Abstract
The reflection seismic technique is the most widely used geophysical method world-wide, being used mainly in oil exploration. It is an echo-sounding technique fo r mapping the tectonic structure o f layered sedimentary rocks. Seismic waves are induced in the ground, typically fro m an explosive source, and they are reflected at each geological boundary where there is a change in acoustic impedance (acoustic impedance is the product o f density and seismic velocity). The reflected waves are detected at the surface using geophones on land, or hydrophones at sea. The outputs fro m the detectors are recorded on digital magnetic tape and are then computer-processed. A field technique called common-depth-point recording is used so that noise and multiple reflections can be cancelled by “stacking”, which is carried out during the computer processing. In the computer various types o f filters are applied to the seismic results to remove noise, to improve resolution, and to correct geometrical distortion which occurs in areas o f complex tectonic structure. The final output is displayed as a seismic record section, which is made up o f many individual seismic traces, and resembles a cross-section through the earth, showing the structure o f the sedimentary rocks. Very high-quality reflection seismic results have been obtained on the South African continental shelf, and have been extremely valuable in siting oil exploration wells.
Highlights
Geophysical methods which are used in exploration for oil and gas include gravimetric surveys, magnetometric surveys, seismic reflection and seismic re fraction surveys
By far the most extensively used is the seismic reflection method. This technique will be described in the present paper
The reser voir must be overlain by an impermeable “ cap rock” such as shale, and there must be a geological trapping mechanism which confines the oil to the pool
Summary
Geophysical methods which are used in exploration for oil and gas include gravimetric surveys, magnetometric surveys, seismic reflection and seismic re fraction surveys. By far the most extensively used is the seismic reflection method. This technique will be described in the present paper. In 1978 a total of 1 672 million US dollars was spent on all methods of geophysical exploration world-wide. 93 per cent was spent on seismic reflection surveys for oil, onshore and offshore.1As a result of its extensive use, the technology in reflec tion seismic prospecting has been advancing rapidly, especially in the last twenty years. Oil pools are located in porous reservoir rocks, usually sandstones or porous limestones. The reser voir must be overlain by an impermeable “ cap rock” such as shale, and there must be a geological trapping mechanism which confines the oil to the pool. There are two basic classes of traps (see Fig. 1): structural traps, such as anticlines and fault traps, and strati-
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
