The 33-year-old Maui gas field platform shrugged off the magnitude 7 earthquake off the Taranaki coast on Tuesday night.
Located near the quake's epicentre, the Maui A platform, which has been producing gas since 1979, carried on through the shaking.
"It was business as usual," said a spokesman for one of Maui's owners.
Inspections were carried out shortly afterwards and yesterday morning to make sure the A and nearby B platforms were safe. About 60 people working on the platform were shaken but the quake was not large enough to shut down operations.
Maui, which is owned by Shell with 83.75 per cent, Austrian company OMV (10 per cent), and Todd Energy (6.25 per cent), produces about 20 per cent of the country's gas.
The platforms have been designed to survive the worst of earthquakes.
"It would take an earthquake considerably greater than that to cause collapse," said Shell Todd Oil Services general manager Rob Jager.
The platforms are continually inspected above and below water to make sure they are safe.
"Even if we experienced shaking as vigorous as the major Christchurch events, in the worst case we would anticipate some damage, but not collapse of the structures," Jager said.
Petroleum Exploration and Production Association chief executive David Robinson said quakes were "fairly normal".
Production platforms were designed to withstand them.
Oil companies had a good understanding of the geology in the areas they drilled and wells were generally not drilled through fault lines.
"When wells are constructed there are valves down the well that can shut the well off in the event of an emergency," Robinson said.
"There are lots of fail safes. We are well protected against any problems."
The engineering was thorough and platforms built to survive quakes and heavy seas, Robinson said.
The partners in the field are now trying to maximise reserves and extend the field life, with a new drilling programme to target gas bypassed earlier.
Meanwhile, Jager said the AD ihi prospect would be redrilled from the Maui A platform and up to seven existing wells would be sidetracked in coming months.
Drilling continued from the existing wells on the Maui B platform where up to seven wells were being sidetracked.
Drilling started about eight months ago in an effort to extract more natural gas.