Natural gas traffic is scheduled to resume Thursday on the Alliance Pipeline to Chicago from northern British Columbia and Alberta, after a six-day halt off to clean poisonous contamination out of the system.
Alliance announced Tuesday imminent completion of flaring off shipments fouled by sour gas steeped in hazardous hydrogen sulphide (H2S) (see Daily GPI, Aug 11; Aug. 7). The cleanup began last Saturday at a remote compressor station in rural southeastern Saskatchewan.
The volume of shipments burned to clean out the contamination was not disclosed but was said to be large. Alliance said the first step to resuming service would be to purchase up to 400 MMcf of gas needed to assure a steady, high-pressure flow. The sour gas contamination was the first traffic-stopping incident on Alliance since deliveries began 15 years ago.
The pipeline had called the disruption a force majeure event beyond its control. Keyera Corp. disclosed that a “brief operational upset” at its Simonette processing plant in northwestern Alberta put the sour gas into Alliance last Friday.
H2S, which smells like rotten eggs and can be lethal even in low concentrations measured in parts per million if it leaks into the atmosphere, often occurs naturally in Western Canada wells. An undisclosed volume sneaked into Alliance by eluding industry-standard fail safe sensors and hardware. Strictly controlled waste disposal methods burned off the contamination without endangering human health or the natural environment.
Business damages of the incident remain to be sorted out. During the pipeline traffic halt independent producers NuVista Energy, Crew Energy, Seven Generations Energy, RMP Energy, Cequence Energy and Athabasca Oil warned their shareholders to expect sales interruptions.
Alliance carries about 1.6 Bcf/d of liquids-rich gas. High-value byproducts are extracted at Aux Sable near Chicago.