Geology _ Geophysics in Oil Exploration

Bnon impulsive sources the main common is vibroseis

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Unformatted text preview: ons for landfills, and characterize how an area will shake during an earthquake, but they are primarily used for oil and gas exploration (Seismic acquisition) Before starting discussion about Seismic acquisition, we must know some concepts about the seismic theory. Seismic waves: Seismic waves are sound waves that travel through the Earth or other elastic bodies, for example as a result of an earthquake, explosion, or some other process that imparts forces. Types of seismic waves: 1‐Body waves: A wave that propagates through a medium rather than along an interface. It is faster than Surface waves • P‐wave: An elastic body wave in which particles motions are parallel to the direction the wave propagates. It`s velocity is faster than S-wave. P-waves incident on an interface at other than normal incidence can produce reflected and transmitted Swaves, in that case known as converted waves. • S‐wave: An elastic body wave in which particles motions are perpendicular to the direction the wave propagates. S-waves are generated by most land seismic sources, but not by air guns. 2‐Surface waves: A wave that propagates at the interface between two media. • Rayleigh wave: It is a surface wave in which particles move in an elliptical path. Because Rayleigh waves are dispersive, with different wavelengths traveling at different velocities, they are useful in evaluation of velocity variation with depth. It is called Ground Roll in seismic exploration. • Love wave: It is a surface wave in which particles oscillate horizontally and perpendicularly to the direction of wave propagation. • Stoneley wave: It is a surface wave generated by a sonic tool in a borehole. It can propagate along a solid-fluid interface, such as along the walls of a fluid-filled borehole. It can allow estimation of the locations of fractures and permeability of the formation. It is a major source of noise in vertical seismic profiling (VSP). • Tube waves: It occurs in cased wellbores when Rayleigh waves enc...
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