March 7, 2024 • 31 mins
In this informative episode, Brendan McDougall and William Belevance delve into the fascinating realm of rock geology, emphasizing the key concepts of porosity and permeability critical to the oil and gas industry. They explain how fossil fuels are formed, what distinguishes a productive oil and gas repository, and why oil and gas get trapped in underground pools. Using everyday examples, the hosts illustrate these critical geological terms and their significance to oil extraction.
The conversation further covers a detailed discussion on reservoir rocks like sandstone, limestone, and shale. They illuminate the intricacies of these reservoir rocks, such as the self-explanatory composition of sandstone, the unique origin of limestone from sea creature shells, and the dual nature of shale acting as a barrier in conventional reservoirs and a target in fracking applications.
Gain an in-depth understanding of the journey of fossil fuels, starting from their formation under high temperature and pressure conditions to traveling upwards through permeable rocks. With their simplified narrative, Brendan and William make understanding geology terms and their implications in the oil and gas industry easy and exciting, making this episode a must-listen for anyone passionate about getting familiar with the oil and gas industry.
Enhance your knowledge about the exciting techniques like seismic reflections, outcrops, and offset wells used to locate oil and gas. Get a sneak-peek into the future of this industry, with the hosts hinting towards the upcoming unconventional reservoirs. Click 'Play' now to reveal the secrets of oil and gas extraction and appreciate the captivating science behind it.
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
(00:03):
From fossil to fuel with Brendan McDougall and William Belevance.
This is Oil and Gas 101, 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, right up your alley. Here you go. Episode one,
(00:26):
we talked about formation of fossil fuels.
We talked about how they're formed, why they form, the high temperature,
the high pressure, and then how they start to accumulate in the reservoir.
Today for rock geology, we're going to talk about porosity and permeability.
We'll dig into that a little bit more.
We're going to talk about, of course, rocks.
(00:47):
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 porosity and 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?
(01:07):
What is permeability? Let's revisit that. Okay.
For permeability, the way I understand it from like a science background.
So permeability is kind of like, I guess, maybe similar to penetration,
but in regards to maybe like a
membrane or some sort of surface that some
(01:28):
other substance can flow through so something
like a piece of plastic like a sandwich bag won't have a lot of permeability
because it 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.
(01:49):
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.
(02:15):
So, with regards to 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, honestly, the only time in oil and gas you're looking
(02:36):
for low permeability is for that barrier, that cap rock that's going to trap.
Right, one on top. Yeah. So really that's permeability.
Porosity 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 permeability, we talked about that.
(02:58):
Porosity, what do you think porosity is?
Porosity, 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
(03:22):
touching each other but they're not completely fused together so in between
those grains there's little air bubbles and pores yep and the more pores you
have the more Or porosity.
Yeah. You've learned this in school, clearly.
That's exactly right. Yeah. So the pores, I guess for the listeners out there,
(03:45):
so the pores, that's pores, porosity. That's how it got its name.
The pores, like you exactly just explained, they're the spaces in between the rocks.
And when I say rocks, really, we're talking the grains. 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.
(04:06):
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 threw 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, right?
If you imagine then we've got a reservoir that's made of whatever kind of rock.
(04:31):
And no matter which kind of rock you have, you're going to have some porosity.
Might be a little, might be a lot.
The porosity 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 to be in between the grains of the rock. right for porosity
then do you think you want high porosity or
(04:53):
low porosity for oil and gas for oil
and gas you probably want high porosity as well
because the more pores you have the more oil and gas you can fit inside of a
rock you're ace in this already nice yeah exactly high porosity the more porosity
you have the higher the probability of more oil just because you have porosity
(05:15):
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 conventional reservoirs, and we'll talk about
conventional versus unconventional in a later episode,
generally you're looking for high permeability and high porosity.
(05:39):
You know, you talked about a sponge. That was a pretty good example for both,
right? So a sponge is something that has high porosity, like you said,
because when you pour water on it, it has the ability to absorb water into those pores.
But when you squeeze the sponge, the water can come out easily. So high permeability.
