What is petrophysics? Petrophysics (or rock physics) is the branch of geology that is concerned with the physical properties and behavior of rocks. Oil exploration requires direct and indirect measurements of the underground rock strata, the totality of which commonly is referred to as “the geology.” Well cores provide actual rock samples extracted from a well. Downhole instruments placed in oil wells provide direct measurements, or well logs, of the rocks in place. Cores and well logs are used to determine the petrophysics of the strata to help reveal potential oil-bearing reservoirs. Of interest in petrophysics are things such as rock type (e.g., sandstone, shale, limestone, etc.) and rock characteristics (e.g., porosity, permeability, fracturing, etc.).
The seismic method provides indirect measurements in the form of seismic records. The word indirect is appropriate because the seismic method uses a noninvasive technique (seismic waves and seismic recording instruments) to penetrate and record data from a remote body (the underground rocks). Similar techniques are radar, sonar, and ultrasonic medical imaging. Seismic records are made up of signals called traces, which record reflections of the seismic waves from the boundaries of different rock layers. Such rock-layer boundaries are called interfaces (or horizons). In some cases, horizons are approximately horizontal planar surfaces with low to moderate dips. In other cases, horizons are curved and contorted surfaces with steep dips.
Most familiar to us are water waves. Ancient Greek philosophers, many of whom were interested in music, hypothesized that a parallel exists between water waves and
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Digital Imaging and Deconvolution: The ABCs of Seismic Exploration and Processing
Digital Imaging and Deconvolution: The ABCs of Seismic Exploration and Processing (SEG Geophysical References Series No. 15), covers the basic ideas and methods used in seismic processing, concentrating on the fundamentals of seismic imaging and deconvolution. Most chapters are followed by problem sets. Some exercises supplement textual material; others are meant to stimulate classroom discussions. Text and exercises deal mostly with simple examples that can be solved with nothing more than pencil and paper. The book covers wave motion; digital imaging; digital filtering; various visualization aspects of the seismic reflection method; sampling theory; the frequency spectrum; synthetic seismograms; wavelets and wavelet processing; deconvolution; the need for continuing interaction between the seismic interpreter and the computer; seismic attributes; phase rotation; and seismic attenuation. The last of the 15 chapters gives a detailed mathematical overview. Digital Imaging and Deconvolution, nominated for the Association of Earth Science Editors award for best geoscience publication of 2008–2009, will interest professional geophysicists, graduate students, and upper-level undergraduates in geophysics. The book also will be helpful to scientists and engineers in other disciplines who use digital signal processing to analyze and image wave-motion data in remote-detection applications. The methods described are important in optical imaging, video imaging, medical and biological imaging, acoustical analysis, radar, and sonar.