THE IMPACT OF RESERVOIR CONDITIONS ON WETTING AND MULTIPHASE FLOW PROPERTIES MEASUREMENTS FOR CO2-BRINE-ROCK SYSTEM DURING PRIMARY DRAINAGE

摘要

The wettability of CO2-brine-rock systems will have a major impact on the management of safe carbon sequestration in subsurface geological formations. The wetting properties of a system controls the mobility and trapping efficiency of CO2 during injection processes for carbon storage as well as for enhanced oil recovery operations. Recent contact angle measurement studies have reported significantly different wetting behaviour with regard to pressure,temperature and water salinity. We report the results of an experimental investigation into the wetting properties of CO2 and brine solutions in a single Berea sandstone utilising measurements of the multiphase flow properties under a wide range of reservoir conditions with pressures(5 to 20 MPa),temperatures(25 to 50 °C)and ionic strengths(0 to 5 M kg-1 NaCl). Primary drainage capillary pressure curves were measured in a horizontal core flooding apparatus using the semi-dynamic method to investigate the wetting properties during CO2 injection process. The observations were made using a reservoir condition core-flooding laboratory that included high precision pumps,temperature control,the ability to recirculate fluids for weeks at a time and in situ saturation monitoring with x-ray CT scanner. The wetted parts of the flow-loop are made of anti-corrosive material that can handle co-circulation of CO2 and brine at reservoir conditions. Measurements in the Berea sample were made using CO2-brine and N2-water. The capillarity of the system,scaled by the interfacial tension,were equivalent to the N2-water system. Thus reservoir conditions did not have a significant impact on the capillary strength of the CO2-brine system through a variation in wetting. The capillarity is consistent with general characteristics of drainage in strongly water-wet rocks. The fluid distributions were observed using x-ray computed tomography and the spatial saturations were investigated and were found to be invariant with different reservoir conditions in homogeneous samples.