Minimizing Scale Precipitation in Carbonate Cores Caused by Alkalis in ASP Flooding in High Salinity/High Temperature Applications

Abstract

Abstract Using an inorganic alkali in alkaline/surfactant/polymer (ASP) flooding resulted in scale precipitation when multivalent cations exist in mixing and/or formation brine in some extended field studies. This issue can be critical in the un-swept zones, which are the major target for EOR process, where formation brines can have high concentrations of Ca2+ and Mg2+. Any precipitation can result in plugging the pores in the target zone and loss of injectivity. Several alkalis were evaluated to assess their scaling potential in high salinity formation brines and seawater as mixing brine at high temperatures. Four alkalis were evaluated; three inorganic alkalis sodium hydroxide, sodium carbonate, and sodium metaborate, and one organic alkali. Eliminating the need to soften the mixing brine will result in expanding the ASP application to more challenging applications and will reduce the softening cost for the mixing water. Preventing precipitation of scale when chemical slug enters the unswept zones will result in improving the efficiency of the ASP flood, reduces chemical consumption and prevent scale precipitation that can cause formation damage and operational problems in the producers.