Carbonate systems and reservoirs

The carbonate research group in the School of Earth and Environmental Science is led by Dr Cathy Hollis, and comprises a a team of over 10 post-graduate and post-doctoral researchers. Our group is focused upon determination of the processes that govern carbonate porosity distribution at multiple scales, through consideration of the post-depositional evolution of carbonate sediments through time.  Through collaborative, multi-disciplinary research we then evaluate the impact of pore shape, size and connectivity on rock physical properties and fluid flow, in particular on hydrocarbon recovery efficiency.  This is a key challenge in carbonate systems, which have multi-modal pore size distributions, high pore/pore throat ratios and complex pore shapes.

Carbonate rocks have huge economic importance. They host over 50% of the world’s hydrocarbon reserves, and can also host significant volumes of economic mineral resources. They have a simple mineralogy, and yet they are highly heterogeneous on the pore (sub-millimetre) to flow unit (kilometre) scale. This in large part reflects their high chemical susceptibility and their ability to fracture. Furthermore, carbonate rocks form by marine precipitation and the accumulation of organisms. Therefore, understanding their depositional environment requires consideration of the interplay between water depth and temperature, ocean chemistry and circulation patterns, the input of detrital (clastic) material and faunal evolution. All of these factors make prediction of the properties of carbonate rocks extremely challenging.

One of the key challenges in the hydrocarbon industry is to characterise and model carbonate reservoirs, often using limited and ambiguous subsurface datasets. This research area aims to use traditional and digital field and laboratory techniques to constrain the geometry of flow units. To achive this, an understanding of the interplay between carbonate sedimentology, diagenesis, structural geology and pore system analysis is required. Current focus is upon how fluids flow and evolve within the burial environment to generate and occlude porosity, and determination of the petrophysical and flow properties of the resultant pore system. To facilitate this research, we can utilise LIDAR-based digital outcrop analysis, 3D seismic interpretation, petrographical (optical microscopy, cathodoluminescence and scanning electron microscopy), electron microprobe and rock mechanical techniques within the School.


The post-rift Albian, Namibe Basin.
Stromatolitic carbonates in the pre-salt of the Namibe Basin

Key publications

de Azevedo Lima Neto, I., Misságia, R.M., Ceia, M.A., Archilha, N., Hollis , C., 2015. Evaluation of carbonate pore system under texture control for prediction of microporosity aspect ratio and shear wave velocity. Sedimentary Geology. doi:10.1016/j.sedgeo.2015.04.011

Jivkov, A., Hollis, C., Etiese, F., McDonald, S and Withers, P., 2013. A novel architecture for pore network modeling with applications to permeability of porous media. Journal of Hydrology, 486, 246-258.

Hollis, C., 2011. Diagenetic controls on reservoir properties of carbonate successions within the Albian-Turonian of the Arabian Plate. Petroleum Geoscience, 17-3, 223-241.

Hollis, C., Vahrenkamp, V., Tull, S., Mukherji, A., Taberner, C., Huang., Y. 2010. Pore system characterisation in heterogeneous carbonates: an alternative approach to widely used rock-typing methodologies. Marine and Petroleum Geology, 27 (4), 772-793.

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