Effects of Lithology of Deep Layered Geologic Formations on Trapping of Dissolved CO2

Tuesday, 16 December 2014
Elif Agartan1, Abdullah Cihan2, Jens T Birkholzer2, Quanlin Zhou2 and Tissa H Illangasekare1, (1)Colorado School of Mines, Department of Civil and Environmental Engineering, Golden, CO, United States, (2)Lawrence Berkeley National Laboratory, Earth Sciences, Berkeley, CA, United States
Secure and long-term trapping of supercritical CO2 (scCO2) in deep geological formations is important for the reduction of leakage risk. Agartan et al. [2014] through controlled laboratory experiments in a test tank using surrogate fluids for scCO2 and brine showed that the dissolved scCO2 can be stored in geological formations containing low permeability layers, thus effectively enhancing dissolution trapping. As this finding was limited to a few test configurations, its validity was evaluated using a numerical modeling study focusing on the influence of different permeabilities and thicknesses of low permeability layers on trapping of dissolved scCO2. A Finite Volume Method (FVM)-based, single-phase, density and viscosity-dependent flow and transport model was employed to determine the effects of porosity and permeability perturbations, and numerical grid resolution on model results and density-dependent finger formations. The experimental data, generated by Agartan et al. [2014], was used to demonstrate the ability of the model to capture the observed transport behaviors. To demonstrate the role of heterogeneity characterized by layering on dissolution trapping at field-scale, a two-dimensional numerical model containing a geological structure similar to the Utsira formation in the Sleipner field was used in a set of test simulations. This formation provided a good test setting as it has the similar features with shale layers interbedded in-between composite sand layers that were used in the experiments. The results highlight that the thicker and lower permeability layers are able to store significant amounts of dissolved scCO2 for a long time. On the other hand, although the thinner and higher permeability layers slow down the vertical spreading, they cannot trap dissolved mass long enough to contribute the storage through immobilization. These findings have practical implications as effective strategies can be developed to enhance trapping by taking the advantage of natural heterogeneity of the formation.
Agartan, E., L. Trevisan, A. Cihan, J. Birkholzer, Q. Zhou, and T.H. Illangasekare (2014), Experimental Study on Effects of Geologic Heterogeneity in Enhancing Dissolution Trapping of Supercritical CO2, Water Resour. Res., (in review).