the value proposition of 3d and 4d marine seismic data
TRANSCRIPT
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The Value Proposition of 3D and 4D MarineSeismic Data
May 10 2017
By Dr. Taylor Goss
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https://www.linkedin.com/in/taylor-goss/
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Brief notes on open-source
• Fedora Linux or Ubuntu – free Unix OS
• Seismic Unix – free seismic processing system (CSM)
• OpendTect – free interpretation system (dGB Earth Sciences)
• Open source seismic data – multiple sources, including:
• CD-ROM’s that accompany “Seismic Data Processing with Seismic Unix” (Forel, Benz, & Pennington)
• Colorado School of Mines
• Several 3D volumes in OpendTect format (dGB Earth Sciences)
• The DOE, BOEM, USGSPage
2
https://en.wikipedia.org/wiki/Comparison_of_free_geophysics_software
http://wiki.seg.org/wiki/Open_data
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OVERVIEW
•SEISMIC IMAGING GEOPHYSICS
•OFFSHORE IS RELEVANT
•THE ROLE OF SEISMIC
•MARINE SEISMIC ACQUISITION
•RESERVOIR MONITORING (4D)
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Seismic Imaging is Upstream
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http://www.slideshare.net/UPES_Dehradun/financing-of-downstream-projects-in-oil-gas-sector
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Active Seismic & Passive
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S R R
S
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Reflection Seismic & Borehole
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S R S
R
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Land Seismic & Marine
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S
R
S R
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OVERVIEW
•SEISMIC IMAGING GEOPHYSICS
•OFFSHORE IS RELEVANT
•THE ROLE OF SEISMIC
•MARINE SEISMIC ACQUISITION
•RESERVOIR MONITORING (4D)
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Offshore and Onshore
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http://www.ogfj.com/articles/print/volume-12/issue-4/features/offshore-vs-shale.html
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Offshore and Onshore
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http://www.ogfj.com/articles/print/volume-12/issue-4/features/offshore-vs-shale.html
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Break-even Oil price
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http://www.resilience.willis.com/articles/2015/01/07/impact-oil-prices-energy-sector/
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My Offshore projects
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Canada
West Africa
Brazil
Trinidad
Australia
Northern& Southern GOM
$35
$36
$36 $40
$20 ??
$41
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OFFSHORE IS RELEVANT
• The majority of global oil production and E&P investment continues to be offshore.
• Some offshore fields continue to be profitable at current prices, especially outside of the Northern GOM.
• Not all onshore shale plays are profitable at current prices either.
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OVERVIEW
•SEISMIC IMAGING GEOPHYSICS
•OFFSHORE IS RELEVANT
•THE ROLE OF SEISMIC
•MARINE SEISMIC ACQUISITION
•RESERVOIR MONITORING (4D)
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Exploration RiskWell Class U.S. Canada
New pool Wildcats1 0.53 0.48
Deeper pool Wildcats2 0.15 0.54
Shallower pool Wildcats 0.62 --
Outpost (extension) Wildcats 0.42 0.68
New-field Wildcats3 0.14 0.30
All exploratory wells 0.30 0.56
All development wells 0.79 0.85
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1988 success rates, United States and Canada
http://wiki.aapg.org/Risk:_expected_value_and_chance_of_success
3New-field Wildcat – A new-field wildcat is a well located on a structural feature or other type of trap which previously has not produced oil or gas.
1New pool Wildcat – A new-pool wildcat is a well located to explore for a new pool on a structural feature or other type of trap already producing oil or gas but outside the known limits of the producing area.
http://www.searchanddiscovery.com/documents/murray/index.htm
2Deeper pool Wildcat – A deeper pool test is an exploratory hole located within the productive area of a pool, or pools already partly or wholly developed. It is drilled below the deepest productive pool to explore for deeper unknown prospects
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Seismic to reduce Risk
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20% 40%
65% 75%
WILDCAT
DEVELOPMENTWELLS
2D SEISMIC 3D SEISMIC
CHANCE OF SUCCESS
http://www.offshore-mag.com/articles/print/volume-55/issue-4/departments/drilling-production/exploration-3d-seismic-boosting-wildcat-success-reducing-well-count.html
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Cost: Rig vs Seismic Acquisition
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$10 - $40 million2D – $12,000/km
3D – $100,000/km2
LAN
D
http://www.investopedia.com/ask/answers/061115/how-do-average-costs-compare-different-types-oil-drilling-rigs.asp
$200 - $900 millionAverage $650 millionM
AR
INE
$85 million to build Ramform Sovereign
(excluding seismic equipment)
https://www.netl.doe.gov/File%20Library/Research/Energy%20Analysis/Publications/seismic-data-acquisition-costs-fe-netl-co2-storage-cost-model-v2-1.pdf
http://www.marineinsight.com/types-of-ships/ramform-sovereign-the-most-advanced-3d-seismic-vessel-in-the-world/
55 crew50 - 100 crew
RIG SEISMIC DATA
COST OF SEISMIC PROCESSING IS SIGNIFICANTLY LOWER THAN ACQUISITION
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Sound: A vibration of matter
• Initially, focus on the pressure wave aspect of sound.
