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July 12, 2019

Let's talk about Directional Drilling Basics

Season 2
This episode is sponsored by
Gibson Reports
Let's talk about Directional Drilling Basics

Why do we directional drill? It’s as simple as drilling straight down and... BOOM oil gushes out? Right or Wrong? Or why can’t we use Wifi or cellular data to communicate to MWD tools? David and Ken explain the main components of directional drilling and its importance.     

***Thank you to our Sponsor Gibson Reports!***


This episode is sponsored by

Gibson Reports
Gibson Reports

Episode Transcription

Welcome to the Erdos Miller New Technologies podcast. We spend our nonproductive time talking about everything drilling technology. I'm Ken Miller-

And I'm David Erdos.

And today's episode is about directional drilling basics. Our podcast is sponsored by Gibson Reports, where you can find the best directional drilling and NWD market share reports. Check them out on gibsonreports.com. And remember to check us out the podcast on Spotify and iTunes, just search for Erdos Miller.

Today we have a list of questions. Some of these were submitted by our team and some of these were by clients, but just asking us to take it back to the basics, right? Why do we directionally drill at all, all those kinds of things. Why don't you walk us through the questions and I will try my best to answer them. We'll see how wrong I am. And I'm sure we'll get lots of angry, "That's not right, you got it wrong" kind of stuff to our inbox. Take it away.

So, first question. Why do we drill directionally at all? I thought people used to just drill straight down, oil gushes out. Isn't that how it works?

Well, I think that a long time ago we used to just find it in the ground-

Right, seeping out-

Oil seeps and you'd just walk over it and say "Hooray." Right?

Found oil.

You're right, the very first wells were all vertical wells. We had the rock crushing tools early on, and then we got into the rotating tools, to kind of the rotating scrapers. And then, the big thing was the Tricone bit was a big deal. Or the cone bits at all. So I think the basic answer is we ran out of resources that you could drill straight down for. We ran out of oil seeps, we started vertically drilling. And then once we were done with all the resource conservations...


Reservoirs, there you go. Reservoirs that had resource to be reached for vertical wells, we just had to start getting more innovative. I think a lot of the first directional work was like, if you needed to kind of drill at a tangent or kind of do an S, or kick out and then go down or whatever else, but I think it's only been the last probably 20 years that we've been doing these kind of... Just completely go straight down, curve and then way out lateral right.

Rolling laterals.

And the biggest reason for that is this shale oil. We have to drill through it to produce it. You can't just tap into it and it's not pressurized, it doesn't flow through the rock. We got to get in there and get it out.

Yeah. Hmm. Okay. And so you just mentioned a horizontal and directional wells, and so how does that curve created? How do you make a directional well?

Yeah, it can't just be the bit by itself, because the bit just kind of cuts through the rock.

Why use a hand drill. It only drills straight.

Yeah. So we need two tools, right. One is what's you would typically call...in a conventional BHA. It's called a mud motor. And the other one is some sort of survey instrument. And so the motors have been around for a long time, or at least, even before that bend subs. So you need some sort of bend. So the basic idea is if you make a piece of the BHA that has a slight bend to it, so just imagine kind of taking your hand, laying it flat and then kind of kicking your fingers up a couple degrees. But when you rotate, that bend is kind of pointing in all directions and it gets evened out. And so you drove kind of a little bit bigger hole, but it's straight.

But when you slide then what you're able to do is if you have a mud motor, which is going to have a bend and a power section, the bit can still turn. The bend will not be turning, and so the bend will actually guide that bit along a curve. And that's depending on how aggressive the bend is, and how much weight you put on it, that kind of stuff. And so you need that tool. You need some sort of bent housing somewhere, and really a power section to be able to create the actual deviations in the well and control them.

Then you also have to have some way to know where the hell you went, because you can't just do this all by feel at the surface and hope that it works out the way that you want. So you need some sort of survey instruments. A lot of the early ones were memory log instruments, or the camera, the little plump balls of the camera-

Yeah, I've seen those.

