To reduce the volume of chemicals required to treat hydrates and eliminate produced water contamination and pipeline corrosion risk associated with methanol carryover into the amine plant, a hydrate inhibitor program using GT-7569 kinetic hydrate inhibitor was initiated. Not only were these goals met, but chemical and operational costs were lowered by more than 50%.

Decrease hydrate formation, produced water contamination, and corrosion risk

A gas pipeline in a remote area of Alberta was used to transport approximately 90,000 ft³/d [2,430 m³/d] of gas across difficult terrain to a remote amine plant. Produced water was introduced into the pipeline at various locations throughout the system, with the majority of produced water entering the pipeline after a compressor station.

The pipeline connecting the compressor station to the gas plant was treated with 1,057 galUS [4 m³] of methanol to prevent hydrate formation in the gas pipeline. Although methanol is effective at reducing hydrates, it contaminates the produced water, increases corrosion risk to the system, and adds to the operational costs. The customer had previously tried reducing the volume of methanol entering the pipeline, but this resulted in an increase in the formation of hydrates.

Eliminate hydrate formation with GT-7569 hydrate inhibitor to resolve concerns of produced water contamination and corrosion

To help the customer mitigate hydrate formation, Schlumberger recommended a hydrate inhibitor program using GT-7569 kinetic hydrate inhibitor. Initial application of GT-7569 inhibitor commenced at 0.28 galUS/min [1.5 m³/d], or approximately 40% of the methanol injection rate. The pipeline from the compressor station to the gas plant was pigged twice a week and the pig returns checked for the presence of hydrate crystals.

The pressure on the inlet of the gas plant was also monitored because a pressure decrease was known to indicate hydrate formation. Optimization of the GT-7569 hydrate inhibitor injection rate continued without hydrate formation. Analysis of the produced water during the optimization trial confirmed reduction in contaminant levels.

Following approximately 6 days between the first and second pig run, when no hydrate crystals were found, GT-7569 hydrate inhibitor injection rate was reduced to 0.18 galUS/min [1 m³/d]. This rate was then maintained for two pigging cycles (12 days) while the operator monitored the pig returns and line pressure. After 12 days, the rate was reduced further to deliver an optimal injection rate that was determined to be 0.13 galUS/min, the rate at which hydrate formation, inlet pressure reduction at the gas plant, and produced water contamination were eliminated.

The volume of chemicals required to treat hydrates was reduced by more than 80% and the contamination of produced water by 100%. Operational costs were lowered by more than 50%. Operational costs have been reduced by over 50% since the implementation of the kinetic hydrate inhibitor program. Contamination of the reflux water has been eliminated and corrosion concerns associated with methanol carryover into the amine plant have been resolved. The program has been optimized from an initial injection rate of 1,500 liters per day to 700 liters per day. The volume of chemical required to prevent hydrates has been reduced by over 80%.