Wettability measurement under high P-T conditions using X-ray imaging with application to the brine-supercritical CO2 system

We present a new method for measuring wettability or contact angle of minerals at reservoir pressure-temperature conditions using high-resolution X-ray computed tomography (HRXCT) and radiography. In this method, a capillary or a narrow slot is constructed from a mineral or a rock sample of interest wherein two fluids are allowed to form an interface that is imaged using X-rays. After some validation measurements at room pressure-temperature conditions, we illustrate this method by measuring the contact angle of CO2-brine on quartz, muscovite, shale, borosilicate glass, polytetrafluoroethylene (PTFE or Teflon), and polyether ether ketone (PEEK) surfaces at 60-71 degrees C and 13.8-22.8 MPa. At reservoir conditions, PTFE and PEEK surfaces were found to be CO2-wet with contact angles of 140 degrees and 127 degrees, respectively. Quartz and muscovite were found to be water-wet with contact angles of 26 degrees and 58 degrees, respectively, under similar conditions. Borosilicate glass-air-brine at room conditions showed strong water-wet characteristics with a contact angle of 9 degrees, whereas borosilicate glass-CO2-brine at 13.8 MPa and 60 degrees C showed a decrease in its water-wetness with contact angle of 54 degrees. This method provides a new application for X-ray imaging and an alternative to other methods.