1. APPENDIX A: SEISMIC EQUIPMENT - Open Research: Home... · Drum diameter 1.5 m Winch Weight 650...
Transcript of 1. APPENDIX A: SEISMIC EQUIPMENT - Open Research: Home... · Drum diameter 1.5 m Winch Weight 650...
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1. APPENDIX A: SEISMIC EQUIPMENT
EQUIPMENT:
To achieve a good trade-off between penetration and resolution, a seismic source consisting of a 420 in3 (7 litres) linear array of two GI-gun was adopted. The data were logged by a complete acquisition system composed by a 300 m long digital streamer interfaced to a Geometrics CNT-2 Recorder. The complete block diagram is illustrated in Figure A-1.
Figure A-1. Equipment block diagram.
SEISMIC SOURCE
The GI GUN is made up of two independent chambers within the same casing, used to control and reduce bubble oscillations. The first chamber is called the Generator, as it generates the primary pulse and creates the bubbles. The second one is called the Injector, as it injects air inside the bubble. Each gun has its own reservoir, its own shuttle, its own set of exhaust ports, and its own solenoid valve. A common hydrophone provides both the time break and the shape of the near field signal. This gun phone is located inside the bubble and responds to the actual air blast.
Basic principle Phase 1: The Generator (G) is fired. The blast of compressed air produces the primary pulse and the bubble starts to expand.
Phase 2: When the bubble approaches its maximum size, it encompasses the Injector ports, and its internal pressure is far below the outside hydrostatic pressure. At this time, the Injector (I) is fired, injecting air directly inside the bubble. Due to the quasi-static state of the bubble, the timing of the Injector is not critical.
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Phase 3: The volume of air released by the Injector increases the internal pressure of the bubble, and prevents its violent collapse. The oscillations of the bubble and the resulting secondary pressure pulses are reduced and re-shaped.
The bubble represents a secondary blast of energy that eventually appears in the seismic trace as a fake signal following the primary reflection with a delay equal to the bubble period. In Figure A-2, the sensor response is illustrated (green line) when only the Generator is activated (top) and when both chambers (Generator Injector) are activated (bottom). The reduction of the bubble effect (between 130 ms and 160 ms in the top) is evident.
Figure A-2. Gun controller display, basic principle and GI gun underwater bubble.
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Table A-1. Source characteristics.
SOURCE ARRAY
Manufacturer SERCEL
Model 2 GI Gun (CSIRO)
Volume 210 cu.in. (3.44l)
Mode Harmonic 105 G / 105 I
Weight 1. 74 Kg
Firing cycle 1. 7 sec
Air pressure 2000 psi (140 bar)
ARRAY GEOMETRY
Figure A-3. Gun array deployment.
Air Compressor and high pressure manifold
Manufacturer Hamworthy (Wärtsilä)
Model 4TH565EW100
Number of compressors 2
Air delivery 678 m3/h
Speed 1200 RPM
Power 205 kV
Pressure max 207 bar
Number of stage 4
Total weight 2680 kg
Receiver tanks 8 x 50 litres
Regulation Fisher valve
4
Gun
synchronization
GUN CONTROLLER FEATURES AND TECHNICAL SPECIFICATIONS
Manufacturer Real Time systems
Model Big Shot
Installation Fixed
Number of modules 2
Number of guns 16
Gun types Bolt, Sleeve, G and G.I.
Timing resolution 0.1 msec
Record out 100 msec closure (programmable time)
Predicted fire out 5 ms TTL high going
Field Time Break Out Summed sensor or hydrophone signal
Sensors and hydrophone signature 16 bit D / A
Aim Point 25 – 75 msec after trigger
Fire pulse width 1 -80 msec
Delta error Q / C limits 0.1 – 5.0 msec
Auto-fire detect level 0 – 10 Volts
Sensor signal gain x 0.1 – x 5
Sensor detection look window 2 – 40 msec
Sensor peak threshold 0 – 10 Volt
Sensor peak type Threshold, Peak or Zero Cross
Figure A-4. Starboard side air compressor High-pressure manifold
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Figure A-5. The Big Shot gun controller main window. It is possible to see the first four bursts of energy perfectly centred on the 50 ms aim point (red vertical solid line), that is the delay between the navigation trigger arrival and the actual shot time.
