DC6-PhD: Use of Invasion Percolation methods to model gravity segregation in CO2/HC/brine systems

This PhD research concerns the processes which control CO2 migration in complex rock systems. We will look at this from a geochemical and geomechanical point of view, mainly using the Invasion Percolation (IP) method, and comparing this to other multi-phase modelling approaches. As CO2 migrates upwards through a rock system, due to buoyancy forces, it gets held back by capillary interfaces. The IP method is ideal for studying these migrating clusters of CO2. Open CO2 storage site datasets will be used to test and demonstrate these concepts. The main output of the PhD will be an improved understanding of CO2 migration in saline aquifer storage systems, including fluid mixing and possible leakage scenarios.

Objectives: Advance in the understanding of gravity segregation of CO2, hydrocarbon (HC) and brine systems by enhancing modelling capabilities of mixing HC and CO2 phase in highly heterogeneous brine-saturated rock, coupling Invasion Percolation approach with geomechanics

Expected Results: Project will mainly use the Permedia® modelling tool which has been widely applied to CO2 migration problems, as well as various open source research codes to develop enhancements for handling fluid mixing between HC and CO2 phases in brine-saturated media. The Invasion Percolation modelling approach has the advantage of being able to solve CO2 migration phenomena in very high-resolution rock models, but generally neglects fluid exchange and mixing phenomena. Simplified fluid mixing functions (e.g., flash calculations with gravity segregation) would be applied to a range of scenarios in order to better understand gravity segregation in CO2/HC/brine systems as well as application to hydrogen storage. The Invasion Percolation solutions will be tested against multiphase-flow models of the same system in order to improve the Invasion Percolation formulation for CO2 migration problems. Methods for improved handling of the fluid pressure field, which is normally neglected in conventional Invasion Percolation models, will also be developed. The calculation of the fluid pressure field will be used to incorporate, in collaboration with DC 5, the geomechanical response of the rock to CO2 injection. The concept of separately solving the brine-phase pressure field and then modifying the threshold pressures which control the percolating CO2 clusters will be developed and tested using the database of CO2 storage sites provided by Equinor. The approach could lead to much improved methods for handling CO2 migration problems within saline-aquifer CO2 storage systems, both at the reservoir and basin scales.

Doctoral Candidate: Mateja Macut

Host Institution: Norwegian University of Science and Technology

Secondments: ETH Zurich, Consejo Superior de Investigaciones Científicas (CSIC)