The rig Henry Goodrich spilled 26,400 litres of synthetic-based drilling mud on the Grand Banks seabed Monday morning.
The rig is drilling an exploration well for Suncor Energy, operator of the Terra Nova oilfield.
Suncor said Thursday the spill occurred during the cleaning of a mud storage tank aboard the drill rig — not during drilling operations.
The cause of the spill is under investigation, but the offshore regulator said it likely started with an open valve on a mud storage tank.
“It appears that a valve may have been open from one of the mud pits, which led to the release of the synthetic-based mud,” said Sean Kelly, spokesman for the Canada-Newfoundland and Labrador Offshore Petroleum Board (CNLOPB).
“We’re in the process of gathering information to determine what happened and make sure the causes have been addressed.”
Suncor said it’s still investigating the root cause of the spill and will report its findings to the CNLOPB.
“We take this situation very, very seriously,” said Suncor spokesman John Downton. “It occurred during a cleaning operation in the mud system. There was a transfer operation going on at the time.”
Once the spill was discovered, Downton said the cleaning operation was stopped.
During drilling operations, mud is circulated through the drill pipe to lubricate equipment.
The mud is also used to control oil and gas pressure in the well bore and help prevent well blowouts.
To assess the environmental impact of the spill, Kelly said an underwater remotely operated vehicle (ROV) will be used to collect water and soil samples at the site.
“It’s a heavy, dense mud and it goes straight to the bottom.”
Kelly said offshore spill equipment is designed for cleaning up oil slicks — not mud spills.
“It doesn’t float on the surface.
“It goes straight through the water column down to ocean floor, so it’s not something that you can catch in a boom or a skimmer.”
Downton said the company monitored the site following the spill and the mud has widely dispersed on the seabed.
“We did an ROV survey and it has dispersed.”
The CNLOPB said the food-based oil used in synthetic-based mud has “extremely low toxicity.”
“The base is non-toxic to humans, marine and wildlife,” said Downton. “It’s also biodegradable.”
Larger mud spills
Monday’s mud spill is the third-largest off Newfoundland since 1997, the year CNLOPB started keeping spill statistics.
The largest mud spill occurred in October 2004, when 96,600 litres of mud flowed from drill rig GSF Grand Banks.
“It appears that a valve may have been open from one of the mud pits, which led to the release of the synthetic-based mud.” - Sean Kelly
It was drilling wells for Husky Energy at the White Rose oilfield. Husky was later fined $50,000.
The second-largest spill occurred in January 2007 as the rig Eirik Raude drilled an exploration well for Chevron Canada in the Orphan basin — sending 74,000 litres of mud to the seabed.
NDP questions CNLOPB
Provincial NDP Leader Lorraine Michael questioned the CNLOPB’s delay in reporting Monday’s mud spill.
The information was released Wednesday afternoon in spill statistics on the board’s website. No news release was issued at the time.
“This incident happened on Monday and we are only hearing about it today,” said Michael in a Thursday release. “That fluid has been four days in the ocean.”
She called the delay unacceptable.
“Once again we see the crying need for an independent offshore safety authority. It would appear industry and the CNLOPB have not learned the importance of timely communication with the public on matters of public importance.”
Kelly said the CNLOPB will tighten up its reporting process, but does need some time to verify spill information before releasing it.
Future updates on Monday’s spill will be posted on the board’s website: http://www.cnlopb.nl.ca/incident_bulletins.shtml.
Other mud spills
It’s not the first mud spill at the exploration well known as Ballicatters M-96Z, which is located northeast of the Hibernia oilfield.
A day before Monday’s spill, five litres of mud leaked from the rig’s drill string.
On Jan. 19, the Henry Goodrich also spilled 78 litres of mud from a hose called a blowout preventer kill line.
Downton said it occurred during a test of the well control system.
“Typically, before we move from phase to phase in the (drilling) program, we will test the equipment.
“They were testing the line and discovered it had a crack in it.”
Some of the drilling mud leaked from the line. Downton said the hose was replaced in the matter of days.
“We didn’t do any well operations while that hose was being replaced. So, the well would have been secured during that period.”