Chapter 1 - Fundamentals of Seismic Data for Reservoir Characterization

01-01 - Seismic Reflection Principles for Reservoir Detection (15 min.) Sample Lesson
01-02 - Reservoir Rock Physics and Wave Propagation (13 min.)
01-03 - Seismic Wavelets and Signal Characteristics (9 min.)
01-04 - Acoustic Impedance, Reflection Coefficients and Seismic Resolution (17 min.)
01-05 - Seismic Acquisition Methods (16 min.)
01-06 - Basics of the Seismic Processing Workflow (16 min.) Quiz: 01-06 - Basics of the Seismic Processing Workflow

Chapter 2 - Structural and Stratigraphic Reservoir Interpretation

02-01 - Structural Mapping from Seismic Data (15 min.)
02-02 - Sequence Stratigraphy in Seismic Data (12 min.)
02-03 - Reservoir Facies Identification (11 min.)
02-04 - Seismic Attributes for Reservoir Characterization (10 min.)
02-05 - Advanced Structural Analysis Using Geometric Attributes (13 min.)
02-06 - Frequency-Based Analysis using Spectral Decomposition (6 min.)
02-07 - Integrated Analysis of Structural and Stratigraphic Reservoirs (22 min.) Quiz: 02-07 - Integrated Analysis of Structural and Stratigraphic Reservoirs

Chapter 3 - Overview of Seismic Analysis Techniques for Reservoir Properties

03-01 - Direct Hydrocarbon Indicators and Amplitude Analysis (24 min.)
03-02 - AVO Analysis for Fluid and Lithology Prediction (12 min.)
03-03 - Reservoir Property Prediction through Seismic Inversion (10 min.)
03-04 - Time-Lapse Seismic for Production Monitoring (12 min.) Quiz: 03-04 - Time-Lapse Seismic for Production Monitoring

Chapter 4 - Applied Seismic Interpretation for Reservoir Insights

04-01 - Near-Surface Characterization and Drilling Risk Assessment (16 min.)
04-02 - Fluvial-Deltaic Reservoir Systems (12 min.)
04-03 - Deepwater Reservoir Architecture (12 min.)
04-04 - Carbonate Platform Architecture in Seismic (12 min.)
04-05 - Unconventional Resource Plays (11 min.)
04-06 - AI/ML Applications in Reservoir Production (16 min.) Quiz: 04-06 - AI/ML Applications in Reservoir Production

Petroleum Geophysics for Engineers / Chapter 1 - Fundamentals of Seismic Data for Reservoir Characterization

Lesson 01-01 - Seismic Reflection Principles for Reservoir Detection

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Transcript

01. Lesson 1.01: Seismic Reflection Principles for Reservoir Detection 02. Acknowledgements 03. What do you see?04. For interpretation, need to understand:05. Three main purposes for collecting seismic data 06. Deep crustal structures 07. ...or higher frequency CHIRP or Boomer data 08. Sedimentary & Tectonic history 09. ...and for Reservoir Characterization 10. Geologic principles still apply in seismic analysis 11. Know seismic limitations:12. Importance of modern analogues 13. It is also important to clearly communicate your results!14. Integrate your analysis with other data types to reduce interpretation uncertainty 15. What is the purpose of your seismic interpretation?

01. Lesson 1.01: Seismic Reflection Principles for Reservoir Detection

Welcome to Petroleum Geophysics for Engineers and maybe also for not engineers. So I'm Heather Bedle. I am a professor at the University of Oklahoma, where I teach petroleum geophysics, seismic data analysis for both geologists, geophysicists, and also engineers. And so I'm going to start off this course with trying to just show you why you might want to use seismic data. I want to overall in this course, give you a good introduction about what we're trying to do as geophysicists and geologists when we're using seismic data, and also just kind of let you get familiar with some of the terms. So this won't be a deep dive into the same level or depth of concepts that I would do with geologists and geophysicists, but rather I want this course to be informative and just maybe help you see why we get so excited about seismic data analysis. So let's get going.

02. Acknowledgements

Of course, with any course, we always want to acknowledge all the folks that have helped us, all the folks who have given us material that we're using in the course. And so I've listed a whole range of them here, from mentors, to former students, to current collaborators. A lot of this material comes from Kurt Marfurt, who has been teaching geophysics and seismic analysis for decades, decades more than me. And I also listed here a couple of textbooks. If you do find yourself being one of those engineers or non-engineers who finds geology interesting, and I promise from my semesters of teaching that every once in a while I do get an engineer who ends up with a great appreciation for what we do. But there's some great textbooks out there and I'm always willing to, if you want to shoot me an email, recommend different textbooks to give you more information, even if there's just one topic you want to dive into a little bit more, I'm happy to point you in the right direction.

