| Title | CO2 as an EGS Working Fluid--The Effects of Dynamic Dissolution on CO2-Water Multiphase Flow |
|---|---|
| Authors | Stacey, Robert; Pistone, Sarah; Horne, Roland |
| Year | 2010 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | CO2-EGS; Active phase change; Carbon dioxide; Hysteresis; Relative permeability; Dynamic dissolution |
| Abstract | The idea of using carbon dioxide (CO2) as the working fluid in engineered geothermal systems (EGS) has been receiving attention as a means to provide baseload renewable energy while simultaneously sequestering CO2. The research presented herein investigated the fundamental flow behavior of CO2-water system as might be encountered in an EGS reservoir. Experimental and theoretical work was conducted to evaluate the effect of CO2 solubility on the relative permeabilities of the two-phase system. A series of drainage and imbibition cycles were performed on a Berea sandstone core using CO2-water, and N2-water. These core-scale data were used to quantitatively analyze the effect that CO2 dissolution has on relative permeability. A two-dimensional silica micromodel that mimics the pore structure of Berea sandstone was used to qualitatively evaluate the two-phase flow of CO2 and water. A digital camera was used to image the CO2 front as it moved through the micromodel and observed CO2 dissolution and bubble nucleation as the CO2 migrated through the pore network. The theoretical portion of our research uses the bundle of capillary tubes concept combined with Statistical Rate Theory (SRT) to produce a preliminary relative permeability model that included CO2 dynamic dissolution effects compared to results that only consider capillary forces. |