Geological storage of CO2 – Reservoir Engineering Considerations
Speaker: Mehran Pooladi-Darvish, Fekete Associates
CMC Research Project: Secure storage of impure CO2 in the form of solid hydrate in depleted gas pools in northern Alberta
Location: Calgary Petroleum Club, Devonian Room, 11:45 a.m.
Registration Deadline: Noon on February 5, 2012
Carbon dioxide under the pressure and temperature conditions encountered in most geological settings remains more buoyant than water. However, CO2-hydrate formation – that leads to trapping of CO2 in the solid form – provides the opportunity for secure storage of CO2.
Thermodynamic calculations suggest that CO2 hydrate is stable at temperatures that occur in a number of formations in northern Alberta, in an area where significant CO2 emissions are associated with production of oil sands and bitumen. Simulation results are presented demonstrating that upon CO2 injection into such depleted gas reservoirs, pressure would initially rise until conditions are appropriate for formation of hydrates, enabling storage of large volumes of CO2 in solid form. Numerical results suggest that because of tight packing of CO2 molecules in the solid (hydrate), the CO2 storage capacity of these pools, is many times greater than their original gas in-place. This provides a local option for storage of a portion of the CO2 emissions there.
Permanent trapping of CO2 at a depth of a few hundred meters beneath the ocean floor, where it is of little or no harm to the ocean ecosystem, is also presented. Simulation results indicate that injection of CO2 at a few hundred meters below the ocean floor, would lead to rise of the CO2 until it arrives at a depth where its density becomes heavier than water. The zone above this depth, where CO2 becomes heavier than water is called the negative buoyancy zone (NBZ). Beneath the negative buoyancy zone, the CO2 may become naturally trapped by a gravity barrier. Furthermore, formation of CO2 hydrate will further reduce permeability and introduce a second barrier against CO2 rise.