Simple tweaks to oilfield practice could provide the offshore industry with a more sustainable, money-saving solution to health and safety, environmental and commercial threats posed by harmful bacteria in subsea oil deposits.
Easy-to-implement, cost-cutting measures - such as adjusting the water temperature used during oil production - could offer a way of tackling problems linked to sulphate-reducing bacteria (SRB) that is greener and more effective than those currently relied on. SRB 'breathe' sulphates but exhale toxic, corrosive hydrogen sulphide (H2S).
The Engineering and Physical Sciences Research Council (EPSRC) is funding the research, which is led by Newcastle University. The work involves a range of private sector, public sector and academic partners from the UK and overseas.
First evolving billions of years ago, SRB thrive in oxygen-free, watery environments like those that can be found in offshore oil deposits. The H2S they produce, however, is a key cause of 'reservoir souring', increasing the oil's sulphur content and so reducing its market value. H2S 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.
As part of its work to understand how SRB - some of which can lie dormant for very long periods - become activated in oil reservoirs, the Newcastle-led 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 SRB use for their metabolism, says Dr Casey Hubert of Canada's University of Calgary, who is leading the research in his role as Visiting Professor at Newcastle University.
Our results suggest that warming the injected seawater, so that the temperatures in a hot reservoir drop down to say 70°C rather than 50°C, could prevent SRB activity without significantly affecting the oil extraction process.
Industry has already shown substantial interest with additional funding secured from large supermajors in the oil and gas sector.
One method currently used by the offshore industry to mitigate the impact of SRB in oil reservoirs is to inject nitrates to stimulate the growth of another type of bacteria that out-compete SRB for food. 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, Dr Hubert says.
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.
The project is also exploring whether the presence of heat-loving ('thermophilic') bacteria on cold sea-floors might 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. Testing of the idea is now beginning off Canada's Atlantic coast.
Dr Hubert concludes:
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.
Notes for Editors:
The Deepbioengineering project, which began in March 2012 and is due to run until March 2018, is receiving a total of nearly £986k in EPSRC funding.
Key statistics on the UK oil and gas sector (source: Oil & Gas UK):
- Oil and gas provides over 70 per cent of the UK's total primary energy
- The UK Continental Shelf meets half of the UK's oil and gas demand
- There could be up to 20 billion barrels of oil and gas still to recover from the UK's offshore areas
Engineering and Physical Sciences Research Council (EPSRC)
As the main funding agency for engineering and physical sciences research, our vision is for the UK to be the best place in the world to Research, Discover and Innovate. By investing £800 million a year in research and postgraduate training, we are building the knowledge and skills base needed to address the scientific and technological challenges facing the nation. Our portfolio covers a vast range of fields from healthcare technologies to structural engineering, manufacturing to mathematics, advanced materials to chemistry. The research we fund has impact across all sectors. It provides a platform for future economic development in the UK and improvements for everyone's health, lifestyle and culture. We work collectively with our partners and other Research Councils on issues of common concern via Research Councils UK.
Newcastle is a Russell Group University and ranked in the top 1% of universities in the world (QS World University Rankings 2016). Ranked 16th in the UK for global research power (REF 2014), it is ranked joint 22nd in the Sunday Times 2017 Good University Guide. The university has a world-class reputation for research excellence and is spearheading three major societal challenges that have a significant impact on global society: Sustainability, Ageing and Social Renewal.
Reference: PN 38-17