03. What do you see?

Let's get going. So this is seismic data. I don't know if you've seen seismic data before but what we're looking at here is kind of like an outcrop. So if you've ever driven down an interstate or through a road where you have a whole bunch of rock layers that you can see on the side of the road where they've probably blasted through to level off the road, that would be an outcrop. And our seismic data, when we look at it in this direction, like a vertical slice, I'll call them, it's kind of emulating an outcrop. And when we look at this, we see a lot of geometric patterns, we see changes in the amplitude, so sometimes it's bright white, sometimes it's gray. And we can also see frequency changes, where we have higher frequency shallow and lower frequency, so kind of repetition of those layers aren't as often with those lower frequencies deeper. And so these are all the things I'm going to be explaining in quick kind of terms as we move through this course.

04. For interpretation, need to understand:

But to be able to interpret seismic data, there's a lot of fundamentals that we want to understand to help us make a good interpretation. So some of the things I'll start off talking with early on is explaining how reflections are generated. So just a hint, it's Snell's Law, if you remember that from physics. I'll talk about what we can see and can't see in seismics. That would be our seismic resolution. Also, I'll talk just a little bit—but not too much—about how acquisition and processing parameters affect the seismic image, ways in which we can display the seismic data, ways that we can analyze it. And a lot of this is just to bring out patterns that the geologists can recognize. So maybe changes in porosity for the reservoir or different geologic structures that may be acting as a hydrocarbon trap. We want to see those patterns in the seismic data. And then also I'll talk a little bit about how we can link seismic data to other types of data, like well logs, in order to calibrate the seismic images. So we turn them, rather from seismic data into this part of the seismic data is a high porosity sandstone filled with hydrocarbon. And we can do that with the use of well logs.

05. Three main purposes for collecting seismic data

There's a couple of different purposes for collecting seismic data. Some of them are to define the structure in the subsurface. So find those faults, find those folds, find these hydrocarbon traps. We also will use seismic data to better understand thestratigraphy. So this is the way the sediments are laid down and deposited through time. We can understand the structure of the sediments to understand the earth's history. We can use seismic data to understand where aquifers are. And we can also understand the stratigraphy in terms of traps or seals and reservoirs. So the reservoir quality, if it's a very porous, highly connected permeable sandstone, or if we have a nice seal or trapping layer, so perhaps a shale that the hydrocarbon kind of molecules can't migrate upwards through. And then we'll also use seismic data, just as I was talking about, but we can use it to help quantify and understand porosity variations, fluid variations, lithologies, and pressures. And later on in the course, I'll even show you a few case studies. One of them that I threw in there just for you engineers is some case studies about how we would use seismic to identify shallow drilling hazards.

06. Deep crustal structures

Seismic comes in many flavors, I would say, and these flavors all have to do with the frequency. So higher frequencies don't travel as deep into the Earth's crust, while lower frequencies can penetrate much further. So we can use the lower frequencies, as I'm showing in this example, to look at deep crustal structures. So you can see we're going 18 km deep and looking at large-scale structures.

07. ...or higher frequency CHIRP or Boomer data

Or we can use higher frequencies. So in this case, this would be CHIRP or boomer data, where we're perhaps only capturing the upper one second of the Earth's surface.

08. Sedimentary & Tectonic history

A lot of what I'm going to be showing, most of what I'm going to to be showing, probably 99% of what I'm going to be showing are the reflection seismic data at frequencies from about 10-85 Hz. And these are the frequencies that we use in order to identify hydrocarbon reservoirs and those related structures that we would be interested in for theenergy industry. And this is a good example of some where we can see indications of the sedimentary history from the layers that are being deposited here to seeing some faults. Kind of marked in red below so we've got it interpreted below that give us information about the tectonic history.

09. ...and for Reservoir Characterization

Overall, what I'm trying to do in this course is kind of boil it down to some of the essentials that you would want to understand about seismic data analysis so that you could doreservoir characterization. So you can understand some of the terms that your team members may be using.

10. Geologic principles still apply in seismic analysis

One of the things I want to remind you all of, if you haven't or had taken a geology course before, is the same geologic principles that we talk about in Geology 101 are ones that we want to make sure when we're interpreting, we're still paying attention to. So we're not creating made up interpretations that don't really go along with how we think earth processes have happened. So some of those that I just want to highlight on this slide are the Principle of Uniformitarianism which just means that processes that are active in the past are still active today. So this would be gravity, erosion, uplift, those types of processes. So we're not making up new processes to explain our seismic interpretation. We also have the Principle of Original Horizontality, which is that when sediments are deposited, they're deposited originally in horizontal layers. The third one is the Principle of Superposition. And this means that in undisturbed sediments, so ones that haven't gone through uplift and tilting, the oldest layers will be at the bottom. And then the fourth one is the Principle of Cross-Cutting Relationships, which is one where if there is an intrusion or fault, it has to be younger than the sediments that it's cutting through. So all of these just kind of ground us in terms of reality, honestly, and how we would expect the earth processes to work and interpreting the different layers.