(06:00):
So in the sponge, it's like 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, cheese
you still got holes in those swiss cheese but they
might not be really connected so it'd be
like higher porosity maybe but not really high permeability
(06:20):
in that cheese yeah yeah that's a great that's a
good segue i like it another example of that sort of high porosity low permeability
that i usually use is bubble wrap oh nice 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 trapped, it cannot flow.
(06:42):
So that would be an extreme example of high porosity and literally zero permeability.
Swiss cheese is probably actually a better analogy because you might have high
porosity 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 porosity, high permeability.
Bubble wrap or Swiss cheese, a good example of high porosity, low permeability.
(07:05):
Last one's a tricky one. Can you think of any examples of something that might
be low porosity, high permeability?
Took me a long time to think of one. 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 highly permeable? Yeah.
(07:27):
So here's what I thought of. This is a hard one to think of an example.
And it's almost irrelevant because in oil and gas, even if you have high permeability,
if you have no porosity, you would never look at that, right?
Because there's no oil and gas there.
But really just to kind of, I guess, complete the trifecta of analogies for
what we're talking about. what I thought about was a single lane highway.
(07:49):
A single lane highway would have high permeability for traffic, right?
Like cars can flow through easily and quickly, but if traffic's at a standstill,
there's not a lot of space for those cars to be.
Whereas if you had like a 10 lane highway, you still have high permeability for traffic.
(08:10):
And lots of spaces. But you have more More space, right? So maybe not the greatest
analogy, but it 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 then it's like just a single pore that is connected. One single.
One single. So it'll flow through the middle of the rock and that's it. Yeah.
(08:32):
Yeah, no, that would actually be a good, because then the permeability would
be high through that crack or that straw. Yeah, no, that's a great example.
So, I'd be curious actually to know, you did some of these courses 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.
(08:56):
Yep. Something that has very low porosity and permeability.
So when oil is rising up
through permeable rocks so
they're typically kind of more more
permeable or also have more porosity
maybe like a sandstone or something yep yep sandstone's one of them and then
(09:17):
it could hit like shale which would be maybe a cap rock yeah 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 flow through it well. Yeah, you're setting this up perfectly.
Those are two of the main ones I wanted to talk about. Sandstone,
shale, limestone is another.
(09:38):
We'll 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,
(10:01):
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. rocks igneous rocks
and metamorphic rocks and sandstone
(10:22):
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 yeah and then compacted together
well 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 And just compressing
(10:43):
it so that it became like a block of sand.
It's literally sandstone is exactly kind of what it sounds like.
Yeah, it's like self-explanatory in the name.
Yeah, and so sandstone is probably one of the bigger workhorses of the conventional
oil and gas industry because typically sandstone does have high porosity and
(11:05):
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 porosity and permeability, which one's which.
The way I remember it for myself is porosity is like pores. So the pores in your skin.
So the ability to store sweat. So it is space.
(11:29):
Permeability, for whatever reason, I think of a perm, something I clearly don't
have, but like a hair perm.
And if you think of somebody who's like, if they got like a really nice perm,
they're like, oh, dude, check out your flow, right?
Like check out your hair, your flow, right? So permeability is like the ability
to flow through something.
Thing so anyway if that helps remember between the
two next you'll probably laugh next time
(11:51):
you see someone with a perm permeability okay so
sandstone we talked about limestone's another one so did you did you guys ever
talk about limestone in school what is it it's a i think also sedimentary rock
or maybe because i'm pretty sure it's it's composed of of calcium or calcite
Yeah, calcium carbonate.
(12:12):
Calcium carbonate. Calcium carbonate. Which is like made of like sea creature shells and stuff.
You're killing it. Yeah, you're exactly right. Yeah. 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 100 million years old.
Skeletons and stuff. Yeah. Yeah. But it's literally like imagine,
(12:34):
you know, you see a snail's shell.
Imagine 100 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 these shells accumulate and
(13:01):
that becomes 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 shales.
Super cool. The third one you talked about already is shale.
Shale is a super interesting one because when we look at conventional oil and gas,
(13:25):
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 accumulate beneath
(13:48):
it yeah that's shale's role 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.
