Roberto Loza (Cardiff University) and Rory Leslie (University of Edinburgh) shares their takeaways from “Parallel 1b: Storage” at the UKCCSRC Knowledge Exchange Conference 2023.
During the recent UKCCSRC Knowledge Exchange Conference in Sheffield (6-7 September 2023), there were a rich variety of talks discussing the challenges and solutions of different topics related to carbon capture and storage (CCS). Some of the talks ran in parallel to allow delegates to learn more about a specific topic and to keep up to date with the latest advances in the field. Storing CO2 in the subsurface is a crucial element of CCS. The storage session, chaired by Dr Roberto Loza, was very thought provoking and facilitated plenty of interesting discussions.
Dr Lee Hosking, from Brunel University London, opened the session talking about cement sheath bond integrity in CO2 injection wells. Analysing cement integrity in a mix of new, repurposed and legacy wells is challenging. The wells have varying cement quality and CO2 flow requires the consideration of unique properties. This is especially true in the UK, as the Track 1 clusters include new wells (East Coast Cluster, in the Endurance aquifer) and repurposed wells (HyNet, offshore Liverpool Bay).
Parameters that affect well integrity include chemical degradation, thermal loading (due to variations in CO2 and formation temperature) and thermal cycling (due to shutdowns or intermittent shipments). Dr Hosking presented various coupled hydro-mechanical-thermal numerical models aiming to predict cement failure in CO2 wells. Multiple simulation scenarios were considered.
The second presentation was given by Dr James Verdon, from the University of Bristol, in which he discussed the importance of monitoring induced seismicity caused by CO2 injection. Even though small seismicity may not cause damage, it can raise serious concerns to the public and damage a project’s reputation. One example is the closure of the Castor Natural Gas Storage Project 20 km off the coast of Spain after seismic activity was detected after gas injection. Many projects use a traffic light scheme (TLS): (i) Green, for low magnitude events with no concerns, (ii) Amber, for moderate magnitude events that require intervention, and (iii) Red, for high magnitude events when injection must stop, either temporarily or permanently (Fig. 2). Dr Verdon explained that the magnitude does not always increase gradually, and sudden jumps are common. Data suggests that high magnitude events can occur “out of the blue” regardless of the low magnitude of prior events. James’ results showed that the occurrence of seismic events is not purely random and sudden magnitude jumps very rarely exceed a magnitude increase of 1.5 Therefore a TLS with an expectation of magnitude jumps of 1.5 is a reasonable approach for minimizing the occurrence of high magnitude induced seismic events.
The closing presentation was delivered by Ian Watt, from the University of Edinburgh, talking about the potential to store CO2 through mineralisation in basaltic/mafic rocks. This storage method is being used at the innovative Carbfix project in Iceland. CO2 trapping occurs when acidic water saturated with CO2 interacts with minerals in basaltic rocks to precipitate carbonate minerals such as calcite and dolomite. Ian’s key questions were: (i) does the precipitation of minerals block fluid pathways in the rock? – which could reduce injectivity, permeability and the volume of accessible rock for mineralisation; or (ii) can injected CO2 induce fractures within the rock? – which could create more pathways for fluid flow and mineralisation.
To answer these questions, Ian developed a high-precision laboratory experiment which flowed CO2-saturated water through a mafic rock sample under reservoir conditions over a timescale of months. Ian shared computed tomography (CT) images showing the development of pore space and fractures over time. Subsequent Scanning Electron Microscope (SEM) analyses confirmed the formation of new carbonate minerals (Fig. 3). The experiment shows that carbonate mineralisation and fracture formation can occur within weeks to months. This result supports CO2 mineralisation in basalts as a promising method to storing CO2 in locations where saline aquifers and depleted oil and gas fields are not present.
It is clear after these talks that CO2 storage is an interesting topic, bringing state-of-the-art research from multiple institutions. Having a conference like the one organised by the UKCCSRC is a great opportunity to bring researchers, industry professionals and government together to discuss challenges and opportunities. The support to ECRs is fantastic. The support allows us to be part of the community implementing CCS for Net Zero. We are looking forward to the upcoming conference in March 2024.