TORONTO (miningweekly.com) – Hydrocarbon pipeline operator Alliance Pipeline declared a force majeure event and closed its mainline pipeline early on Friday after hydrogen sulphide entered into the system on Thursday evening, as a result of complications experienced by an upstream operator.

The pipeline operator called on all natural gas producers using the Alliance pipeline to suspend injections for an unspecified period of time.

Alliance would flare the impacted natural gas to safely dispose of it as part of its mitigation activities.

This was planned to take place within the confines of Alliance's Alameda compressor station, in Saskatchewan. The company said there would be no risk to human health and no environmental impact was expected.

The 3 719 km integrated Canadian and US natural gas transmission pipeline delivered rich natural gas from the Western Canadian Sedimentary basin and the Williston basin to the Chicago market hub. The US portion of the system consisted of about 1 577 km of infrastructure, including the 128 km Tioga Lateral, in North Dakota.

The Alliance system delivered, on average, about 45.3-million standard cubic metres of natural gas a day.

Natural gas producers were impacted by the closure.

TSX-listed NuVista Energy on Friday reported that it had suspended production of about 8 000 bbls of oil equivalent a day from its 3-36 Bilbo compressor station.

Fellow TSX-listed RMP Energy reported that the temporary suspension would result in the shut-in of almost all of its output, including its light oil, until the situation was resolved. The company would use this temporary-outage event to conduct maintenance activities of its production and processing facilities.

Another TSX-listed firm, Crew Energy, said the suspension would result in a deferral of essentially all of Crew's Montney output of about 60-million cubic feet a day of natural gas and associated liquids, until the situation had been resolved. The company was working to mitigate a portion of the lost service; however, with ongoing service outages at other pipelines in the region, limited options were currently available.

However, the temporary outage was not expected to affect the continued commissioning of Crew's new West Septimus facility or the completion of the Lease Automatic Custody Transfer unit tie-in and would allow the company to conduct minor maintenance on the existing Septimus facility.