• Shear waves can only exist in solid materials.
• Pressure sensors (Hydrophones) do not measure Shear waves
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http://www.colorado.edu/physics/phys2900/homepages/Marianne.Hogan/waves.html
VP > VS
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Seismic is imaging by sound
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Nankai data (Prof. Greg Moore, U. of Hawaii)
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Seismic can see below the surface
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Imaging using sound
• Seismic data is acquired using sound, which is vibrations that travel through a material. The speed of sound varies by material:
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Material Density (kg/m3) Vp (m/s) Impedance Z = rv
Shale 2400 - 2800 1800 - 5000 4.5x106 – 1.3x107
Sandstone 2200 - 2800 1500 - 4500 3.8x106 – 1.1x107
Oil (40 API) 830 1226 1.0x106
Water (brine) 1030 1507 1.6x106
Air @ sea-level 1.225 343 420
Salt 2170 4500 9.8x106
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Reflection at an interface
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R = Z2 - Z1
Z2 + Z1
Reflection coefficient
T = 2Z1
Z2 + Z1
Transmission coefficient
Z1=r1v1
Z2=r2v2
T + R = 1
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Imaging the Reservoir
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Shale
Oil
Shale
Gas
Water
rshale > rwater > roil > rgas
Sandstone
Bright spot indicators
R +1-1
Reflectivity series
OWC
GOC
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OVERVIEW
•SEISMIC IMAGING GEOPHYSICS
•OFFSHORE IS RELEVANT
•THE ROLE OF SEISMIC
•MARINE SEISMIC ACQUISITION
•RESERVOIR MONITORING (4D)
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Marine Seismic Boat & Towed Streamer
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Air-GunHydrophone Streamer8m 9m
3.6km
Sea Floor
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Air-gun array
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http://www.geoexpro.com/articles/2010/01/marine-seismic-sources-part-I
Numbers are gun volumes in in3
24 air-guns in total
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Hydrophone Streamer
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http://www.sercel.com/products/Pages/sentinel-rd.aspx
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Hydrophones & Geophones
• A hydrophone is a pressure sensor designed to be used underwater. It is a piezoelectric device that converts pressure into an electrical signal. The measurement of pressure is insensitive to direction. Hydrophones measure only P-waves.
• A geophone converts the movement of the ground, or velocity, into an electrical signal. The measurement of velocity is directional. The vertical component of the geophone measures P-waves, and the lateral component of the geophone measures S-waves.
• In practice often an accelerometer.
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https://en.wikipedia.org/wiki/Hydrophonehttp://www.geol.lsu.edu/jlorenzo/ReflectSeismol03/Geophones_files/geophones.htm
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Seismic Cable Bird
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http://www.geospace.com/product-listings/marine-seismic-products/https://www.km.kongsberg.com/ks/web/nokbg0238.nsf/AllWeb/1C507A27559FD548C12578410035F8C7?OpenDocument
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Sub-surface grid = 0.5 x surface grid
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25m
R1 R2 R3 R4
M2M1
12.5m
The spacing between mid-points is half the receiver-group spacing = 0.5 X 25m = 12.5m
The mid-point is half-way from the source to the receiver-group
S
M3
O1
The surface offset O1 is the distance from the source to the receiver-group R1
M4
Number of receivers is cable-length/(receiver-group spacing) = 3600m/25m = 144
R5
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Offset spacing = 2 x shot spacing
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The distance between offsets at a common mid-point is 2 x shot spacing = 100m
The surface offset O1 is the distance from the source to the receiver-group R1
CMP
R1S1
O1
R5S2 50m
S3 R950m
The CMP fold of coverage is the cable-length/(2 x shot-spacing) = 3600m / 100m = 36
Common Mid-Point
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2D Seismic Acquisition
• 1 air-gun array, 1 streamer cable
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R1 R2 R3 R4S
• Acquires one sub-surface line at a time.• Real-world example: Offshore Namibia
• Date: 2012, Survey Size 8156km2
• Streamer Length: 10050m, 804 channels, 12.5m receiver-spacing• Mid-point spacing: 0.5 X 12.5m = 6.25m• Shot interval: 25m• Offset spacing: 2 X 25m = 50m• Record Length: 10s, 2ms sample-rate, boat-speed 2.5m/s• Nominal CMP fold: 10050m / 50m = 201
R5
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CGG 2D multi-client offshore Namibia
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http://www.cgg.com/en/What-We-Do/Multi-Client-Data/Seismic/Africa-ME-and-Kazakhstan/Namibia
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2D line from offshore Namibia
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http://www.cgg.com/en/What-We-Do/Multi-Client-Data/Seismic/Africa-ME-and-Kazakhstan/Namibia
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50m
3D Narrow Azimuth Seismic• 2 air-gun arrays (flip-flop), 4 streamer cables
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SP
SS
100m
Acquires 8 interleaved sub-surface inlines at a time:4 from port gun, 4 from starboard gun. Inline spacing is 25m.Sub-surface area acquired is 8 X 25m = 200m wide
25m
Inline direction
Crosslinedirection
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Netherlands Offshore F3 Block
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Inline View Crossline View
Time Slice
https://www.opendtect.org/osr/pmwiki.php/Main/NetherlandsOffshoreF3BlockComplete4GB
Inline (sailing direction)
CrosslineTime
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Efficiency in 3D acquisition
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10km
# sail-lines to acquire = 2 X width of survey / (# cables X streamer separation)e.g. 4 cables 100m apart, 50 sail-lines at min. (+ 12 lines infill & reshoot) = 62 linese.g. 8 cables 100m apart, 25 sail-lines at min. (+ 6 lines infill & reshoot) = 31 lines
Surface Coverage Sub-Surface Coverage
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Efficiency in 3D acquisition
• Increasing the number of cables towed reduces the number of sail-lines to be acquired, which in turn reduces the time of acquisition.