You know, I'm sure everybody who's listening in, in some context has heard about
(14:09):
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. Yeah.
So that it can flow upwards. Yeah, exactly. So in conventional reservoirs,
we like shale for its low permeability because it's a barrier.
(14:31):
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 porosity so there's lots of oil
and gas in them they're just trapped because there's
no permeability there right and we'll talk about
(14:51):
fracking more later but basically what fracking is high
level definition is you're creating
artificial artificial permeability when you when you frack and
you create those little cracks in the rock right so
it's like a fracture yeah it's like your straw 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 we're putting a little channel
(15:14):
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
different types of scenarios.
One, like we talked about, is the cap rock. And two, is it can actually be the target.
That's what you're actually going after for your oil and gas.
(15:36):
Yeah, that's interesting that shale can also have high porosity too.
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 depositional environments.
Although I'm sure that would probably be right up your alley too.
I do know that you do. but we'll keep it high level.
So yeah, shale's an interesting one because it kind of plays both sides.
(15:59):
Plays the good guy, you know, where it has the oil. It plays the bad guy where
it's trapping 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 oil and gas in kind of a solid form.
And we talked about that last episode. So that's the concepts of like porosity
(16:22):
and permeability and cap rocks don't really apply to coal. Exactly.
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.
(16:46):
And then the last piece is chalk. And I wanted to talk about this one because
I thought this one was pretty cool.
So chalk is a type of reservoir formation. It's It's actually a type of limestone.
Okay, yeah. Yeah. Because it's just like even finer shells and stuff, right?
It's more of the single cell type.
So like think you have to see these things under a microscope to see them, right?
(17:09):
But chalk is a different type of formation that can have oil and gas too.
But I thought it was interesting because, you know, when I went to school.
The teachers were always writing on the blackboard in chalk.
Well, it'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 oil and gas out of so okay yeah if you took a
(17:30):
piece of chalk and again you're studying to be a teacher did teachers still
use chalk anymore is it all like whiteboards we got ipads and stuff now i'm
dating myself yeah all right yeah so everything's still using lead in your pencils.
Fair point. Yeah. Okay. Touche. So I guess what I was trying to say is that
(17:54):
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 would actually see that it's made up of little shells.
Shell bits. Yeah, yeah. I don't know if that's cool or creepy or whatever it
(18:14):
is that you're writing on a blackboard with. With like skeletons.
Yeah. That's right. Yeah, weird.
Yeah. Anyway, so I just wanted to share that too. Sometimes you'll hear of reservoirs.
There's one in Texas, for example, that comes to mind. It's called the Austin Chalk.
Anyway, just wanted to throw that out there because I thought that was a cool
one too. So those are high level when we talk about reservoir rocks.
(18:34):
There's different kinds of rocks.
It really just kind of depends on how those rocks were deposited over time to
determine, is it a sandstone?
Is it a limestone? Is it 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.
(18:56):
And this one, I don't know if you guys would have talked about this in school
or not. Yeah, not too much what they are, but not really how you go about finding them as much.
I imagine the geologists that I know are probably going to slaughter me for
oversimplifying this, but this is the way I picture it in my head.
Apologies to the geologists out there. I picture it as three really kind of
(19:20):
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 yeah have you heard of that before yep so what would you when
I say seismic reflection what 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
(19:46):
through the rocks. Kind of like, it's like an earthquake.
Yep. Seismic activity is an earthquake.
Yep. 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
(20:09):
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 know more math stuff about how fast it was traveling,
you can probably make an inference as to what kind of rocks that you just went through.
(20:30):
Yep, you're absolutely right. Right. Yeah. So all we're really doing seismic waves,
like a microwave or a radio wave or an x-ray, 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.
(20:52):
In some cases, depending on the technology, you can actually generate an image.
And so the analogy I use to really just kind of keep it simple is you 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 inside, right?
