Flood characteristic and fluid rock interactions of a supercritical CO2, brine, rock system: South West Hub, Western Australia

- High levels of residually trapped CO2 may be expected in the Lesueur Sandstone of the South-West Hubas measured by core-flood experiments.
- The post-flood samples showed about 25%-60% reduction in permeability while the changes in their porosity values were almost negligible.
- The results of all the auxiliary analysis performed point towards fines migration to be the likely cause of the permeability reductions observed.
- Given the characteristics of the Lesueur Sandstone, results presented may be relevant for most sandstone storage sites globally.

Chemical and/or physical interactions between the storage rock and injected and in-situ created solutes are expected to occur during many underground CO2 storage projects. The intensity of the reactions, however, depends on the abundance of susceptible minerals (e.g. carbonates, clays) in the pore space of the host rock. Such interactions may impact on the multiphase flow characteristics of the underground fluids-rock system over short as well as long time frames.In this research the in-situ multiphase flow characteristics of four sandstone samples have been investigated using a set of laboratory measurements. The samples tested were taken from the Wonnerup Member of the Triassic Lesueur Sandstone which is under consideration as a storage formation in the South-West Hub CO2 geo-sequestration site in Western Australia.All the samples tested show favourable characteristics in terms of storage capacity in the form of residual capillary trapping with residual CO2 saturation varying between 23% and 43%. They underwent a degree of alteration to their petrophysical characteristics which was most significantly pronounced in the case of their absolute gas permeability which showed drops of 25%-60% in the post-flood samples. Formation damage by fines migration is proposed as a mechanism for the observed reduction in permeability. The fines are believed to have originated from the kaolinite particles present in the pore space of the samples.