CO2 Sequestration in Saline Formation

Deep saline aquifers are reported to have the largest estimated capacity for CO2 sequestration. Knowledge of possible geochemically-induced changes to the porosity and permeability of host CO2 storage sandstone and seal rock will enhance our capability to predict CO2 storage capacity and long-term reservoir behavior. An experimental study of the potential interaction of CO2/brine/rock on saline formations in a static system under CO2 sequestration conditions was conducted. Chemical interactions in the Mount Simon sandstone environment upon exposure to CO2 mixed with brine under sequestration conditions were studied. Samples were exposed to the estimated in-situ reaction conditions for six months. The experimental parameters used were two core samples of Mount Simon sandstone; Illinois Basin model brine; temperature of 85 degrees C, pressure of 23.8 MPa (3,500 psig), and CO2. Micro-CT, CT, XRD, SEM, petrography, and brine, porosity, and permeability analyses were performed before and after the exposure. Preliminary permeability measurements obtained from the sandstone sample showed a significant change after it was exposed to CO2 saturated brine for six months. This observation suggests that mineral dissolution and mineral precipitation could occur in the host deposit altering its characteristics for CO2 storage over time.