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STREAMER
Table A-2 Streamer characteristics.
STREAMER
Manufacturer Geometrics
Model GeoEel Digital
Active streamer length 300 m
Number of groups 96
Active group length 3.125 m
Hydrophones per group 16
Streamer towing depth 2 m 1 m
Source to 1st channel offset 25 m
Figure A-6. Geometrics GeoEel streamer detail
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Table A-3 Streamer characteristics.
FEATURES AND TECHNICAL SPECIFICATIONS 1
Manufacturer Geometrics
Model GeoEel Digital
Number of channels 96
Length 300 m
Number of active sections 12
A/D Modules
Channels per module 8
Sample Rates 1/16 msec, 1/8 msec, ¼ msec, ½ msec, 1 msec, 2 msec
Programmable gains 0 dB, 8 dB, 18 dB, 30 dB, 42 dB
Record Length Up to 30,000 samples/trace
I/O Communications 100Base TX Fast Ethernet, IEEE 802.3 compliant
Dead Time Between Shots 100 msec
Bandwidth DC to 8 kHz
Resolution 24 bits including sign
Maximum Input Range +2.25V
Dynamic Range 120 dB typical @ 1 msec, 70 dB typical @ 1/16 msec
Common-mode Rejection 90 dB @ ¼ msec, 190 Hz
Gain Accuracy +6.25% @ ¼ msec, 30 dB, 100 Hz; +6.0% @ 2 msec, 30 dB, 25 Hz
THD 0.007% @ ¼ msec, 30 dB, 100 Hz; 0.003% @ 2 msec, 30 dB, 25 Hz
Crosstalk -105 dB @ 30 dB, ¼ msec, 190 Hz
Noise Floor 1.4 μV rms @ 30 dB, ¼ ms; 0.2 μV rms @ 30 dB, 2 msec
Power Consumption Approximately 100 mA at 48VDC (12.5 mA/channel)
Dimensions 44 mm diameter x 330 mm long (1.75” by 11”)
Weight in air 900 grams (2.0 lbs)
Weight in water 520 grams (1.1 lbs)
Packaging Titanium body
Connectors Waterproof, high-density stainless, 41-pin
Data Format SEG2, SEGD, SEGY
Deck Unit
Power Requirements 115/230 VAC, 3.0/1.5 A max, 50/60 Hz
Voltage to Streamer 36-72 VDC
I/O Communications 100Base TX Fast Ethernet, IEEE 802.3 compliant
Ethernet Connection RJ-45
Trigger Connection BNC
Trigger Requirements Contact closure, positive or negative TTL
Auxiliary Inputs 4 analog channels with 24-bit resolution
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Table A-4. Streamer characteristics.
FEATURES AND TECHNICAL SPECIFICATIONS 2
Deck Cable
Electrical Conductors 7 twisted 24GA pairs and 10 16GA conductors
Strain Member Vectran
Length 50 m
Diameter 18.6 mm
Weight 21 kg for 50 meters
Termination Water tight connector
Bend Diameter 12 inches Tow Cable
Electrical Conductors 7 twisted 24GA pairs and 10 16GA conductors
Strain Member Vectran
Break Strength Over 2200 kg (5000 lbs)
Length 70 m
Diameter 18.6 mm
Weight 21 kg for 50 meters
Active Section
Number of channels 8 per section
Group Interval 3.125 m
Section Length 25 m
Hydrophones per Group 4
Hydrophones per Section 32
Hydrophone Type Benthos RDA Geopoint
Group Sensitivity 9 V /bar
Jacket Material Clear polyurethane, 70 duro, 3.18 mm (1/8 in) wall thickness
Diameter 41 mm (1.6 in)
Ballast fluid Inert, high flashpoint, non-polluting silicone oil, 100 cSt to 3 cSt
Weight 1.35 kg (3 lbs) /m
Strain Member Vectran
Break Strength 2200 kg (5000 lbs)
Typical Towing Noise <7 μbars at 4.5 knots, 8 Hz low-cut filter, Beaufort 5-6 seas
Minimum Bend Radius 750 mm (30 in)
Compass / Bird Coil I/O Model 587
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Table 2 Streamer winch characteristics.
