The migration of common midpoint slant stacks

Geophysics ◽  
1984 ◽  
Vol 49 (3) ◽  
pp. 237-249 ◽  
Author(s):  
Richard Ottolini ◽  
Jon F. Claerbout
Keyword(s):  
Seismic Data ◽  
Lateral Velocity ◽  
Velocity Inversion ◽  
Interval Velocity ◽  
Reflection Seismic ◽  
Straightforward Method ◽  
Velocity Surface ◽  
Velocity Variations ◽  
Migration Equation ◽  
Ray Parameter

Reflection seismic data can be imaged by migrating common midpoint slant stacks. The basic method is to assemble slant stack sections from the slant stack of each common midpoint gather at the same ray parameter. Earlier investigators have described migration methods for slant stacked shot profiles or common receiver gathers instead of common midpoint gathers. However, common midpoint slant stacks enjoy the practical advantages of midpoint coordinates. In addition, the migration equation makes no approximation for steep dips, wide offsets, or vertical velocity variations. A theoretical disadvantage is that there is no exact treatment of lateral velocity variations. Slant stack migration is a method of “migration before stack.” It solves the dip selectivity problem of conventional stacking, particularly when horizontal reflectors intersect steep dipping reflectors. The correct handling of all dips also improves lateral resolution in the image. Slant stack migration provides a straightforward method of measuring interval velocity after migration has improved the seismic data. The kinematics (traveltime treatment) of slant stack migration is also accurate for postcritical reflections and refractions. These events transform into a p-τ surface with the additional dimension of midpoint. The slant stack migration equation converts the p-τ surface into a depth‐midpoint velocity surface. As with migration in general, the effects of dip are automatically accounted for during velocity inversion.

Seismic attributes — A historical perspective

Geophysics ◽  
2005 ◽  
Vol 70 (5) ◽  
pp. 3SO-28SO ◽  
Author(s):  
Satinder Chopra ◽  
Kurt J. Marfurt
Keyword(s):  
Seismic Data ◽  
Quantitative Measure ◽  
Seismic Attributes ◽  
Seismic Attribute ◽  
Black And White ◽  
Interval Velocity ◽  
Reflection Seismic ◽  
Color Displays ◽  
Attribute Analysis ◽  
Other Information

A seismic attribute is a quantitative measure of a seismic characteristic of interest. Analysis of attributes has been integral to reflection seismic interpretation since the 1930s when geophysicists started to pick traveltimes to coherent reflections on seismic field records. There are now more than 50 distinct seismic attributes calculated from seismic data and applied to the interpretation of geologic structure, stratigraphy, and rock/pore fluid properties. The evolution of seismic attributes is closely linked to advances in computer technology. As examples, the advent of digital recording in the 1960s produced improved measurements of seismic amplitude and pointed out the correlation between hydrocarbon pore fluids and strong amplitudes (“bright spots”). The introduction of color printers in the early 1970s allowed color displays of reflection strength, frequency, phase, and interval velocity to be overlain routinely on black-and-white seismic records. Interpretation workstations in the 1980s provided interpreters with the ability to interact quickly with data to change scales and colors and to easily integrate seismic traces with other information such as well logs. Today, very powerful computer workstations capable of integrating large volumes of diverse data and calculating numerous seismic attributes are a routine tool used by seismic interpreters seeking geologic and reservoir engineering information from seismic data. In this review paper celebrating the 75th anniversary of the Society of Exploration Geophysicists, we reconstruct the key historical events that have lead to modern seismic attribute analysis.

Prestack migration by split‐step DSR

Geophysics ◽  
1996 ◽  
Vol 61 (5) ◽  
pp. 1412-1416 ◽  
Author(s):  
Alexander Mihai Popovici
Keyword(s):  
Phase Shift ◽  
Square Root ◽  
Variable Velocity ◽  
Step Method ◽  
Lateral Velocity ◽  
Data Set ◽  
Prestack Migration ◽  
Imaging Results ◽  
Velocity Variations ◽  
Migration Equation

The double‐square‐root (DSR) prestack migration equation, though defined for depth variable velocity, can be used to image media with strong velocity variations using a phase‐shift plus interpolation (PSPI) or split‐step correction. The split‐step method is based on applying a phase‐shift correction to the extrapolated wavefield—a correction that attempts to compensate for the lateral velocity variations. I show how to extend DSR prestack migration to lateral velocity media and exemplify the method by applying the new algorithm to the Marmousi data set. The split‐step DSR migration is very fast and offers excellent imaging results.

Generalized form of the Dix equation for the calculation of interval velocities and layer thicknesses

Geophysics ◽  
1989 ◽  
Vol 54 (5) ◽  
pp. 659-661 ◽  
Author(s):  
Ali A. Nowroozi
Keyword(s):  
Root Mean Square ◽  
Seismic Data ◽  
Approximate Equation ◽  
Mean Square ◽  
Interval Velocity ◽  
Reflection Seismic ◽  
Interval Velocities ◽  
Horizontal Layers

Over three decades ago, Dix (1955) derived an approximate equation for the determination of interval velocity from observed reflection seismic data. Assuming a stack of m horizontal layers, with interval velocities [Formula: see text], layer thicknesses [Formula: see text], j = 1, m, and near‐vertical raypaths, Dix (1955) showed that [Formula: see text]where [Formula: see text] and [Formula: see text] are the two‐way vertical times and [Formula: see text] and [Formula: see text] are the root‐mean‐square (rms) velocities to interfaces j + 1 and j, respectively.

Automated interval velocity inversion

2000 ◽  
Author(s):  
Weijian Mao ◽  
Robin Fletcher ◽  
Swavek Deregowski
Keyword(s):  
Velocity Inversion ◽  
Interval Velocity
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