MONITORING FLUID CONCENTRATION AND PHASE CHANGES IN FLOW EXPERIMENTS AT THE PROPOSED DUSEL CO2 FACILITY

DUSEL CO2 is a proposed experimental facility at DUSEL for studying CO₂ migration and trapping mechanisms associated with geologic sequestration of CO₂. The proposed facility consists of three sand-filled long column pressure vessels with a length of ~500 m and a diameter of ~1 m supported within a 3 m-diameter raised bore shaft. Each vessel will have an inner fluid-filled tube with a diameter of ~25 cm designed to house an array of detectors to monitor fluids within the sand-filled annulus during the flow experiments. External heaters will be used to control the temperature and compressors will be used to adjust the pressure gradient. One of the proposed experiments consists of the evaluation of fluid flow processes and associated residual gas trapping and dissolution during the upward rise of a buoyant CO₂ slug in a sand-filled column saturated with brine under hydrostatic pressure and “natural” geothermal gradient conditions spanning the range from supercritical to gaseous conditions for CO₂.

Critical to the experimental facility is the monitoring of fluid conditions at high resolution within the vessels. The tube in the center of each vessel will serve as a proxy well to accommodate a variety of existing down-hole technologies to monitor flow column conditions. A combinable nuclear magnetic resonance tool will be used to discriminate between water and CO₂-filled pores; similar measurements will be conducted using a reservoir saturation tool. Sonic (1-20 kHz) and ultrasonic (100s of kHz) tools will also be used to image fluids, using differences in acoustic impedance to distinguish liquid from gas phases. These measurements will be used to construct a vertical saturation profile, and to determine how it changes over time as the CO₂ plume moves upwards. Distributed temperature and pressure sensors will also be deployed outside of the inner tube to provide continuous in situ data. The various data and interpretations from the suite of technologies deployed will collectively be used to calibrate models that predict the vertical flow of CO₂ and brine in porous media, and to compare the spatial resolution and sensitivity of different logging tools.