FEATURES AND TECHNICAL SPECIFICATIONS
Engine Lombardini DIESEL 15LD350
Drum diameter 1.5 m
Winch Weight 650 kg
Overall Weight (winch + 300 m long streamer + tow cable) 960 kg
Dimensions 200 cm X 125 cm X 200 (H) cm
Figure A-7. The GeoEel streamer wrapped around the winch drum
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Table A-6. DigiSCAN system characteristics.
DigiSCAN STREAMER DEPTH CONTROL Manufacturer
DigiCourse
Model DigiBIRD5010
Operating Range 0 to 122 m
Resolution 0.15 m
Number of birds 4
Power Supply 4 D cell Lithium batteries
Figure A-8. Shipboard control: Real time birds depth monitoring In water device: DigiBIRD
Figure A-9. Seismic acquisition workstation on board the RV Investigator: DigiSCAN shipboard control (A), navigation PC with PDS200 software (B), seismic acquisition PC with CNT 2 Marine controller software (C), CNT 1 topside (D) and QINSy / deck camera screen monitor (E).
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SEISMIC LINES
Table A-7. Seismic line acquisition. Li
ne
Nam
e
Star
t /
End
Dat
e
[dd
/mm
/yyy
y]
Tim
e
[UTC
hh
:mm
]
Du
rati
on
[m
m]
Sho
t P
oin
t
Sho
ts /
lin
e
An
ten
na
Lat
E [d
d°m
m.m
mm
'S]
An
ten
na
Lon
S
[dd
°mm
.mm
m'E
]
An
ten
na
X
[m U
TM50
S w
gs84
]
An
ten
na
Y
[m U
TM50
S w
gs84
]
Be
arin
g
Surv
eye
d D
ista
nce
[m
]
Ave
rage
SP
dis
tan
ce [
m]
IN2017-V01-MCS01 SOL 22/01/2017 00.24
174 100
1214 064°15.005'S 115°37.557'E 433398 2874398
91.0 20498 16.9 EOL 22/01/2017 03.19 1313 064°15.391'S 116°02.909'E 453887 2874056
IN2017-V01-MCS05 SOL 23/01/2017 22.21
214 100
1176 064°33.311'S 116°08.834'E 459120 2840842
90.0 23010 19.6 EOL 24/01/2017 01.55 1275 064°33.313'S 116°37.620'E 482119 2841062
IN2017-V01-MCS05B SOL 24/01/2017 03.12
149 100
817 064°33.219'S 116°36.765'E 481434 2841233
90.0 15891 19.5 EOL 24/01/2017 05.41 916 064°33.316'S 116°56.623'E 497302 2841107
IN2017-V01-MCS02 SOL 24/01/2017 22.03
155 100
861 064°36.674'S 115°11.112'E 413187 2833629
91.0 16878 19.6 EOL 25/01/2017 00.38 960 064°36.623'S 115°32.261'E 430044 2834161
IN2017-V01-MCS06 SOL 27/01/2017 04.12
358 99
1977 064°41.646'S 114°36.248'E 385750 2823477
60.0 38684 19.6 EOL 27/01/2017 10.10 2075 064°31.987'S 115°19.122'E 419342 2842508
IN2017-V01-MCS07 SOL 29/01/2017 04.11
46 100
260 064°15.801'S 115°59.927'E 451491 2873258
90.0 5088 19.6 EOL 29/01/2017 04.57 359 064°15.794'S 116°06.226'E 456578 2873346
IN2017-V01-MCS07B SOL 29/01/2017 05.59
17 100
91 064°15.747'S 116°13.030'E 462070 2873506
90.0 1811 19.7 EOL 29/01/2017 06.16 190 064°15.742'S 116°15.273'E 463881 2873537