(21:19):
So generally the same kind of concept for
seismic reflection is they're using waves to generate
an image the only difference with ultrasound is you know
baby's like a couple inches below your skin
compared to the rocks are like a couple kilometers low yeah yeah
so seismic reflection that would be one way we
could see it another way would be outcrops did
(21:41):
you guys ever go see any outcrops or a little bit it's just like rock exposed
at the surface yeah so just like i know me going to the mountains and and seeing
things that are layers that have been brought up or layers that that have been
eroded away so you can see what they are?
Yeah, yeah, that's exactly it. And so, you know, the way I picture it in my
(22:01):
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
(22:23):
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 rock that was deposited at like, I don't know, let's say it's at like three kilometers.
(22:44):
Over time, that layer of rock or a portion of it might get pushed higher and
higher until 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.
(23:07):
Yeah, 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
(23:29):
visualize what I'm saying here is the next time you're in the mountains or 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 are deposited at different times.
But if you look at those layers, they're usually at an angle, right?
(23:53):
Like they're not flat. typically never flat 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
(24:13):
underneath yeah how in one spot it could be at surface and then like you know
50 kilometers away it could be
three kilometers deep awesome so seismic reflection to generate an image,
outcrops to physically see what's at surface.
And then another technique that we use is called offset wells.
(24:33):
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 2000 meters deep and they get oil and gas.
They're cheering because they found oil and gas. Yeah.
(24:53):
And then I get company C over on the far right-hand side.
And they drill a well, but they have to go down to 3,000 meters to find the
same oil and gas. So, 2,000 meters, 3,000 meters.
Company M comes in and they buy up the land right exactly in the middle.
Without having any other knowledge. They can extrapolate. They can extrapolate, right?
(25:17):
And so, they would, if you've got 2,000 meters here and 3,000 meters here and
these guys are right in the middle.
Their target depth would be... 2,500. Yeah. So I'm probably way oversimplifying
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 on.
(25:40):
That's where that comes from. Yeah. So what geologists can do is they can actually
use the data from those offset wells on the left and 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.
(26:01):
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 randomly
drilling somewhere, which I was thinking was going to be the third method.
Just luck, chance. And you know what? That's probably how it happened initially, right? Probably.
I probably should have mentioned that. There probably is a fourth factor then,
(26:23):
but the geologists will probably deny that till the day they die.
Yeah, because it's expensive. All skill, baby. Yeah.
So the nice thing too is that, you know, we talked about 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.
(26:46):
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 Montney.
Some people may or may not have heard of that before.
The Montney, that formation will have like specific biomarkers,
which are really just like specific characteristics for that.
(27:07):
Like a specific fossil that you find in there?
No, it's just like physical characteristics of the rock. So just like we look
different, you have hair, I have none.
I have a biomarker that can distinguish me from you.
Okay, so it's not really related to like a biological aspect.
(27:29):
It's more just bio as in like your biography of the rock or something like that.
Yeah, just characteristics of the rock that you could measure.
Kind of like, yeah, like facial recognition or something like consider facial
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 geologists here, they do actually have
(27:51):
a super important role to play.
Because it's the geologist's job to find the best rocks.
Like you may have an idea that there's oil and gas here.
But that might be a wide area. So where's the best spot? What has the highest porosity?
What has the highest permeability? And that would kind of define what your best rocks are.
(28:15):
So it's super important. So kudos to the geologists. Yeah.
That's basically it for rock geology, right? So keeping with the theme here,
our key topics today, permeability, porosity, reservoir rocks,
and how we find the oil and gas.
You want to give us a quick recap of what we talked about? A little synopsis.
It's a little synopsis, yeah. Yeah. Okay, so first few concepts,
(28:37):
permeability and porosity.
Porosity is the spaces in between grains in rocks.
And permeability is the ability for something to flow through.
Flow. Material. Through, yeah. The flow.
Yeah. And different kinds of reservoir rocks.
You have sandstones, which are made of different kinds of grains of sands and
(29:03):
typically have a high porosity and high permeability.
Same with limestones and chalk, 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,
(29:25):
which generally has low permeability, but I guess sometimes can also have high porosity.
Yeah. So it can have oil as well.
And in order to find the oil and gas, you can go to the mountains or anywhere
else and look for an outcrop.
