A pressure test aimed at finding out whether an underwater pipeline might be the source of natural gas bubbles surfacing in an Assumption Parish waterway did not have any effect, a parish official said Friday.
Bubbles continued to appear on the surface of Bayou Corne after Acadian Gas Pipeline of Houston, Texas, lowered pressure in the line, said John Boudreaux, director of the parish Office of Homeland Security and Emergency Preparedness.
Personnel monitoring the situation would have expected the bubbles to dissipate with lowered pipeline pressure if the pipeline had been leaking natural gas.
Boudreaux said the test was a step toward locating the source, but did not entirely eliminate Acadian. The company has two 20-inch pipelines buried 4 feet beneath the bottom of Bayou Corne.
State and parish officials are using the process of elimination to find the source of natural gas bubbling up in about dozen spots on Grand Bayou and Bayou Corne.
Residents also reported mysterious tremors on June 8 and this week but authorities have no answers yet on whether possible movement of the earth is tied to the gas bubbles.
James Bergeron, 76, of Bayou Corne, said Thursday he felt the ground shake on Wednesday afternoon while he worked on his fence.
“It scared me more than anything else,” he said.
Authorities have been examining pipelines, salt dome caverns, orphan wells and other oil and gas infrastructure crisscrossing the swamps. They are also waiting on the results of testing to identify the composition of the gas, thereby perhaps pinpointing its source.
Twice-daily atmospheric testing at the bubbling locations continues to show the gas is not a risk of fire or explosion, Boudreaux said. His office is posting daily reports and other information on the parish government website at http://www.assump
Samples are taken every two seconds as a boat idles past the bubbles with measuring equipment deployed. Ignition risk shows up on reports as the LEL percentage, or the “lower explosive limit.”
Boudreaux said LEL occurs when the air contains about 10 percent natural gas. Tests have shown the LEL percentage at zero in the vicinity of the bubble outbreaks. He said parish officials would begin taking precautions at an LEL percentage of 60.
He said carbon monoxide that shows up sporadically in reports is coming from boat engines.
Phyllis Darensbourg, DNR spokeswoman, said inspectors visited seven of 17 orphan wells Friday that officials identified after checking well records. She said they did not have special Louisiana Department of Environmental Quality camera equipment to detect invisible gases venting from the capped wells.
She said inspectors could not see any bubbling, but planned to revisit those wells and check additional wells when the DEQ cameras are available.
Joseph “Joe” Ball Jr., director of the DNR Injection and Mining Division, explained Thursday that if older well bores were releasing gas underground, it could migrate through the earth to the surface.