Author - Christophe McGlade.
The oil and gas industry is one of the global leaders in developing and deploying CO2 capture. Of the approximately 30 Mt CO2 captured today from industrial activities in large-scale carbon capture, utilisation and storage (CCUS) facilities, nearly 70% is captured from oil and gas operations. The oil and gas industry is also often in a position to make use of this captured CO2, either by selling it to industrial facilities or by injecting it into the subsurface to boost oil recovery.
This process of injecting CO2 into existing oil fields is a well-known “enhanced oil recovery” (EOR) technique: the addition of CO2 increases the overall pressure of an oil reservoir, forcing the oil towards production wells. The CO2 can also blend with the oil, improving its mobility and so allowing it to flow more easily. The IEA’s new global database of enhanced oil recovery projects shows that around 500 thousand barrels of oil are produced daily using CO2-EOR today, representing around 20% of total oil production from EOR.
In CO2-EOR, some portion of the injected CO2 remains below the ground. If the CO2 that returns to the surface is separated and reinjected to form a closed loop, this results in permanent CO2 storage. Today, between 300 kg CO2 and 600 kg CO2 is injected in EOR processes per barrel of oil produced in the United States (although this does vary between fields and across the life of projects). Given that a barrel of oil releases around 400 kg CO2 when combusted, and around 100 kg CO2 on average during the production, processing and transport of the oil, this opens up the possibility for the full lifecycle emissions intensity of oil to be neutral or even “carbon-negative”.
The idea of “carbon-negative” oil is attractive. It could help reduce emissions from hard-to-decarbonise sectors such as aviation and trucks that are heavily dependent on energy-dense, liquid fuels. However, the logic of “carbon-negative oil” critically depends on the boundaries of the analysis and the origin of the CO2.
Today the majority of CO2 injected in CO2-EOR projects is produced from naturally occurring underground CO2 deposits. This may appear a somewhat ironic situation, but the reason for this is the absence of available CO2 close to oil fields. Using natural sources clearly provides no benefit in terms of the emissions intensity of the produced oil. In the United States, more than 70% of the CO2 injected today for CO2-EOR is from natural sources.
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