Semi-regional subsurface modelling of formation fluid movement in response to CO2 injection with a focus on the impact at existing wells

This project aims to utilise subsurface modelling in an appropriate part of the UKCS, to simulate CO2 injection and the related impact of pressure changes and formation fluid movement at existing wells. Identifying the magnitude and timing of pressure changes in relation to a range of well situations (e.g. open/closed to rock at different stratigraphic levels) is a key measure of success. Additionally, in the event that modelling suggests plausible scenarios where formation fluid may be expected to escape to the water column, the NSTA are interested in quantifying the potential impacts. For example, the duration, distribution and magnitude of salinity changes on different scales. In detail, the NSTA expects that any proposal would incorporate, but not be limited to consideration of: • pressure changes associated with CO2 injection on a variety of scales at existing well locations; • pressure changes, across multiple stratigraphic intervals, at the well locations and the timing over which they occur; • the relative susceptibility to fluid escape of wells based on 'typical' abandonment scenarios and their relationship to subsurface architecture (e.g. open to one penetrated interval, closed to another) and CO2 injection activity; • the volume of formation fluid that could enter a wellbore at different stratigraphic intervals as a result of CO2 injection; • impacts of formation fluid escape on the water column on a variety of scales; This project does not seek to explicitly model CO2 migration or any form of CO2 leakage but rather the pressure effects and movement of formation fluid in the context of existing wells as a consequence of CO2 injection. This project is a subsurface focussed objective rather than a well focus and should not enter into detailed well design or abandonment status.