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From Fossil To Fuel™
From Fossil To Fuel™

Episode 9 · 2 years ago

Episode 8 - Hydraulic Fracturing

ABOUT THIS EPISODE

What actually is hydraulic fracturing and how does it work?

My name is Brendan McDougall and I'm a professional engineer. Or the last decade I've worked in many different facets of the oil and gas industry. While I have a pretty solid technical background in oil to gas, I don't really know a whole lot about the other non technical departments that help run an oiling gas company. Recently I took a course to help develop my business acumen and better understand how the financial side of the business works. What a novel concept to educate the technical people on the business and financial side. I thought it would be a really cool idea to return the favor and educate the non technical people on the technical side. This is how the concept from fossil to fuel was born. Through these twenty four episodes, we will take a journey from how oil and gas was formed millions of years ago how it is refined into the fuel that runs our cars and heats our homes. Come join me on this adventure as we learn how the oiling gas industry operates. From fossil to a few a hydraulic fracture operation. There are two basic schools of thought, blug and Perf, or single point entry, plug and perf seems to be the more common strategy because it is simpler, but single point entry has the potential to give you more bang for your buck. Ultimately, it becomes a question of whether you go with the tried and true or you take a bigger risk and go for the bigger reward. Plug and PURF is short for plug and perforate, which basically describes the whole process in three words. Set a plug down hole in your casing, perforate the casing above the plug so you can...

...fract through the holes and pump the frack. Then set the next plug above that, perforate again and FRAC repeat until you're done. Whenever we're doing hydraulic fracturing, typically we start at the toe of the well, and when I say the toe of the well, the terminology there means the very far end of the well. So if you think about a horizontal well, you're drilling down and then you're drilling out and it kind of looks like an l shape or a boot, and so the toe of the well is the far end and the heel is the corner section where the horizontal part meets the vertical part. So when we're fracking we start at the toe and we move our way back towards the heel. I'm simplifying the whole process, but that's essentially what it is. You can look into the details about all the different types of plugs or different perforating strategies, but for the sake of simplicity will leave that out here. Remember, when the drilling rig is finished with a well, the casing is usually cemented, which means if you were to try and pump fluid right off the bat to frack it, it wouldn't be able to go anywhere because the metal casing is in place. It's kind of like if you can imagine putting your finger on the bottom of a Straw and trying to blow air through it, and unless you take your finger off or you punch holes in the straw, you're not going to be able to blow anything through. That's why the first step is always to perforate holes in the casing. This is usually done with explosive charges that are done in clusters. Let's look at an example here. If you have a well board that's a thousand meters long and you want to do ten fracts or, as we call them, ten stages, each stage would be a thousand divided by ten, a hundred meters...

...long, and if each stage was going to have five clusters of perforations, then the clusters would be a hundred meter stages divided by five clusters, or twenty meters apart. Generally speaking, most companies will use this type of geometric sequencing, meaning equal will distances between everything, for clusters and stages. It just keeps it simple and really just reduces your chance of error. In this example, that would mean all of the clusters from the Toe to the heel are twenty meters apart for the whole length of the well bore. The perforations are created while using a piece of equipment called a wireline truck. The wireline truck is basically a truck with a very big spool of cable capable of transmitting electronic signals. Will talk more about wireline trucks in episode twelve, but I'll give a bit of an overview here so that you can understand the context of the operations. The perforating guns, which are the ones that are going to punch holes with the explosive charges, and when I say punch holes, I guess that's kind of slang. They make holes in the casing, in the cement by use of an explosive charge. So the perforating guns and the plug are both hooked up to the end of the wire from the wireline truck, the Spool of wire, and they're lowered or pump down the whole. And again bit of slang there. When we say whole, we mean the casing. It's just that if you're looking at the casing from surface and looking down, it looks like a hole. So the terminology is if you're pumping something or putting something down on the casing, we typically say that you're putting something or pumping something down the hole, just kind of like letting the lure on...

...your fishing line drop down into the water until you get it to the depth that you want. Once you're at the depth that you want for your perforating guns and your plug, the wireline truck can then send an electronic signal down the wire which triggers the plug to set into place. So when I say plug, you can pretty much picture something that would look like the plug in the drain of your Bath Tub. So if you imagine you've got this metal piece of tube which is your casing, and you're basically trying to set a bathtub style plug into it so that you can isolate the previous stage, which ensures that the next fract that you're going to pump is going to be placed where it needs to go. So the plug is an isolation tool to make sure that your fract fluid doesn't go past the plug into the zone that you've already fract. So once you've set your plug, the wireline unit can then pull up the wire so that the perforating guns can shoot. And so the PREVICTI. Previous example that we were talking about, had five clusters. So your perforating guns would have five sets of charges. So you would set your plug and then you would pull your wire line up a little bit. You would shoot the first gun, then you would pull up another twenty meters, you would shoot the second gun, pull up another twenty meter, shoot a gun and keep doing that until you've shot all of your perforating guns or charges. To remember, the guns or charges are able to penetrate through the metal casing, through the cement and into the rock and this creates the pathway for the frack fluid to flow through. Say That ten times fast for the frack fluid to flow through, out of the casing and into the Rock. So...

