SEG Distinguished Instructor Short Course (DISC) on DAS by Mark Willis

Geoscientists and engineers are very comfortable using seismic data sets acquired with geophones, hydrophones, and accelerometers because we have a long, well-defined set of standards for acquiring, processing, and interpreting them. However, distributed acoustic sensing (DAS) seismic measurements are rapidly augmenting, and in some cases replacing, the data from these conventional tools. Technologists are frequently unaccustomed to using DAS seismic data sets since it directly acquires relative strain or strain rate measurements and not the more familiar pressure, displacement, velocity, and acceleration data. There are also acquisition parameter selections that must be made to optimize the acquired data to accomplish the purpose of the seismic survey. This course is designed to build an intuition and understanding of the value, limitations, and applications of DAS seismic technology. In addition to the lecture and accompanying book, software will be provided which will allow the student to interactively explore DAS seismic technology.

This course will cover

• What are many of the applications for DAS technology?
• How do conventional and DAS seismic measurement systems compare?
• How can we convert between DAS and geophone measurements?
• What is the physics behind DAS measurements and the composition of optical fiber? Do different types of fiber optic cables offer advantages?
• How is a DAS acquisition system architected? How does the fiber optic cable deployment method affect the DAS measurements?
• What is the gauge length and how does it affect the acquired data? How does the pulse width interact with the gauge length to improve data quality?
• What is the angular response of the fiber optic cable to incoming seismic signals? How does the angular response of the fiber affect VSP, surface seismic, and microseismic measurements?
• What are the sources of DAS noise and how are they mitigated? Can we remove the effects of poor fiber optic cable coupling from the seismic data?
• How can we plan and prepare for a DAS seismic survey? What are the key decisions that need to be made and can we model them?
• What are the field deployment issues that we should address? How is handling fiber optic cables different from standard electrical cables? Can the health of the deployed fiber be determined before the survey begins? How is the depth (or distance along the fiber) of each channel of seismic data determined?