Lecturers:
Dr Steve Hearn
Dr Peter Furness
Course Summary:
This course builds on the introduction provided by ERTH3020, examining the common applied-geophysical techniques in more detail. The course is divided approximately equally into seismic and non-seismic components, reflecting the broad makeup of the exploration geophysics industry. The seismic component of the course concentrates on the seismic reflection method, and includes discussion of acquisition, processing, and structural and stratigraphic interpretation. The non-seismic component includes discussion of the potential field methods (gravity and magnetics), DC electrical techniques, and electromagnetic techniques (time and frequency domain).
Contact:
4 contact hours per week
Lecture Room:
First Year Laboratory - Steele Building
Assumed Background:
The normal prerequisite for ERTH3021 is ERTH3020. The subject assumes a background of introductory mathematics (algebra, calculus, trigonometry), as well as prior exposure to basic geology and geophysics. For further details contact Dr. Hearn.
References:
Hatton, L. , Worthington, M.H., Makin, J. , Seismic Data Processing, Blackwell.
Sheriff, R.E., Encyclopedic Dictionary of Geophysics, 3rd Edition, SEG.
Sheriff, R.E. and Geldart, L.P., Exploration Seismology. Cambridge University Press.
Telford, W., Geldart, L., Sheriff, R., Applied Geophysics, Cambridge University Press.
Yilmaz, O., Seismic Data Processing, Society of Exploration Geophysicists.
Course Outline:
Introductory Seismic Reflection (Steve Hearn)
Lectures and tutorials introducing the seismic reflection method of exploration. The material emphasises hydrocarbon exploration but is of increasing relevance in other mining and engineering applications, as well as in large-scale crustal studies. The course includes the following topics.
Review of Basic Concepts
Common wave types (P, S, Surface).
Distinction between seismic reflection and refraction.
Travel time equations for seismic reflection.
The reflectivity concept and reflection coefficients.
Seismic Reflection Acquisition
Seismic sources and detectors.
Multi-channel recording, the roll-along technique, land and marine recording geometries, geophone groups.
Survey and parameter design, 2D and 3D recording.
Common Mid Point acquisition concepts.
Production of Seismic Sections
Common Mid Point Processing (Normal Moveout, velocity analysis, CMP stacking).
Basic processing techniques for image enhancement (amplitude equalisation, bandpass filtering, deconvolution, static correction, velocity filtering, migration).
Seismic Modelling
Forward modelling - construction and use of synthetic seismograms.
Inverse modelling - seismic trace inversion, impedance mapping.
Structural Interpretation of Seismic Sections
Tieing to synthetics.
Picking a survey
Use of 2D versus 3D data.
Horizon contour maps and depth conversion.
3-D seismic volumes and time-slices.
Aspects of Sequence Stratigraphic Interpretation
Significance of sea-level rise and fall.
Identification of seismic sequence boundaries.
Reflection configurations within seismic sequences.
Systems tracts and their significance to hydrocarbon exploration.
Non-Seismic Techniques (Peter Furness)
A number of surface geophysical methods are examined in greater detail than in ERTH3020. Analysis of the gravity, magnetic, electrical resistivity and electromagnetic methods includes basic theory, instrumentation and field procedures. These non-seismic methods have traditionally been used in mineral exploration, but are increasingly used in groundwater, environmental and engineering applications.
Gravity Technique
Basic theory - Newton's Law,superposition,acceleration,potential,gravity anomalies.
Gravity meters - units, simple spring meter, Lacoste-Romberg meter.
Gravity field procedure - drift correction.
Gravity field of the Earth - Geoid, reference spheroid, standard (normal) gravity.
Gravity corrections - latitude, free-air, Bouguer, topographic.
Separation of regional and residual gravity effects.
Magnetic Technique
Theory - Coulomb's law, magnetic field, potential, dipole.
Instrumentation - Proton Precession magnetometer.
Magnetics field procedures.
Direct-Current Electrical Resistivity Technique
Practical aspects of resistivity surveying.
General electrode array and equivalent circuit
Pesistivity transmitters, electrodes, receivers.
Noise problems in resistivity surveys.
Resistivity sounding using the Schlumberger array.
Use of expanding potential electrodes in Schlumberger sounding.
Electromagnetic Technique
Time-Domain Electromagnetic systems.
Low Induction Number (LIN) Electromagnetic surveying.
Assessment Procedures:
Final Examination 85%, Practicals 15%
Examination material and practical work is assessed on the technical accuracy of submitted work, scientific logic, and presentation. Further details on assessment procedures are provided prior to each assessable task.
Except where group work is specified, all work must be that of the author. Departmental policy on non-compliance with assessment procedures can be obtained from the Department of Earth Sciences office in the Steele Building.