Seismic Reflection Data: Acquisition and Processing

Objectives:
The seismic reflection method is one of the main tools used by geophysicists to probe the Earth' s crust and uppermost mantle. The goal of this course is to provide students with an overview of how seismic reflection data are collected and processed to form high-resolution images of the subsurface. Upon completing the course, students will be able to understand the entire process that goes into generating the seismic sections they may come across during their career, either in the industry or in academic research. They will have acquired a critical understanding of the strengths and limitations of these images, and will be able to use this knowledge to guide their interpretation of seismic sections.

Content:
The course is divided into two parts. Part I introduces a theoretical basis in signal processing and seismic wave propagation. It then builds on this knowledge to describe the common processing steps used to transform raw seismic data into 2-D images and to estimate seismic velocities of the subsurface. Part II is concerned with the acquisition of seismic data. It provides an overview of the seismic instrumentation used in both marine and land surveys, and describes how these instruments (both sources and receivers) can be arranged optimally to ensure the collection of high-quality data.

On completion of the course the student should have the following learning outcomes defined in terms of knowledge, skills and general competence:

Knowledge
The student can

• explain key concepts of time series analysis and digital signal processing: frequency, phase, amplitude, Fourier series, Fourier transform, aliasing, filtering
• explain basic concepts of seismic wave propagation: P-waves, S-waves, elastic constants, reflection, refraction, attenuation
• explain the processing sequence that leads to the generation of 2-D seismic sections: trace gathers, NMO stacking, velocity analysis, migration
• describe the various types of instruments used for seismic data acquisition and explain how these instruments work
• explain key concepts associated with seismic survey design and data quality: bubble pulse, ghost, directivity, and signal-to-noise ratio (SNR)

Skills
The student

• can carry out basic operation in time series analysis and digital signal processing: compute frequency, phase and time shift of a sinusoid; convolve and correlate two time signals; apply the sampling theorem
• can compute ray paths, travel times and amplitudes of seismic waves propagating in simple layered media, and assess the resolving power of these waves as a function of their dominant frequency
• can carry out velocity analysis on simple CMP gathers
• is able to plan simple and efficient surveys combining various seismic techniques

General competence
The student

• has acquired general working knowledge of time series analysis and digital signal processing that is applicable to other scientific disciplines
• has acquired a critical understanding of the importance of selecting the right instruments and designing surveys optimally to ensure the collection of the highest possible quality data
• can critically evaluate the strengths and weaknesses of seismic profiles based on how the data are collected and processed
• has acquired basic knowledge in Health, Safety and Environment (HSE) issues relevant for seismic data acquisition
• has demonstrated competence in scientific ethics and the ability to work independently and as part of a team