...this is really the initiation point for your frack. Once the plug is set and all the perforations for that stage have been fired, the wire line unit will pull the cable or the wire out of the hole and make way for the frack to start pumping down the water and sad there's all kinds of frack theory out there, but to be honest, no one really knows a hundred percent what's going on down there. We have a pretty good idea thanks to some pretty ingenious technology, like something called micro seismic, which will cover later, but you really never know for sure. It's not like we have camers down there and we're talking about rock that's several thousand kilometers away that we can't even see. What I'm trying to get at is that when I explain what happens in the frack portion, I'm explaining one generic way of doing it. Understand that there are many different ways and it all depends on the area you're in and what theories your technical team subscribes to. Generally speaking, though, it comes down to fluid, sand and chemicals, like we talked about in the previous episode. You pump fluid downhole through the perforations at very high pressure. Let's look at an example here to try and paint a visual in your head of what's going on, and bear with me through this one for a little bit here. So imagine a large group of people in a big room, and this room is absolutely pactful of people. You guys are shoulder to shoulder and the room is scattered with Easter eggs and you need to collect as many as you can. If you want to get through, you're going to have to push hard. You're also going to have to take the path at least resistance, which means you're probably not going to go in a straight line. That's kind of like what happens in a frack. The fluid is trying to find the path of least resistance and it's going to have to push hard...

...to get through the rock and it's not like it's going to go in a straight line. So you're going to have this kind of almost like spiderweb type pattern as you're going through the Rock, or as you in the room would be trying to navigate your way to these Easter eggs. Remember, you've got to pump hard enough to overcome the forces holding the rock together so that little fracture. But as you're going through the room and you're pushing through the people, you need to leave something behind to keep them apart so you can get out, or they're just going to close up the space you just created as soon as you move past. This is the same for a FRAC. You can create fractures in the rock with high pressure, but if you don't leave something behind to prop the fracture open, it's just going to close on itself and now you've done all that work for nothing. This is where the sand comes in. You pump sand in your fluid so that it will settle out in the fractures and help keep them open long after you stop pumping fluid. The chemicals just help optimize the whole system. Some help reduce friction or some kill bacteria, like we talked about. Some help you create fractures if you're in a tight rock where it's difficult to do so. There are many different chemicals out there and each company will have its own special house blend, but they're all there to either make the frack easier to do or cheaper to do, and preferably both. Once you've placed all the fracts, and therefore all of the sand into the fractures you've created, you're now ready to produce hydracartets. Almost don't forget that you're well bore is still full of plugs. You need to use another piece of equipment called Coil Tubing to go down and drill up all the plugs so that they aren't restricting any flow of hydrocarbons up the well boar. Coil tubing is basically like a giant version of one of those...

...snake tools that hopefully none of you have ever had to use to clean out the drain in your kitchen sink if it ever gets plug with food or debris. A picture is worth a thousand words here. If you can get it on Google, check it out. Will get into the details about coil tubing and episode thirteen. The other main type of fract that we mentioned at the very beginning is called single point entry. Instead of having the clusters or multiple perforations or multiple points of entry that we had in plug and PERF, single point entry pumps the fract through one single point. So in the example above that we had the thousand meter well bore and you're pumping ten big fracts. If we did single point entry rather than ten big fracts, we might pump something like fifty smaller fracts. The benefit in theory is that you get better coverage over the length of the well bore, which should mean better production. But they're harder to do and more complicated. In this system the casing will already have single entry points, sometimes called sleeves, that are placed at predetermined intervals. EACH FRAC will open up one sleeve, which becomes your single point of entry for that FRAC. Once that FRAC is done, you pump another FRAC on the next sleeve and so on. So the idea is is that in the previous example, if one stage on my thousand meter horizontal lateral is a hundred meters long and I've got five clusters that are twenty meters apart, poos to say that I'm getting a hundred percent access to all of the hydrocarbons in the rock that's between those two clusters. So there's twenty meters of rock in between each cluster and there's no guarantee that I'm getting the hydrocarbons or getting...

...access to the hydrocarbons and when I say getting access, I mean there's no guarantee that I'm creating artificial pathways for those hydrocarbons in between clusters to flow, because at the end of the day, are objective as engineers is to try and get as much oiling gas out of that rock as possible, and if you're leaving some oil and gas behind that's stuck in between those two clusters, you haven't really done an efficient job. Now, with single point entry, instead of having your clusters twenty meters apart, you might have each sleeve or each single point of entry five meters apart, and so you're doing a FRAC every five meters or maybe every ten meters, and so you have a much higher chance of accessing the oil and gas molecules that are in the Rock, whereas in the plug and perf method there's a higher chance that you might be leaving some of that behind. Now again, like we talked about in the beginning, plug and PERF is kind of a tried and true it's simple, it's a little bit cheaper, but you might be giving up some of the upside that you might get if you're doing with single point antruy. Ultimately, the best system really depends on what you're trying to achieve, what your budget is and what your risk tolerance is. By most industry reports and standards, I would say more than eighty percent of completions are plug and PERF. Hey guys, if you like today's episode, make sure you subscribe to the podcast. Unlike most podcasts that release an episode every week or two, I did all twenty four at once, Netflix style, so you can listen to them...

...all right now if you just hit subscribe. If you like today's episode, make sure you leave me a comment or thumbs up, or you can email me at from fossil to fuel at GMAILCOM or look me up on Linkedin. I'm Brendan McDougall.

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