Pumping more CO2 into oil wells could remove greenhouse gases from the air and make crude oil carbon negative. Ceri Jones reports.
Doubling the amount of CO2 pumped into oil wells could save emissions and money, according to a Stanford University, USA, research proposal.
The paper, titled Advancing enhanced oil recovery as a sequestration asset and published in Joule, was written by Sally Benson, Professor of Energy Resources Engineering at the School of Earth, Energy & Environmental Sciences, and John Deutch, Professor Emeritus of MIT, who argue that the USA can exploit existing technology and tax structures to tackle greenhouse gas emissions.
The team believes this approach can help improve the currently inefficient and small-scale carbon capture and sequestration methods in use across the oil and gas industry.
Production at ageing wells often falls due to pressure changes caused by the lower oil reserves. Gas injection with CO2 is the most common way to stabilise the pressure and encourage crude displacement, as the gas lowers the oil viscosity, making it easier to extract.
But by pumping in twice the amount of carbon than normal, companies could take advantage of new tax breaks in the USA – signed in February 2018 to reward oil companies for capturing and storing CO2 – thereby reducing the production cost per barrel.
Today, typically 2.5 tonnes of carbon is used for every barrel of crude obtained by carbon gas injection – almost the equivalent of that produced when burning it, said Benson. Also, by switching from natural to man-made sources of carbon, such as fertiliser plants instead of reservoirs, they can take more carbon directly out of the atmosphere.
The paper proposes that the industry trials the techniques at smaller facilties, before applying it at fossil-fuelled power plants and refineries. Forecast firgures suggest that sourcing 10 times as much CO2 from industrial plants could decrease the USA’s climate emissions by 9.5%, although no timeframe is set for this.
But doubling the amount of carbon injected would inevitably increase production costs, estimated to be at around US$22 per barrel in a hypothetically model where oil is at US$100 per barrel. But in a Stanford University press release, Benson and Deutch proposed trialling a reverse Dutch auction scheme that could cost the government just US$25 per tonne of captured CO2.
In this style of auction, the USA could incentivise change by requiring that oil companies bidding for new projects estimate how much CO2 the project would be able to store, and how much government money they would want as a reward for reaching this target.
‘If 30 projects earned that amount for a decade apiece, the programme would trap 264 million tonnes of CO2, and government spending on the experiment would total US$6.6bln. For comparison, the newly expanded tax credits offer $35/t of CO2 captured and put to use, or US$50 per tonne if the carbon is simply buried,’ the release stated.
Benson said this alternative initiative would help all producing oil companies, including those that would not have otherwise benefited from tax incentives. While this appears as something of a silver bullet, what are the real costs and practicalities of setting up the framework?
Carbon capture and sequestration schemes have repeatedly failed at industrial plants, famously at the Kemper ‘clean coal’ testbed, which proved too inefficient and uneconomical to be sustained. So how does this plan differ? It would be a risk for companies to invest in carbon capture equipment at fertiliser and power plants when they could use existing setups and still reap the double-carbon tax benefits.
Benson was approached for comment but was unable to respond by the deadline.
The full paper is available to read here, for a fee: