Sorry for the alarmist title, I swear that Iâ€™m not attempting to bait your clicksâ€¦ well not much. Â This is awesome. I was talking with a couple of guys who work at a directional drilling company. They drill conventional oil recovery wells in order to extract a substance made from bits of old plants and animals. Drilling is way more complicated at that scale than the drilling a hole in you wall scale. The holes are thousands of feet down and, in many cases, in a weird crooked line (hence the directional drilling part). You have to do that because it may be more efficient to drill through a certain substrate at 500 feet and then move over a bit at 1000 feet. The level of accuracy these guys can do now is out of this world.
I was really intrigued about how they got information back from the drill head. There are tons of interesting readings you can gather from the head but the problem is that it is way under ground. Getting that data back is difficult. I have trouble getting wi-fi in my bedroom when the router is in the living room so clearly wi-fi is out as a technology.
Running a cable down there is also difficult. Unlike the putting a picture on the wall sort of drill these drills have lubricants and rock cuttings to deal with. Mud is pumped down the inside of the shaft and then recovered out the sides.This means that any cable path is already full of highly abrasive mud. The guys told me that does work but it is flaky and you end up spending a lot of time replacing cables and also signal boosters every 200 or 300 feet.
Another way is to use low frequency radio waves which are a bit better than wi-fi at getting through rock. However there are some rocks through which it just doesnâ€™t work to send radio waves.
The final method, and the coolest, is to use mud pulses. The mud being pumped down the well is at huge pressure (as you would expect from pumping mud). On the drill head there is a valve which can be opened and closed by the sensors on the drill head. When closed the pressure in the mud pumps increases and when opened it decreases. They literally send pulse waves through the mud theyâ€™re pumping into the well and measure them at the surface. It is outrageously low bandwidth but that it actually works at all is amazing to me. It is effectively a digital signal in mud. What a cool application of technology!
It gets better, though. If you have a valve with various open and closed settings you can vary the pressure to create a waveform varying both amplitude and frequency.
At shallow depths you can get as much as 40bit/s through mud pulsing although at deeper depths that drops off significantly to perhaps 1.5bit/s at 12 000m. 40 bit/s means that weâ€™re running at 40Hz which is fricking huge for a mechanical valve under that much pressure to open and close.
I would not have invented this.