Physico-chemical and dielectric parameters for the monitoring of carbon sequestration in basalt and silica media

Abstract

Abstract Currently, there are concerns about the safety of carbon sequestration in the geological media. To assuage this concern, scientists and engineers have the tasks to demonstrate fool-proof and comprehensive techniques that can monitor the movement, or otherwise, concentration of the injected CO2 in the subsurface. In this work, well-defined laboratory experiments were used to demonstrate the key physico-chemical characteristics and dielectric parameters that are useful in monitoring carbon sequestration sites. The porous materials used were basalt and silica sand samples to demonstrate the possibility of CO2 injection into different media. To simulate the resident fluids, distilled and brine water samples were used in separate experimentations. Also, the pressures and temperatures were chosen to correspond to different geological depths which are relevant for CO2 injection. The pH, bulk electrical conductivity ( σ b ) and bulk dielectric permittivity ( e b ) of the system were measured for the two different media. On one hand, the decrease in pH was clearly observed in both the basalt and silica sand after the exposure to CO2. On the other hand, σ b and e b increased as CO2 was injected. Our results further revealed a higher ion mobilisation​ potential in basalt medium than that in silica sand. This results in lower pH and higher electrical conductivity in the basalt medium than the silica medium. Thus, a simultaneous measurement of pH, σ b and e b are proposed as a multiparameter approach to monitor CO2 leakage from the storage reservoir. As far as we are aware, this is the first work in the open literature that reports simultaneous dielectric and electrical behaviours of CO2 –water–porous media system for basalt porous medium in connection with carbon sequestration.