The Impact of CO2 Saturated Brine on Petrophysical Properties of the Angel Storage Formation

Petrophysical interpretation and modelling plays a key role in assessing storage capacity, injectivity, sealing capacity and ongoing conformance monitoring for a CCS project. To understand any impact the introduction of pure CO2 saturated brine might have on the Angel storage formation petrophysical properties, 20 core plug samples capturing the range of petrophysical property groups representing the Angel storage formation underwent baseline petrophysical measurements. The plugs after static ageing in CO2 saturated brine for 20 and 40-days at in-situ reservoir conditions were re-tested and reimaged to evaluate the impact of static fluid-rock interactions on the petrophysical properties.

The results showed negligeable changes to porosity and a varying increase in permeability. Generally greater increases in permeability were associated with higher permeability samples. SEM images show evidence of pore throat scale microstructural differences and dissolution of reactive dolomitic cement. The study showed that no impairment to the Angel storage formation in place volume capacity would be expected with the introduction and long-term storage of CO2 at the planned injection site within the aquifer. Small scale improvement in permeability could occur at the injection site although this is not expected to propagate far into the formation during injection of CO2.