A new publication from SCCS, with experiments under subsurface conditions undertaken by Dr Katriona Edlmann, led by Dr Chris McDermott, with Prof Stuart Haszeldine, has revealed new insights into the sealing capability of supercritical CO₂.
Experiments undertaken on a new high pressure, high temperature supercritical flow rig indicated that supercritical CO₂ does not flow through natural micro-fractures in Kimmeridge Clay mudrock seal, unless very high entry pressures of 51 MPa are exceeded. By contrast, it was found that CO₂ gas finds an easy escape. This means that supercritical CO₂ acts as a helpful hydraulic barrier.
The research suggested that, in cases of unplanned leakage, overpressuring rather than reducing pressure could be the best remediation. CO₂ storage sites should therefore be positioned deep enough to keep CO₂ securely supercritical throughout the vertical thickness of a primary seal rock.