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CLIMIT-Forskning, utvikling og demo av CO2-håndtering

Application of noble gas signatures in monitoring schemes for offshore CO2 storage

Alternative title: Bruk av edelgassignaturer i overvåkningssystemer for offshore CO2-lagring

Awarded: NOK 5.5 mill.

The ICO2P-project aims to answer whether measurement of noble gases and CO2 by use of new, portable technology is suitable as a geochemical and quantitative monitoring method in long-term, safe storage of CO2 on the Norwegian continental shelf. The miniRUEDI-instrument is developed by researchers at Eawag [1]. It is unique in its ability to measure low concentrations of noble gases (He, Ne, Kr, Xe, Ar), as well as CH4, CO2 and N2 on-site and semi-continuously. This is a significant step forward compared to analysing noble gas isotopes in single samples, which is a method that has been tested at small-scale CO2 storage facilities, at field analogues and in connection with Enhanced Oil Recovery-projects. In this study we are analyzing the noble gas composition of samples from producing gas fields, at CO2 capture facilities and CO2 storage sites, gaining knowledge of geochemical and isotopic signatures. Semi-continuous analysis with the miniRUEDI -instrument [1] is used to document noble gas content and variability during CCS operations. Knowledge of the chemical/physical fingerprint of these gases gives scientific insight to the capture process imprint and traceability of stored CO2. The ICO2P project started in June 2018, and Ulrich Weber was employed as a PhD fellow student. A test campaign was completed at the Technology Center Mongstad, including monitoring of noble gases in the CO2-rich gas stream before and after capture operations. In august 2018 the method was tested at Equinors plant at Melkøya (Snøhvit) where CO2 capture and storage is ongoing. Single samples were collected from both sites and analysed in Eawags noble gas laboratory at ETH-Zurich during autumn 2018 and spring 2019. Samples were also collected from the Klemetsrud waste incineration facility in Oslo, where CO2 capture is being tested. Analysis of noble gas concentrations and isotopic signatures at three different capture facilities show that the noble gas content in captured CO2 is much lower than in the atmosphere, while there are significant differences in signatures between capture operations. Temporal variation at different stages in the capture process was also documented and provides insight into process dynamics. Knowledge about the noble gas signature in captured CO2 provides a basis for evaluating traceability and detectability in and above CO2 storage reservoirs, where distinguishing anthropogenic, captured CO2 from other natural sources is essential. The new knowledge gained from analyzing captured CO2 was applied in modelling studies of how signatures of injected CO2 change when in contact with other reservoir fluids (mostly fossil salt water). Calculations show that the signature will change with time, as noble gases will accumulate into the injected CO2. The acquired signature will still be distinct from atmospheric gas, fossil natural gas and gas hydrates. To increase traceability, noble gas tracers may be added to injected gas, e.g. Xenon. New calculations show, however, that this is rather costly (> 1$ /t CO2), and often not necessary. During summer 2019 groundwater samples were collected from the CO2 field laboratory at Svelvik, run by Sintef. In fall injection tests were monitored with the miniRUEDI instrument. Results are being processed and will contribute to improved understanding of CO2 distribution and traceability in the reservoir. The PhD scholar has also participated in a study of CO2 migration in fault zones, in Mt Terri, where noble gases proved to be excellent tracers. Results from all of the above-mentioned studies are part of Ulrich Webers PhD, which was publicly defended on the 3rd of December 2021. In summer 2020 ICO2P joined a research cruise with the Norwegian Oceanographic Survey and collected sediment cores from the seafloor of the North Sea. In addition, new samples from natural gas reservoirs have been attained. With detailed analysis of noble gases and pore water chemistry we will learn about the natural processes in pore fluids in and above potential storage sites for CO2, and we are designing a portable, cost-effective monitoring scheme for CO2 storage sites, which is specific to CO2 sources. Reliable monitoring methods are of crucial importance in gaining public acceptance for CCS, which will be key in Norways climate mitigation plan to reduce emissions by 40 % by 2030. ICO2P recommends that noble gases form part of base line studies, reservoir characterization and monitoring schemes for CO2 storage sites. [1] Brennwald et al. (2016) in Environ. Sci. Technol. 50(24), 13455-13463.

OUTCOMES -Set-up and calibration procedure for on-site noble gas (NG) monitoring established -Reference data set of background isotopic signatures provided -Temporal variations in CO2-streams from different capture processes documented. The common NG signature is depletion. -Improved estimations of intra-reservoir mixing and fluid composition, inherent signatures and detectability -Added NG tracers are expensive, Xe most feasible. Inherited signatures often sufficient. IMPACT -Mobile mass spectrometry (miniRUEDI) provides new opportunities for cost-effective, reliable and semi-continuous on-site CCS monitoring -NG data improved characterization of natural vs. injected fluids, and strengthens confidence in leakage detection / source attribution -Significant cost reduction in using inherent NG tracers and targeted sampling for verification of CO2 storage integrity -Innovative monitoring methods presented are globally applicable -ICO2P has added to the pool of future CCS

Norway is at the forefront of carbon capture and storage (CCS), with operating storage sites at the Sleipner and Snøhvit fields, and with a national plan to realize full scale CCS with storage at Smeaheia. In order to verify containment and ensure long-term storage security, cost-effective and reliable monitoring methods are needed. The ICO2P (reads: "isotope") project aims to provide a new, cutting-edge and cost-effective method to monitor gas dynamics in CO2 storage reservoirs by recording and tracking noble gas fractionation and isotopes during their evolution in time and space. This approach will allow for source-specific identification of fluids; differentiating injected (anthropogenic) CO2 from natural methanogenic/biogenic CO2 rich gases. The proposed project is building on experiences and results achieved in a CLIMIT-Demo feasibility study conducted during 2017. The project partners are UiO, Statoil, NTNU and Eawag (Switzerland), with a central and essential Ph.D. candidate hosted by UiO. ICO2P will utilize new technology; the portable miniRUEDI [1] membrane inlet mass spectrometer which provides a unique never-seen-before capability for real time analysis of noble gas contents in gas production and CO2 injection lines. Reliable monitoring is fundamental for gaining public acceptance for CCS and a requirement from policy makers. ICO2P will provide a background data set of natural occurrences of noble gases and design source-specific leakage detection and monitoring schemes for Norwegian CO2 storage sites. Increased confidence in CCS may be crucial in reaching the goal of 40 % national cuts within 2030. [1] Brennwald, M. S., Schmidt, M., Oser J. & Kipfer, R. (2016) A portable and autonomous mass spectrometric system for on-site environmental gas analysis. Environ. Sci. Technol. 50(24), 13455-13463.

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CLIMIT-Forskning, utvikling og demo av CO2-håndtering