Spec Tech: Learning the Drill
I know I’ve got a request for a topic (don’t worry, I haven’t forgotten about building things with sandstone!) but this last month I spent a week on drilling rig in the wilds of Wyoming, so I thought I’d write about that experience while it was still fresh in my mind. Other than looking at rocks generally, drilling is something that geologists tend to be involved with often.
I was involved in a scientific project where we were drilling cores from a subsurface formation. My experiences aren’t by any means a perfect parallel to commercial drilling (for oil, natural gas, water, etc) but will hopefully provide some insight. If you’re curious about the project I was on, here’s a link to the Bighorn Basin Coring Project website.
While there are other methods that can be used for drilling holes of various sizes into the depths of a planet, the one that’s most common right now is rotary drilling. The simple explanation for how this works is that there’s a pipe (called the drill string) with a drill bit at the end of it, and the entire pipe is turned by a motor at the surface. Weight is put on the drill string from above; the combination of weight and rotary motion lets the bit cut downward through rock. The pipe that makes up a drill string comes in sections of standard size. At our site, we were using eight foot pipes, which meant that every time the drill had cut down eight feet, a new section of pipe needed to be added.
This way of drilling really dictates how drill rigs look. There has to be some sort of tower with a pulley system to raise and lower the drill string, for example. This also means that the deeper the hole you’re drilling, the bigger your drill rig has to be. A deeper hole means a longer (heavier) drill string, which in turn means you need a bigger motor to keep that thing cutting. And a longer, heavier drill string also takes a lot more power to lift out of the hole when you have to start breaking it down.
In Wyoming, we were cutting core through a formation that was barely under the surface, and never got down to even 800 feet in depth. Our rig was, when you come down to it, tiny and adorable. The tower could just fold down onto the back of a truck, so the rig could be easily moved from place to place. Larger rigs on land have to be transported on a series of trucks and constructed on site.
And of course, the size of the rig will also dictate just how many people are required to crew it. A small one like what we used in Wyoming had a total crew of four, split between two twelve-hour shifts. Each shift had a driller and a helper, and that was all we needed to keep things running smoothly.
I don’t know enough about the nuts and bolts of drill rigs to give you more than a general overview of what the driller does; if you ever want to write a story about a driller, your best bet is to actually interview one. Most drillers I’ve ever met have been friendly, talkative guys (if a little rough around the edges) who are happy to chat about what they do.
I can say a few things generally, however. Being a driller isn’t a job that requires higher education, but there is a lot of skill involved that is learned on the job. The driller controls how fast the drill string (and therefore the bit) spins, how much weight is put on it, and a lot of other operational details that constantly change depending on the type of rock he’s trying to get through. A lot of the information is indicated in readouts on the control panel for the drill. A lot of it is also feel. There were many times we saw our driller “listen” to what the drill was doing by putting a wrench against the rig’s frame and resting the other end of it on his jaw, or by pressing his hard hat against the frame and feeling it.
Because of the cost, drills are normally run 24/7 until a hole is finished, and drillers (as well as the rest of the crew) usually work 12 hours shifts. It’s hard, dirty work. And considering it involves heavy machinery spinning pipes, it’s also dangerous. Unless the rig breaks down (or there’s a quick lunch break) the driller never stops working.
For example, on the science crew we’d get to be bored for several hours at a time if the bit got worn down. If the bit’s not cutting any more, it has to be replaced. Which means pulling the entire drill string out of the ground, one or two pipes at a time, changing the bit, and then putting the whole thing back down. (This is called tripping out of or in to the hole.) We also had a long break when we finished drilling one hole and the rig had to be moved to a new site. This involved pulling all of the drill string and breaking it down. The driller and his helper didn’t get to sit around and eat cookies like us; they were scrambling the entire time.
Playing in the Mud
Another important component in drilling is the “mud.” Drilling mud isn’t literally mud; it’s actually just the generic term for whatever fluid is being used. Drilling mud also serves a lot of functions. At its most basic, it helps cool the bit and carries the fragments of chewed-up rock that have been cut by the bit (“cuttings”) up to the surface. Pressure from the drilling mud filling the hole keeps the hole from collapsing around the drill string. And importantly when you’re drilling through rock that contains natural gas, the mud column can keep the gas from blowing out of the hole and potentially causing an explosion.