State of the art today is NWD. So you have two parts. One allows you to make the change and then one tells you what you changed. And so you have to be able to walk and see, because that's a decent analogy.

Okay. That makes sense. And so I think a lot of what is being done these days with these directional wells is a term called pad drilling. What is a pad?

So pad just kind of refers to a little bit bigger drill site where there is a plan to put lots and lots of wellbores. I've heard of them from four to over 20.


This kind of goes back to, this is all a means to an end. Like, it's a means to exploit the resource. With the shale rocks, we really have to get down there and expose the borehole to as much of that formation as we can, in order to produce it. And you go down there and you hydraulically fracture it or whatever, and you only get as much oil as you break rock. So the fracking only goes out so far from the wellbore. So the basic thing they came up with was all of these walking rigs and stuff like that, where you can just scoot over 20 feet, go down there and just drill an identical hole right next to it and do it again.

So that, if you have a lease with so many acres and it's this big, you might end up with four or 10 back-to-back kind of wellbores that are all designed to exploit that shale rock. And so a pad usually refers to anytime that you have more than one wellbore that you're planning on drilling to exploit the resources below.

Okay. That sounds a lot more efficient than moving the rig to a different well site every time.


Starting over from scratch. All right, so what's the difference between MWD and LWD?

This is what I got wrong when I got in the industry, because I came from a computer background. So measuring while drilling, I was like, "Okay, well, they're sending the data up. That's pretty obvious." And then logging while drilling, I thought that just meant they wrote the data to memory or something.

That's what I thought too, at first.

Yeah, because log has a different word in computer science. Really the measurement, and then the logging refers to different types of measurements that are being taken. And because a lot of these tools all go back to wireline tools. Because what we used to do before we had MWD and LWD was you've stopped drilling, pull your BHA out, and then send the wireline BHA down to... Or wireline string, I don't think they call it a BHA, to go in and take all the measurements.

And so you've got two different kind of classes of measurements. One class of measurement tells you the three-dimensional picture, or the three-dimensional path of the borehole.

Right, where you're going.

Those are called DNI or directional or survey instruments. And then you have logging while drilling or sorry, logging instruments that are formation evaluation instruments, that are actually trying to tell you some property of the rock or what the rock contains. What kind of rock is it? How much radiation is it putting off? Is there oil in it? Is there water in it? Is there nothing in it? These kinds of things. MWD, your basic measurements are inclination, magnetic azimuth, gyro azimuth, tool face measurements, magnetic and gravity tool face, gyro tool face, these kinds of things.

LWD measurements would be gamma ray. I think technically the gamma ray, I think a lot of people these days-

[inaudible 00:07:20]-

Gamma is so common that it kind of gets lumped into the MWD side, but most of the time we don't call it MWD, LWD even though it has a gamma tool on it. But gamma is an LWD measurement. Resistivity, neutron density, neutron porosity, sonic caliper stuff, it just goes on forever. So there's way more LWD measurements than there are MWD measurements, because we only need so many measurements to tell us where we are in three-dimensional space. And then we need a ton of measurements to tell us what's going on in the rocks.

I think there's a lot of different ways to get the same data, those LWD measurements.


All right. So what does the term tripping mean?

Okay. So the way that we actually get the bit and all of our bottom hole assembly tools all the way down to where we're going, is we build up a drill string with increments of 30 foot pipe. Usually 30 feet, sometimes it's different depending on what you're doing and what kind of rig it is. I was just on a rig the other day that had 43 foot pipe, I think? It's an interesting type of rig, I think nominally it's 45, but it's called the super single, it's just a little bit different rig and they use a different type of pipe. And then, where we actually were doing a lot of work in the horizontal directional drilling industry as well, and so they're using 20 foot pipe, some of the times.

