Post on 04-Jun-2018
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Reflection Seismic Geophysics
Marine Aqusition
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Surface Seismic Exploration Cycle
ACQUISITION
PROCESSING
INTERPRETATION
Drillhere
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2D Reconnaissance Survey 2D Detailed Survey
2D Surveys
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Source to Receiver Ray Path
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Ray Paths
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Ray Paths
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Ray Paths
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Ideal Seismogram
The seismic data recorded should give us theEarths reflectivity sequence:
Surface
Depth
Time
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Marine
Source Receiver Vessels Equipment Handling
Acquisition sequence
4C
Q
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Marine Acquisition System
Sea bed
Boat
Cable with hydrophones
Sea Surface
Source(Airguns)
Sedimentary Layers
Incident waves Reflected
waves
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Marine - Recording Equipment
Streamer
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Sea bottom
Subsurface interface
Marine Acquisition
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Common Mid Point (CMP) gather
Marine Acquisition
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Common Mid Point (CMP) gather
Primary reflections
Common Midpoint Gather
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Reflection Seismic Geophysics
Land Aqusition
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Surface Seismic Processing Sequence Step 1
Where are the shotsand receivers located?
? ? ? ? ? ?
Geometry Definition
Depth
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Surface Seismic Processing Sequence Step 3
How do we remove thenoise? Geometry Definition
Amplitude Recovery
Velocity Filtering
Offset
Time
Mud Roll500 m/s
Reflector2000 m/s
Direct wave
1500 m/s Refractor1800 m/s
Multiple< 2000 m/s
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Surface Seismic Processing Sequence Step 4
How do we improve theresolution? Geometry Definition
Amplitude Recovery
Velocity Filtering
Deconvolution
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Surface Seismic Processing Sequence Step 5
Geometry Definition
Amplitude Recovery
Velocity FilteringDeconvolution
CMP Gather
How do we order the data?
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Surface Seismic Processing Sequence Step 6
How do we correct for timedifferences due to offset within the CMP gather?
Geometry Definition
Amplitude Recovery
Velocity FilteringDeconvolution
CMP Gather
NMO Correction
Offset
Time
Time Difference
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Surface Seismic Processing Sequence Step 7
How do we get a normalincidence section? Geometry Definition
Amplitude Recovery
Velocity FilteringDeconvolution
CMP Gather
NMO Correction
CMP Stack
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Surface Seismic Processing Sequence Step 8
Geometry Definition
Amplitude Recovery
Velocity FilteringDeconvolution
CMP Gather
NMO Correction
CMP Stack
Migration
How do we get the events in theright place?
Midpoint location
Actual reflection point
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Ideal Seismogram
The recorded seismic data should give us theearths reflectivity sequence
Surface
TimeDepth
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Seismic Waves - Generation
Explosive
Vibrational
Dynamite (Land)Airguns (Marine)
Marine VibroseisLand Vibroseis
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Recording Seismic Data
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Seismic WavesSu r face Wav es
Body Waves
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Body Wave Types 2 types defined by the direction of particle motion
1. P-wavesParticle motion parallel to wave propagation
wavedirection
2. S-waves
Particle motion perpendicular to wave propagatio
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Wave Energy On land, the energy division can be as poor as:
P-wave 6%
S-wave 26%
Surface waves 68%
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Wavefronts
Wavefronts How waves actually travel Surface of equal travel time Surface of equal phase
Reflectionpoints
surface wave
RaypathsRays perpendicular to wavefrontsSimple to useRay trace modelling
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Flat Earth Primary Reflections
Source ReceiverIdeal Primaries
Trace
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Flat Earth - Primary Section
Source Receiver
Ideal PrimaryTraces
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Flat Earth - Common Mid Points
Source Receivers
3,1 4,2 5,3 6,4
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Layer Cake - Common mid-point gather
Source Receiver
Common mid-point
Ideal cmpTraces