Conceptual modelling for migration assisted storage

There are countless subsurface factors that influence the regional suitability and ultimate success of storing (and monitoring) CO2 in an "unconfined" saline aquifer. The behaviour of a plume of CO2 and the associated pressure changes resulting from displaced formation fluid will respond to geological heterogeneity on multiple scales e.g. hydraulic connectivity as a function of lithology, facies or poroperm variation; or physical connectivity as a function of structure e.g. dip, fault presence/throw/transmissibility or the presence or shape of salt bodies. To help the NSTA understand and better define migration assisted storage potential on the UKCS, it is first necessary to understand boundaries or constraints that impact plume behaviour. This project aims to determine, under defined geological conditions ("scenarios"), subsurface factors that influence or control the behaviour of CO2 injected into an unconfined, saline aquifer. Using subsurface concepts relevant to the offshore UKCS and under defined geological conditions, we seek to run simulations using representative fluid properties of CO2 to investigate the subsurface factors that most influence or control the behaviour of migrating CO2. In detail, the NSTA expects that any proposal would incorporate, but not be limited to consideration of: • Define and run a series of experimental simulations that could represent the primary controlling factors in plume behaviour when CO2 is injected into an unconfined saline aquifer offshore e.g. plume behaviours within a laterally and vertically heterogenous braided channel sequence where dip is opposed to the main depositional trend. • What are the most important geological parameters that could be considered in scenario testing to understand plume behaviour e.g. what has a higher relative impact on plume behaviour - dip or facies variation? • How might a migrating CO2 plume interact with top and bottom sealing units and what are the implications for plume behaviour?