Aluminum silicate scale formation and inhibition (2): scale solubilities and laboratory and field inhibition tests

The solubilities of pure silica\ iron!silicate and aluminum!silicate scales were measured in water from 14 149>C in a laboratory pressure reactor[ Iron! and aluminum!silicate scales are signi_cantly less soluble than pure amorphous silica[ Aluminum! and iron!rich silica scales at equilibrium con! ditions are predicted to deposit from near!neutral\ low salinity brines at tem! peratures that are 14 and 64>C above the saturation point for pure amorphous silica\ respectively[ This laboratory study demonstrates that higher brine injec! tion temperatures are required to mitigate aluminum! and iron!rich silica scaling compared with pure amorphous silica[ In a laboratory scale test\ pure amorph! ous silica and aluminum!rich silica deposition rates have been measured at high degrees of supersaturation in the presence of potential inhibitors[ Scale deposition was best inhibited by brine pH modi_cation techniques[ A com! mercially available dispersant successfully inhibited amorphous silica scalingbut exacerbated aluminum silicate scaling[ Scale inhibition was also achieved in the presence of aluminum complexing:sequestering agents in a patent!pending process[ Screening of these potential silica! and aluminum!silicate scale inhibi! tors in the laboratory will focus the e}orts of ongoing _eld pilot scale testing[ The e}ect of complexing:sequestering agents on scale inhibition was monitored in preliminary _eld pilot tests[ These complexing agents achieved 14) to 79) aluminum silicate scale inhibition[ 0887 CNR[ Published by Elsevier Science Ltd[ All ri`hts reserved