Seismic Processing Velocities - Geophysics from Udemy

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Syllabus

Introduction

This introduction to seismic velocities will show how seismic data is acquired in the field (land or marine). It will show how reflected events look on gathers. It will show why picking accurate velocities is important and how accurate velocities produce flat gathers.

The students will learn the fundamental differences between velocities used for time migration and used for depth migration. How inaccurate velocities in depth migration can introduce wrong depths and wrong dip.

The students will understand why depth migration is needed to image geology in areas of lateral velocity changes.

Students will learn the traditional top-down procedure for building a deep-water, sub-salt velocity model used in depth migration.

Students will learn about tomography. How it uses non-flat gathers to update the depth velocity field.

Students will learn the basics of full waveform inversion, and how it optimizes velocities used for depth migration. Plus how fwi differs between land datasets and marine datasets.

Students will learn about vertical fractured anisotropy, rocks with fractures. How it's seen on seismic gathers and how 5D interpolation helps.

I show some of the often-hidden details when merging 2 or more surveys together. Often neighboring surveys are acquired differently - different fold, vibroseis sweeps, inline/xline grids. The surveys gets merged into a seemingly-uniform grid. How can the interpreter reference these differences - to distinguish seismic character changes due to geology or due to changing seismic acquisition?

You'll learn some of the basic terms and definitions of common seismic nomenclature. Nothing fancy, just the basics.

You'll learn why refraction statics is done on land seismic processing projects. You'll learn the absolute minimum (it can get complicated!) on how tomo refraction statics is done. Apologies - only graphical images are shown as have not received permission to show real dataset examples.

This is a simple way to estimate seismic interval velocities when picking rms velocities. The legendary Fred Hilterman taught me this technique.

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Explores anisotropy, including VTI and HTI, which can be used to identify horizontal rock layering and vertical fracturing, enhancing subsurface imaging

Covers tomography and full waveform inversion (FWI), which are used in depth migration to refine PSDM velocity fields, improving subsurface imaging

Details the traditional top-down procedure for building sub-salt velocity models, which is a foundational technique in depth migration for deep-water environments

Requires understanding of seismic data acquisition and processing, which may necessitate prior coursework or experience in geophysics or a related field

Focuses on standard NMO velocities and multiples, which are fundamental concepts, but may be too basic for experienced professionals seeking advanced techniques

Examines the differences between time and depth migration velocities, which is crucial for accurate subsurface imaging, especially in areas with lateral velocity variations

Reviews summary

Geophysics seismic velocity processing explained

According to learners, this course provides a clear and concise overview of seismic velocities as they relate to processing and exploration. Many students found the explanations of complex topics like time vs. depth migration, tomography, FWI, and anisotropy to be particularly well-presented, often thanks to the effective use of graphics. The inclusion of real-world examples, such as the South Dakota project and discussions on merging surveys, is highlighted as a major strength, offering valuable practical insights. While the course is seen as highly relevant for geophysics professionals, some students noted that a basic prior understanding of seismic data is helpful to fully grasp the material.

Provides good conceptual understanding; some desire more practical detail.

"Gives a good conceptual overview but doesn't go deep into software application."

"Could benefit from more practical exercises or examples of velocity picking workflows."

"Excellent for theory, could use a bit more detail on implementation nuances."

Best suited for those with some existing seismic background.

"This course assumes you have some basic familiarity with seismic data."

"Might be challenging for someone completely new to geophysics processing."

"A solid understanding of seismic fundamentals is beneficial before taking this."

Visuals significantly aid understanding of technical material.

"The hand-drawn graphics are excellent and make the material accessible."

"Visual aids are very helpful in grasping abstract concepts."

"Appreciate the clear diagrams used throughout the lectures."

Focuses on real-world processing issues and practical applications.

"The discussion on velocity sags and pull-ups was very practical for interpreters."

"The South Dakota case study was a great real-world example."

"Learning about merging volumes was directly applicable to my job."

"The course covers practical aspects of velocity picking and avoiding multiples."

Complex seismic processing concepts are made easy to understand.

"The course explains complex topics like FWI and tomography very clearly."

"I finally understood the difference between time and depth migration velocities."

"The graphical explanations really helped clarify difficult seismic processing ideas."

"The concepts are explained in a way that is easy to follow."

"Provided a solid foundation for understanding velocity models in depth migration."

Activities

Be better prepared before your course. Deepen your understanding during and after it. Supplement your coursework and achieve mastery of the topics covered in Seismic Processing Velocities - Geophysics with these activities:

Review Seismic Data Acquisition Fundamentals

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Reviewing seismic data acquisition fundamentals will provide a solid base for understanding how velocities are derived and their impact on processing.

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Review basic seismic acquisition techniques.
Study different types of seismic sources and receivers.
Understand the geometry of seismic surveys.

Read 'Basic Seismic Theory' by Enders Robinson and Sven Treitel

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Reading 'Basic Seismic Theory' will provide a strong theoretical foundation for understanding seismic velocities and their role in processing.

