Experimental Investigation of the Impact of Injection Strategies in CO2 Storage Applications

This study explores the integration of multiple scientific disciplines to address the challenges and opportunities in expanding CO2 storage technologies, particularly in sandstone and carbonate formations. By employing different CO2 injection strategies and varying the salinity of injection water, the research mimics the use of produced water (PW) in Water-Alternating-Gas (WAG) and Supercritical Alternating Injection (SAI) strategies. These approaches aim to enhance CO2 storage capacity while managing PW disposal from the oil and gas industry, offering a dual benefit of environmental impact mitigation and optimized carbon sequestration. Two novel injection strategies were explored in detail and compared with the traditional method. The WAG method successfully preserved rock properties, effectively maintaining mechanical strength and enhancing CO2 trapping efficiency. This method alternates between CO2 and water injections, which dilutes the aggressive effects of CO2 on rock formations and ensures the structural integrity of sandstone and limestone. As a result, WAG offers a more stable long-term storage solution in saline formations by preventing rapid mineral dissolution and helping maintain porosity and permeability. This also affects injected brine salinity below 50g/L. The SAI method, while equally effective in trapping CO2, has been shown to cause more significant changes in the mechanical properties of the rock, especially in high-salinity conditions. This strategy accelerates mineral dissolution, particularly in limestone formations, which leads to a decline in permeability and mechanical strength over time. Though SAI provides an efficient method for CO2 trapping, the mechanical weakening of rock formations under this method poses a higher risk to long-term reservoir stability. Both strategies contribute to an optimized storage mechanism by balancing the effects of salinity, ensuring that key rock properties remain largely intact while providing an environmentally friendly method for PW disposal. The research highlights that salinity variations significantly influence reservoir rocks' geomechanical and petrophysical properties, with the WAG method emerging as a preferred approach for minimizing adverse effects while maintaining CO2 storage efficiency; however, SAI methods gave a detrimental result for both limestone and sandstone. In conclusion, this study emphasizes the significance of the WAG method for the oil and gas industry and broader environmental applications. By integrating CO2 storage with PW management, WAG presents a viable solution for expanding carbon capture and storage (CCS) technologies. Its ability to enhance geological stability, combined with efficient CO2 trapping mechanisms, positions it as a crucial tool in mitigating climate change and advancing the sustainability of energy production practices.