But normally most pipe out there I think is 30 feet. And so you build up a drill string 30 feet at a time, and so when you're drilling ahead, that's really easy because you're just kind of drilling 30 feet, you put the next 30 feet on there, you just keep going and feeding and feeding and feeding. Well, unfortunately most of the time we can't just start drilling and then stop drilling with nothing happening. Most of the time we have what we call planned trips to change out a tool, where we have issues, like where a motor or a bit wears out or starts chunking, or an [inaudible 00:09:11] fails or whatever. And that's a failure trip.

But tripping is the process of basically pulling all that pipe out or putting it all back in without drilling. And so, if you were at the end of the vertical and you're planning on going with a curve assembly, you might drill down 9,000 feet to your vertical, stop there, and have a planned trip where you pull all the pipe and the BHA tools out and go back in with a different BHA that's going to drill your curve and lateral. Or you might just have one for the curve and then do the lateral. There's all sorts of different combinations. Usually that means the guys are pulling out 45 or 30 feet at a time. One of the big rigs will do 90 feet at a time. So they'll leave three of the little joints together for a stand and they'll pull them 90 feet at a time and stack them up on the rig. And that's less painful than 30 feet at a time, over and over again.

That's tripping, and so once you're ready to go back in you'll put your new bit and BHA and all that kind of stuff together. And then you'll just put the pieces of pipe, one by one, as you kind of reinsert the BHA into the hole.

Yeah. It sounds like it could be a slow process.

It takes somewhere in the order of like... I don't know, big fractions of a day.

Many hours.

Many hours, four hours, eight hours, 12 hours, 24 hours, depending on how deep you are and if there is issues or whatever else. The worst is like, I don't know why this happens, but sometimes you end up pulling the pipe wet, which is basically there's still mud inside the pipe. And so every time it's disconnected, everybody gets soaked and-

Mud gushes out.

It's miserable. It's really miserable.

All right. Next question is, why is MWD accuracy so important?

So it's really important because we really have to know where we're actually putting that wellbore. We want to make sure that we are, especially in shale rock... Like a conventional reservoir, you could probably hit it in a number of locations and you would produce just as well. But especially in an unconventional, we really need to make sure that we're actually putting the BHA and everything where that formation really is. Depending on where you're drilling the formation, the producing formation might only be two foot or four foot in thickness, or it might be 10 or 20, right? Either way when you've got 10 or 20,000 feet of drill pipe, 10 feet is a big deal. That's like a-

Small percentage-

Very small percentage. So we need to make sure we're putting the BHA where we think we are. We talked about pads earlier. By the time we're putting well after well after well together, it's important that those two wells don't collide. A lot of times for rigs, we want to make sure that we're staying within property lines and all this kind of stuff. So, that's important. We also don't want to hit old wells. So we don't want to navigate off of where we're supposed to. The underground is not just some wonderfully open place where you can do whatever you want. There's obstacles down there and you need to stay clear of them. And so there's a lot of implications on accuracy, as far as what we can produce as well as safety. And so it's really important that the tools are just as accurate as humanly possible, and that we remove any sort of error sources.

And they're probably never going to stop doing research and development for better and better accuracy. Now, what's really interesting is in the HTD industry, known gas, we just drill down and we're like 10,000 feet deep, 20,000 feet out north. We were never really going to know exactly where that bit ended up, even with the best survey techniques. A poor survey instrument is something like 10 feet per thousand. Most of the survey instrument accuracies, I think are two to five feet per thousand error. And then kind of the best are in kind of the one-ish range. And I think that's like NWDs plus gyros plus all the magnetic corrections. I could be wrong on that. It's just kind of what I've seen, just kind of looking around.

Even at two feet per thousand, if you drill 20,000 feet you could still be off by 40 feet.

That's a lot.

Well, it's a very small percentage as far as the overall length, but if you were trying to hit it within a foot or two, bad deal. But it's interesting in the HTD industry, the bit comes out of the ground.

You know exactly where you end up-

You know exactly where it went, and what worked and what didn't.

And whether you hit something.

Yes. There's an extra level of accountability there versus the bits in the ground, we will never really know where it is in oil and gas. Be nice to know.