You can also use existing data from wells that have already been dug.
(29:47):
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.
Reflections so you can use a device that creates a
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
(30:10):
just like an ultrasound yeah yeah yeah well done there we go maybe you'll teach
the next episode episode three episode three i'm willing about that all right
thanks everybody for listening to episode two next on episode three we're going
to be talking about conventional and unconventional conventional reservoirs.
So we talked so far primarily about the conventional reservoirs.
(30:31):
We'll 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 is an unconventional reservoir?
How is it different from conventional? And why is it important?
So dial in next time for episode three. Thanks, everybody.
From fossil to fuel with Brendan McDougall and William Belevance.
(30:53):
Subscribe now on your favorite podcast platform and share with your network.
From fossil to fuel with Brendan McDougall and William Belevance.
This is Oil and Gas 101, 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, right up your alley. Here you go. Episode one,
(00:26):
we talked about formation of fossil fuels.
We talked about how they're formed, why they form, the high temperature,
the high pressure, and then how they start to accumulate in the reservoir.
Today for rock geology, we're going to talk about porosity and permeability.
We'll dig into that a little bit more.
We're going to talk about, of course, rocks.
(00:47):
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 porosity and 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?
(01:07):
What is permeability? Let's revisit that. Okay.
For permeability, the way I understand it from like a science background.
So permeability is kind of like, I guess, maybe similar to penetration,
but in regards to maybe like a
membrane or some sort of surface that some
(01:28):
other substance can flow through so something
like a piece of plastic like a sandwich bag won't have a lot of permeability
because it 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.
(01:49):
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.
(02:15):
So, with regards to 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, honestly, the only time in oil and gas you're looking
(02:36):
for low permeability is for that barrier, that cap rock that's going to trap.
Right, one on top. Yeah. So really that's permeability.
Porosity 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 permeability, we talked about that.
(02:58):
Porosity, what do you think porosity is?
Porosity, 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
(03:22):
touching each other but they're not completely fused together so in between
those grains there's little air bubbles and pores yep and the more pores you
have the more Or porosity.
Yeah. You've learned this in school, clearly.
That's exactly right. Yeah. So the pores, I guess for the listeners out there,
(03:45):
so the pores, that's pores, porosity. That's how it got its name.
The pores, like you exactly just explained, they're the spaces in between the rocks.
And when I say rocks, really, we're talking the grains. 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.
(04:06):
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 threw 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, right?
If you imagine then we've got a reservoir that's made of whatever kind of rock.
(04:31):
And no matter which kind of rock you have, you're going to have some porosity.
Might be a little, might be a lot.
The porosity 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 to be in between the grains of the rock. right for porosity
then do you think you want high porosity or
(04:53):
low porosity for oil and gas for oil
and gas you probably want high porosity as well
because the more pores you have the more oil and gas you can fit inside of a
rock you're ace in this already nice yeah exactly high porosity the more porosity
you have the higher the probability of more oil just because you have porosity
(05:15):
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 conventional reservoirs, and we'll talk about
conventional versus unconventional in a later episode,
generally you're looking for high permeability and high porosity.
(05:39):
You know, you talked about a sponge. That was a pretty good example for both,
right? So a sponge is something that has high porosity, like you said,
because when you pour water on it, it has the ability to absorb water into those pores.
But when you squeeze the sponge, the water can come out easily. So high permeability.
(06:00):
So in the sponge, it's like 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, cheese
you still got holes in those swiss cheese but they
might not be really connected so it'd be
like higher porosity maybe but not really high permeability
(06:20):
in that cheese yeah yeah that's a great that's a
good segue i like it another example of that sort of high porosity low permeability
that i usually use is bubble wrap oh nice 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 trapped, it cannot flow.
(06:42):
So that would be an extreme example of high porosity and literally zero permeability.
Swiss cheese is probably actually a better analogy because you might have high
porosity 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 porosity, high permeability.
Bubble wrap or Swiss cheese, a good example of high porosity, low permeability.
(07:05):
Last one's a tricky one. Can you think of any examples of something that might
be low porosity, high permeability?
