Fingerprinting captured CO2 using natural tracers: Determining CO2 fate and proving ownership

Lead Research Organisation: University of Edinburgh
Department Name: Sch of Geosciences

Abstract

Carbon capture and storage (CCS) has emerged as a promising means of lowering CO2 emissions from fossil fuel combustion. However, concerns about the possibility of harmful CO2 leakage are contributing to slow widespread adoption of the technology. Research to date has failed to identify a cheap and effective means of unambiguously identifying leakage of CO2 injected, or a viable means of identifying ownership of it. This means that in the event of a leak from a storage site that multiple operators have injected into, it is impossible to determine whose CO2 is leaking. The on-going debate regarding leakage and how to detect it has been frequently documented in the popular press and scientific publications. This has contributed to public confusion and fear, particularly close to proposed storage sites, causing the cancellation of several large storage projects such as that at Barendrecht in the Netherlands.

One means to reduce public fears over CCS is to demonstrate a simple method which is able to reliably detect the leakage of CO2 from a storage site and determine the ownership of that CO2. Measurements of noble gases (helium, neon, argon, krypton and xenon) and the ratios of light and heavy stable isotopes of carbon and oxygen in natural CO2 fields have shown how CO2 is naturally stored over millions of years. Noble gases have also proved to be effective at identifying the natural leakage of CO2 above a CO2 reservoir in Arizona and an oil field in Wyoming and in ruling out the alleged leakage of CO2 from the Weyburn storage site in Canada.

Recent research has shown amounts of krypton are enhanced relative to those of argon and helium in CO2 captured from a nitrate fertiliser plant in Brazil. This enrichment is due to the greater solubility of the heavier noble gases, so they are more readily dissolved into the solvent used for capture. This fingerprint has been shown to act as an effective means of tracking CO2 injected into Brazilian and USA oil fields to increase oil production. Similar enrichments in heavy noble gases, along with high helium concentrations are well documented in coals, coal-bed methane and in organic rich oil and gas source rocks. As noble gases are unreactive, these enrichments will not be affected by burning the gas or coal in a power station and hence will be passed onto the flue gases. Samples of CO2 obtained from an oxyfuel pilot CO2 capture plant at Lacq in France which contain helium and krypton enrichments well above atmospheric values confirm this.

Despite identification of these distinctive fingerprints, no study has yet investigated if there is a correlation between them and different CO2 capture technologies or the fossil fuel being burnt. We propose to measure the carbon and oxygen stable isotope and noble gas fingerprint in captured CO2 from post, pre and oxyfuel pilot capture plants. We will find out if unique fingerprints arise from the capture technology used or fuel being burnt. We will determine if these fingerprints are distinctive enough to track the CO2 once it is injected underground without the need of adding expense artificial tracers. We will investigate if they are sufficient to distinguish ownership of multiple CO2 streams injected into the same storage site and if they can provide an early warning of unplanned CO2 movement out of the storage site.

To do this we will determine the fingerprint of CO2 captured from the Boundary Dam Power Plant prior to its injection into the Aquistore saline aquifer storage site in Saskatechwan, Canada. By comparing this to the fingerprint of the CO2 produced from the Aquistore monitoring well, some 100m from the injection well, we will be able to see if the fingerprint is retained after the CO2 has moved through the saline aquifer. This will show if this technique can be used to track the movement of CO2 in future engineered storage sites, particularly offshore saline aquifers which will be used for future UK large volume CO2 storage.

Planned Impact

The liability issues which have arisen from the lack of a robust method to determine CO2 ownership is one of the barriers to the global implementation of CCS. The research output from this work will address this issue by developing a reliable and inexpensive method for determining ownership of CO2 injected into the subsurface using natural tracers. This will be especially important for formulating monitoring strategies for CO2 storage sites around the globe. Hence, the proposed research will benefit regulators and operators planning CCS development worldwide.

