Cutting Edge > Courses > Sedimentary Geology > Sedimentology, Geomorphology, and Paleontology 2014 > Teaching Activities > An Introduction to Seismic Interpretation Using Open Source Software (OpendTect)

An Introduction to Seismic Interpretation Using Open Source Software (OpendTect)

Jeannette Wolak, Tennessee Technological University
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This page first made public: Jun 6, 2014

Summary

This is a series of three lab exercises integrating seismic interpretation and sedimentary geology. Each lab uses freely available software from dGB Earth Sciences, OpendTect. The seismic volume is the F3 Block in the North Sea, which is publicly available via dGB's Seismic Repository. The software is very user-friendly. The exercises are written so that no experience is needed using the software prior to the labs. Students are guided through the program as they answer questions on sedimentology, stratigraphy, geomorphology, structural geology and petroleum geology.

Context

Audience

I use this activity in a senior-level undergraduate course on subsurface geological exploration. It is suitable for junior/senior undergraduate students or graduate students. Given the diverse range of tasks (i.e. mapping faults, drawing stratigraphy), it is suitable for modification and use in any of the following courses: sedimentation/stratigraphy, structural geology, introductory geophysics or petroleum geology.

Skills and concepts that students must have mastered

Prior to this activity, students need an introduction to geophysical reflection surveys. I address this in a one-hour lecture sometime prior to beginning the lab sequence. The lecture covers the following topics:
  1. What is seismic data? How is it acquired? Assuming students have not had a geophysics course, most will recall seismic principles from discussions on earthquakes or earth structure. I build on this knowledge and describe the general differences between deep earth seismic data (from passive sources like earthquakes) vs. shallow earth seismic data (from active sources like controlled explosions or compressed air).
  2. How do waves travel through different rock or fluid mediums? How is that expressed on a seismic image?I also introduce concepts of wave velocity, amplitude, reflection and impedance. However, not all students have completed their physics sequence prior to this course so only a select few fundamental equations are used.
  3. What are the practical applications of seismic data? Finally, I emphasize how we use seismic data to 'see' into the subsurface. I describe a few key applications in regional mapping and petroleum geology.

The labs are exploratory, and students develop their own questions about other content: stratigraphy, faults, "funny-looking blobs", salt diapirs, geophysics principles. I prefer to address these topics as they naturally come up instead of front-loading too much information into the lecture.

How the activity is situated in the course

This lab series is used in a course on Geological Exploration Techniques. Senior students spend the first half of the semester on mining geology and the second half on petroleum geology. This activity falls in the latter half of the semester.

Goals

Content/concepts goals for this activity

The main content of this lab is based on seismic interpretation of a 3D volume. However, the geophysical principles of seismic acquisition/processing are not covered in depth. The intended audience are students who have not completed a geophysics course. All exercises use a reflection survey (time volume) without the additional component of time-to-depth conversion. For those who wish to take the exercises further, a time-depth volume is available from dGB Earth Sciences.

Within the F3 Block seismic volume, the geomorphology of the present-day ocean floor is visible in 3D. Differences in compaction/lithification and biogenic gas seeps are evident in the shallow interval. Features such as regional faults, salt diapirs and clinoforms characterize the rest of the volume. A number of marker horizons are available for download as well as data from four wells.

Content Goals (Geophysics)

  1. Students learn how seismic waves travel through different earth materials (unlithified sediments, rocks, fluids).
  2. Students navigate through a 3D seismic survey using knowledge of inlines, crosslines and z-axes.

Content Goals (Sedimentary Geology)

  1. Students combine data from seismic and wells to interpret the depositional environment of a setting.
  2. Students demonstrate knowledge of how sediment moves from source to sink, particularly via processes in the deep ocean.

Content Goals (Structural Geology)

  1. Students map fault planes in three dimensions.
  2. Students characterize faults as extensional or compressional structural features.
  3. The timing of fault movement is constrained using three-dimensional geometries.

Content Goals (Geomorphology/Marine Geology)

  1. Students identify the impact of sediment compaction on a seismic signal (i.e., velocity increases in tightly packed sediments).
  2. Students describe the geomorphology of the ocean floor, paying special attention to features such as biogenic gas seeps.

Higher order thinking skills goals for this activity

  1. Students visualize geologic features in three-dimensions. This series of labs compliments traditional field-based observation (e.g., outcrop work, cores, wireline logs). Within the 3D volume, students are able to continuously trace geologic features such as faults and salt diapirs.
  2. Students think critically about the features they observe in order to determine relative geologic ages of different events.

Other skills goals for this activity

  1. Software Skills: Students learn to use a new software package, OpendTect.
  2. Creative skills: Students describe features that they observe in the seismic data via sketches and written description.

Description and Teaching Materials

OpendTect, an open-source software package developed by dGB Earth Sciences, is needed to complete these exercises. OpendTect is freely available for Mac or PC. Academic licenses will add functionality to the software; however, an academic license is not required to complete the exercises. Each activity uses the F3 Block Seismic Data, which is included during the download. (Note: The F3 Block is dGB's training volume for new users so the data is exceptionally easy to work with!)

It is recommended that you load and test the software on lab computers prior to the exercises. The labs assume the software has already been loaded locally and do not provide instructions to do so. Installation information is available via the OpendTect website.

OpendTect Seismic Lab I (Microsoft Word 2007 (.docx) 803kB Jun6 14)

OpendTect Seismic Lab II (Microsoft Word 2007 (.docx) 2MB Jun9 14)

OpendTect Seismic Lab III (Microsoft Word 2007 (.docx) 1.9MB Jun9 14)

For those wishing to take the exercises a step further using the North Sea dataset, a number of journal articles are available to share with students. Please see the information page for the F3 Seismic Volume to download articles.

Assessment

There are two main forms of assessment for the lab series.

  1. I score the individual labs each week using a simple rubric. (Please don't hesitate to contact me via email for lab keys and copy of the rubric.)
  2. A portion of the final grade also comes from evaluation of OpendTect files that the students are asked to create. For example, they construct a fault plane in the second lab, which is saved as "StudentInitials_FaultB". Once students have completed the labs, I review the individual files.

References and Resources

OpendTect Website

Universities Using OpendTect

OpendTect Open Seismic Repository (Free Seismic Data!)

Netherlands Offshore F3 Block - Complete

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