Took me a long time to think of one. 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 highly permeable? Yeah.
(07:27):
So here's what I thought of. This is a hard one to think of an example.
And it's almost irrelevant because in oil and gas, even if you have high permeability,
if you have no porosity, you would never look at that, right?
Because there's no oil and gas there.
But really just to kind of, I guess, complete the trifecta of analogies for
what we're talking about. what I thought about was a single lane highway.
(07:49):
A single lane highway would have high permeability for traffic, right?
Like cars can flow through easily and quickly, but if traffic's at a standstill,
there's not a lot of space for those cars to be.
Whereas if you had like a 10 lane highway, you still have high permeability for traffic.
(08:10):
And lots of spaces. But you have more More space, right? So maybe not the greatest
analogy, but it 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 then it's like just a single pore that is connected. One single.
One single. So it'll flow through the middle of the rock and that's it. Yeah.
(08:32):
Yeah, no, that would actually be a good, because then the permeability would
be high through that crack or that straw. Yeah, no, that's a great example.
So, I'd be curious actually to know, you did some of these courses 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.
(08:56):
Yep. Something that has very low porosity and permeability.
So when oil is rising up
through permeable rocks so
they're typically kind of more more
permeable or also have more porosity
maybe like a sandstone or something yep yep sandstone's one of them and then
(09:17):
it could hit like shale which would be maybe a cap rock yeah 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 flow through it well. Yeah, you're setting this up perfectly.
Those are two of the main ones I wanted to talk about. Sandstone,
shale, limestone is another.
(09:38):
We'll 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,
(10:01):
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. rocks igneous rocks
and metamorphic rocks and sandstone
(10:22):
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 yeah and then compacted together
well 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 And just compressing
(10:43):
it so that it became like a block of sand.
It's literally sandstone is exactly kind of what it sounds like.
Yeah, it's like self-explanatory in the name.
Yeah, and so sandstone is probably one of the bigger workhorses of the conventional
oil and gas industry because typically sandstone does have high porosity and
(11:05):
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 porosity and permeability, which one's which.
The way I remember it for myself is porosity is like pores. So the pores in your skin.
So the ability to store sweat. So it is space.
(11:29):
Permeability, for whatever reason, I think of a perm, something I clearly don't
have, but like a hair perm.
And if you think of somebody who's like, if they got like a really nice perm,
they're like, oh, dude, check out your flow, right?
Like check out your hair, your flow, right? So permeability is like the ability
to flow through something.
Thing so anyway if that helps remember between the
two next you'll probably laugh next time
(11:51):
you see someone with a perm permeability okay so
sandstone we talked about limestone's another one so did you did you guys ever
talk about limestone in school what is it it's a i think also sedimentary rock
or maybe because i'm pretty sure it's it's composed of of calcium or calcite
Yeah, calcium carbonate.
(12:12):
Calcium carbonate. Calcium carbonate. Which is like made of like sea creature shells and stuff.
You're killing it. Yeah, you're exactly right. Yeah. 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 100 million years old.
Skeletons and stuff. Yeah. Yeah. But it's literally like imagine,
(12:34):
you know, you see a snail's shell.
Imagine 100 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 these shells accumulate and
(13:01):
that becomes 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 shales.
Super cool. The third one you talked about already is shale.
Shale is a super interesting one because when we look at conventional oil and gas,
(13:25):
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 accumulate beneath
(13:48):
it yeah that's shale's role 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.
You know, I'm sure everybody who's listening in, in some context has heard about
(14:09):
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. Yeah.
So that it can flow upwards. Yeah, exactly. So in conventional reservoirs,
we like shale for its low permeability because it's a barrier.
(14:31):
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 porosity so there's lots of oil
and gas in them they're just trapped because there's
no permeability there right and we'll talk about
(14:51):
fracking more later but basically what fracking is high
level definition is you're creating
artificial artificial permeability when you when you frack and
you create those little cracks in the rock right so
it's like a fracture yeah it's like your straw 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 we're putting a little channel
(15:14):
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
different types of scenarios.
