SEISMIC INTERPRETATION JIM KELLOGG UNIVERSITY OF SOUTH CAROLINA
Slide 2 Instructor Dr. James Kellogg has 30 years experience in
regional tectonics, satellite geodesy, structural modeling, and
potential field studies. He is a Professor in the Department of
Earth and Ocean Sciences and Director of the Andean Geophysical
Laboratory, at the University of South Carolina, President of
Kellogg International Associates, and Editor-In-Chief of the
Journal of South American Earth Sciences. He obtained his M.A.
(1978) and Ph.D. (1981) in geology and geophysics at Princeton
University. In 1987 he joined the faculty of the University of
South Carolina as professor of applied geophysics. He has
coordinated regional geophysical basin studies for petroleum
exploration using seismic, well, gravity, and magnetic data. He has
published over 60 papers and taught short courses in volume
balanced structural and seismic reflection interpretation,
potential field modeling, 3-Dimensional modeling, and regional
tectonics. http://www.AndeanGeophysical.com
http://www.KelloggInternational.com Slide 3 SEISMIC INTERPRETATION
1.Seismic Data Acquisition and Processing 2.Pitfalls 3.Volume
Balanced Solutions and Kink Method of Seismic Interpretation
4.Extensional Tectonics 5.Salt Tectonics 6.Seismic Attributes for
Reservoir Characterization 7.3D Seismic Data Slide 4 SEISMIC DATA
ACQUISITION AND PROCESSING Slide 5 Acquisition Shot, Wavelet, Trace
Acoustic Impedence, Polarity Acoustic Well Logging Synthetic
Seismic Traces Common Depth Point (CDP) Stack Processing and
Migration Slide 6 DATA ACQUISITION Shot initial bang Shotpoint
geographical location Source pulse or wavelet resulting sound
Reflections echoes Trace stream of reflections recorded by geophone
Slide 7 Slide 8 SEISMIC ACQUISITION Slide 9 Slide 10 Land Seismic
Data Acquisition Highlands Transition Zone HeliportableSpecialists
Jungle DesertArctic Slide 11 Slide 12 Geophone Team Slide 13 Marine
Seismic Acquisition Slide 14 Slide 15 For some applications, it is
desirable to put the receivers directly on the seafloor using
ocean-bottom cables (OBC). The acquisition of shear wave seismic
data is one such use. Shear waves do not travel through water, and
so conventional marine sources do not generate them and hydrophones
will not record them. Slide 16 DATA ACQUISITION Seismic reflector
or acoustic- impedence boundary boundary across which the hardness
changes. Reflection coefficient type and size of acoustic impedence
change. Slide 17 DATA ACQUISITION Seismic reflector or
acoustic-impedence boundary boundary across which the hardness
changes. Reflection coefficient type and size of acoustic impedence
change. Acoustic impedence (Z) = density ( ) x velocity (V) Z = V
Slide 18 TRACE ANALYSIS Positive reflection overlying layer is
softer than underlying layer Negative upper layer is harder
Polarity peak or trough for positive reflection Slide 19 TRACE
ANALYSIS Positive reflection overlying layer is softer than
underlying layer Negative upper layer is harder Polarity peak or
trough for positive reflection Slide 20 TRACE ANALYSIS Two-way time
time from bang to recording Amplitude reflection strength Wavelet
shape Slide 21 REFLECTION COEFFICIENT LOG AND NORMAL POLARITY
WAVELET Slide 22 The main instrument used is called the sonde. A
basic sonde consists of a source and two receivers one-foot apart.
The sonde is lowered down the borehole and waves are generated and
recorded continuously. The sonde is usually positioned in the
borehole center using centralizing springs. Frequencies used are in
the range of 2 - 35 kHz. Typical investigation radius is 0.2 1.2 m.
Acoustic Well Logging Operation Slide 23 Acoustic Well Logging
Sonde types Slide 24 Acoustic Well Logging Transit time Slide 25
Acoustic Well Logging Example Slide 26 Note high resolution of
sonic log vs the seismic trace Slide 27 Synthetic Seismic Trace
Reflection coefficients and velocity log used with a zero phase
wavelet to produce a synthetic seismic trace Slide 28 Wavelet
minimum phase wavelet = front loaded energy i.e. at time zero
minimum energy and elsewhere maximum. zero phase wavelet has
maximum energy at time zero. Most seismic sources do not generate a
zero phase pulse, because that implies output before time zero. For
instance an air gun source generates a minimum phase pulse. We can
use minimum phase wavelet for acquisition and during processing
convert to zero phase. Slide 29 EFFECT OF WAVELET FREQUENCY ON
SEISMIC RESPONSE Slide 30 Which display do you prefer? Slide 31 Are
the faults clearer in this display? Slide 32 Or in this display?
Slide 33 CDP RECORDING METHOD TO INCREASE SIGNAL TO NOISE RATIO
Common-depth-point (CDP) or Common-mid-point (CMP) reflections
recorded from the same subsurface point with different offsets.
Fold number of traces 2 fold 2 traces 96 fold 96 traces Slide 34
SEISMIC ACQUISITION Slide 35 CDP-CMP METHOD Slide 36 SEISMIC
ACQUISITION Slide 37 MIGRATION Migrated restore dipping reflector
to correct subsurface position.
