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From Fossil To Fuel™
From Fossil To Fuel™

Episode 27 · 2 years ago

Rock Geology

ABOUT THIS EPISODE

The different types of rocks and rock formations that are critical in oil and gas.

From fossil to fuel with Brendon McDougal and William Bella Bass this is oil and gas, one and one, taking you through the entire fundamentals, from geology to refining, without the use of a textbook. All Right, here we are, back at it, episode two. Episode two, Rock Geology, rate up your alley. Here you go. Episode one we talked about formation of fossil fuels. We talked about how they're formed, why they formed, the high temperature, the high pressure and then how they start to accumulate in a reservoir. Today, for rock geology, we're going to talk about processing permeability. Will dig into that a little bit more. We're going to talk about, of course, rocks and we're going to talk about how we find oil and gas. So now that it's actually there in the reservoir, what do we do? So let's get right into it. Let's talk processing permeability. We talked a little bit about permeability last episode. So why don't you tell me? What do you understand, both from last episode and probably a little bit from your education? What is permeability? Let's revisit that. Okay, for permeability, the way I understand it from like a science background. So permeabilities kind of like, I guess, maybe similar to penetration, but in regards to maybe like a membrane or some sort of surface that some other substance can flow through. So something like a piece of plastic, like a sandwich bag, won't have a lot of permeability because you won't flow through it, but then something like a sponge, for example, water will soak right through that. So it has a layer that is permeable. Yeah, no, that's fair. Yeah, permeability really is just how easy something can flow through a material. So, given that we're talking about oil and gas,...

...right, and we're talking about being able to well permeability in one regard, having oil and gas migrate up and get trapped in a reservoir, but also when we're producing the oil and being able to get the oil out and up to surface. So with regards the permeability, what do you think we're looking for? You think we're looking for high permeability or you think we're looking for low permeability? Well, for a reservoir, you probably want high permeability because that will allow oil to flow more freely. Yeah, exactly. Yeah, really, the honestly, the only time in oil and gas you're looking for. Low permeability is for that barrier, that cap rock that's going to trout on top. Yeah, so really that's permeability. PEROSITY is another important thing. These are two fundamentally important concepts when it comes to oil and gas in general. So I think it's really important for you and really for all the listeners to understand what these are. So the permeability, we talked about that perosity. We think prosody is parosody. Like, for example, if you have a bunch of sand on the beach and you put some sand in your hand to make a rock you want to just just like we talked before, like bury, it gets a lot more pressure and temperature and that rock starts to fuse together, but it's made of small little grains that are all touching each other but they're not completely fused together. So in between those grains there's little air bubbles. Yeah, pores, Yep, and the more pores you have, the more proosody. Yeah, you've learned this in school, clearly. Yeah, it's exactly right. Yeah. So so the pores, I guess for the listeners out there, so the pores. That's pores perosity. That's how it got its name. The pores, like you exactly just explained, there the spaces in between the rocks. And when I say rocks, really we're talking the grain. So you take a rock and you look at...

...it under a microscope, it's exactly what you said. You imagine these little grains of sand that are basically kind of glued together. But because the rocks don't perfectly fit together, there's going to be spaces in between them, kind of like if you took like a bunch of pillows and through them in a big pile, there's going to be little spaces in between the pillows. Those are the pores, right. So pores is the space between the rocks. If you imagine, then we've got a reservoir that's made of whatever kind of rock and no matter which kind of rock you have, you're going to have some perosity. Might be little, might be a lot. The perosity is going to be the place where the oil and gas is going to accumulate. You're not going to find oil and gas inside the grain of the Rock. It's going great in between the grains of the Rock. Right for Perosity, then, do you think you want high perrosity or low perosity for oil and gas. For Oil and gas, you probably want high perosody. Is Well, because the more pores you have, the more oil and gass you can fit inside of a rock. Your ace in this already. Thanks. Yeah, exactly. High perosity. The more perosity you have, the higher the probability of more oil. Just because you have prosody doesn't mean it's all oil in the pores, but the more space you have the more oil you can store. So generally speaking, as you correctly deduced, when we're looking at oil and gas reservoirs, especially the the conventional reservoirs, and we'll talk about conventional versus unconventional in a later episode, generally you're looking for high permeability and high perosity. You know, you talked about a sponge. That was a pretty good example for both. Right. So a sponge is something that has high perosity, like you said, because when you pour water on it has the ability to absorb water into those wars, but when you squeeze the sponge...

