Page 132 - Introduction to Petroleum Engineering

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RESERVOIR GEOPHYSICS

A picture of the large‐scale structure of the reservoir can be obtained using vibrations
called seismic waves that propagate through the earth. The study of vibrations in the
earth is one aspect of geophysics, which is the study of the physical properties and
processes associated with the earth and surrounding space. This chapter reviews
the process for acquiring and analyzing vibrational data in porous media, discusses
the resolution of vibrational data, and introduces modern applications.

7.1 SEISMIC WAVES

Seismic waves are vibrations that propagate from a source and through the earth until
some of the vibrational energy is reflected back to the surface where it is detected by
receivers (Figure 7.1). Sources include explosions, mechanical vibrators created
by vibrating trucks, and expulsion of compressed air from seismic air guns in marine
environments.
Receivers include geophones on land and hydrophones offshore. A geophone
converts ground motion to a voltage, and a hydrophone is a microphone that detects
underwater sound. Receivers record travel time from the source to the receiver during
the data acquisition phase of a seismic survey.
Geophones and hydrophones are seismometers. A seismometer detects vibra-
tional energy and sends a record of the vibrations to a seismograph, which displays
the signal as a seismogram. The seismogram records the motion of the seismometer

Introduction to Petroleum Engineering, First Edition. John R. Fanchi and Richard L. Christiansen.
© 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/Fanchi/IntroPetroleumEngineering