Accurate laboratory measurements and analysis of electrical properties of core samples are a prerequisite step to the evaluation of oil and gas reserves. In recent times, this evaluation technique has been adopted in carbon dioxide sequestration projects for estimating and monitoring carbon dioxide (CO₂) accumulation in saline aquifers. Several papers have reported laboratory success in the use of resistivity measurements to monitor the flow and also estimate the volume of CO₂ plume in geological formations. Such laboratory experiments did not capture the effect of CO₂ -brine-rock interaction (CBRI) on saturation estimation. The possibility of a change in value resistivity due to CO₂/brine/rock interactions, and the possible effect on CO₂ monitoring and estimation are of immediate interest here. Preliminary results of an ongoing research work showed that a much longer experiment time accommodates CO₂-brine-rock interaction which ultimately lead to change in rock resistivity. We hereby present the electrical behavior of carbonates to CO₂/ brine/rock interaction during prolonged CO₂ sequestration and the effect on saturation estimation. This electrical behavior and its possible effect on CO₂ monitoring and estimation are discussed.