11. Know seismic limitations:

With seismic data, there are things that we can't solve. And so I'll be talking about these throughout the course, but seismic data is essentially a series of reflections in the time domain. It's not rocks. And as I'll explain to you, what we're seeing are the interfaces because energy sent down, and just like we learned in Snell's Law, it will bounce back up whenever there's an interface. So these seismic images over here are just interfaces, and it's just a waveform. So it doesn't really tell us just by looking at seismic data whether or not it's a sandstone or a shale. So we don't know what the lithologies are unless we have core data. If we have some seismic wave velocities, we might be able to say, oh, this is a very high seismic wave velocity, so maybe this is a basalt or carbonate as opposed to a very loosely consolidated sandstone.
Seismic data also can't tell us the absolute ages of the deposit. So I can't look at this and say, oh, this dark kind of black sedimentary line is 350 million years old. Again, we can't do that unless we have information from cores, which may be fossils or ash beds, some sort of datable material. But we can tell the relative ages. So I could say, using those principles I talked about, that this kind of darker black sedimentary layer is younger than what's below it, or it's older than some of these features up above it.
And then also, because we're often looking at seismic data, like in this case, just a 2D line, we can't tell what caused the shape. So in this case, we have a U-shaped feature in here that I'm trying to trace out. So just by looking at this one line, I can't tell what it is, but rather I'd need a 3D perspective. Luckily, a lot of the modern seismic data that we're shooting, particularly for reservoir characterization, is in 3-dimension. So we can slice it and dice it and map it in different ways that I'll be showing you in order to understand the origin of some of these features.
And then finally, we don't know definitively how thick a layer might be because we're measuring this in time. And so in order to get the thickness, we also need to know the velocity. And so we may be able to make some assumptions about the velocity and then we can convert it to a thickness or a depth, which might be more useful for a lot of the engineers in terms of well planning.

12. Importance of modern analogues

Geologists love analogues. And so you'll see your geologist that you're working with compare the features that they're seeing inseismic data with modern-day analogues. And luckily, this is pretty easy and convenient to do with satellite imagery or Google Earth is what a lot of my students do. And so you should always be able to feel free to ask your geologist, if you're looking at seismic data with them, to point you to a modern analogue. And so in this case, in this upper row, we're looking at some channel features, so some river features that are buried deep in the earth. Here this geologist has interpreted it, so they've given us a nice cartoon so that we see what they're seeing in the seismic data. And then they're using some satellite imagery to show us how this would look in the modern day. And so if we understand the modern day expression, like particularly in these channels, we can see where we have perhaps sandier point bars, which could be potential reservoir vs. some muddier facies that could be acting as a trap or a seal.

13. It is also important to clearly communicate your results!

I always tell my geologists that it's very important to clearly communicate your results. And so you may start seeing, as you work with more geologists, figures like this, where they're showing a couple of different expressions of seismic data with a large scale channel that they're showing in both a time view, so kind of like a map view and then a vertical section, along with some cartoons that help them relate or tell you exactly what they're seeing so that you can see what they are seeing also.

14. Integrate your analysis with other data types to reduce interpretation uncertainty

One of the last things I want to mention in this intro lecture is that we're always trying to integrate our data with other types of data. So we may be using well logs to do some forward modeling and this helps us reduce our uncertainty in our interpretation. So it could be well logs, gravity data, outcrops. When I teach a class for engineers at the university, one of the first things we do on the first day is we just brainstorm all the different types of information that engineers have access to like production data, perhaps some issues with drilling, so drilling reports. And all of that information can help the geologists out in terms of understanding some of the details of what's going on in the subsurface. So, you guys may have some of that secret data that we would love to get our hands on. So I encourage you to talk to the geologist that you know to see if you have data in your engineering files that can improve their interpretation.

15. What is the purpose of your seismic interpretation?

Oftentimes, as we move forward through this course, I'm going to treat you a little bit more like budding geophysicists or geologists. So I'll tell my seismic interpreters that when they're doing a study, they often want to know the objectives of why they're doing it. So they could be interpreting, or you could be interpreting, in terms of okay, well, here we have a development area. We want to do some infill drilling because we think we bypassed some hydrocarbons. So it may be a very small-scale mapping project. Or perhaps you're working in a frontier basin where you don't have a lot of information and you're just trying to map it on the large scale to see if all thehydrocarbon system elements are present. So depending on what the geologist is trying to do, that will affect the tools that they're going to use for seismic interpretation.
Thanks for listening to this intro lecture and hopefully you'll continue on through it and I'll start talking about the different tools and techniques that we use so that you can kind of start to unwrap the secret language of the geologist.