A pipeline in a remote part of Alberta transports gas to an amine plant for sweetening. Produced water is introduced with the gas into the pipeline at various locations, with the majority entering after a compressor station. The operator was treating the line from the compressor station to the amine plant with 4,000 L [1,055 galUS] of methanol daily to prevent hydrates. However, the methanol carried into the amine plant despite use of a separator at the plant inlet, contaminating the reflux water and increasing corrosion risk. Reducing the amount of methanol led to hydrate formation.
To address the challenge, SLB proposed replacing the methanol with its kinetic hydrate inhibitor GT-7569. The inhibitor was initially applied at a rate of 1,500 L/d [395 galUS/d], about 40% the rate of methanol injection. When pig returns showed no hydrate crystals and pressure at the gas plant inlet held steady (formation of hydrate crystals would have caused a drop), the injection rate was gradually reduced to 700 L/d [185 galUS/d].
Reflux water was analyzed throughout the trial and showed no contamination. The operator saved more than 50% in chemical and operational costs; the inhibitor was removed at the inlet separator and disposed of in the operator's water disposal wells.