...the water can come out easily. So high permeability. So in the sponge it's like this. The pores are more connected. So that is kind of what allows the water to flow through. But, for example, if you had like a block of Swiss cheese, you still about wholes in those Swiss cheese but they might not be really connected. So it'd be like higher prossy maybe, but not really high permeability in that cheese. Yeah, yeah, that's a great that's a good segue. I like it. Another example of that sort of high perosity low permeability that I usually use is bubble wrap. Oh, nothing but bubble wrap. It's got all of these pores, right, and I'm using air quotation marks here. It's got all these little pores filled with air, but the air's trapped. It cannot flow. So that would be an extreme example of high perosity and literally zero permeability. Right. Swiss cheese is probably actually a better analogy because you might have high perosity for air in there, but the air might still be able to flow through a little bit. So sponge is a good example of high perrosity high permeability. Bubble wrap or Swiss cheese a good example of high perosity low permeability. Last one's a tricky one. Can you think of any examples of something that might be low perosity, high permeability. took me a long time to think of what give me wow, the permeability is kind of dependent on the connected pores. But if it has like not a lot of pores, how can it be? Yeah, highly permeus. Yeah, it's so. So here's what I thought of. This is a hard one to think of an example and it's almost irrelevant because an oil and gas even if you have high permeability, if you have no prorosity, you would never look at that, right, because I'm going to find oiling gas there. But really just to kind of, I guess, complete the Trifecta of analogies for what we're talking about, what I had thought about was a single lane highway. A single lane highway would have, you know, high permeability for traffic, right, like cars...

...can flow through easily and quickly, but if traffics hat a stand still, there's not a lot of space for those cars to be, whereas if you had like a ten lane highway, you still have high permeability for traffic and lots of spaces, but you have more space. Right. So maybe not the greatest analogy, but was what I came up with on short notice. Here. Maybe like a stone with like just a tube, yeah, going through it of air, so that it's like just a single poor that is connected, one single one single still flow through the middle of the Rock and that's it. Yeah, yeah, no, that would actually be a good because then the permeability would be high through that, that cracker, that Straw. Yeah, no, that's a great example. So I'd be curious actually to know that you did some of these courses in in university on Geology. Yep. Do you guys ever talk about different kinds of reservoir rocks a little bit? I know a little bit about a Cap Rock, kind of what we talked about earlier. Yep, some that has very low prosody and permeability. So when oil is rising up through permeable rocks that are typically kind of more permeable or at also have more porosity, maybe like a sandstone or something. Yep. Yep, sandstones one of them. And then it could hit like shale, which would be maybe a cat rock. Yep as well, just because it's like made of clay minerals, which are super small and packed densely together, so it doesn't really flow through it. Well, yeah, you're you're setting this up perfectly. Those are two. Two of the main ones I wanted to talk about sandstone. Shale limestone is another. Will probably talk a little bit about coal, just because it is a material made of oil and gas, not typically a reservoir rock, though, I guess, and we'll also talk about chalk. That one is maybe not as common as the other three, but something probably just touch on quickly just to cover it...