One, like we talked about, is the cap rock. And two, is it can actually be the target.
That's what you're actually going after for your oil and gas.
(15:36):
Yeah, that's interesting that shale can also have high porosity too.
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 depositional environments.
Although I'm sure that would probably be right up your alley too.
I do know that you do. but we'll keep it high level.
So yeah, shale's an interesting one because it kind of plays both sides.
(15:59):
Plays the good guy, you know, where it has the oil. It plays the bad guy where
it's trapping 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 oil and gas in kind of a solid form.
And we talked about that last episode. So that's the concepts of like porosity
(16:22):
and permeability and cap rocks don't really apply to coal. Exactly.
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.
(16:46):
And then the last piece is chalk. And I wanted to talk about this one because
I thought this one was pretty cool.
So chalk is a type of reservoir formation. It's It's actually a type of limestone.
Okay, yeah. Yeah. Because it's just like even finer shells and stuff, right?
It's more of the single cell type.
So like think you have to see these things under a microscope to see them, right?
(17:09):
But chalk is a different type of formation that can have oil and gas too.
But I thought it was interesting because, you know, when I went to school.
The teachers were always writing on the blackboard in chalk.
Well, it'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 oil and gas out of so okay yeah if you took a
(17:30):
piece of chalk and again you're studying to be a teacher did teachers still
use chalk anymore is it all like whiteboards we got ipads and stuff now i'm
dating myself yeah all right yeah so everything's still using lead in your pencils.
Fair point. Yeah. Okay. Touche. So I guess what I was trying to say is that
(17:54):
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 would actually see that it's made up of little shells.
Shell bits. Yeah, yeah. I don't know if that's cool or creepy or whatever it
(18:14):
is that you're writing on a blackboard with. With like skeletons.
Yeah. That's right. Yeah, weird.
Yeah. Anyway, so I just wanted to share that too. Sometimes you'll hear of reservoirs.
There's one in Texas, for example, that comes to mind. It's called the Austin Chalk.
Anyway, just wanted to throw that out there because I thought that was a cool
one too. So those are high level when we talk about reservoir rocks.
(18:34):
There's different kinds of rocks.
It really just kind of depends on how those rocks were deposited over time to
determine, is it a sandstone?
Is it a limestone? Is it 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.
(18:56):
And this one, I don't know if you guys would have talked about this in school
or not. Yeah, not too much what they are, but not really how you go about finding them as much.
I imagine the geologists that I know are probably going to slaughter me for
oversimplifying this, but this is the way I picture it in my head.
Apologies to the geologists out there. I picture it as three really kind of
(19:20):
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 yeah have you heard of that before yep so what would you when
I say seismic reflection what 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
(19:46):
through the rocks. Kind of like, it's like an earthquake.
Yep. Seismic activity is an earthquake.
Yep. 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
(20:09):
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 know more math stuff about how fast it was traveling,
you can probably make an inference as to what kind of rocks that you just went through.
(20:30):
Yep, you're absolutely right. Right. Yeah. So all we're really doing seismic waves,
like a microwave or a radio wave or an x-ray, 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.
(20:52):
In some cases, depending on the technology, you can actually generate an image.
And so the analogy I use to really just kind of keep it simple is you 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 inside, right?
(21:19):
So generally the same kind of concept for
seismic reflection is they're using waves to generate
an image the only difference with ultrasound is you know
baby's like a couple inches below your skin
compared to the rocks are like a couple kilometers low yeah yeah
so seismic reflection that would be one way we
could see it another way would be outcrops did
(21:41):
you guys ever go see any outcrops or a little bit it's just like rock exposed
at the surface yeah so just like i know me going to the mountains and and seeing
things that are layers that have been brought up or layers that that have been
eroded away so you can see what they are?
Yeah, yeah, that's exactly it. And so, you know, the way I picture it in my
(22:01):
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
(22:23):
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 rock that was deposited at like, I don't know, let's say it's at like three kilometers.
(22:44):
Over time, that layer of rock or a portion of it might get pushed higher and
higher until 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.
