A 12 km long pipe seems like a ridiculous length for any of that to be possible. Isn’t it like trying to drill a hole with a 258 ft long piece of spaghetti?
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You actually don’t push down on the bit at all. You suspend the weight of the drill string, except for a few thousand pounds. For example, if your string weighs 500,000 lbs the draw works might be holding 480,000. Every bit/motor/rock type has an ideal “weight on bit”. Otherwise you would become incredibly stuck as the pipe, which you accurately describe as behaving as spaghetti, would be shoved into the sides of the borehole.
A traditional drilling rig has no ability to push, and the first joint of pipe or two will be special, super heavy weighted stuff called drill collars.
The rig is used to pull up on the pipe, and as the hole gets deep this pulling force can be a hundred tons. That leaves just a little weight on the bit, just enough to do it’s job.
Yes, the pipe is like a wet noodle, and spinning the top takes just a bit to make it to the bottom, winding up the pipe. Same happens when the rig lifts the pipe, it stretches.
In a related development there is now what is essentially a microwave powered “drill”
>The company’s drill—it is building three prototypes in laboratories—is about 100 feet tall and looks like conventional equipment used in the oil and gas industry. Except built into the center of the drill is a gyrotron, an electrical vacuum designed to heat plasma in thermonuclear fusion machines. It’s designed to go as much as 12 miles deep and access steam as hot as 500C.
[https://www.quaise.energy/](https://www.quaise.energy/)
[https://www.youtube.com/watch?v=g8sjdOjNxIE](https://www.youtube.com/watch?v=g8sjdOjNxIE)
[https://www.bloomberg.com/news/articles/2022-10-21/drilling-12-miles-down-to-tap-geothermal-energy?leadSource=uverify%20wall](https://www.bloomberg.com/news/articles/2022-10-21/drilling-12-miles-down-to-tap-geothermal-energy?leadSource=uverify%20wall)
I worked on underground coring rigs 1000m hole is considered deep. I would run downhole gyro surveys to get an idea of where the hole is headed (deviation) and sometimes the amount of “corkscrewing” the rod string would do amazed me. In that world it’s all about water. Pump water down the line and return it up the hole. The string is fitted with a reaming shell that bores the hole a bit bigger than the bit. Aside from that is grease (to fill small cracks), and mud to reduce torque.
In a related development there is now what is essentially a microwave powered “drill”
>The company’s drill—it is building three prototypes in laboratories—is about 100 feet tall and looks like conventional equipment used in the oil and gas industry. Except built into the center of the drill is a gyrotron, an electrical vacuum designed to heat plasma in thermonuclear fusion machines. It’s designed to go as much as 12 miles deep and access steam as hot as 500C.
[https://www.quaise.energy/](https://www.quaise.energy/)
[https://www.youtube.com/watch?v=g8sjdOjNxIE](https://www.youtube.com/watch?v=g8sjdOjNxIE)
[https://www.bloomberg.com/news/articles/2022-10-21/drilling-12-miles-down-to-tap-geothermal-energy?leadSource=uverify%20wall](https://www.bloomberg.com/news/articles/2022-10-21/drilling-12-miles-down-to-tap-geothermal-energy?leadSource=uverify%20wall)
I worked on underground coring rigs 1000m hole is considered deep. I would run downhole gyro surveys to get an idea of where the hole is headed (deviation) and sometimes the amount of “corkscrewing” the rod string would do amazed me. In that world it’s all about water. Pump water down the line and return it up the hole. The string is fitted with a reaming shell that bores the hole a bit bigger than the bit. Aside from that is grease (to fill small cracks), and mud to reduce torque.
They drill with water, or “muds”. The bit on the end is larger than the drill rods themselves, creating an annulus for water to pass through. This film of water prevents hole drag by keeping the rods from grabbing the rock.
As far as pushing goes, after about 400 meters, the drill is no longer pushing, the weight of the rods is what’s pushing the bit into the ground. After around 800 meter, the drill is being used to hold the weight of the rods back a little bit, creating tension on the rod string which helps keep them straight.
