The Effect of Architectural Element Scale Heterogeneities on CO2 Injection, Migration and Storage

Reservoirs within deep-water deposits are well understood for hydrocarbon production, but specific parameters important for CO2 storage are less well constrained. Previous research has shown that a certain level of reservoir heterogeneity is beneficial for CO2 storage, as intra-formational baffles will increase the available surface area for CO2 to react with the reservoir. However, these findings have not been vigorously tested with realistic reservoir geometries.

Here we present a dataset from Eocene-aged deep-water outcrops from the Jaca and Aínsa basins in the Spanish Pyrenees. We collected data on reservoir architecture and heterogeneity to build reservoir models for channel lobe transition zone (CLTZ) architectural elements, and both medial and distal lobe elements, on comparable scales of 10s–100s of metres. The integration of sedimentary logging, sampling and UAV imagery allows for stacking geometries and reservoir quality to be well characterised. The heterogenies of interest here are siltstones and mudstones generally 5–100 cm thick, and metres to 10s of metres in width. Numerical simulations of CO2 injection into these reservoirs demonstrate that although the CLTZ has a higher percentage of net reservoir, the baffles and barriers are not extensive, which will be detrimental for CO2 injection efficiency (total pore space utilisation). Comparatively, medial and distal lobe architectural elements are better injection targets, as the baffles and barriers to flow are more extensive, which will improve CO2 injection efficiency. This work adds to current understanding of how baffles and barriers play a significantly different role for CO2 injection and flow than for conventional hydrocarbon extraction.