Introduction to Geophysics

Ali Onceloncel@kfupm.edu.

saDepartment of Earth SciencesKFUPM

Seismic Reflection 3: Acquisiton, Processing, and Waveform Analysis

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Previous Lecture

Example:  Data Acquisition in Shaybah Field (Alfaraj et al., 1998, GeoArabia, Vol. 3, No 2)Over 120 million seismic traces and over 100,000 shot points, covering an area of about 1,100 sq km. Primary Reflection Multiples NMO – Normal Moveout Correction Velocity Analysis Example: Gathers and NMO Corrected CMP Mute

Static Corrections

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Average Velocity

( )

j

i ii

average j

ii

V tV j

t

Vav= average velocity above the interface

Z= depth from the surface to the interfacet= one-way travel from surface to interface

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Root Mean Square (RMS) Velocity

1/2

2

1( )

1

j

irms j j

i

V tV

t

VRMS= root mean square velocity

Vi= seismic velocity of the ith layer

ti= two-way travel time within the ith layer

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Interval Velocity (Vint)

122 2

1 1interval

1

n n n n

n n

V t V tV

t t

For n=2V1= Stacking velocity for reflection from upper interface [VRMS(1)]

V2= Stacking velocity for reflection from lower interface [VRMS(2)]

Dix, 1955 (p.130 of Sheriff and Geldart, 1995)

Vint=ΔZ/ Δt

Vint= average velocity between two interfaces

ΔZ= thickness of layer between the two interfacesΔt= one-way travel time between the two interfaces

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Mid-Term ExamMay 3

Field-Trip April 26, 12.30 PM

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12.10 AM- 13.00 AM

We may recover two classes time

1. What does fold mean in the CMP method? Give an example.

2. What are the two advantages of the CMP method over previous methods?

P.C: Open Book

The quiz of the weekIn

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