Muhammad Ali1, Sarmad Al-Anssari2, Muhammad Arif3, Ahmed Barifcani4, Mohammad Sarmadivaleh5, Linda Stalker6, Maxim Lebedev7, Stefan Iglauer8. 1. Department of Petroleum Engineering, Curtin University, 26 Dick Perry Avenue, 6151 Kensington, Western Australia, Australia; School of Engineering, Edith Cowan University, 270 Joondalup Drive, Joondalup, WA 6027 Australia. Electronic address: Muhammad.ali7@postgrad.curtin.edu.au. 2. Department of Chemical Engineering, Curtin University, Kent Street, 6102 Bentley, Western Australia, Australia; Department of Chemical Engineering, University of Baghdad, Baghdad 10071, Iraq. 3. Department of Petroleum Engineering, Curtin University, 26 Dick Perry Avenue, 6151 Kensington, Western Australia, Australia; Department of Petroleum Engineering, University of Engineering and Technology, G. T. Road, Lahore 54890, Pakistan. 4. Department of Petroleum Engineering, Curtin University, 26 Dick Perry Avenue, 6151 Kensington, Western Australia, Australia; Department of Chemical Engineering, Curtin University, Kent Street, 6102 Bentley, Western Australia, Australia. 5. Department of Petroleum Engineering, Curtin University, 26 Dick Perry Avenue, 6151 Kensington, Western Australia, Australia. 6. Commonwealth Scientific and Industrial Research Organisation (CSIRO), 26 Dick Perry Avenue, 6151 Kensington, Western Australia, Australia. 7. Department of Exploration Geophysics, Curtin University, 26 Dick Perry Avenue, 6151 Kensington, Western Australia, Australia. 8. School of Engineering, Edith Cowan University, 270 Joondalup Drive, Joondalup, WA 6027 Australia; Department of Petroleum Engineering, Curtin University, 26 Dick Perry Avenue, 6151 Kensington, Western Australia, Australia.
Abstract
HYPOTHESIS: CO2 geological storage (CGS) involves different mechanisms which can store millions of tonnes of CO2 per year in depleted hydrocarbon reservoirs and deep saline aquifers. But their storage capacity is influenced by the presence of different carboxylic compounds in the reservoir. These molecules strongly affect the water wetness of the rock, which has a dramatic impact on storage capacities and containment security. However, precise understanding of how these carboxylic acids influence the rock's CO2-wettability is lacking. EXPERIMENTS: We thus systematically analysed these relationships as a function of pressure, temperature, storage depth and organic acid concentrations. A particular focus was on identifying organic acid concentration thresholds above which storage efficiency may get influenced significantly. FINDINGS: These thresholds (defined for structural trapping as a water contact angle θ > 90°; and for capillary trapping when primary drainage is unaffected, i.e. θ > 50°) were very low for structural trapping (∼10-3-10-7 M organic acid concentration Corganic) and extremely low for capillary trapping (10-7 M to below 10-10 M Corganic). Since minute organic acid concentrations are always present in deep saline aquifers and certainly in depleted hydrocarbon reservoirs, significantly lower storage capacities and containment security than previously thought can be predicted in carbonate reservoirs, and reservoir-scale models and evaluation schemes need to account for these effects to de-risk CGS projects.
HYPOTHESIS: CO2 geological storage (CGS) involves different mechanisms which can store millions of tonnes of CO2 per year in depleted hydrocarbon reservoirs and deep saline aquifers. But their storage capacity is influenced by the presence of different carboxylic compounds in the reservoir. These molecules strongly affect the water wetness of the rock, which has a dramatic impact on storage capacities and containment security. However, precise understanding of how these carboxylic acids influence the rock's CO2-wettability is lacking. EXPERIMENTS: We thus systematically analysed these relationships as a function of pressure, temperature, storage depth and organic acid concentrations. A particular focus was on identifying organic acid concentration thresholds above which storage efficiency may get influenced significantly. FINDINGS: These thresholds (defined for structural trapping as a water contact angle θ > 90°; and for capillary trapping when primary drainage is unaffected, i.e. θ > 50°) were very low for structural trapping (∼10-3-10-7 M organic acid concentration Corganic) and extremely low for capillary trapping (10-7 M to below 10-10 M Corganic). Since minute organic acid concentrations are always present in deep saline aquifers and certainly in depleted hydrocarbon reservoirs, significantly lower storage capacities and containment security than previously thought can be predicted in carbonate reservoirs, and reservoir-scale models and evaluation schemes need to account for these effects to de-risk CGS projects.