Suitability of the Dryland Fluvial-Aeolian Sediments and Its Depositional System for CO₂ Sequestration, Analogues Study from Umbum Creek, Lake Eyre, Central Australia

Saju Menacherry¹, Simon Lang², Tobias Payenberg³, and John Kaldi^4
1Australian School of Petroleum, University of Adelaide, Adelaide, SA, Australia
²Woodside Energy Ltd, Perth, WA, Australia
³Chevron Energy Technology Pty Ltd, Perth, WA, Australia
⁴Australian School of Petroleum, University of Adelaide, Adelaide, SA, Australia

The efficiency of CO₂ geological storage is determined by the depositional system of the sedimentary basins, in which the storage reservoir qualities of subsurface reservoir rocks are primarily controlled by their composition, texture and grain size. The ability to quantifiably predict such porosity and permeability is a significant factor in storage reservoir quality forward modeling
The degree of reaction, reaction rates and mineralogical storage of CO₂ are dependent on mineral assemblage, concentration of CO₂ in the gas and CO₂-water ratios. Immediately after injection, the CO₂ will be stored as a free phase within the host rock. Over time, it will dissolve into the local formation water and initiate a variety of geochemical reactions.

Sediments from the modern dryland fluvial-aeolian Umbum Creek, western Lake Eyre Basin, Central Australia reflect the nature of the hinterland region, drainage basin and depositional environment. Initial rock compositions such as mineralogy, texture and grain size are the main influence on geochemical processes to become permanently trapped in the sedimentary basin by ‘ionic’ or ‘mineral’ trapping.

In the case of the Umbum Creek sands, the medium to coarse grain size, 88-92% of quartz, less than 2% of feldspar and less than 10% of lithic fragments, together with subrounded to rounded grains, moderately well sorting and very little in clay content, leads to a suitable candidate for good storage reservoir quality, if buried. However, the high evaporation conditions in the terminal splay complex environment lead to the growth of gypsum, anhydrite and salt in the sands. A similar analysis of a sedimentary basin could lead to a better assessment of CO₂ geological storage quality prior to sequestration.

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