Simulation of CO2 Sequestration

The disposal of carbon dioxide (C02) in deep saline aquifers and oil reservoirs is one of the options being considered for mitigation of greenhouse gas emissions. C02 sequestration was simulated using the UTCOMP compositional simulator. For disposal and containment of C02 into deep, brine-saturated formations, an idealized 2D vertical cross-section of an aquifer was simulated and then the effect of various factors such as brine salinity, permeability heterogeneity, the ratio of vertical to horizontal permeability, physical dispersion, boundary conditions, etc were studied. Brine salinity, heterogeneity, the ratio of vertical to horizontal permeability and residual gas saturation all had a significant effect on the C02 injectivity, how much C02 could be stored in the aquifer and what fraction of the C02 was dissolved in the brine after 1000 years of storage. Preliminary studies on the effect of dispersion and diffusion suggest that these phenomena are negligible within the aquifer under the assumed conditions and for times up to 1000 years. However, diffusion coupled with geochemical reactions that were not modeled could possibly have a long-term effect on the overburden or sealing faults, so much more simulation research is needed to evaluate these potentially important mechanisms. Trapping of C02 in the form of carbonate minerals also needs to be included in future studies. A grid refinement simulation of the base case showed that the main trends in the transport of the C02 within the formation could be captured with the coarse grid. All of these conclusions are based on the results of preliminary simulations performed with a number of assumptions and for an idealized 2D aquifer. However, they do serve to illustrate the benefits of numerical simulation. A three-dimensional simulation showed similar results as for the base case 2D simulation. A few simulations were completed for C02 injection into a typical depleted oil reservoir that might be a candidate for both enhanced oil recovery and C02 sequestration.Petroleum and Geosystems Engineerin