Since we had a small rig and a two man crew, the driller helper pretty much took care of all our mud needs. On bigger rigs, there’s often at least one person who does nothing but take care of the mud. There are even mud engineers, who are in charge of making sure the mud is the right mix for the particular formation that’s being drilled through at the time.
Pure water can technically be used as the “mud” for drilling. That’s what we actually did at most of our sites, to prevent additives from contaminating our samples. Even if pure water went into the hole, what came out really did look like mud. Also because we were doing the environmentally friendly thing and just using straight water, all our drillers had to do was dig a trench to direct the water away from the site.
Plain water doesn’t cut it most of the time, however. Even for us, at one of our sites the hole kept collapsing and we eventually had to put in a couple of additives. Having a whole suite of additives in mud is how things normally go. This can sometimes give the mud an absolutely dizzying chemical stink that just pervades the area – which also means the mud has to be collected in pits and disposed of safely later, and that the mud can even irritate your skin pretty badly if you’re not wearing gloves. Other times, the mud isn’t necessarily going to be dangerous, but it’ll be unpleasant to handle. We had to add a polymer to our mud that basically turned it into slime; everything that came out of the hole was incredibly slippery and difficult to hang on to.
Whether it’s just water or a slimy mix of polymers and bentonite, mud ends up everywhere. It sprays from fittings that aren’t tight enough, runs out of pipes that you pick up. You end up covered in the stuff and feel permanently damp. Our drillers did the smart thing and wore two sets of gloves to keep their hands relatively dry. We scientists didn’t, and after a while, we just ran out of dry rags and even spots on our pants and shirts where we could wipe our hands. We used lotion by the gallon to try to keep our hands from chapping. And after a while, I sort of got used to my skin being covered with a dusting of stiff clay, because it wasn’t worth washing my hands constantly when in just five minutes, I’d be getting a fresh coating of mud.
Dirt and Noise and Smells
So what’s it actually like being around a drilling rig? As I said before, it’s damp, dirty work. You’re outside. In the summer, you boil, in the winter, you freeze. I worked night shift in Wyoming, so the temperature was nice enough, but we got eaten alive by mosquitoes, and rained on, and were whipped with dusty wind. Since drilling so often happens in out of the way places, the environment – and any wildlife dropping in for a visit – can vary greatly. And sometimes, it can be plain beautiful.
The noise on site is constant. There will normally be at least one generator and a light tree running, and the rig as well. If you spend any amount of time near the rig, ear protection is a must. Otherwise, it’s just a constant grind of sound that can’t be drowned out except with extremely loud music. Sometimes a pipe will be a little bent, and it makes a horrible metallic clatter as it spins.
After a while, you learn the sounds of the rig, what the motor sounds like when the driller is blasting through sandstone, and how the tone of it changes when the rig switches from spinning the bit to hauling up pipe. And then when the rig motor gets shut off for any reason, it’s almost like hitting a wall. Suddenly, the noise is just gone, and you find yourself heading over the rig to see if something had gone wrong.
Between the rig and the generators on site, everything smelled of diesel fumes, though after a while I just stopped noticing. Thankfully, our mud didn’t smell bad, or like much of anything but damp dirt. There was also the occasional unpleasant whiff off of the port-a-potty when the wind blew the wrong way. We were out in the middle of nowhere, so we had the most scenic port-a-potty in Wyoming, but that came with a price.
There’s really no good way to keep anything clean on site. From the start of shift, we were all splattered with dried mud and dirt from pretty much the neck down. And of course, since we were in Wyoming, there was also dust constantly kicking around in the wind, so everything got a coating of that as well. As an added bonus, we’d sometimes get stubborn smears of sticky black grease coming off the pipes. It’s not a friendly environment for anyone that can’t take dirt. I tend to be a quasi-obsessive hand washer myself (thanks to spending time in the medical field) and by the middle of my second shift I had basically just given up.
If you have any questions, please don’t hesitate to ask. I was only on the rig for a week, but those seven days were packed with so many experiences that I’ve probably left a lot out in this post. Drilling can and often does take us to places at or beyond the edge of civilization. It’s dirty, dangerous, fascinating work – and work that I think has a lot of stories in it.