Laboratory measurements of seismic velocities of CO2/brine mixtures at elevated temperatures up to 70°C and pressures up to 38 MPa

Abstract

Phase equilibrium of CO2-brine fluids is important to studies related to CO2 sequestration in deep saline aquifers and CO2 enhanced oil recovery. Furthermore, the study of the seismic properties of CO2 saturated and not saturated brines as pore fluids helps to understand their influence on the 4D seismic properties of rocks.In this work we reported results of measurements of the acoustic velocities in brines with dissolved CO2. We investigate the effects of pressure (from 2 MPa to 38 MPa), temperature (from 30 °C to 70 °C), and salinity (0, 10,000 ppm, 20,000 ppm, 40,000 ppm, 100,000 ppm) of KCl-NaCl brines on ultrasonic velocities. We also study the time lapse effect of CO2 dissolution into the brine.It has been found that CO2 dissolution in brine has significantly changed acoustic properties of brine.