Public fears of the consequences of unplanned CO2 migration from the storage site are another issue which is impeding the global deployment of CCS. Debates surrounding secure retention of CO2 among scientists and between scientists and the public are often seen in the popular press and in specialised scientific publications. This is because research to date has not managed to fully address the many uncertainties surrounding monitoring the secure retention of CO2. This has led to considerable public opposition surrounding CCS, particularly in areas close to onshore storage sites. The work we proposes aims to address this issue by developing a simple monitoring strategy using the natural tracers already present in captured CO2. This will improve public confidence in CCS by providing assure that the fate of CO2 in a storage site can be determined and that monitoring for certain noble gases could provide an early warning of an unplanned migration of CO2 and allow re-meditative action to be taken.

The industry partners directly involved in the project will benefit from determination of the natural tracer fingerprint measurements made of their captured CO2. The Aquistore project will directly benefit from the tracking and determination of the fate of the CO2 injected into the saline aquifer. This work could also lead to focusing the development of new monitoring equipment, such as a means of determining carbon and oxygen isotope chemistry of fluids downhole meaning that sensor and mass spectrometer manufacturers will benefit.

Other industrial sectors will find the data of interest as we will investigate how the conventional oil industry tracer SF6 flows through reservoir and fractured cap rocks samples compared to the noble gases and CO2. These tracers not only have a role in CCS but could also be used to trace CO2 in enhanced oil recovery (EOR) operations, the migration of fluids in geological nuclear waste disposal and in limiting water resource pollution from the fracking of shales to produce methane gas. The types of experiment proposed could also be applied to low permeability and fractured hard rock and to very low permeability clay rocks which are the most likely nuclear geological disposal scenarios in the UK.

The work proposed is directly relevant to accelerating the development of the future UK CCS industry by helping to address the liability issues which will arise from multiple operators injecting CO2 into the same North Sea saline aquifer. Identifying the potential use of the noble gases as early warning tracers of diffuse CO2 leakage will reassure the general public on the safety of CO2 storage. This will also be of use to industrial and academic workers developing and operating CO2 storage sites. Hence, our research program will assist public engagement efforts and the development of these robust means of fingerprinting CO2 has the potential to lead to a national or international service business, contributing to the green knowledge economy of the UK.

Publications

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Roberts J (2017) Geochemical tracers for monitoring offshore CO 2 stores in International Journal of Greenhouse Gas Control

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Serno S (2017) Oxygen isotopes as a tool to quantify reservoir-scale CO 2 pore-space saturation in International Journal of Greenhouse Gas Control

