The CO2-Upslope project was investigating the potential for storing CO2 in geological reservoirs on the Norwegian continental shelf and ways to enhance immobilization and reduce risk. Aquifers are porous and water-filled underground layers (e.g. sandstone). These reservoirs hold potential to store large volumes of CO2. The Gassum Formation is an aquifer in the Skagerrak basin between Norway and Denmark, which is well suited for storing CO2. By studying this and other reservoirs, we aim to improve the understanding of long-term physical and chemical behaviour of CO2 during storage.
Capturing CO2-gas from an industrial emission source on land or offshore and injecting it into porous, water-filled rocks several kilometers below the sea floor is an effective way of preventing CO2 from ever reaching the atmosphere and a climate mitigation measure. To ensure that the stored gas never leaks out, geologists, chemists and physicists are working together, making 3-dimensional computer models to predict how the injected gas will move in the subsurface. Some reservoirs are layers of water-filled, porous rock that are tilted, with one end buried at a shallower depth than the other. By injecting CO2 into the deeper end, the buoyant gas will move upwards. These types of reservoirs are termed sloping aquifers by geologists. In such reservoirs, with time and given the high pressures in the sub-surface, CO2-gas will dissolve in water (just like bottled, carbonated water) and also react chemically with the minerals in the rock. In this way, CO2 becomes trapped in the water phase and inside precipitated minerals, and less CO2 is present as a buoyant gas. Chemically bound CO2 is a very safe storage method, as it immobilizes carbon and prevents injected gas from reaching the shallow outlet of a sloping aquifer. There is a need, however, to estimate how much CO2 can be stored in this way. In CO2-Upslope we aim to improve the geological understanding of the reservoir, before we quantify chemical and physical processes during CO2 injection and storage by means of new methods for simulation.
This project is in line with Norway s ratification of the Paris agreement in 2016, and the government is committed to reducing national CO2 emissions by 40 % within year 2030. In order to achieve these ambitious goals, several means for cutting emissions must be realized and/or upscaled. CO2 capture and storage (CCS) is a proposed measure that holds great potential offshore Norway. The Gassum reservoir is located close to several industrial emission sources for CO2 (e.g. cement and ammonia production) and could provide as a future storage site. Additionally, more knowledge of chemical immobilization and safe storage of CO2 may contribute to improved understanding and broader acceptance of CCS as a climate mitigation measure amongst decision makers and the general public. In 2019 the first licence for CO2 storage was awarded to an operator consortium for an area offshore Bergen. The Johansen Formation ? a sloping aquifer, would be the main storage unit. The numerical tools and methods for reservoir characterization and estimations of migration and reactivity developed in CO2 Upslope will be applicable for this storage site.
The main challenge, but also the strength in CO2-Upslope may be the interdisciplinarity of the scientific work. The project links geology, geophysics, chemistry and mathematics in interpreting reservoirs and in numerical models for CO2 storage.
RESULTS SO FAR:
The CO2 Upslope project is now finished after 2.5 years (2017-2019). During this period there has been several meetings and workshops between the participants and partner institutions UiO, Sintef and GEUS. A project web page was establisehd at: https://www.mn.uio.no/geo/forskning/prosjekter/upslope/
In the initial part of the project we were working on a new geological model for the Gassum Formation, using mainly 2D seismic data. This provided the framework needed for evaluating mineralogy and reservoir properties. In the final and main phase of CO2-Upslope new models and methods were developed and applied in order to estimate how much CO2 that will dissolve in water and be bound in minerals, and how much will be trapped during migration along the seal in sloping aquifers. Also models for estimating salt precipitation during injecion have been included. The results from the various models may be interlinked and developed further to be applied also for evaluating other storage reservoirs. The project results are compiled in a Best Practices Manual. It is a live document which will be updated as results are published (also after the project is finished). It will be openly available for industry and anyone who may be interested in dynamic storage and storage security. Efforts have been made also towards outreach through popular science lectures and in teaching.
Det overordnede målet i CO2 Upslope har vært å utvikle bedre metoder for å estimere effekt av lagringsmekanismer i dynamiske reservoarer. Nye beregningsmetoder for topografisk innfangning, injektivitet (spesielt saltutfelling) og mineralisering er svært relevant for en rekke aktuelle lagringsprospekter, både på norsk sokkel og internasjonalt. Det har vært god måloppnåelse i prosjektet. Prosjektet har i høy grad vært tverrfaglig, med samarbeid mellom UiO, Sintef og GEUS, og har ført til bedre forståelse av reservoaregenskaper i Gassum mellom norsk og dansk side av Skagerak. Metoder og modeller publiseres åpent tilgjengelig, og vil kunne brukes videre til øvrige caser og i alternative applikasjoner. Formidling om lagringssikkerhet har vært prioritert. Med økt kunnskap om lagringsmekanismer vil det kunne bli større aksept for og initiativ til CCS blant folk flest og beslutningstakere, et skritt i retning av rask utslippsreduksjon i tråd med nasjonale mål.
There are several storage candidates on the Norwegian Continental Shelf which may be characterized as semi-open, sloping aquifers. Improved reservoir characterization of such candidates is needed in order to fulfil an overview of national storage options, in which the chemical and physical immobilization potential is considered as enhancing storage security and capacity. The CO2-UPSLOPE project seeks to demonstrate how CO2 storage in sloping aquifers is feasible and even a suitable measure for increasing estimates of available storage volumes on the Norwegian Continental Shelf. Moreover, CO2-UPSLOPE will demonstrate optimized storage applying innovative use of commercial software and advanced in-house modelling tools, estimating the storage potential in the Gassum Formation in Skagerrak. CO2-UPSLOPE benefits greatly from the extensive knowledgebase and technical experience on CCS modeling from the three main partners UiO (FME-SUCCESS), GEUS, and SINTEF Oslo. CO2-UPSLOPE will provide invaluable knowledge on the long-term safety of CO2 storage in sloping and open aquifers; a fundament for policy makers and CCS stake holders. Increased confidence in CO2 storage in such aquifers may be crucial in reaching the goal of 40% national cuts within 2030.