Yeah. So next question is a little bit basic, but why can't we use wifi or cellular data to communicate to our MWD tools?

Wouldn't that be nice?

I wish, yeah.

So we're still a lot of times stuck with this ancient technology of mud poles. Which is still a really cool technology. I love-

I was pretty blown away by it when I first heard about it.

Yeah, I love talking to people that are out of the industry about mud poles. Especially when you talk to somebody whose in semiconductor or whatever else, and we're telling them that we're sending digital data through 20,000 feet of mud, they all look like they don't believe me, they think I'm just pulling their leg. So that's cool, even though it's an older technology.

So the basic issue is the ground is not radio transparent. So a lot of the wifi technologies use signals and the frequency of 2.4 gigahertz or five gigahertz, or 900 megahertz or whatever else. A lot of these signals, they hit the ground, they cannot deal with the impedance mismatch or just the fact that it's not very transparent and it just bounces off.

It gets absorbed.

It gets absorbed, or reflected. And so, a good example would be if you have a Sirius XM radio or something like that, that'll cut out when you go under a bridge, or in a parking garage. Because that's wifi from a satellite in space and it can't penetrate through the roof of the parking garage and it won't go underground. If you go into a parking garage that's four or five levels deep, a lot of times you'll lose the FM radio. Even the FM signals that are like a hundred megahertz, won't get down there. And so these high frequencies we use just won't penetrate the ground. Otherwise we'd be using them. There's ground penetrating radar. Do you know what the frequency that is?

It's usually in the multiple gigahertz. And I don't think it travels very deep.

It's like 80 or a hundred feet deep or 200 feet deep. It's not very deep at all. So we kind of use it for MWD. We have the electromagnetic MWD tools. Those are the best things we have that are akin to wifi. But they are a very different animal because they were actually inspired by American and Soviet submarine communication systems.


So, there's actually these giant sort of transmit antennas that are, I think there's like one in Pennsylvania or something, there's like three or four installations around the US and I'm sure the Russians have their own. They are these massive, I don't know, 10 mile long antennas. They're huge, they're absolutely huge. And they'll send out what's called, I think it's extremely low frequency-

Yeah, ELF.

ELF, like 80 Hertz.

I think it's lower than that.

Maybe 10 to 80 Hertz, something like that. And they'll send out this really, really slow moving, it's still speed of light, but it's low frequency radio wave. And that radio wave is so big and so low frequency and they need such a big antenna, like 10 miles to do it, that it'll actually go through the earth. What's cool about this is a submarine can be on the other side of the world and it has to trail a three or 500 foot long kind of like wire antenna out behind it to receive the signal. But what they'll use this for is when the submarines are under the water, submerged secretly, they'll use it to send them a command to say, "Come up surface and talk to us." Otherwise they'd have no way to talk to them.

Because even the radio they use to talk to the submarines, won't go through the water. So they use these huge, huge installations with massive antennas to send these world spanning radio communications, to tell the submarine to come up and talk to you. But then when it surfaces, it still has to use a standard radio to have real conversations.

So we took that concept and we applied it to, what would you call it, electric magnetic, or people used to call them FM tools, to oil and gas. And so basically we use the entire drill string, we have 20,000 foot drill string, kind of is a big antenna. We'll send them an electromagnetic wave, anywhere from two Hertz to 16 Hertz, which is monumentally slow. So two Hertz is two cycles per second, two up and downs per second. Versus your wifi in your house, which will be these days mostly five gigahertz.

5 billion times-

5 billion times per second.

That's a big difference.

That's a big difference. And so we'll kind of use that. It's wifi, but it's not the wifi that you're used to, in a roundabout way. But it works.

Okay. All right. Well, that's all the time we have for today's show.

I'm Ken Miller-

And I'm David Erdos.

And this has been another episode of the New Technology podcast. Check out our sponsor Gibson Reports at gibsonreports.com for the latest MWD and directional drilling market share reports, and write to the podcast at podcast@erdosmiller.com and then we might put your questions on the show.