather than heavy oil.

Petrobank is applying for permission to expand this to 10,000 barrels a day, though there is a potential for this to rise to 100,000.

The 50,000 acre site owned by Petrobank contains an estimated 2.6 billion barrels of bitumen. The Athabasca Oil Sands region is the single largest petroleum deposit on earth, bigger than that of Saudi Arabia.

‘When the Canadian engineers at the Christina Lake site turned on the new system, in three separate sections, it worked amazingly well and oil is being produced at twice the amount that they thought could be extracted,’ said Prof Greaves.

‘It’s been quite a struggle to get the invention from an idea to a prototype and into use, over the last 17 years. For most of the time people weren’t very interested because heavy oil was so much more difficult and expensive to produce than conventional light oil. But with light oil now hitting around $100 a barrel, it’s economic to think of using heavy oil, especially since THAI can produce oil for less than $10 a barrel,’ he added.

Professor Greaves, who was previously Assistant Professor at the University of Saskatchewan in Canada, and who also worked with Shell and ICI in the UK, is looking at making THAI even more efficient using a catalyst add-on process called CAPRI.

This process was also developed by Prof Greaves’ team at Bath and is intended to turn heavy oil into light while still in the reservoir underground. The CAPRI research has recently been awarded funding of £800,000 from the Engineering and Physical Sciences Research Council, including £60,000 from Petrobank.