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From Fossil To Fuel™
From Fossil To Fuel™

Episode 3 · 2 years ago

Episode 2 - Rock Geology

ABOUT THIS EPISODE

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

My name is Brennan 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 Oilon 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 the 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 keeps our homes. Come join me on this adventure as we learn how the oiling gas industry operates from fossil to you. Last...

...episode we talked about how oil and gas is formed. Now we're going to talk more about how it's trapped and what it's trapped in. But before we get into this, we need to make sure that everyone understands a couple of concepts. The first one is density. Density is fairly simple, but it can sometimes be misunderstood. Density isn't necessarily how heavy something is, it's kind of how compact it is. So, for example, I weigh a lot more than the gold ring that I'm wearing, but the gold ring is denser than I am. So when something has a lower density, it will float...

...on top of things that have a higher density. This is what we call buoyancy. This is true for Solids, liquids and gases. For our sake, though, we're worried really only about three specific things, water, oil and gas. No matter where you go, water will be heavier than oil and oil will be heavier than gas. So when we're looking at a conventional oil reservoir, the water will be at the bottom because it has the highest density, and the gas will be at the top because it has the lowest density, with the oil in between. This is important to know because it's the oil and gas that will make us money, so we need to know where to find it in the reservoir. If I go and drill a well into the bottom of the reservoir where all the water is. That's really not going to do me any good. The next concepts to understand our perosity and permeability. PEROSITY is the open space in immaterial and comes from the word poor,...

...which is the open space in a rock, similarly like the pores in our skin, which are also open spaces. The easiest way to explain perosities probably to think of a sponge. Two sponges have tiny holes in them, big holes in them, but essentially lots of perosity that can absorb water. If I were to take a piece of concrete the same size as a sponge and pour water over it, it would absorb a little bit of the water, but not nearly as much as the sponge can. That's because the sponge has way more perosity than the concrete. More perosity means more storage space, so if we're looking at an oil and gas reservoir, you want high or more perosity, because it basically means you can store more oil and more gas. permeability, which we talked about last episode, is the ability, or...

...black thereof, to flow from one poor or storage space to another. Think of it kind of like the roadways in your community. If you only have one road in and out of the community that you live in, then everybody has to go through that one entrance or exit. Therefore, or you would say that the road system is not very permeable. It's hard to get from one space to another. However, if there are lots of roads to get in and out, then there are lots of paths and we would say that the system is very permeable. Let's look at it from another perspective here. So think of bubble wrap. Bubble wrap has a lot of perosity because the bubbles can store lots of air, but none of the bubbles are connected, so the air is trapped, and so we could say that bubble wrap has high perosity but zero permeability. So when we're looking at an oil and gas reservoir, remember that high perosity is generally good because it means you're storing more...

...oil, and high permeability is generally good because it means that the oil can flow through the reservoir. When we talked about density, we talked about how things with lighter density will tend to rise above things with heavier density. Well, when oil and gas forms deep in the earth, it will continue to rise up and it will rise all the way to the surface unless it gets trapped by something. Once it gets trapped, it will continue to accumulate there. This is basically the reservoir. This is where perosity and permeability are really important when we look at the geology of the rocks, because in order to find oil and gas, we need two things. We need a rock that can store oil and gas. This is the reservoir, so think high perosity, and we need a rock that can trap the oil and gas. This is the CAP rock. Think low perosity and again low permeability, because we...

...don't want the oil and gas to flow through the Cap Rock, we want it to be trapped, so we need that cap rock to be an impermeable barrier. The three most common types of rock that fill these rolls, at least the three that you'll hear of most, are sandstone, limestone and shale sandstones. Basically just what it sounds like. It's a bunch of sand grains stuck together that have lots of spaces in between the grains. Generally high perosity with lots of channels between the spaces. So high permeability. Really Sandstone, if you think about it, if you took a big scoop of sand off the beach and basically kind of compacted it together so that it's stuck together, that's really kind of what sandstone is and what it looks like. Another type of reservoirs limestone. Limestone is commonly found in marine environments and therefore is made up of primarily what we call calcium carbonate, which is the same kind of...

...material you'd find in the shells of snails or what coral would be made of. Shale, which is the third one, is basically composed of mud and lots of really fine mineral and clay components. There's not really a whole lot of space in it, so it's generally very low porosity and very low permeability. So in a conventional reservoir, shale is typically the cap or sometimes the trap rock, because it has that very low permeability. Oil and gas can't flow past it, so it acts like the lit on a jar and keeps everything in place. Now bit of a side note here. In future episodes will talk about conventional reservoirs and unconventional reservoirs, unconventional reservoirs being kind of the hot topic right now, in the media you hear about fracking and shale gas.

