The weekly Reflektion Week 28 / 2019

This week’s Reflektion concerns the incident at Lake Peigneur in Louisiana where communication between a well and a salt mine shaft led to serious consequences.

Reflekt will be organising another Breakfast Seminar in September, so keep your eyes peeled for further details.

Are you lucky enough to avoid Major Accidents? What happens if your luck runs out?

Oil is often found in the vicinity of salt domes as it provides an impermeable cap rock. On November 20, 1980, an oil well being drilled from a barge-mounted rig in Lake Peigneur, Louisiana, from a was spudded with an assumed good safety margin to active salt mines beneath the lake. While drilling 14” hole, the drill string became stuck, and while trying to work it free, circulation was lost. The rig began to tilt, and the crew abandoned it, and watched as the 150 foot tall rig disappeared into the 10 foot deep lake. The well had been drilled into one of the salt mine shafts.

As the lake continued to drain into the salt mine, 55 miners working 1500 feet underground managed to escape as the water level rose in the mine. The water dissolved the salt pillars left supporting the horizontal mine shafts, and the shafts collapsed as it filled with lake water. A whirlpool developed sucking in 11 barges, trucks, trees, and 70 acres of soil as the lake’s 3.5 billion gallons of water drained into the mine. As the water level in the lake dropped, a river running from the lake into the Gulf of Mexico changed direction and sea water flowed into the lake as the mine filled with water, causing a 150 foot waterfall, the tallest ever seen in Louisiana. Air displaced by the water flowing into the mines caused a 400 foot high geyser from the mineshafts.

When the water pressure equalized several days later, 9 of the 11 barges popped out of the whirlpool on to the surface of the lake. Since the accident, the once 10 foot deep freshwater lake is now the deepest lake in Louisiana at 200 foot and has been permanently changed to salt water.

The direct cause was never officially concluded, but communication between the well and the salt mine through a fault is the generally accepted direct cause of the incident. Formations around salt domes are often severely faulted, and an assumption that the faults are sealing under Lake Peigneur would have given assurance that well integrity was not an issue. In this case, such an assumption could have resulted not just in lost circulation problems, but in multiple fatalities. A risk assessment covering, not just downhole risks, but risks on the periphery of the drilling operation could have prevented this accident. Considerations of the uncertainty of the data, in this case the sealing faults, or their connection to the mine workings, may have triggered some thoughts about “What if ….?”.

In our Reflektion from week 51/2018 we introduced the concept of the ‘pre-mortem’, where personnel involved in risk assessments would construct major accident scenarios. The chain of events necessary for these scenarios to occur can be identified, and the barriers that would have to fail for the individual events in the chain would become more obvious.

A potential chain of event leading to a Major Accident could be interrupted by coincidental factors, such as the weather was OK, a safety margin was large enough, or someone happened to notice something and fixed it. These factors are often determined by nothing more than luck. In this case 55 people were lucky and got just enough time to escape.

From the point of view of Major Accidents, we probably rely on luck more than we realise. Do you rely on luck to avoid Major Accidents in your operations?