kdorian (kdorian) wrote in little_details,

Fact entry: Mudlogging

If anyone is interested in info relating to oil rigs and mudlogging (a specialist/tech job around oil wells), info is here.

Background: Tech guy for a mudlogging company. Mudlogging is the process of analyzing the rock and gas that come out of an oil/gas well to help the suits get a better understanding of what areas produce well. I'm sitting out on a gas well for a stint, testing some new equipment we're developing; this is a relayed suck from one of the loggers in my shack.

Oil rig hands are not well-known for intelligence; a strong back ranks well ahead of a strong mind in the hiring criteria for your average roughneck. Still, they usually know well enough not to touch our gas traps, if for no other reason than it'll make their bosses mad when they don't have gas data.

The gas trap is attached to a part of the rig called the shaker or "'possum belly." (Don't ask me how it got that name, I don't know.) The purpose of this device is to take the drilling fluid (it's called mud, but it's not native minerals so much as stuff to lubricate the bit) that's pumped out of the hole, shake out the rock cuttings and dump it down into the reserve pit to be recirculated. The trap itself stirs the mud, eggbeater-like, to extract the gas that it picks up downhole, and it's this gas that's interesting to us.

So here's the trick. A couple days ago, the company man on one of the rigs out here decided to bypass the shaker. This is not uncommon, though I don't know the specific benefits, but it tends to annoy the loggers because no mud = no gas = no data. Fine, whatever, not our fault. we note it and move on. It's what came next that sucked.

So this same company man observed that he wasn't reading any gas on his display. This should have been easily explained by the fact that he was bypassing, but instead he went out to look at the gas trap and found it sitting well above the level of what little mud remained in the shaker. So, in an effort to help, he cranked the trap all the way down to the level of the mud, a fairly logical course of action at any other time, but we prefer to do it ourselves since it can be a somewhat delicate balance.

Skip ahead several hundred feet -- drilling is slow, so we're talking hours here. He finally decided to stop bypassing, so the shaker filled up again. WAY UP. Think of what happens when you submerge the beaters on a hand mixer all the way up to the motor housing -- your cake batter's gonna get where it doesn't belong and gunk up the mixer good.. And indeed, it went everywhere, including up the gas hose, through the bubble jar (full of glycol to dry the gas), through the tube full of calcium chloride (to dry the gas some more), finally clogging the thin poly tube that connects the trap to the logging device in our trailer.

Then, and only then, did the logger get a phone call: "Hey, I'm not reading any gas..."

Note: In the comments the OP (teknomantik) notes "...I would recommend fact-checking me anyway just to be sure; being just the tech guy (i.e. mostly computers), my descriptions of rig operations may not be 100% accurate."

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