Carbon Capture and Storage

Capturing large volumes of CO2 and storing it safely for thousands of years in the subsurface (known as carbon capture and storage – CCS) is a key process in meeting emissions reduction targets. Carbon dioxide can be captured at point sources where it is generated, for example cement factories, thereby limiting its emission to the atmosphere. Alternatively, CO₂ can be removed directly from the atmosphere using scrubbing technology and engineering solutions. It can then be pressurised and injected into deep subsurface rock successions as a supercritical fluid where it will be stored long-term in a stable state.

One storage option is the re-purposing of depleted and decommissioned subsurface hydrocarbon reservoirs, which have the necessary proven attributes and properties for CO₂ sequestration: porous and permeable sedimentary rock formations overlain by an impermeable cap rock to prevent leakage of injected CO₂ back to the surface or to shallow groundwater aquifers.

Yet, the very large volume of CO₂ to be sequestered underground in coming decades means that the storage capacity of re-purposed former hydrocarbon reservoirs will eventually be reached. In addition, very-large subsurface saline water aquifer successions can be used for CCS on a much larger scale. Here, supercritical (liquefied) CO₂ can be stored alongside saline water present in the pore spaces (e.g., between sand grains) of deeply buried sedimentary rock successions.

The University of Leeds is well-placed to support CCS projects, both in the former oil and gas fields and in giant saline aquifer reservoirs, through its long history of research relating to geological characterisation of the subsurface.

Seafloor sediments are naturally important stores of CO₂ that is bound in organic remains of microorganisms that previously extracted it from the atmosphere by photosynthesis. Understanding, preserving and potentially harnessing this natural global CO₂ sink is a major research focus that we are approaching with a combination of laboratory experiments, chemical analyses, and numerical modelling.

Injection of liquid CO₂ lowers the temperature of the surrounding rock, changing its physical properties and causing thermal contraction. With our state-of-the-art multiphase flow, petrophysics and geo-mechanical laboratories, Leeds researchers can analyse the mechanical and hydraulic properties of the reservoir rock to take these temperature changes into account, to reduce the risks of CO₂ leakage.

Our innovative seismic monitoring research, which uses satellite observations to interpret seismic waves in the subsurface, can help to monitor for potential earthquakes caused by large injections of CO₂ that can threaten seal integrity and cause leakages.