28.09.2014, 20:03:42 (GMT+1)

Low-cost solution to unlock offshore oil reserves

Technology breakthrough for North Sea oil production has global potential

Researchers in Scotland believe they have found a clean and cost-effective way to maximise oil extraction from existing offshore fields.

They are confident that using new gas and water technologies could “add decades” to the lifespan of oil reserves in the North Sea.

This hugely-significant technological breakthrough could potentially have a massive impact not only on North Sea oil production but on oil recovery techniques and production worldwide.

As global exploration moves into ever-harsher environments and more remote locations, finding new oil and extracting it is becoming increasingly more challenging and expensive. With production declining in existing offshore oil fields, improving recovery through cost-effective means is an absolute priority. The application of appropriate, enabling technologies is crucial in both respects.

Currently the global recovery factor – the percentage of the total conventional oil volume likely to be produced from the world’s oil fields – is estimated at just 22 per cent. This means that 78 per cent of the global oil reserves will remain untapped and left behind after the oil fields have closed down.

Scientific research has been focusing on the implications of using various enhanced oil recovery (EOR) technologies to significantly increase the global recovery factor.

The Centre for Enhanced Oil Recovery within the Institute of Petroleum Engineering at Heriot-Watt University in Edinburgh has been testing out new techniques to increase the lifespan of oil reservoirs in the North Sea and help secure the future of the oil industry in the region.

Now, following years of studies into EOR technologies, Heriot-Watt researchers believe they have come up with a practical, low-cost solution – by using a technique known as low-salinity water injection.

It works by reducing the salt levels in seawater already injected in reservoirs containing further oil reserves which are difficult to access using conventional extraction methods. The new technique involves reducing the salt content in water before it is injected. Apparently low-salinity water recovers more oil, possibly because of the formation of emulsions or changing water acidity.

Heriot-Watt researchers have developed a screening technique which identifies the reservoirs that will respond best to the low-salinity water injection operation. This will determine how much additional oil could be extracted cost-effectively using their advanced EOR technology.

The research team, led by Professor Mehran Sohrabi, director at the university’s EOR facility, has also identified new gas injection technologies which could be used in reservoirs which are already flooded with water.

Professor Sohrabi believes their discoveries could be ‘game changing’ for the offshore energy industry and is urging the UK Government and businesses to increase their investment in new gas and water technologies to reverse the decline in North Sea oil production.

“After 40 years of production the North Sea oil reservoirs are now mature and in rapid decline,” he says. “Urgent action is needed now. Low salinity water injection is relatively inexpensive and can be economically implemented in the North Sea reservoirs. It has the potential to make a huge impact on the current output of North Sea oil production.”

By developing a robust method to screen oil reservoirs, the team can calculate how much extra oil could be produced and whether it would be cost-effective to do so using EOR techniques.

“This is a massive leap forward, especially in an offshore setting,” says Professor Sohrabi. “The process is relatively inexpensive meaning the costs for EOR could fall dramatically while yields could rise. It’s also cleaner as you’re removing the need for potentially toxic chemicals.”

With the gas injections, it is more difficult to simulate its performance accurately because it is part of a “complex, three-phase flow regime". However, the Heriot-Watt team has developed an algorithm to accurately predict gas and water alternating gas-injection performance in oil reservoirs.

“The government and industry must invest in new gas and water technologies to reverse the decline in production in North Sea oil reservoirs,” he added.

Sources:

http://www.hw.ac.uk/news-events/news/heriot-watt-scientists-unlocking-oil-reserves-18619.htm

http://www.bbc.co.uk/news/uk-scotland-edinburgh-east-fife-29342142

http://large.stanford.edu/courses/2013/ph240/alshakhs1/