Experimental Rig to Improve the Geophysical and Geomechanical Understanding of CO2 Reservoirs

Abstract

We intend to perform experiments that simulate real Carbon Capture and Storage (CCS) conditions in the laboratory, and hence provide the necessary knowledge to interpret field seismic surveys. Primarily, our research is focused on determining seismic rock properties (i.e., wave velocities and attenuation) of real and artificial 50mm diameter brine-CO2-bearing sandstone and sand samples that are representative host rocks of real CCS scenarios. Accordingly, we have integrated into a new triaxial cell system both an ultrasonic pulse-echo method for accurate velocity (± 0.3%) and attenuation (± 0.1dB cm-1) measurements, and an electrical resistivity tomography (ERT) method to monitor homogeneity of pore fluid distribution within the samples. The use of ERT provides calibration data for field scale techniques (such as marine controlled source electromagnetic surveying) but also allows measurements of bulk resistivity, fluid diffusion monitoring, flow pathway characterization, and determination of the relative permeability for different brine/brine-CO2 ratios. By simultaneously measuring ultrasonic P- and S-wave velocities and electrical resistivity, we also provide data for joint inversion of seismic and electric field data. Furthermore, the stress-strain behaviour of the sample is continuously monitored with the aid of electrical gauges, so that we deal consistently and simultaneously with the geophysical and geomechanical response of the reservoir when submitted to CO2 injections.