ExxonMobil pipe leaks toxic gas
No injuries reported
by Julia Stuble

A cracked flowline carrying sour gas from ExxonMobil’s Black Canyon Well Field to a dehydration facility leaked large amounts of hydrogen sulfide, carbon dioxide and methane gases last Wednesday night.

The flowline developed a crack at a welded seam; the cause of the crack is still under investigation. At the time of the leak, the company’s automatic safety mechanisms were activated, the well was shut in, and the leak isolated. No personnel were injured. The pipe vented 3.54 tons of hydrogen sulfide gas.

Bob Davis, with ExxonMobil, said that after the well was shut in, product was still in the line. This gas continued to vent; Davis noted that the event lasted for about an hour.

The gas pipe was about four feet below ground level. The release of gas blew to ground level, creating a hole about eight to ten feet in diameter, with some associated swelling of the ground around it. ExxonMobil checked the dirt and snow around the hole for residual hydrogen sulfide; none was found. The company reported that the ground is tightly compacted. It appeared that the soils surrounding the pipeline were evacuated quickly and the gas vented to the atmosphere.

Hydrogen sulfide is a highly toxic, flammable gas. The National Institute for Occupational Safety and Health rates 100 parts per million of hydrogen sulfide “Immediately Dangerous to Life and Health.” In low concentrations, the gas causes respiratory and eye irritations. In high concentrations it can damage the central nervous system and be fatal. ExxonMobil reported that directly following the leak, all personnel were outfitted with hydrogen sulfide monitors.

The site is approximately 15 miles southwest of Big Piney and 20 miles northwest of LaBarge, according to Davis.

Bob Hanson, with the Sublette Emergency Management Team said that he was notified of the leak by some truck drivers who were downwind of the site and smelled the gas. These drivers called the Emergency Team; to Hanson’s knowledge ExxonMobil did not. When he talked with ExxonMobil officials, the well was shut in and the situation being controlled. The Emergency Team did not respond to the site.

Exxon searched the area and did not find any injuries to animal species. Len D’Eramo, a representative for Exxon, noted that the company’s “top priority is to ensure the health and safety of our neighbors and local communities in which we operate.”