IN2017-V01-MCS07C SOL 29/01/2017 06.55
119 100
656 064°15.792'S 116°20.052'E 467742 2873488
90.0 12824 19.8 EOL 29/01/2017 08.54 755 064°15.921'S 116°35.920'E 480557 2873355
IN2017-V01-MCS08 SOL 03/02/2017 21.14
587 100
3271 065°03.643'S 118°49.100'E 585543 2783548
38.6 64207 19.6 EOL 04/02/2017 07.01 3370 064°36.903'S 119°39.294'E 626966 2831788
IN2017-V01-MCS09 SOL 06/02/2017 04.02
77 100
414 064°44.685'S 118°14.513'E 559118 2819412
48.2 8101 19.6 EOL 06/02/2017 05.19 513 064°41.362'S 118°20.174'E 563739 2825491
IN2017-V01-MCS09B SOL 06/02/2017 05.56
39 100
221 064°40.202'S 118°23.122'E 566130 2827596
48.2 4229 19.2 EOL 06/02/2017 06.35 320 064°38.659'S 118°27.026'E 569301 2830393
IN2017-V01-MCS09C SOL 06/02/2017 06.55
131 100
725 064°37.989'S 118°28.641'E 570616 2831606
48.2 14114 19.5 EOL 06/02/2017 09.06 824 064°32.642'S 118°40.998'E 580722 2841291
IN2017-V01-MCS09D SOL 06/02/2017 09.41
73 103
398 064°31.284'S 118°44.360'E 583477 2843739
48.2 7844 19.8 EOL 06/02/2017 10.54 500 064°28.401'S 118°51.515'E 589357 2848929
IN2017-V01-MCS10 SOL 13/02/2017 23.48
153 100
838 064°30.373'S 118°59.893'E 595953 2845064
114.6 16191 19.3 EOL 14/02/2017 02.21 937 064°33.717'S 119°18.549'E 610653 2838350
IN2017-V01-MCS10B SOL 14/02/2017 02.39
347 100
2000 064°34.144'S 119°20.671'E 612317 2837496
116.5 37293 19.6 EOL 14/02/2017 08.26 1999 064°42.336'S 120°03.389'E 645674 2820842
IN2017-V01-MCS11 SOL 17/02/2017 21.37
139 100
762 064°58.716'S 119°25.873'E 614718 2791725
100.9 14863 19.5 EOL 17/02/2017 23.56 861 064°59.912'S 119°44.554'E 629305 2788903
IN2017-V01-MCS11B SOL 18/02/2017 00.04
15 100
85 064°59.971'S 119°45.621'E 630139 2788757
101.0 1635 19.5 EOL 18/02/2017 00.19 184 065°00.081'S 119°47.684'E 631750 2788482
IN2017-V01-MCS11C SOL 18/02/2017 00.51
76 100
416 065°00.353'S 119°52.052'E 635157 2787824
100.6 8069 19.4 EOL 18/02/2017 02.07 515 065°01.003'S 120°02.188'E 643057 2786246
IN2017-V01-MCS12 SOL 24/02/2017 04.30
5 100
26 064°44.460'S 118°59.099'E 594499 2818930
291.3 483 19.3 EOL 24/02/2017 04.35 125 064°44.367'S 118°58.531'E 594053 2819117
IN2017-V01-MCS12B SOL 24/02/2017 05.51
101 100
530 064°43.300'S 118°51.720'E 588708 2821260
291.3 10254 19.4 EOL 24/02/2017 07.32 629 064°41.661'S 118°39.455'E 579051 2824575
IN2017-V01-MCS12C SOL 24/02/2017 09.16
6 100
28 064°39.978'S 118°30.253'E 571812 2827882
291.3 531 19.7 EOL 24/02/2017 09.22 127 064°39.884'S 118°29.623'E 571315 2828069
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