Low-salinity waterflooding has been an emerging EOR/IOR technique in the recent times. LSW-alternating-CO2 injection has been particularly strong in yielding higher oil recoveries in some cases. Limited simulation studies haven been performed to properly exhibit the interpretation of experimental studies in this area.
Low permeability sandstones of significant clay content, and heavy west Texas crude oil with 29 °API were targetted for evaluating the potentials of LSWF and CO2 flooding. Coreflood experiments were conducted and interpreted by reservoir simulation, which enabled a better understanding of the underlying science of the studied IOR and EOR techniques. Five secondary waterflooding experiments and two LSW, CO2 hybrid processes were performed using aged 3 in. outcrop grey bandera sandstone cores. The wettability of the rock was tested using axisymmetric contact angle measurements to study the effect of injected brine salinity. The interfacial tension values were measured for the different brines and heavy crude oil systems. The corefloods were interpreted using reservoir simulation, by history matching the experimental oil RF and the pressure drop across the core. A detailed focus was laid on interpretation of SCAL relative permeability curves for the various waterflooding operations, by comparing curves generated from published correlations, history matched curves by simulation and that by Corey's correlations.
Fines migration and viscosity override of low salinity waters over heavy oil were highly influential on the oil recovery profile during low salinity waterflooding. Wettability alteration proved as effective during low salinity waterflooding, for longer injection and production periods. Corey's exponents were found to be premature indications of rock wettability during LSWF, proving importance and reliability of experimental wettability characterization. Low-salinity wateflooding proved to be marginally effective than conventional waterflooding for sandstones with high clay contents and low permeabilities. Low permeability sandstone reservoirs proved as great targets for Hybrid EOR techniques utilizing CO2 and LSW.