Unsteady-state CO2-Brine relative permeability measurements of reactive cores

Abstract:

Relative permeability (k_r) of supercritical CO₂ (scCO₂) and brine were determined in rock samples from various representative potential carbon storage reservoirs. A computed tomography (CT) scanner was utilized to determine in-situ saturation at one-minute intervals during core flooding experiments where scCO₂ was displacing brine. The CT scans and flow measurement data were used to derive four empirical constants. These constants were determined by evaluating the post-breakthrough changes in pore volumes injected versus volumes of injected fluids within the core and the pore volumes of injected fluids versus the pressure decline.

Multiple flow rates were used to characterize each sample and determine variability of k_r as a function of flow rate. This provided an opportunity on each flow test to reevaluate the absolute permeability with respect to brine and the total pore volumes injected. This feature of the testing was used to determine k_r in samples undergoing active dissolution, as the dynamic change in permeability and pore dissolution could be accounted for as the test proceeded.

The application of this methodology allowed for the determination of k_r in a rapid fashion (< 10 hours). The raw data and empirical relationships developed with this method have been made publicly available through https://edx.netl.doe.gov/hosting/co2bra/. This methodology facilitated the examination of several depositional environments, including those with reactive cores where the geometry of the pore network is actively evolving.