 
Description • The project provided important new insights into the inherent fingerprint of captured CO2 streams.
o A comprehensive literature review was carried out to collate existing data for captured CO2 and to make predictions of the captured CO2 inherent fingerprint when data was unavailable for CO2 derived from specific feedstocks or processes. This review was published as a critical review in Environmental Science and Technology (DOI: 10.1021/acs.est.6b01548).
o The CO2 stream was sampled from a number of CO2 capture plants using amine capture, gasification, and oxyfuel combustion processes on coal, gas and biomass feedstocks. The inherent tracer fingerprint (carbon and oxygen stable isotopes of the CO2, and concentrations and isotope ratios of trace noble gases - He, Ne, Ar, Kr, Xe) were analysed.
o The carbon stable isotope composition (d13C) of the captured CO2 is similar to (± 5‰) that of the carbon-rich feedstock. Carbon-isotope fractionation during amine capture remains poorly constrained and the limited results available suggest that isotopic fractionation is very different to that expected from CO2 dissolution into and exsolution from fresh water.
o The oxygen stable isotope composition (d18O) of the captured CO2 is similar to that of atmospheric O2 (mostly within ±10 ‰). For amine capture, the CO2 does not appear to be strongly influenced by the d18O of water used to dilute the amine solution. The controls on d18OCO2 from gasification (steam reforming) are poorly constrained.
o A large proportion of atmospheric noble gases are introduced during most CO2 generation processes, and so noble gas isotope ratios in captured CO2 streams are mostly atmospheric, often with evidence of isotopic fractionation of air.
o A crustal helium isotopic signature (3He/4He < 1 RA) may be preserved in CO2 streams derived from fossil fuels, but this is not guaranteed. Expected crustal argon-isotope signatures were not observed in fossil-fuel derived CO2, most likely due to the high concentration of Ar in air.
o Noble gas concentrations in captured CO2 are generally low, with noble gases being lost during CO2 purification processes. Air-normalised noble gas elemental ratio patterns are different to air saturated water and may exhibit enrichments in Xe.
• Our data suggest that transport of the captured CO2 stream between the capture plant and the injection site is unlikely to modify the bulk of the stream, but that fractionation may occur when sampling high-pressure streams.
• The inherent fingerprint of the captured CO2 stream will be modified upon injection into the subsurface, where it will mix with pre-existing gases, dissolve and migrate, but these processes can be modelled to infer the fate of the injected CO2.
o Captured CO2 was injected into, and subsequently produced from the Otway 2BX storage project. d13C changed slightly but this change can be used, in conjunction with baseline data, to calculate the proportion of CO2 dissolved into the formation waters. The noble gases took on a signature assumed to be that of the local formation fluids.
o CO2 sampled from the Aquistore storage site after subsurface migration from the injection to the monitoring well shows an enrichment in crust-derived 4He, indicating that the presence or absence of crustal noble gases can be used to identify the source of CO2 during suspected leaks.
Exploitation Route • The results of this research can be used to aid in selecting the most appropriate source of CO2 for pilot-scale, proof of concept CO2 storage projects that wish to test the use of inherent CO2 tracers.
• This research demonstrates the feasibility of using "naturally" occurring stable isotopes and noble gases as tracers for subsurface gas storage and will thus feed into future research, monitoring techniques, and policy regarding subsurface gas storage.
o This research is likely to encourage the use of stable isotopes as tracers for geological storage of CO2.
o Further work researching the behaviour of noble gases inherent to the CO2 stream, once injected, is clearly desirable. At present there is a lack of experiments that combine reliable reservoir baseline noble gas data with injection of captured CO2.
• Recent political and industrial developments suggest that early CCS adoption in many countries is likely to be via industrial CO2 sources, rather than power generation. Similar work characterising the inherent tracer fingerprint of CO2 from other industrial applications would be a welcome test of the predictions made in the critical review paper stemming from this work.
Sectors Energy,Environment

 
Description • This research strengthened collaboration between Gilfillan's research group and the Petroleum Technology Research Centre (PTRC), Canada, which runs the Aquistore CCS project in Saskatchewan. Flude and Serno were present at Aquistore when CO2 injection began and PTRC continue to involve the University of Edinburgh in Aquistore Research. • Collaboration with PTRC on Aquistore has also developed collaborative links with the University of Alberta. Prof. Rick Chalaturnyk is a co-author on the (recently submitted) peer reviewed paper presenting the results of the research project, and his research group remain in contact with Gilfillan regarding ongoing Aquistore research. • To facilitate sample supply for our research we developed collaborations with staff at RWE Generation's Niederaussem power plant, and with UKCCSRC's PACT core facility. • Our separately funded but related work on the UKCCSRC International Exchange Fund has cemented an ongoing collaboration between Gilfillan's research group and Carbon Management Canada, who are keen for noble gas research to be carried out at the FRS.
First Year Of Impact 2016
Sector Energy,Environment
Impact Types Societal,Economic

 
Description New-Isotope Coupling and Classical tools: Applications to Reservoir and Exploration
Amount £956,000 (GBP)
Funding ID RB0398 
Organisation Total E & P 
Sector Private
Country Unknown
Start 08/2015 
End 07/2018
 
Description UKCCRSC Travel Grant
Amount £25,000 (GBP)
Organisation UK Carbon Capture & Storage Research Centre 
Sector Academic/University
Country United Kingdom
Start 03/2016 
End 09/2016
 
Description Aquistore 
Organisation Petroleum Technology Research Centre
Department Aquistore Project
Country Canada 
Sector Charity/Non Profit 
PI Contribution We have sampled the CO2 being transported inot and injected into the Aquistore CO2 storage site
Collaborator Contribution They allowed us to collect the samples from the pipeline entering the site and the injection well
Impact Samples collected
Start Year 2013
 
