offshore geotechnical workshop - 17 nov 14
TRANSCRIPT
SEISMIC FOR NON-GEOPHYSICIST
SUB-BOTTOM PROFILER, 2D-HI RES SEISMIC AND GEOHAZARD
08th December 2014OFFSHORE GEOTECHNICAL WORKSHOP IIwww.asiangeos.com
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SUB BOTTOM PROFILE
History
Types
How They Work
Frequency/Resolution
Use For Interpretation
Boomer Plate Sparker System: 50 Hz to 4KHz
Pinger System: 10 to 24 kHz Pinger 4 X 4 Transducer
Boomer System: 0.2 to 3KHz
Pinger Chirp System: 0.5 to 24KHz
Air Gun System
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HISTORY OF SUB BOTTOM PROFILE
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Towed
Pinger 4 X4Pinger Chirp
Mounted
Pinger 2 X2Boomer
Sparker
Mini Air Gun
TYPE OF SUB BOTTOM PROFILER
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How They Work
Some of the sound will
reflects off and some will
penetrates the seafloor
The sound pulse
from the source
travels down to the seafloor
The reflected
sounds travel
back to surface
Received by
transceiver or hydrophones
D=V t/2D is the depth in meter , ‘V’ is the velocity, ‘t’ is the two way time (TWT)
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How They Work
The sub bottom profiler data recorded in millisecond (ms) twoway time (TWT)
Two way time = time travel to seafloor/layer + time travel toreceiver
Velocity assume value of 1600m/s-consider of solid velocity ishigher than water velocity. The water velocity range in Malaysiais around 1540m/s
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FREQUENCY AND RESOLUTION
HIGER FREQUENCY
SYSTEM
HIGER FREQUENCY SIGNALS HAVE
SHORTER WAVE LENGTHS AND ARE
ABLE TO DISCRIMINATE
BETWEEN LAYERS THAT ARE CLOSE
TOGETHER
PINGER AND CHIRP
LOW PENETRATION
HIGH RESOLUTION
LOWER FREQUENCY
SYSTEMS
LONGER SOUND PULSE LENGTHS
TRANSMIT MORE ENERGY AND
YIELDS DEEPER PENETRATION
BOOMER, SPARKER
AND MINI AIR GUN
HIGH PENETRATION
LOW RESOLUTION
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SUB BOTTOM PROFILER SYSTEM CHARACTERISTICS VARIOUS CLASSES OF SUB BOTTOM PROFILER
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PINGER AQUISITION
Side Mounted Pole
Hull Mounted Pole
Transducer
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BOOMER AQUISITION
Mini Streamer Frame Deployment
Mini Streamer-Hydrophone
Boomer Plate with Catamaran
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PINGER
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CHIRP
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BOOMER
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SPARKER
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MINI AIR GUN
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CODA GEO SURVEY SOFTWARE
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USE FOR INTERPERTATION
PROFILES
ISOPACH MAP
CHANNEL MAP
SHALLOW ANOMALY
SHALLOW FAULT
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GEOLOGICAL PROFILE
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ISOPACH MAP
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SHALLOW CHANNEL MAP
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SHALLOW ANOMALIES AND FAULT MAP
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CORRELATION BETWEEN SBP AND GEOTECHNICAL SOIL DATA
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2D HI-RES SEISMIC DATA
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2D HI-RES SEISMIC DATA ACQUITION SYSTEM
EQUIPMENT
• FUGRO STARFIX POSITIONING SYSTEM
• 96-CHANNEL SEAMUX 3 SOLID
• HYDOSCIENCE NTRS 2
• 150 CU.IN GI GUN
AQUISTION PARAMETERS
• SHOT INTERVAL:12.5 M
• GOUP INTERVAL: 12.5 M
• SAMPLING RATES: 1MS
• RECORDING LENGTH: 2S
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EQUIPMENT LAYOUT
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EQUIPMENT DEPLOYMENT
Streamer Winch and Birds
Streamer
GI Gun
Tail BuoyStreamer and birds deployment In Operation
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2DHR SEISMIC DATA INTERPRETATION
0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
0.900
1.000
1.100
1.200
1.300
1.400
1.500
1.600
1.700
1.800
1.900
2.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
0.900
1.000
1.100
1.200
1.300
1.400
1.500
1.600
1.700
1.800
1.900
2.000
120.0150.0180.0210.0- D28-AD-20 -
240.0270.0300.0SP:0.000
0.100
0.200
0.300
0.400
0.500
0.600
0.700
0.800
0.900
1.000
1.100
1.200
1.300
1.400
1.500
1.600
1.700
1.800
1.900
2.000
D28-AD-36, 129.66D28-AD-34, 130.00D28-AD-33, 130.24D28-AD-32, 130.09D28-AD-31, 129.99D28-AD-30, 130.15D28-AD-29, 243.96D28-AD-28, 243.97D28-AD-27, 244.36D28-AD-26, 243.90D28-AD-25A, 1244.12D28-AD-24, 244.28
Seismic Section Equalized Data-EQL Seismic Section Real amplitude pulse-RAP
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2DHR SEISMIC DATA INTERPRETATION
Seismic Section Equalized Data-EQL Seismic Section Real amplitude pulse-RAP
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2DHR SEISMIC DATA INTERPRETATION
Seismic Section Equalized Data-EQL Seismic Section Real amplitude pulse-RAP Anomalies and Faults Chart
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GEOHAZARD
Definition:
a geological state that may lead to widespread damage or risk.
