As early as the late 19th century, a link between carbon dioxide (CO2) and temperature in the atmosphere was suspected (Arrhenius, 1896; Chamberlin 1899). During the 20th century this link was further studied and by the beginning of the 21st century there is no doubt that global warming is due to human activity (Lynas et al., 2021). Anthropogenic CO2 has thus far contributed to a global temperature rise of 1 °C, increasing with 0.2 °C per decade following current trends (IPCC, 2021). Carbon Capture and Storage (CCS) is a promising process to combat the increasing concentration of CO2 in the atmosphere. From 2020 to 2021, the capacity of CO2 sequestration from CCS projects grew from 75 million tonnes per annum (year) (Mtpa) to 111 Mtpa in 2021 (Global CCS Institute, 2021).
For a CCS project to be considered as having a successful mitigation on the effects of climate change, it is proposed that CO2 emissions to the atmosphere should be less than 0.01% (Hepple & Benson, 2004) or even 0.001% (Shaffer, 2010) of the total injected volume. Every active CCS project must have a robust monitoring, measurement, and verification (MMV) program in place, that aims to meet 3 monitoring objectives (Furre et al, 2017): conformance, containment, and contingency monitoring.
A wide range of geophysical measurements, such as seismic, well logging, gravity surveys, and tiltmeters and interferometric synthetic aperture radar (InSAR) for surface deformation measurements, can be used to design a robust MMV program. Seismic waves contain information about both the sources of seismic energy (earthquakes, roads, cities, ocean waves, wind, etc) and the structure and properties of the Earth. By studying seismic waves recorded by dense arrays of sensors, we can construct 3D images of the subsurface. Monitoring changes over time allow to observe and interpret Earth processes that change the subsurface. This is important both for natural hazard assessment (e.g. volcanic monitoring), monitoring effects of climate-change (e.g. glacial melting), or monitoring of subsurface-related industrial activity such as geothermal energy production and waste storage.
Time-lapse monitoring is a tested and trialled technology commonly used in oil and gas production. Despite step-change innovations during the last decade, in the areas of compressive sensing, seismic inversion, and machine learning, practices of seismic surveying for time-lapse monitoring have not changed. However, the cost-benefit for CCS is drastically different, requiring ground-up redevelopment of acquisition and processing practices. This forms a formidable barrier to CCS projects, because regulators are expected to require extensive monitoring during CO2 injection, and for several decades after CO2 injection ceases, to detect undesirable plume migration and any developing pathways of leakages. Furthermore, the subsurface near prospective CO2 storage reservoirs is often relatively well known from decades of oil and gas exploration, accompanied by detailed seismic surveying. This spurs the question of whether the data requirements for monitoring could be substantially relaxed.
Aims and objectives
During this project, you will develop cost-effective geophysical methodologies for an effective and robust monitoring, measurement, and verification (MMV) program. The specific deliverables can be agreed based on your specific interests and expertise. Example objectives that may be explored as part of the project:
1) Which geophysical measurements (or attributes) are most sensitive to a particular leakage scenario.
2) How to design an optimal survey for an MMV program given a particular target.
3) How to adapt an MMV program dynamically based on detected changes.