...as well. I'm not going to go into some of the specifics for rocks again. This is really just the fundamentals here. So Sandstone. Let's start with that one, because that's probably the most common. Tell me a little bit about sandstone. What is it? So I know that rocks kind of fall into three categories. There's sedimentary rocks, igneous rocks and and metamorphic rocks, and sandstone would be a sedimentary rock because it's made, it's composed of a bunch of sediments which are just broken up pieces of other rocks and grains and minerals, Yep, and then compacted together. That's exactly right. When I try to explain sandstone I literally tell people imagine taking a giant scoop of sand off the beach and just compressing it so that it became like a block of sand. It's literally sandstone is exactly kind of what it sounds like. It's yeah, it's like self explanatory. Yeah, yeah, and so sandstone is probably one of the bigger workhorses of the conventional oil and gas industry because typically sandstone does have high perosity and high permeability, exactly what we talked about before. And I guess you know, just quick note here for the listeners to try and differentiate, if you're trying to remember the difference between parosity and permeability, which ones which. The Way I remember it for myself is perosity is like poor so the pores in your skin. So the ability to store sweat. So it is space permeability. For whatever reason I think of a perm, something I clearly don't have, but like a like a hair perm as if you think of somebody's, like they got like a really Nice Perm, they're like God, do you check out your flow? Right, like check, like your hey, well, right. So permeability is like the ability to flow through something. So anyway, if that helps remember between in the two. Next you'll probably laugh next time you see someone with a Perm...

...permeability. Okay, so sandstone, we talked about limestones, another one. So did you? Did you guys ever talk about Limestone and slime stone? Is it? It's a I think, also sedimentary rare or maybe, because I'm pretty sure it's it's composed of calcium or calcite. Yet calcium carbonate, calcium carbonate, calcium carge, which is like made of like sea creature shells, all stuff. You're killing it. Yeah, you're exactly right. Yeah, right. So it's literally like, and I remember the first time I learned this, it was kind of hard to picture these like giant rocks that are composed of like miniature seashells that were like a hundred million years old. Yeah, yeah, but it's literally like imagine, you know, you see us snails, she'll imagine a hundred million years ago there's like a gazillion of these things living in the ocean and they die and the seashells all fall to the bottom of the ocean and then over time, you know, these gazillions and and they might not be as big as like a snail. It might just be like microscopic, you know, like single cell organisms, and over time the shells accumulate and that becomes limestone behind sandstone limestone would probably be like the next most representative rock of like a conventional reservoir. So that one I thought was kind of cool because it's shells. Super Cool. The third one you talked about already, a shale, shales, is super interesting one because when we look at conventional oil and gas, which is kind of everything we've been talking about so far, shale is important because that's typically the material that's going to be your cap rock or your barrier right at the top of the reservoir. It's your low permeability rock that, generally speaking, oil and gas, when it's flowing up, is not going to be able to flow through, so it gets trapped and forms this right so as humanly. Yeah, yeah, that's shales roll in a conventional sense. Later on, when we...

...start talking about unconventional oil and gas, one of the things that will be common when we start talking about unconventional is fracking, right. You know, I'm sure everybody WHO's listening in in some context has heard about fracking and has some sort of visual in their head of what it is generally speaking for fracking. What we're actually targeting for the oil and gas is shale, because you're trying to break that. You Try? Yeah, so that it can flow. Yeah, yeah, exactly. So in conventional reservoirs we like shale for its low permeability because it's a barrier. But if you're targeting a rock that has oil and gas in it, you don't want to go after something that has low permeability because the oil and gas can't flow right. Right. But there are some shales out there that have high perosity, so there's lots of oil and gas in them. They're just trapped because there's no permeability. The right and we'll talk about fracking more later, but basically what fracking is, high level definition, is you're creating artificial permeability when you when you frack and you create those little cracks in the raw. Right. So it's like a fracture. Yeah, it's like your strong example. Right, you're talking about a straw before you put a Straw on a rock. Right. That's kind of what we're doing with fracking, is we're putting a little channel or a highway for the oil and gas to flow through. Yeah, so shale, because by the very definition of what it is, has low permeability. It's important for two different types of scenarios. One like we talked about as the Cap Rock, and to is it can actually be the target. That's what you're actually going after for your oil. And Yeah, that's interesting that she'll can also have highperosity to yeah, I think it probably really just depends on the environment in which it deposited and we're totally not going to nerd out here and go down, yeah, depositional environments, although I'm sure that would probably...

