Rheological Characterization of Olivine Slurries, Sheared Under CO2 Pressure

摘要

The injection of reactive mineral suspensions is a possible process to either reinforce or seal wells in geologic carbon sequestration sites. Among others, olivine slurries could be used as CO2-triggered cements, as they carbonate under the thermodynamic conditions of deep storage. However, injection of such slurries requires to control their initial fluidity and its evolution during the displacement. For this purpose, we have characterized the rheological evolution of olivine suspensions, of particle sizes 1 — 10 μm, sheared at 100 s~(-1), in the ranges of 10—40% for the volume fractions, 20-50 bars for the CO2 pressure, and 60-110°C for the temperature. The apparent viscosity, measured at 100 s~(-1), increases exponentially, with a characteristic time ranging from less than 1 h to more than 10 h, and decreasing with olivine concentration, CO2 pressure, and temperature. Moreover, a careful characterization of the slurry rheology carried out in the initial stages of slow evolution, shows that the slurry obeys a Bingham plastic law, with a yield stress Σ_BB, and a Bingham viscosity μ_B increasing from 1 to 20 Pa and from 4 to 110 mPa s, respectively, when the olivine volume fraction φ is increased from 10 to 30%. Such variations can be accounted by classical models (Wildemuth and Williams [1984]: Rheologica Acta, 23,627-635, Krieger [1972]: Advances in Colloid and Interface Science, 3, 111-136).