Graham Benham (University of Cambridge)Cambridge Fluids Network - fluids-related seminars2 December 2021 11:30amOpen Plan Area, BP Institute, Madingley Rise CB3 0EZThe injection of CO2 into porous subsurface reservoirs is a technological means for removing anthropogenic emissions which relies on a series of complex porous flow properties. During injection, geological heterogeneities, often in the form of sedimentary layering, can play a significant role on CO2 migration through the action of small-scale capillary forces. Despite the sensitivity of the flow to these heterogeneities, it is difficult to quantify them with detailed field measurements owing to the vast range of scales involved, presenting an outstanding challenge. In this talk I will use some simple modelling approaches to investigate different types of heterogeneities and how they may affect CO2 migration, making comparisons with both field data and analogue experiments. To start with I will investigate the case of constant injection beneath an impermeable caprock, for which the CO2 spreads out as a two-phase gravity current. Modelling this with an upscaled thin-film equation facilitates studying many different arrangements of sedimentary layers to create ensemble forecasts for injection scenarios (as well as the uncertainty associated with such forecasts). I will discuss the role of heterogeneities in post-injection migration, as well as the different mechanisms for trapping CO2. Finally, I will cover some recent work studying injection in extremely heterogeneous media, for which large pressure gradients due to impermeable layers may delay transition to a buoyancy-driven flow for 1-100 years.