Chevron Canada is using the Stena Carron for an exploratory drill in the Orphan Basin. (CBC)

Chevron Canada executives defended Monday their decision to pursue an unprecedented exploratory well off Newfoundland, so soon in the wake of the Gulf of Mexico oil spill disaster.

Chevron started work on the Lona 0-55 exploration well in an area called the Orphan Basin, which is just north of the Grand Banks and about 430 kilometres northeast of St. John's.

The project has attracted increasing international attention — and scrutiny — because Chevron is drilling a well in more than 2,600 metres of water, significantly deeper than the Deepwater Horizon project in the Gulf of Mexico, where a blowout in April continues to have a devastating environmental impact.

But vice-president Mark MacLeod said Chevron has an industry-leading safety record.

"Chevron has drilled over 300 deepwater wells. We've never had a blowout in deep water," MacLeod told reporters during a conference call.

Nonetheless, Chevron has taken extraordinary steps to ensure a blowout does not happen at the Orphan Basin.

The drill pipe has several blowout preventers, ready to shear off the pipe and seal it shut.

Chevron admits there are times when that cannot be done, because some sections of the pipe are too thick. However, MacLeod said that is only one per cent of the time.

"In that event, an experienced driller like we have on the [drilling ship] Stena Carron would know to simply raise or lower if any unshearable part of the drill pipe were across the blind or shear ram," MacLeod said.

He said there would be hours of advance warning before a blowout, and that it would take only minutes to raise the pipe and use the blowout preventers to seal it off.

Moratorium needed: NDP

Meanwhile, at Newfoundland and Labrador's legislature, there were renewed calls for a moratorium on new deepwater drilling.

"At this moment, we do not know what the reasons are for the disaster in the Gulf. Potentially, there could have been technical issues that contributed to the blowout," said NDP Leader Lorraine Michael.

She asked whether the "government would be willing to put a halt to the drilling in the Orphan Basin until an assessment could be made of the relevancy of any identified technical issues to the Lona-O55 drilling program."

Natural Resources Minister Kathy Dunderdale said increased government oversight has been applied to Chevron's plans.

"If all of the safety measures and regulations were not being observed, were not available, [and the] requirements for safety were not available, then we would certainly agree to shutting down drilling in our offshore," Dunderdale told the house of assembly.