Ask the Experts

Storing CO2 while pumping for oil and gas

What if oil and gas production could be used to store carbon dioxide (CO2) permanently and thus limit climate change? That is the premise behind EOR+, and in a new report and a webinar presentation,  the IEA has examined the opportunities, challenges and necessary drivers to develop this novel approach to carbon capture and storage. Juho Lipponen, the head of the IEA Carbon Capture and Storage Technology Unit, explains the engineering behind EOR+, what can make it a success and the net effect on global greenhouse gases.  

Head, Carbon Capture and Storage Technology Unit

What is EOR+, and what future does the IEA see for the technology?

Let’s start with some background on technologies that contribute to EOR+. First there is carbon capture and storage, or CCS, which can capture CO2 from fuel combustion or industrial processes, then transport it and store it underground, often in depleted oil and gas fields, keeping it out of the atmosphere where it would contribute to climate change. This would be your “classic” CCS.

Then there’s EOR, or enhanced oil recovery, which involves injection of material into a reservoir to increase the pressure so much that it alters the properties of the oil or reservoir, improving recovery. For nearly 50 years, the oil industry has used CO2-EOR, where it injects the carbon dioxide, usually with water, into a reservoir; the CO2 mixes with the oil, improving flow. The gas is recycled over and over again, but in today's EOR operations, its long-term behaviour in the depleted reservoir is not monitored or verified. Despite the large technical potential of EOR, its use with CO2 currently contributes only about 0.35% of global oil production. But CO2-EOR can make early, large-scale CCS projects viable by partly offsetting capture costs, and hence benefiting CCS in the longer term.

But what if we used CO2-EOR not just to generate more oil but also to store the greenhouse gaspermanently? That’s what we call EOR+, and it offers a win-win solution:  commercial opportunities for oil producers while also ensuring permanent storage of large quantities of CO2 underground. EOR+ could store 60 gigatonnes to 360 gigatonnes of CO2 in the next 50 years: that range covers half to more than three times the amount of total CO2 storage required through 2050 under the IEA 2 Degree Scenario to limit climate change.

The IEA recently published the report Storing CO2 through Enhanced Oil Recovery, which outlines the economic and CO2 storage potential of EOR+ but also the challenges involved.

Remember how I said EOR+ is a win-win solution? According to our analysis, EOR+ practices can result in net emissions savings, as the amounts of CO2 stored would be vastly superior to the additional CO2 resulting from the combustion of the recovered oil.

What are those challenges to making EOR+ industry practice?

Adding the “plus” to EOR will require a paradigm shift from current industry practices. EOR+ is technically viable, but to turn CO2-EOR into EOR+ requires at least four extra steps:

• Additional site characterisation and risk assessment about the reservoir’s cap-rock and geological formations, as well as abandoned wellbores, to assess the potential for CO2 leakage.

• Extra measurement of venting and fugitive emissions from surface processing equipment.

• Monitoring and enhanced field surveillance to assess that the reservoir behaves as anticipated.

• Changes to abandonment processesto assure long-term containment of injected CO2, such as plugging and removal of the uppermost components of wells so they can withstand the corrosive effects of CO2-water mixtures.

CO2-EOR operators would need sufficient incentive to offset the costs of the extra steps for EOR+: that could be accomplished through carbon pricing or linking the regulatory framework for oil production to that for tackling climate change. 

But wouldn’t the captured CO2 just produce more oil that produces more CO2?

Remember how I said EOR+ is a win-win solution?

EOR+ involves injecting more CO2 per barrel of extra oil recovered than is the practice today. In addition, EOR+ operators undertake monitoring and verification of the CO2 that remains in the reservoir. According to our analysis, EOR+ practices can result in net emissions savings, as the amounts of CO2 stored would be vastly superior to the additional CO2 resulting from the combustion of the recovered oil.

Still, as EOR+ is implemented, we will need new and appropriate in-depth life-cycle analyses to assess both project-level and cumulative net impact. 

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