Description Ferrybridge 
Organisation Scottish and Southern Energy (SSE)
Country United Kingdom 
Sector Private 
PI Contribution SSE collected captured CO2 samples from their Ferrybridge Carbon capture pilot plant (CCPilot100+) for us to analyse for noble gases and stable carbon and oxygen isotopes.
Collaborator Contribution SSE collected the samples for us and shipped them for analysis
Impact Samples collected and analysed. Results to be published in a forth coming journal paper
Start Year 2013
 
Description Niederaussem Power Station 
Organisation RWE AG
Department RWE nPower
Country United Kingdom 
Sector Private 
PI Contribution We have collected and analysed the stable isotope and noble gas fingerprint of CO2 captured at Niederaussem Power Station
Collaborator Contribution RWE enabled us to collect the samples and spend a day showing us their caputre facilities
Impact Samples of captured CO2
Start Year 2014
 
Description Blog posts on CCS 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact https://thenoblegasbag.wordpress.com/2015/01/09/what-ccs-is-and-perhaps-more-importantly-what-it-isnt/

https://thenoblegasbag.wordpress.com/2014/12/23/why-we-need-to-stop-emitting-co%E2%82%82-a-s-a-p/

https://thenoblegasbag.wordpress.com/2014/11/04/ipcc-2014-report-figure-1-1-explained/
Year(s) Of Engagement Activity 2015
 
Description News article 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Media (as a channel to the public)
Results and Impact News article in the Herald, 25th July 2016
Year(s) Of Engagement Activity 2016
 
Description Poster presentation at AGU Fall Meeting, 2015 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Poster at AGU Fall Meeting, 2015, San Francisco: "Fingerprinting Captured CO2 Using Natural Tracers for CCS Monitoring and Verification" authored by Stephanie Flude, Stuart Gilfillan, Gareth Johnson, Finlay Stuart, Domokos Györe, Stuart Haszeldine
Year(s) Of Engagement Activity 2015
 
Description Presentation at 12th Greenhouse Gas Control Technologies Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact Following my talk at the conference I received a number of questions on my research, both orally in the session itself and afterwards and via email.

After giving my presentation I was asked to present the results of my work at the Gulf Coast Carbon Research centre weekly group meeting at the Bureau of Economic Geology at Austin.
Year(s) Of Engagement Activity 2014
URL http://www.ghgt.info/index.php/Content-GHGT12/ghgt-12-overview.html
 
Description Presentation at ChemEng day, Manchester, April 2014 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Academic researchers and industrial professionals at all levels working within research in chemical engineering and related sectors, particularly those based within the UK attended the ChemEng day at the University of Manchester. I presented a talk entitled 'Opportunities for Engineering Clean Fossil Fuels for a Decarbonised Future' talk which was attended by ~200 delegates. The talk was followed by a panel discussion and I was asked a number of questions on my research in the area.

The chair of the session, President of the IChemE, Geoffrey Maitland reported that my talk had been well received and had promoted discussion following the session.
Year(s) Of Engagement Activity 2014
URL http://www.gnomikos.com/CEDay2014/
 
Description Presentation on CO2 storage - Secure carbon burial for climate mitigation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact The talk was part of the wider CPD course on CCS and prompted significant discussion afterwards.

Following my talk i was asked by a number of participants of the CPD course to provide more detail on my research activities
Year(s) Of Engagement Activity 2014
URL https://ukccsrc.ac.uk/news-events/events/ccs-cpd-course
 
Description SCCS Conference Poster Presentation 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Poster presentation entitled "Fingerprinting Captured CO2 Using Natural Tracers for CCS Monitoring and Verification"
Year(s) Of Engagement Activity 2015
URL http://www.sccs.org.uk/events/51-sccs-conference-2015
 
Description poster presentation at EGU, Vienna - Fingerprinting captured CO2 using natural tracers: Determining CO2 fate and proving ownership 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact o EGU 2016, Vienna, Austria. Flude, Gilfillan et al. "Fingerprinting captured CO2 using natural tracers: Determining CO2 fate and proving ownership"
Year(s) Of Engagement Activity 2016