These can be long term or short term geological and/or
environmental conditions that are associated with normal
geological processes. Geohazard investigation involve using
specialized equipment to determine the severity of this state/risk.
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GEOHAZARD
Blow Out Punch Through
Oil Spill PollutedBlow Out
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GEOPHYSICAL SITE SURVEY
Geophysical site survey:
Survey to support dredging and reclamation projects; determine
filling/dredging quantities; outline seabed train & sub seabed
profile.
Survey to locate underwater objects, ensure under-keel clearance
of fairways
Survey for shallow and deeper geologic study and hazard
definition.
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GEOPHYSICAL EQUIPMENT
Geophysical equipment for geohazard study:
• Echo Sounders- single beam and multibeam
• Side Scan Sonars
• Magnetometer
• Sub Bottom Profilers
• 2D Hi Res Seismic
• Autonomous Underwater Vehicle (AUV).
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GEOPHYSICAL EQUIPMENT
Single beam/multibeam echo sounder
MBES System
MBES 3D Image
Transducers
SBES System Transducer
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GEOPHYSICAL EQUIPMENT
Side Scan Sonar
SSS System SSS-Tow-fish SSS Tow-fish
SSS Data
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GEOPHYSICAL EQUIPMENT
Magnetometer
Magnetometer System
Magnetometer Data Analysis
Magnetometer Fish
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GEOPHYSICAL EQUIPMENT
Sub Bottom Profiler
Mini Streamer-Hydrophone
Transducer-Pinger
Sparker and Catamaran
SBP Data
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GEOPHYSICAL EQUIPMENT
2D Hi- Res Seismic
Streamer with winch
Seismic Source – GI GunSeismic data - Raw
Seismic data - Migration
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GEOPHYSICAL EQUIPMENT
Autonomous Underwater Vehicle (AUV).
AUV-In OperatingHigh Resolution AUV data
AUV-Recovery
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TYPES OF GEOPHYSICAL SURVEYS FOR GEOHAZARD STUDY
• Analogue Debris Survey
• Pipeline Route Survey
a) Proposed pipeline route survey
b) Pre-lay pipeline route survey
c) Post-lay pipeline route survey
d) Pipeline surveillance survey
• Analogue and Digital Site Survey
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THE IMPORTANCE OF SITE SURVEY FOR GEOHAZARD STUDY
It provide high definition data and images of the specific areas for
development and set down of subsea facilities
It provides detailed seabed and sub seabed image and profiles
within the first 50 metres below seabed for seabed and shallow
foundation & design.
It provides (2DHR) high resolution and detailed sub seabed images
and profiles within the first 1 seconds TWT in the attempt to map
delineate shallow gas hazards that may pose a constraint to
drilling- improving/enhancing 3D data interpretation.
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EXAMPLE OF GEOHAZARD
CORAL- Impact for anchoring and rig emplacement activity.
Multibeam Data Side Scan Sonar Mosaic
Seabed Features with Anchor Pattern
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EXAMPLE OF GEOHAZARD
SHALLOW PALEO CHANNEL-Potential to jack-up rig punch through
Seismic Section Equalized Data-EQL
Sub Bottom Profile- Sparker Data
Channel Pattern in Drawing Chart
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EXAMPLE OF GEOHAZARD
SHALLOW PALEO CHANNEL-Potential to jack-up rig punch through
Seismic Section Equalized Data-EQL
Sub Botom Profile- Sparker Data
Channel Pattern in Drawing Chart
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EXAMPLE OF GEOHAZARD
SEISMIC ANOMALIES- Potential Gas seepage/Shallow Gas
Seismic Section Real Amplitude Pulse Anomalies Pattern in Drawing Chart
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EXAMPLE OF GEOHAZARD
SEISMIC ANOMALIES- Potential Gas seepage/Shallow Gas
Sub Bottom Profile Sparker Data
Anomaly Pattern in Drawing Chart
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THANK YOU