Storage of CO2 as hydrate in depleted gas reservoirs

With the increasing concern about climate change, the public, industry, and government are showing increased interest toward reducing carbon dioxide (CO,) emissions. Geological storage CO. is perceived to be one of the most promising methods provide significant reduction in CO, emissions over the short medium term. However, one major concern regarding geological storage of CO. is the possibility of leakage. CO. under the pressure and temperature conditions encountered in most geological remains more buoyant than water. Processes that could lead permanent trapping of CO2 include geochemical reactions, with formation of solid minerals. This trapping mechanism is attractive because it converts the CO, into a solid compound. However, time scale of such reactions is perceived to be centuries to millennia. In contrast, the kinetics of CO,-hydrate formation leading to trapping of CO, in the solid form is quite fast, providing opportunity for long-term storage of CO,. In this paper, geological settings suitable for formation of CO, hydrate are investigated. study storage of CO2 in depleted gas pools of northern Alberta. Thermodynamic calculations suggest that CO. hydrate is stable at temperatures that occur in a number of formations in northern Alberta, in an area where significant CO, emissions are associated with production of oil sands and bitumen. Simulation results presented in this paper suggest that, upon CO, injection such depleted gas reservoirs, pressure would initially rise conditions are appropriate for hydrate formation, enabling of large volumes of CO, in solid form. Numerical-simulation results suggest that, because of tight packing of CO, molecules in the solid (hydrate), the CO. storage capacity of these pools many times greater than their initial-gas-in-place capacity. provides a local option for storage of a portion of the CO, emissions there. In this paper, we study the storage capacity of such depleted gas pools and examine the effect of various reservoir properties and operating conditions thereon. In particular, we study the effect of the in-situ gas in formation of mixed-gas hydrates the effect rise in temperature as a result of the exothermic reaction of hydrate formation; the effect of initial reservoir pressure, temperature, porosity; and conditions for avoiding the deleterious formation hydrate around the wellbore. Copyright © 2012 Society ot Petroleum Engineers.