So really what that means is that, well, in a conventional reservoir shale acts as a barrier so that the oil and gas can't go through. In the unconventional reservoirs, the shale formations or the shale rock actually has oil and gas in it and we're trying to get that out by fracking it. But I'm not going to go down that path right now and we'll chat about that more and later episodes. Just know that for now, when we're talking about traditional or what we call conventional oil and gas reservoirs, the oil and gas targets are in the sandstone, in the limestone, and the shale acts as a cap rock or a trap rock overtop, which is the lid on top of your jar, to keep everything in place. When we're looking for oil and gas, we've got a drill way down into the earth to get to it and that costs a lot of money. So we need to be as sure as possible that it is actually where we think it is. Nobody wants to spend millions of dollars on a wild gas although this does happen more...

...often than you'd probably think. This is where geologists make their money. They're able to locate oil and gas reservoirs using something called seismic reflection. The best analogy to this is an ultrasound that pregnant mothers get to see their baby. You have an ultrasound tool that produces sonic waves that go through your skin and muscle, bounce off the baby inside and come back. The ultrasound tools able to pick up the waves that bounce back and produce an image of the baby inside. This is really pretty much what geologists are trying to do with the Rock. They have to use more powerful signals because the oil and gas is so deep, but the concept is basically the same. The seismic waves that we can generate its surface will go down into the ground and bounce off the different rock layers and come back to surface. Just like we can generate an...

...image of the baby with ultra sound, the geologists can generate a picture of the rocks down below. Using these pictures, the geologists are able to predict with relative certainty where the best spot is to drill your well. Another technique that geologists used to study is something called outcrops. As the tectonic plates below the Earth surface move, it can cause some formations of rock to go deeper, but it also causes some to come up. In some cases, there's a section of an oil reservoir that gets pushed all the way to the surface and sticks out. This is what we call an outcrop. Geologists can now actually physically see and touch the rocks at surface, even though they're millions of years old. Furthermore, because organic material deposited overtime isn't the same, each formation that comes will tend to have different characteristics that we can look at and physically examine. We call these biomarkers. Geologists can use these biomarkers to correlate...

...and identify specific formations. This helps them gather even more information. So, if you think about it, we've got, in most cases, several kilometers, are several miles, of rock below the surface. Each formation or each layer of rock is different depending on when it was deposited in the environment and that it was deposited in, and so really what the geologists are trying to do is identify certain characteristics, unique characteristics or signatures for these different layers so that when they're doing their research they can correlate across different areas where these formations are, are they going up or down and do they even exist anymore? And what they're looking for is these biomarkers. And so if I see a biomarker in one area for a certain formation and I go to the other area...

...or another side of the same area and I see that same biomarker, I can be fairly confident that it's the same formation and you can start to map it almost in d with these different biomarkers, and it really gives you a pretty good picture of the lay of the land below the surface. So as they start to gather more information, like we talked about here, they start to develop a model. So that's kind of like that d map that we are talking about for the whole area or what we would call the basin. The basin is kind of like the the area of study or the area of interest, and with this basin model they can predict how the different formations were deposited and created or over time they update the model as they get more and more information and eventually, and hopefully, get to a point where they can...

...predict optimum drilling locations based on what the model is showing. Developing this models kind of like developing a map. At first you basically start with nothing, but over time you can identify different areas, different counties, and as you get more information, you can start to drill down into specific quadrants. Eventually you gather enough information that you can pick out specific targets for where you want to go. It's kind of like if you were to move to a new city and you've never been there before. You're trying to figure out where everything is, but you really don't know anything, and so there's all kinds of tools, Google maps, marketing, that will help you kind of figure out as you go along, where the restaurants are, where the malls are, and over time, as you start to get more information, you can almost kind of build in your head a map of the community or the city that...

...you live in, so that down the road, if you need something, you basically know exactly where to go. That's basically what geologists are trying to do. They want to build themselves a map so that if in the future, I want to go to a certain area and I'm looking for a specific oil and gas formation, they pretty much know exactly where to go. This is really the job of the geologist to understand the rock formations in the basin that you're working in in order to predict with relative certainty where you're going to get the most bang for your buck. If an oil company has a really good geologists, they can hopefully secure the best land before anybody else does. And if they secure the best land, they'll probably have best access to high quality reservoir and if they access the best reservoir then they really have the highest potential for profitable production. So really it all starts with a good geologist and understanding the rocks below the surface of the ear. 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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