Effect of Salinity and Pressure on the Rate of Mass Transfer in Aquifer Storage of CO2

Abstract

SUMMARYThe growing concern about global warming has increased interest in improving the technology for the geological storage of CO2 in aquifers. One important aspect for aquifer storage is the rate of transfer between the overlying gas layer and the aquifer below. It is generally accepted that density driven natural convection is an important mechanism that enhances the mass Transfer rate.There is a lack of experimental work that study the transfer rate into water saturated porous medium at in-situ conditions, i.e., above critical temperatures and at pressures above 60 bar. Representative natural convection experiments require relatively large volumes (e.g., a diameter 8.5 cm and a length of 23 cm). We studied the transfer rate experimentally for both fresh water and brine (2.5, 5 and 10 w/w %). The experiment uses a high pressure ISCO pump to keep the pressure constant. A log-log plot reveals that the mass transfer rate is proportional to t^0.8, and thus much faster than the predicted by Fick's law. Moreover, the experiments show that natural convection currents are weakest in highly concentrated brine and strongest in pure water.

Effect of Formation Heterogeneity on CO2 Dissolution in Subsurface Porous Media

“…CO 2 is stored in deep saline aquifers by four primary trapping mechanisms: structural, residual, dissolution, and mineral trapping. Even though residual trapping is dominant at the early stages of CO 2 storage, dissolution trapping becomes the primary trapping mechanism with time, capturing almost two-thirds of CO 2 injected in the storage volume. − The precursor for dissolution trapping is a slow process of molecular diffusion. However, the dissolution rate increases subsequently by other mechanisms such as density-driven convection or Rayleigh–Taylor instability, dispersion, and advection. , Several factors can affect the convective-dissolution phenomenon for different geological sites and therefore need to be considered for accurate CO 2 storage prediction.…”