(23:07):
Yeah, 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
(23:29):
visualize what I'm saying here is the next time you're in the mountains or 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 are deposited at different times.
But if you look at those layers, they're usually at an angle, right?
(23:53):
Like they're not flat. typically never flat 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
(24:13):
underneath yeah how in one spot it could be at surface and then like you know
50 kilometers away it could be
three kilometers deep awesome so seismic reflection to generate an image,
outcrops to physically see what's at surface.
And then another technique that we use is called offset wells.
(24:33):
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 2000 meters deep and they get oil and gas.
They're cheering because they found oil and gas. Yeah.
(24:53):
And then I get company C over on the far right-hand side.
And they drill a well, but they have to go down to 3,000 meters to find the
same oil and gas. So, 2,000 meters, 3,000 meters.
Company M comes in and they buy up the land right exactly in the middle.
Without having any other knowledge. They can extrapolate. They can extrapolate, right?
(25:17):
And so, they would, if you've got 2,000 meters here and 3,000 meters here and
these guys are right in the middle.
Their target depth would be... 2,500. Yeah. So I'm probably way oversimplifying
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 on.
(25:40):
That's where that comes from. Yeah. So what geologists can do is they can actually
use the data from those offset wells on the left and 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.
(26:01):
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 randomly
drilling somewhere, which I was thinking was going to be the third method.
Just luck, chance. And you know what? That's probably how it happened initially, right? Probably.
I probably should have mentioned that. There probably is a fourth factor then,
(26:23):
but the geologists will probably deny that till the day they die.
Yeah, because it's expensive. All skill, baby. Yeah.
So the nice thing too is that, you know, we talked about 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.
(26:46):
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 Montney.
Some people may or may not have heard of that before.
The Montney, that formation will have like specific biomarkers,
which are really just like specific characteristics for that.
(27:07):
Like a specific fossil that you find in there?
No, it's just like physical characteristics of the rock. So just like we look
different, you have hair, I have none.
I have a biomarker that can distinguish me from you.
Okay, so it's not really related to like a biological aspect.
(27:29):
It's more just bio as in like your biography of the rock or something like that.
Yeah, just characteristics of the rock that you could measure.
Kind of like, yeah, like facial recognition or something like consider facial
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 geologists here, they do actually have
(27:51):
a super important role to play.
Because it's the geologist's job to find the best rocks.
Like you may have an idea that there's oil and gas here.
But that might be a wide area. So where's the best spot? What has the highest porosity?
What has the highest permeability? And that would kind of define what your best rocks are.
(28:15):
So it's super important. So kudos to the geologists. Yeah.
That's basically it for rock geology, right? So keeping with the theme here,
our key topics today, permeability, porosity, reservoir rocks,
and how we find the oil and gas.
You want to give us a quick recap of what we talked about? A little synopsis.
It's a little synopsis, yeah. Yeah. Okay, so first few concepts,
(28:37):
permeability and porosity.
Porosity is the spaces in between grains in rocks.
And permeability is the ability for something to flow through.
Flow. Material. Through, yeah. The flow.
Yeah. And different kinds of reservoir rocks.
You have sandstones, which are made of different kinds of grains of sands and
(29:03):
typically have a high porosity and high permeability.
Same with limestones and chalk, 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,
(29:25):
which generally has low permeability, but I guess sometimes can also have high porosity.
Yeah. So it can have oil as well.
And in order to find the oil and gas, you can go to the mountains or anywhere
else and look for an outcrop.
You can also use existing data from wells that have already been dug.
(29:47):
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.
Reflections so you can use a device that creates a
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
(30:10):
just like an ultrasound yeah yeah yeah well done there we go maybe you'll teach
the next episode episode three episode three i'm willing about that all right
thanks everybody for listening to episode two next on episode three we're going
to be talking about conventional and unconventional conventional reservoirs.
So we talked so far primarily about the conventional reservoirs.
(30:31):
We'll 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 is an unconventional reservoir?
How is it different from conventional? And why is it important?
So dial in next time for episode three. Thanks, everybody.
From fossil to fuel with Brendan McDougall and William Belevance.
(30:53):
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