...be right up your alley, I do know that, but we'll keep it high level. So, yeah, shils an interesting one because it kind of plays both sides. Plays the the good guy, you know, where has the oil and plays a bad guy where it's trapping the the oil and gas coal. It's not necessarily like a reservoir rock or a formation. But just to touch on that as well, coal is really just oiling gass in kind of a solid form, and we talked about that last episode. So that's the contention of like porosity and probability and cap rocks don't really apply to example. Yeah, and that's why, you know, when you hear people talk about coal, you don't produce coal like you would oil and gas. Like oil and gas, we have to drill for it and then it'll flow up through the pipe to surface coal you're mining for. So you're literally just like digging it up right as is. And then the last piece is chalk, and I want to talk about this one because I thought this one was pretty cool. So Chalk is a type of reservoir formation. It's actually a type of limestone. Okay, yeah, yeah, because it's just like even finer yet shells. Yeah, it's more of the single cell type work. So like think you have to see these things under a microscore ray see them right. But Chalk is a different type of formation that can have oil and gas to but I thought it was interesting because, you know, when I went to school, the teachers were always writing on the blackboard and chalk's the same thing. Chalk that they're writing on the blackboard is the same, generally speaking, as the chalk that we're trying to get oiling gass out of. Sokay, yeah, if you took a piece of chalk and again you're studying to be a teacher, dip the teacher still use chalk anymore? Is it all like well, like boards, you Gott ipath stuff. Now, Sy, I'm dating myself. Yeah, all right, yeah, s every they'll use a lead in your boy. Yeah, fair point. Yeah, okay,...

...to Shay. So I guess what I was trying to say is that the chalk that we used way back when. You know, it would have been cool. I wish one of the teachers would have done this as an experiment when we were in school. If you took a piece of that chalk and you looked at it under a microscope, you'd actually see that it's made up of little shells, Shell bits. Yeah, yeah, like, I don't I don't know if that's cool or creepy or whatever it is that you're writing on a blackboard with like skeletons. Yeah, that's, yeah, weird. Yeah, anyway. So I just wanted to share that to sometimes you'll hear of reservoirs. There's one in Texas, for example, that comes to minds called the Austin Chalk. Anyway, just wanted to throw that out there because I thought that was a cool one to so those are, you know, high level. When we talk about reservoir rocks, there's different kinds of rocks. It really just kind of depends on how those rocks were deposited over time. To determine, you know, is it a sandstone? Is it a limestone? Is a chalk? Is it a shale? But just to give the listeners an idea that there are different types of rocks down there. Right. So we've got the different types of reservoir rocks covered. Let's talk about how we actually find this stuff. And this one I don't know if you guys would have talked about this in school or not. Yeah, not, not too much what they are, but not really how you go about finding them as much. I imagine the geologist that I know we're probably going to a slaughter me for oversimplifying this, but this is the way I picture it in my head. Apologies to the geologists out there. I pictured it as three really kind of different ways that you can try and find the oil and gas below the surface of the earth. The first one is with something that they would call that we would call seismic reflection. Okay, have you heard of that before? Yep. So what would you when I say seismic reflection? Why? How would you picture that? We would use that. So a seismic wave is well, I guess it's just kind of like energy traveling...

