Simple tweaks to oilfield practice could provide the offshore industry with a more sustainable solution to environmental and commercial threats posed by harmful bacteria in subsea oil deposits, according to a University of Calgary researcher currently a visiting professor at Newcastle University in the U.K.
And study of heat-loving, or thermophilic, bacteria on the cold seafloor could help in offshore exploration, a theory soon to be tested of Canada’s Atlantic coast.
The presence of thermophilic bacteria could be a tell-tale sign of the presence of oil reservoirs below. If so, mapping and tracking the distribution of such bacteria, which might have seeped out of the reservoirs, could be a valuable, environmentally less invasive tool for oil companies to use when seeking new reserves—as well as helping to reduce the risk of unsuccessful drilling.
“Our overall aim is to identify ways of making oil recovery more environmentally friendly. If we end up continuing to rely on fossil fuels for a few more years or decades then the imperative must be to meet our energy needs efficiently and with minimum impact on the environment,” research lead Casey Hubert, an associate professor of biological sciences and Campus Alberta Innovates Program (CAIP) chair in geomicrobiology at the University of Calgary, said in a statement.
Research funded by the Engineering and Physical Sciences Research Council (EPSRC) and led by Newcastle University is investigating various ways to tackle the problems linked to sulphate-reducing bacteria in offshore oil deposits.
First evolving billions of years ago, sulphate-reducing bacteria thrive in oxygen-free, watery environments. With the ability to lie dormant for very long periods, sulphate-reducing bacteria “breathe” sulphates but “exhale” toxic, corrosive hydrogen sulphide (H2S) when they are activated.
The resulting reservoir souring increases the oil’s sulphur content and reduces its market value. Hydrogen sulphide is also highly toxic, posing a potentially deadly hazard to workers on offshore platforms, while its corrosiveness can damage pipelines and rigs, leading to oil leaks and spills.
Working with a range of private sector, public sector and academic partners from the U.K. and elsewhere, the Newcastle-led team is investigating a number of easy-to-implement, cost-cutting measures, such as adjusting the water temperature used during oil production, the university said in a statement.
As part of its work to understand how sulphate-reducing bacteria become activated in oil reservoirs, the team is investigating the widespread practice of pumping seawater into an oil reservoir to reduce temperatures and make extraction easier, but which poses problems from a reservoir souring perspective.
“Seawater is rich in sulphates, which sulphate-reducing bacteria use for their metabolism,” said Hubert. “Our results suggest that warming the injected seawater, so that the temperatures in a hot reservoir drop down to say 70 degrees Celsius rather than 50 degrees Celsius, could prevent sulphate-reducing bacteria activity without significantly affecting the oil extraction process.”
Industry has shown interest with additional funding secured from large supermajors in the oil and gas sector.
One method currently used to mitigate the impact of sulphate-reducing bacteria in oil reservoirs is to inject nitrates to stimulate the growth of another type of bacteria that out-compete sulphate-reducing bacteria for nutrients. The Newcastle-led team also see major potential here to improve current practice and make it greener.
“We’re working on ways to predict more accurately the nitrate dose that will be needed in any particular context, taking precise local conditions into account,” said Hubert.
“Adjusting the nitrate dose offers ways to better manage corrosion risks associated with reservoir souring and in some cases could cut costs if lower doses could be used. Our aim is to work with industry so that the nitrate souring control technique is understood thoroughly and sees widespread use.”