Post on 26-May-2015
transcript
Introduction to Geophysics
Ali Onceloncel@kfupm.edu.
saDepartment of Earth SciencesKFUPM
Seismic Reflection 2: Acquisiton, Processing, and Waveform Analysis
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Previous Lecture
What Seismic Reflection Provides? What requires for a successful study of Reflection? What provides Seismic Reflection on subsurface geological Model? On Land- Seismic Reflection On Sea- Seismic Reflection: Photos from Seismic Crew Equipments: Vibrator Track and Receiver Truck, Geophones, Battery What is a seismic section? what is a Seismic Line? Nature of Seismic Section? Acoustic Impedance Enhancement the quality for Compressional waves? Single Channel Seismic Reflection? What is a seismic Profile?
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Reflection SeismologyIn
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Seismic MethodsIn
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Snell’s Law
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Reflection “Presentation”
Refraction (first arrival)
Reflection 1
Reflection 2
Reflection 3 (dipping)
Reflected refractions
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Angle Incidence = Angle Reflection
Multifold Reflections
Four fold coverage of the CMP
Receiver ArraysIn
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Common Depth Point
Common Midpoint
Many Source Receiver Offsets
Sample Same Depth Point
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CMP Method
Figure 6.4 of Reynolds
Sixfold coverage
of the CDP
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CMP
Method
Sample Same Subsurface Point – Common Depth Point 4 Times
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Processing
Fold of Stack
Coverage
Redundancy
Improve Signal to Noise Ratio
21
220 V
XtT f
fT=Travel time from source, to interface, to receiver
X= horizontal distance from source to receiverV1= seismic velocity of layer above distance
T0= T-axis intercept (time directly down to interface,
straight back up to shot location
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h = thickness of layer above interfaceV1= seismic layer of above interface
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TNMO= Tf - t0
Normal moveout is the difference between the travel time and hyperbola (Tf) and the intercept time (t0).
Normal Moveout
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XTNMO
See EQ 4-10 of Robinson and Coruh, 1988