...through the rocks, kind of like it's like an earthquake. Yet seismic activity is is an earthquake. Yeah, but reflection is because seismic waves, I'm pretty sure, travel through rocks at different speeds depending on what they're made up of. You're exactly right. So when they hit a boundary in between two different kinds of rocks, that change in speed sometimes reflects the wave back up to the surface and then you can record that time and see how deep it was and then I guess maybe if you if you know more mass stuff about how fast it was traveling, you can probably make an inference as to what kind of rocks that you just went through. Yep, you're absolutely right. Yeah, so all we're really doing seismic waves like a microwave or a radio wave or an X ray. Right, it's a wave that travels down exactly what you said it is. Depending on the different types of rocks that it travels through, will react differently, and from that information that you get back you can deduce different things about the rock. In some cases, depending on the technology, you can actually generate an image. And so the analogy I used to really just kind of keep it simple. Is it just think of an ultrasound if a mother's pregnant with her baby. So in that case you're using ultrasound waves and so the ultrasound waves go in, bounce off the baby, come back out and they're able to use those waves to generate an image of the baby, baby inside. Right. So generally the same kind of concept for seismic reflections. They're using waves to generate an image. The only difference with ultrasound is, you know, babies like a couple inches below your skin, very good. Rocks are like couple commoners. Well, yeah, so seismic reflection, that would be one way we could see it. Another way would be out crops. Did you guys ever go see any outcrops or a little bit? It's just like rock exposed at the surface. Yes,...

...so just like I go, me go into the mountains and seeing things that are layers that have been brought up or layers that have been eroded away. So you can see, yeah, they are what they are. Yeah, yeah, that's exactly it. And so you know, the way I picture it my head is as these rocks are getting deposited over time. I picture them getting deposited horizontally. But then what happens is as they get deeper and deeper. You've got these tectonic plate or these like massive forces going on and what can happen is one tectonic plate can smash into another and it forces one of the tectonic plates or this rock. It forces this rock up and over time, a long time, those rocks that get pushed up could become mountains right or in some cases what we would call an outcrop. So the the rock that was deposited at like, I don't let's say it's that like three kilometers. Over time that layer of rock, or a portion of it, might get pushed higher and higher till it's actually at surface. So, from a geologist point of view, I'm sure these guys get super stoked about this kind of stuff because instead of actually having to use seismic reflection to try and generate an image of what this stuff looks like, you can literally drive out and physically see just check it out. Yeah, you can check it out right. And so the same reservoir rock that you might be drilling three kilometers deep way over there to try and get the oil and gas out of, you can physically see it at surface and study it and take samples of it and look at it under the microscope. And for the people listening in, you know, maybe the easiest way to try and visualize what I'm saying here is the next time you're in the mountains, are traveling or vacation and you see some mountains, if you look at the different layers of the mountains, you can actually see like there's different layers of rock and sometimes they're different colors or they look different. Right. Those are all different, you know,...

...those little deposited at different times. But if you if you look at those layers, they're usually at an angle right, like they're not flat. Typically never fly out of yeah, so they're at an angle because they got pushed up right at whatever that angle was right. And so in your head, if you kind of obviously probably isn't a straight line, but if you kind of just do like a straight line all the way down below the surface of the earth, you can see how that formation might look underneath. Yeah, how in one spot it could be at surface and then, like you know, fifty kilometers away it could be three kilometers deep. Awesome. So seismic reflection to generate an image out crops, to physically see what's that surface and then another technique that we use is called offset wells. So offset wells is really just kind of like using existing data. Let's use this example. So let's say I've got company a over on my left hand side and they drill a well that's two thousand meters deep and they get oil and gas. They're cheering because they found an oil and gas. Yeah, and then I get company sea over on the far right hand side and they drill a well but they have to go down to threezero meters define the same oil and gas. So two thousand meters, three Thousan and meters. Company M comes in and they buy up the land rate exactly in the middle. Without having any other knowledge. They can extrapolate to they can extrapolate right, and so they would. If you've got twozero meters here and threezero meters here and these guys are right in the middle, their target depth would be twenty five hundred. Yeah, so that I'm probably way over simplifying there, but that's kind of generally the concept with offset wells. Offset meaning they're offset from your property or your acreage that you're going to be drilling. That's where that comes from. Yeah, so what geologist can do is they can actually use the data from those...