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Obtain a copy of 'Basic Seismic Theory'.
Read chapters related to wave propagation and reflection.
Take notes on key concepts and equations.

Practice Velocity Picking on Synthetic Seismic Data

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Practicing velocity picking on synthetic data will help develop the skills needed to accurately estimate velocities on real seismic data.

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Generate or obtain synthetic seismic datasets.
Use velocity analysis software to pick velocities.
Compare your picks to the known velocities.
Analyze and understand the errors.

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Create a Presentation on Time vs. Depth Migration

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Creating a presentation on the differences between time and depth migration will solidify understanding of when each method is appropriate.

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Research the principles of time and depth migration.
Compare and contrast the two methods.
Prepare slides with clear explanations and visuals.
Present the material to peers or colleagues.

Study 'Seismic Data Analysis' by Öz Yilmaz

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Studying 'Seismic Data Analysis' will provide a comprehensive understanding of advanced seismic processing techniques and their impact on velocity estimation.

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Obtain a copy of 'Seismic Data Analysis'.
Focus on chapters related to velocity analysis and migration.
Work through examples and exercises.

Implement a Simple Tomography Algorithm

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Implementing a tomography algorithm will provide hands-on experience with velocity model building and optimization.

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Research tomography algorithms.
Choose a suitable algorithm for implementation.
Write code to implement the algorithm.
Test the algorithm on synthetic data.
Analyze the results and refine the implementation.

Develop a Velocity Model Visualization Tool

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Developing a visualization tool will enhance understanding of velocity model characteristics and their impact on seismic imaging.

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Choose a suitable programming language and libraries.
Design the user interface for the tool.
Implement functionality to load and display velocity models.
Add features for visualizing velocity gradients and anomalies.

Career center

Learners who complete Seismic Processing Velocities - Geophysics will develop knowledge and skills that may be useful to these careers:

Seismic Data Processor

A seismic data processor refines raw seismic data to create clear subsurface images, aiding in oil and gas exploration. This course directly aligns with the role, as understanding seismic velocities is fundamental to effective data processing. The course details various velocity analysis techniques, including Normal Moveout velocities, time versus depth migration velocities, tomography, and Full Waveform Inversion, all crucial for a seismic data processor. Learning to interpret and correct for anisotropy, as covered in the course, further enhances the processor's ability to accurately image complex geological structures, particularly in areas with horizontal layering or vertical fractures.

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Seismic Interpreter

A seismic interpreter analyzes seismic data to identify geological structures and potential hydrocarbon traps. This course directly impacts the interpreter's capabilities by providing a comprehensive understanding of seismic velocities and their impact on subsurface images. Learning the differences between time and depth migration, the use of tomography and Full Waveform Inversion, and the effects of anisotropy provide crucial context to the interpreter's work. The interpreter can then more effectively identify subtle geological features, interpret complex structures, particularly in areas with lateral velocity variations or subsalt formations, and ultimately reduce the risk of exploration and development. The course may be useful.

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Subsurface Modeler

A subsurface modeler creates computer models of underground geological structures, which are used for resource exploration and management. This course is highly relevant, as velocity models are a critical input to creating accurate subsurface models. The course's coverage of time versus depth migration, tomography, and Full Waveform Inversion provides essential knowledge for building geologically sound velocity models. Further, understanding anisotropy and its impact on seismic data is key for accurately representing complex geological features in the model. The course may be useful.

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Seismic Research Scientist

A seismic research scientist advances the understanding of seismic wave propagation and develops new seismic processing and interpretation techniques, often requiring a doctorate. This course may be useful for any research scientist, since it dives into the intricacies of seismic velocities and how they affect subsurface imaging. Understanding the nuances of Normal Moveout, depth migration, tomography, Full Waveform Inversion, and anisotropy will help the scientist develop novel approaches to improve seismic data quality and extract more information from it. The course may be useful.

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Geophysicist

A geophysicist analyzes the Earth's physical properties to explore resources, assess hazards, and understand geological structures. This course helps geophysicists refine their understanding of seismic velocities, which is critical for interpreting seismic data. The course's exploration of Normal Moveout velocities, migration techniques, and anisotropy builds a solid foundation for making informed decisions about subsurface conditions. Furthermore, the course enhances a geophysicist's ability to interpret seismic data from areas with lateral velocity variations, sub-salt geology, and complex geological features. The course may be useful.

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Exploration Geologist

An exploration geologist seeks out new hydrocarbon reserves. This course may be useful, as it provides a deeper understanding of seismic velocities and their impact on subsurface imaging. The course content on depth migration, tomography, and Full Waveform Inversion can aid in interpreting complex geological structures from seismic data. Specifically, the course's coverage of anisotropy and its relationship to rock layering and fracturing may enhance the exploration geologist's ability to identify potential reservoirs and understand their structural context. The course may be useful.

