The Situation

 A gas pipeline transports an average of 2,430 e3m3/d of gas to an amine plant. The pipeline is located in remote part of Alberta and access is difficult due to the changing terrain. Produced water is introduced into the pipeline at various locations throughout the system with the majority of produced water entering the pipeline after a compressor station. The line from the compressor station to the gas plant is treated with 4,000 L of methanol to prevent hydrates. Although the methanol is effective at preventing hydrates it carries into the amine plant, contaminating the reflux water and increases the corrosion risk to the system. The customer has tried to reduce the volume of methanol entering the pipeline but hydrates form as a result.

The Solution

M-I SWACO introduced a hydrate inhibitor program using the kinetic hydrate inhibitor (KHI) GT-7569. The KHI was initially applied at 1,500 liters per day or approximately 40% of the methanol injection. Pig returns were checked for the presence of hydrate crystals and in the inlet pipeline pressure was monitored for any reduction indicating hydrate formation. The KHI was optimized to an injection rate of 700 liters per day without any hydrate formation. The reflux water was analyzed through the trial and showed no contamination. As a result of the KHI application the customer was able to save over 50% in chemical and operational costs.

The Results

The KHI was initially applied at 1,500 liters per day or approximately 40% of the methanol injection. The pipeline from the compressor station to the gas plant was pigged twice a week and the pig returns were checked for hydrate crystals. The pressure on the inlet of the gas plant was also monitored. A decrease in the inlet pressure signaled the formation of hydrates. When no crystals were found between the initial pig run and the second pig run (~6 days difference) the KHI was reduced to 1000 liters per day. This was rate maintained for two pigging cycles (12 days) and pig returns and line pressure were monitored. The rate was reduced to 800 liters per day, which was the rate recommended by M-I SWACO. Optimization of the KHI injection rates continued until a rate of 700 liters per day was achieved without any hydrate crystals, no reduction in inlet pressure and no contamination of the reflux water.

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 have been reduced by over 80%.