Wednesday, September 10, 2014
Methane Venting Hazard
Some years ago, I believe it was 2009, I had written an article about safety in our offshore environment and how some of our flying activities were a bit out of the norm for everyday helicopter operations.
I’m not going to rehash all of the daily problems we face operating in our hostile environment such as bird strikes, communications, blowouts, poison gas and crowded airspace, to name a few. One other issue that I gave some space to was the venting of natural gas and its potential hazard to in-flight helicopters that enter gas-saturated airspace. Of course, the gas itself is invisible, but to add to the hazard, it is also odorless when it comes out of the ground. The gas you smell around your house, for example, has had a chemical added to it called Mercaptan or “stinkum,” as pipeliners call it. It’s a safety feature for anyone working around gas or using it for any reason, like cooking on your kitchen stove. You detect its presence by the odor. Mercaptan is added later, downstream from the wellhead, usually in a processing facility where the gas is cleaned by removing liquids. These liquids, including benzene and water, must be separated out before the gas is transported in pipelines to the final users.
If you are wondering why gas is vented at the wellhead to start with, the answer is that the gas almost always accompanies all hydrocarbons while drilling. If you are drilling for oil, hydrocarbons become a byproduct which, in many cases, is a hazard due to its explosive nature and high pressure.
When the rig encounters gas, it has to be contained via a pipeline or vented to the atmosphere. Pipelines are not available at most drilling sites. In days gone by, the gas was ignited by using a controlled flare and burned off. That option has been reduced mostly due to economics and some regulatory requirements. Most gas flaring today is done as a safety expedient, whereas in the old days, flaring was done to eliminate the gas due to safety and a very limited market value.
Offshore rigs that have a need to flare gas do it through an extended boom, similar to a crane boom, that extends away from the platform and is elevated at a shallow angle to keep the gas from enveloping working areas. Sometimes the gas is ignited to burn freely, but when it is not ignited, it’s vented to the atmosphere. When this occurs, there is a signaling device, usually a red beacon, to alert workers that venting is taking place.
Turning back to helicopter operations, in March of 2011, one of our operators had a near-fatal accident. The helicopter had just completed a hot refueling and was lifting off the oil rig when the pilot encountered a spike on his torque gauge accompanied by a loud bang, all while in the bad part of the H/V diagram. An attempted autorotation ended up with a destroyed helicopter but, fortunately, no fatalities.
It seems that someone on the rig decided to vent gas, perhaps as an emergency, and, due to the wind direction and speed, the gas blew over the take-off route of the helicopter. When turbine engines suck in the enriched air from the venting, all kinds of bad things happen, usually over spikes and burned turbine wheels.
We have a lot going for us safety-wise here in the Gulf. There are at least four alphabet groups, such as HSAC, API, USCG and a new one, BSEE, which is part of the U.S. Department of the Interior, and translates into Bureau of Safety and Environmental Enforcement.
That department has hired a helicopter pilot, Stephen Rauch, as the aviation safety and training manager. I’m not sure we all understand exactly where he will be going with his new job, but so far he has been a welcome coordinator of information between helicopter operations and oil patch operations.
He recently updated a Recommended Procedure (RP) titled “Methane Venting Hazard to Helicopter Operation.” We wish him the best and look forward to his help to spread the word about helicopter operations in the offshore energy business!