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Geothermal Explorationist

A geothermal explorationist identifies and assesses potential geothermal energy resources. Though focused on oil and gas applications, this course on seismic processing velocities has relevance to geothermal exploration, since seismic data is also used to image subsurface geological structures in geothermal settings. Understanding seismic velocities, migration techniques, and anisotropy may aid in interpreting seismic data to identify fractured reservoirs and subsurface permeability, crucial factors in geothermal resource assessment. The explorationist who is competent with the information in this course can leverage their knowledge to find viable geothermal sites. The course may be useful.

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Mining Geophysicist

A mining geophysicist uses geophysical methods to explore for mineral deposits and optimize mining operations. This course may be useful by providing a solid grasp of seismic velocities, which is essential for interpreting seismic reflection data used in mining exploration. Understanding seismic velocities can then help distinguish different rock types, identify ore bodies, and map geological structures that control mineralization. Furthermore, insights into data processing and migration techniques may enhance the resolution of seismic images, leading to more accurate resource assessments, especially around complex horizontal layering and vertical fractures. The course may be useful.

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Carbon Storage Specialist

A carbon storage specialist works to identify and manage underground sites for the safe and permanent storage of carbon dioxide. The course is relevant, because seismic data plays a crucial role in characterizing potential storage reservoirs and monitoring the injected carbon dioxide. A carbon storage specialist will learn to interpret how seismic velocities are used for subsurface imaging, and they can then apply that knowledge when examining the suitability and integrity of carbon storage sites. The course helps carbon storage specialists better ensure long-term containment of carbon dioxide. The course may be useful.

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Reservoir Engineer

A reservoir engineer manages the development and production of oil and gas reservoirs. This course may be useful to reservoir engineers since the material helps one understand how seismic velocities influence subsurface imaging, which informs reservoir models. The course's insights into depth migration, tomography, and Full Waveform Inversion can aid in creating more accurate reservoir characterizations. Furthermore, the course's coverage of anisotropy may enable the reservoir engineer to better understand fracture patterns and their impact on fluid flow within the reservoir. The course may be useful.

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Environmental Geophysicist

An environmental geophysicist uses geophysical techniques to address environmental problems, such as groundwater contamination or subsurface remediation. The course may be useful to environmental geophysicists using seismic reflection or refraction to characterize shallow subsurface conditions. Understanding seismic velocities is helpful for accurately mapping subsurface geology, identifying potential contamination pathways, and monitoring remediation efforts. Furthermore, the course's insights into data processing and migration techniques may improve the resolution and accuracy of seismic images of near-surface environments. The course may be useful.

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Geoscience Technician

A geoscience technician supports geoscientists by managing data, preparing maps, and assisting with analysis. This course may be useful for technicians who work with seismic data. It provides a broader understanding of how seismic velocities are used in processing and interpretation. The course helps the technician better appreciate the importance of data quality and the impact of processing choices. Furthermore, understanding concepts like time versus depth migration and the basics of anisotropy helps the technician more effectively assist geoscientists in their analyses. The course may be useful.

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Engineering Geologist

An engineering geologist applies geological principles to engineering projects, such as dam construction or tunnel excavation. This course may be useful if seismic surveys are employed to characterize subsurface conditions at a project site. Understanding seismic velocities aids interpretation of seismic data to identify rock layers, faults, and other geological features that could impact the stability and safety of engineering structures. Furthermore, knowing about data processing and migration techniques may improve the accuracy of subsurface models used in engineering design. The course may be useful.

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Data Scientist Energy

A data scientist in the energy sector applies advanced analytical techniques to optimize operations and decision making, which can involve workflows related to seismic processing and interpretation. Given the course focuses on seismic velocities and impacts on data processing, it provides a foundation for understanding this specific type of data. A data scientist can then apply machine learning and other computational techniques to improve velocity model building, enhance seismic imaging, and automate interpretation workflows. This understanding, combined with data science skills, may lead to innovative solutions in seismic data analysis. The course may be useful.

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Petroleum Engineer

A petroleum engineer designs and oversees the drilling and production of oil and gas wells. While not directly focused on drilling or production, this course contributes to a petroleum engineer's overall understanding of reservoir characterization. By learning about seismic velocities, migration techniques, and anisotropy, the petroleum engineer gains insights into how seismic data informs reservoir models. This knowledge may enable better decision-making regarding well placement and optimized reservoir management. The course may be useful.

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Reading list

We've selected two books that we think will supplement your learning. Use these to develop background knowledge, enrich your coursework, and gain a deeper understanding of the topics covered in Seismic Processing Velocities - Geophysics.

Walking with Christiaan Huygens

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Provides a comprehensive overview of seismic theory, including wave propagation, reflection, and refraction. It valuable resource for understanding the underlying principles of seismic processing and velocity analysis. The book is commonly used as a textbook in geophysics courses and useful reference for industry professionals. It adds depth to the course by providing a more theoretical foundation for the practical aspects of velocity analysis.

Walking with Christiaan Huygens: From Archimedes'...

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Seismic Processing Velocities - Geophysics

What's inside

Syllabus

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Reviews summary

Geophysics seismic velocity processing explained

Activities

Career center

Reading list

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