They drill with water, or “muds”. The bit on the end is larger than the drill rods themselves, creating an annulus for water to pass through. This film of water prevents hole drag by keeping the rods from grabbing the rock.
As far as pushing goes, after about 400 meters, the drill is no longer pushing, the weight of the rods is what’s pushing the bit into the ground. After around 800 meter, the drill is being used to hold the weight of the rods back a little bit, creating tension on the rod string which helps keep them straight.
The drill rig doesn’t actually push the pipe down at all. In fact, a drill rig is a glorified crane. The weight of the drill string alone can be a million pounds whereas only on the order of 25,000-50,000 pounds of weight pushing the bit is needed to drill. This is accomplished by lowering the drill string and letting some of its own weight push the bit.
Rotating on the other hand is accomplished two ways. First off, the drill rig itself can spin the drill pipe. It takes on the order of 20,000 ft-lbs of torque to turn the pipe due to friction but it has the power to do it. The second method of rotation is called a mud motor. A motor can be placed at the bottom of the drill string. Mud that is pumped through the drill string spins the motor independently of the drill string.
EDIT: A few more details for the interested:
>Isn’t it like trying to drill a hole with a 258 ft long piece of spaghetti?
Yes. As mentioned in the first paragraph, at no point does the drill rig push the pipe. It uses a little bit of the drill string’s own weight to push the bit. The term for lowering the pipe so that it rests on some of its own weight is called “slack-off.” As far as the rig is concerned, it is *always* suspending the drill string like a crane suspends a weight in air. If you hold a wet noodle in the air and lower it to touch your dinner plate, you are always holding the noodle up. The more noodle that you lower onto the plate, the less weight you are holding and the more weight that the noodle is pushing against the plate.
As for rotation, steel is incredible at being able to transfer torque, but at those depths it will twist around 10-15 times before the bottom of the drill string starts turning.
Others mention stabilizers, all stabilizers do is keep the pipe in the center of the hole. Keeping it concentric reduces vibration and some wobble at the bottom of the drill string.
A follow-up question could be, “How do you control where the bit goes?” This process is called directional drilling. The simple explanation is that you **push off the wellbore in the opposite direction that you want to steer the bit**. There are many sophisticate tools to figure out where the bit is, what direction it is pointing, and to get it to drill in a desired direction.
The drill rig doesn’t actually push the pipe down at all. In fact, a drill rig is a glorified crane. The weight of the drill string alone can be a million pounds whereas only on the order of 25,000-50,000 pounds of weight pushing the bit is needed to drill. This is accomplished by lowering the drill string and letting some of its own weight push the bit.
Rotating on the other hand is accomplished two ways. First off, the drill rig itself can spin the drill pipe. It takes on the order of 20,000 ft-lbs of torque to turn the pipe due to friction but it has the power to do it. The second method of rotation is called a mud motor. A motor can be placed at the bottom of the drill string. Mud that is pumped through the drill string spins the motor independently of the drill string.
EDIT: A few more details for the interested:
>Isn’t it like trying to drill a hole with a 258 ft long piece of spaghetti?
Yes. As mentioned in the first paragraph, at no point does the drill rig push the pipe. It uses a little bit of the drill string’s own weight to push the bit. The term for lowering the pipe so that it rests on some of its own weight is called “slack-off.” As far as the rig is concerned, it is *always* suspending the drill string like a crane suspends a weight in air. If you hold a wet noodle in the air and lower it to touch your dinner plate, you are always holding the noodle up. The more noodle that you lower onto the plate, the less weight you are holding and the more weight that the noodle is pushing against the plate.
As for rotation, steel is incredible at being able to transfer torque, but at those depths it will twist around 10-15 times before the bottom of the drill string starts turning.
Others mention stabilizers, all stabilizers do is keep the pipe in the center of the hole. Keeping it concentric reduces vibration and some wobble at the bottom of the drill string.
A follow-up question could be, “How do you control where the bit goes?” This process is called directional drilling. The simple explanation is that you **push off the wellbore in the opposite direction that you want to steer the bit**. There are many sophisticate tools to figure out where the bit is, what direction it is pointing, and to get it to drill in a desired direction.
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