Original Research Article Impact of geochemical and geomechanical changes on CO 2 sequestration potential in sandstone and limestone aquifers Arshad Raza , Department of Petroleum & Gas Engineering, University of Engineering and Technology (UET), Lahore, Punjab, Pakistan Raoof Gholami, Department of Petroleum Engineering, Curtin University, Sarawak, Malaysia Minou Rabiei and Vamegh Rasouli, Department of Petroleum Engineering, University of North Dakota, Grand Forks, North Dakota, USA Reza Rezaee, WA School of Mines: Minerals, Energy and Chemical Engineering, Curtin University, Bentley, Australia Nikoo Fakhari, Department of Chemical Engineering, Curtin University, Sarawak, Malaysia Abstract: CO 2 storage in different geological formations has been recognized as one of the promising mitigation approaches to reduce the emission of CO 2 into the atmosphere. There are many complex hydro-chemo-mechanical interactions (effective stress changes, water acidifcation, and mineral dissolution) that may take place in a storage site during or after injection, reducing the integrity of formations in the short or long term. Although there have been several studies carried out in the past to assess the feasibility of sandstones and limestone formations as a safe CO 2 storage site, the effect of hydrological, mechanical, and chemical processes on the storage site integrity has not been deeply addressed. The aim of this study is to couple thermo-hydro-chemo-mechanical processes upon CO 2 injection and assess their impact on the key storage aspects of quartz-rich sandstone and calcite-rich limestone. A numerical model was built to simulate CO 2 fooding into a saline aquifer with sandstone and limestone composition for 500 years. The results obtained indicated that geochemical activity and CO 2 dissolution are signifcantly higher in limestone and may increase the porosity by 16%. During injection, a decrease in the reservoir strength was observed in both rock types upon exposure to CO 2 . A remarkable variation in the geomechanical characteristics was also revealed in the sandstone after injection. However, ground displacements (subsidence) of 0.0017 and 0.033 m were, respectively, observed in sandstone and limestone aquifers, at the end of 500 years. It is recommended to consider a high-strength reservoir for carbon capture and storage (CCS) projects in order to reduce the likelihood of compaction. It was also found that both rock types have a good storage capacity, Correspondence to: Arshad Raza, Department of Petroleum & Gas Engineering, University of Engineering and Technology (UET), Lahore, Punjab 54890, Pakistan. E-mail: arshadraza212@gmail.com Received May 25, 2019; revised June 18, 2019; accepted July 3, 2019 Published online at Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/ghg.1907 C  2019 Society of Chemical Industry and John Wiley & Sons, Ltd. Greenhouse Gas Sci Technol. 9:905–923 (2019); DOI: 10.1002/ghg.1907 905