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Wettability is one of the main parameters controlling CO2 injectivity and the movement of CO2 plume during geological CO2 sequestration. Despite significant research efforts, there is still a high uncertainty associated with the wettability of CO2/brine/rock systems and how they evolve with CO2 exposure. This study, therefore, aims to measure the contact angle of sandstone samples with varying clay content before and after laboratory core flooding at different reservoir pressures, of 10 MPa and 15 MPa, and a temperature of 323 K. The samples’ microstructural changes are also assessed to investigate any potential alteration in the samples’ structure due to carbonated water exposure. The results show that the advancing and receding contact angles increased with the increasing pressure for both the Berea and Bandera Gray samples. Moreover, the results indicate that Bandera Gray sandstone has a higher contact angle. The sandstones also turn slightly more hydrophobic after core flooding, indicating that the sandstones become more CO2-wet after CO2 injection. These results suggest that CO2 flooding leads to an increase in the CO2-wettability of sandstone, and thus an increase in vertical CO2 plume migration and solubility trapping, and a reduction in the residual trapping capacity, especially when extrapolated to more prolonged field-scale injection and exposure times.

Wettability in unconventional reservoirs is poorly understood. However, it plays a fundamental role in fluid-rock interactions, and an understanding of wetting behavior is essential for capillary seal assessments and hydrocarbon reserve estimation and recovery in clay-rich reservoirs. In this study, the wetting behavior of transitional Shanxi-Taiyuan shale from the southern North China basin was examined via the contact angle (CA) and spontaneous imbibition (SI) measurement methods. Under water-air-shale conditions, water-wet and neutral-wet behaviors were observed, whereas neutral-wet and oil-wet behaviors were observed under water-oil-shale conditions (Young's equation was used to convert the water-air-shale system to the water-oil-shale system). When the CA method was used, the shale was shown to be hydrophobic, whereas when the SI test was used, the shale was observed to be hydrophilic. The water-air CAs are negatively correlated with the total organic content (TOC), carbonate and clay mineral contents (excluding those of illite). Furthermore, iron-containing compounds, such as pyrite and siderite, were shown to decrease the water wetness. A linear negative correlation was found between the surface roughness and the CA value. The relationship between these parameters can be used to predict the CAs at different surface roughness values for a given sample. The contradictory wetting behaviors between the results of SI and CA methods can be explained by: (i) differences between the CAs formed under water-air-shale conditions and those formed under hydrocarbon-brine-shale conditions; (ii) differences in the surface roughness, which is dependent on the texture and mineralogy of the shale sample; and (iii) clay swelling after water sorption and the formation of microfractures due to water–rock interactions.

This research evaluated the wettability characteristics of CO2-brine-rock-clay mineral systems. Wettability is the key physicochemical factor that controls multiphase flow in porous media and influences geological containment security and storage capacities. The study aimed at accurately characterising the wettability of rock and minerals in the presence of CO2 and brine. This work will improve prediction of CO2 storage capacity and containment security, which has important implications for assessing the feasibility of long-term CO2 sequestration projects.

Fauziah, C. A., Al‐Yaseri, A. Z., Al‐Khdheeawi, E. A., Feng, R., Lagat, C., Roshan, H., . . . Barifcani, A. (2021). Dependence of clay wettability on gas density. Greenhouse Gases: Science and Technology, 11(5), 1066-1075. https://doi.org/10.1002/ghg.2118

Al-Yaseri, A., Wolff-Boenisch, D., Fauziah, C. A., & Iglauer, S. (2021). Hydrogen wettability of clays: Implications for underground hydrogen storage. International Journal of Hydrogen Energy, 46(69), 34356-34361. https://doi.org/10.1016/j.ijhydene.2021.07.226

Fauziah, C. A., Al-Yaseri, A., Al-Khdheeawi, E., Jha, N. K., Abid, H. R., Iglauer, S., . . . Barifcani, A. (2021). Effect of CO2 flooding on the wettability evolution of sand-stone. Energies, 14(17), article 5542. https://doi.org/10.3390/en14175542

Fauziah, C. A., Al-Khdheeawi, E. A., Iglauer, S., & Barifcani, A. (2020, June). Influence of Total Organic Content on CO–Water–Sandstone Wettability and CO Geo-Storage Capacity. In SPE Europec featured at 82nd EAGE Conference and Exhibition. Society of Petroleum Engineers. https://doi.org/10.2118/200564-MS

Al-Khdheeawi, E. A., Mahdi, D. S., Ali, M., Fauziah, C. A., & Barifcani, A. (2020, October). Impact of caprock type on geochemical reactivity and mineral trapping efficiency of CO [Paper presentation]. Offshore Technology Conference Asia, Kuala Lumpar, Malaysia. https://doi.org/10.4043/30094-MS

Fauziah, C. A., Al-Khdheeawi, E. A., Iglauer, S., & Barifcani, A. (2020, October). Effect of clay minerals heterogeneity on wettability measurements: Implications for CO 2 storage [Paper presentation]. Offshore Technology Conference Asia, Kuala Lumpar, Malaysia. https://doi.org/10.4043/30449-MS

Fauziah, C. A., Al-Yaseri, A. Z., Jha, N. K., Lagat, C., Roshan, H., Barifcani, A., & Iglauer, S. (2020). Carbon dioxide wettability of South West Hub sandstone, Western Australia: Implications for carbon geo-storage. International Journal of Greenhouse Gas Control, 98, 103064. https://doi.org/10.1016/j.ijggc.2020.103064

Fauziah, C. A., Al-Khdheeawi, E. A., Barifcani, A., & Iglauer, S. (2019, October). Wettability measurements of mixed clay minerals at elevated temperature and pressure: Implications for CO2 geo-storage. In SPE Gas & Oil Technology Showcase and Conference. Society of Petroleum Engineers. https://www.onepetro.org/conference-paper/SPE-198591-MS