Chemical Inhibition of Halite Scaling in Topsides Equipment

Abstract

Abstract Carbonate or sulphate scaling is usually mitigated by using chemical inhibitors that alter the growth mode of the scale mineral, but with halite scaling the apparent absence of a suitable inhibitor has meant that periodic removal with low-salinity water has been favoured. We report laboratory testing and the first field application of a chemical inhibitor for halite scaling. The inhibitor was field-tested in the Leman gas field (North Sea), where halite scaling occurs in gas-compression equipment due to evaporation of water from brine droplets carried over from the gas-water separator. The scale reduces the efficiency of both compressor and cooler, necessitating regular costly cleaning of the internals. After a recent system clean out, the cheap, non-toxic halite inhibitor was dosed continuously for 3 months into the production stream downstream of the gas-water separator. Whilst halite deposition was not completely suppressed, an increase in compressor efficiency was observed for all compression stages compared with recent non-inhibited data. A significant improvement in gas-cooler efficiency and a reduced tendency to block gas-flow meters, were also observed. This indicates that the inhibitor has considerable potential for cost-effective control of halite scaling, possibly as an alternative to periodic removal or in combination with it.