...offset wells and the left in the right and make inferences about where the oil and gas might be on your property. Now it's not always linear, like I just said, but obviously you're probably going to have more than two data points and so they can collect data from all of the offset wells around them to make sort of an educated guess. Right, that makes more sense than just random weight drilling somewhere, which I was thinking was going to be the third. Yeah, that it just luck chance. And you know what, that's probably how it happened. I right, probably I probably should have mentioned that. They're probably is a fourth factor then, but the geologists will probably deny that till the day they die because it's a sad fuel baby. Yeah, so the Nice thing too is that, you know, we talked about boat when you're looking at the mountains and you're looking at these layers, how they look different and how they have different colors, the rocks look different. We talked about seismic reflection, how they will relay different properties. They also have different what we call biomarkers. So, for example, in Canada, one of the big oil and gas bearing shale formations is called the Matney. Some people may or may not have heard of that. Before the Matney, that formation will have like specific biomarkers, which are really just like specific characteristics for that right, I guess, like specific fossil that you find in there. Nor it's just like physical characteristics of the Rock. So just like we look different, you have hair, I have none. I have Right, I have a biomarker that can distinguish me from you. Okay, so it's not really related to the biot like a biological aspect. It's more just bioways in like your biography of the rockers or yeah, yeah, just characteristics of the rock that you could measure kind of like yeah, like facial recognition or something like considered facials recognition for rock formations, identity. Yeah, yeah,...

...exactly. Yeah. And so really, like at the end of the day, for as much as I've been harping on the geologist here, they do actually have a super important role to play, because it's the geologist job to find the best rocks. Like you may have an idea that there's ailing gas here, but that might be a wide area. So where's the best spot? What has the highest perosity. What has the highest permeability? Right, and and that would kind of define what your best rocks are. So it's super important. So kudos to to the geologist. Yeah, that's basically it for rock geology. Right. So, keeping with the theme, here are key topics today permeability, perosity, reservoir rocks and how we find the oil and gas. You want to give us a quick, recappable synopsis? Little Synopsis? Yeah, okay. So first few concepts permeability and perosity. PAROSITY is the spaces in between grains in rocks, and permeability is the ability for something to flow through, material through, yeah, flow. Yeah, and different kinds of reservoir rocks, you have sandstones, which are made of different kinds of grains of sands and typically have a high parosdy and high permeability. Ye, same with limestones and chalk, Yep, which are also sedimentary rocks and made of calcium carbonate, which is the substance that like sea creature shells are made of. Yep, exactly. And then there's we also talked about shale, which is a typical cap rock which generally has low permeability but I guess sometimes can also have high porosity. Yeah, so can have oil as well. Yeah, and in order to find the oil and gas, you can go to the mountains or or anywhere else and look for an outcrop. Yep. You can also use existing data from from wells that have already been...

...dug. Yep, your eyes that well se yeah, and offset wells to see if you can find a spot in between two wells that have found oil. And third one is seismic waves, seismic reflections. So you can use a device that cretic seismic wave to enter the earth, reflect back and give you some information or an image as to what kind of rocks are beneath you. Yep, yeah, just like an ultrasound. Yeah. Yeah, yeah, well done. Maybe you'll teach the next episode, episode three. Episode three, Million Bell Vans. All right, thanks everybody for listening to episode two. Next on episode three, we're going to be talking about conventional and unconventional reservoir so we talked so far primarily about the conventional reservoirs. Will start talking a little bit more about the unconventional reservoirs. We talked about how that's a little bit like fracking. What's that all about? Yeah, exactly. So what what is an unconventional reservoir? How is it different from conventional and why is it important? So dialing next time for episode three. Thanks everybody. From fossil to fuel, with Brendan McDougal and William Bell of vants. Subscribe now and your favorite podcast platform and share with your network.

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