• 2 guns & 4 cables = 8 inlines acquired
• 2 guns & 24 cables = 48 inlines acquired (PGS - Ramform Titan)
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104m
70mBattleship Texas (BB-35): 175m long, but only 29m wide!
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S
Cable Feather & Steerable Cables
CGG Nautilus systemhttp://www.cgg.com/en/What-We-Do/Offshore/Assets-and-Technologies/Enabling-Technology/Streamer-Steering
WGC Q-marinehttp://csegrecorder.com/columns/view/expert-answers-200406
PGS/ION DigiFin
without steerable cable
with steerable cablePrevailing current
Steerable cables help to reduce infill, improving acquisition efficiency (typical ~25% infill w/o steerable cable)
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5 Dimensions of 3D acquisition
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1. X2. Y3. Z 4. S-R Offset5. S-R Azimuth
1. X2. Y3. Z 4. S-R Offset X5. S-R Offset Y
- OR -
S
R
S-R Offset X
S-R Offset YAzimuth
S-R Offset
Narrow Azimuth (NAZ)Rose Diagram
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Wide Azimuth Fleet Config.
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4 air gun arrays, 24 streamers
8100m
4800m
1
2
3
4
300m
Shot spacing in Y = 300m -> S-R Offset Y inc. 600m
Shot spacing in X = 75m -> S-R Offset X inc. 150m X
Y
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Each shot-point is acquired 4 times
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+/-4200m
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Each shot-point is acquired 4 times
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+/-4200m
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Rose Diagrams for NAZ & WAZ
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+ 10o
NAZ WAZ
Full azimuth outto offset 4200m
A narrow range of azimuths
TOTAL CMP FOLD = X-FOLD x Y-FOLD = 54 x 14 = 756
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Significant improvement in image
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NAZ WAZ
http://www.spgindia.org/geohorizon/july2009/andrew.pdf
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Imaging Challenge & Acquisition
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WATER
SALT BODY
Narrow Azimuth
Wide Azimuth
Full Azimuth
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StagSeis (CGG) – Full Az to 9km
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http://www.cgg.com/en/What-We-Do/Offshore/Customer-Challenges/Enhance-Illuminationhttp://www.cgg.com/en/What-We-Do/Offshore/Customer-Challenges/Enhance-Illumination/StagSeis
Full azimuth out to offset 9km Offsets up to 18km acquired
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Traditional race-track acquisition
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SAILING STRAIGHT, SHOOTING, MAKING $
TURNING, NOT SHOOTING, COSTING $
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Dual Coil (WGC) – Full Azimuth
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http://www.slb.com/resources/technical_papers/westerngeco/seg2012255.aspxhttp://www.energy-pedia.com/news/gulf-of-mexico/westerngeco-commences-industrys-first-dual-coil-shooting-surveyhttps://www.researchgate.net/publication/254536994_Dual_Coil_-_Long_Offset_Full_Azimuth_Marine_Towed_Streamer_Acquisition
ALWAYS SHOOTING, ALWAYS TURNING, ALWAYS MAKING $
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Sound: P-waves & S-waves
• Only a solid can sustain a shear wave.
• S-waves can be measured with a multi-component Accelerometer (Geophone), only if that sensor rests on the Ocean Bottom.
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http://www.colorado.edu/physics/phys2900/homepages/Marianne.Hogan/waves.html
VP > VS
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Towed Streamer & Ocean Bottom
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S R SR
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Marine Seismic & Ocean Bottom Cable
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8m
100m
Multi-Component Cable
Sea Floor
Hydrophone (Pressure)
Geophone (VY & VZ)
P-wave only
P-wave& S-wave VZ – VERTICAL VELOCITY
VY – SHEAR VELOCITY
Z
Source boat X
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3D OBC Seismic Acquisition
• 2 air-gun arrays (flip-flop), 3 multi-component OBC cables
• OBC cables much farther apart then towed streamer cables
• Source boat shoots a dense carpet of shots
Page 53
200m
Y
RecordingVessel
SourceVessel
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Geophone vs Hydrophone imaging
Page 54
http://www.cgg.com/en/What-We-Do/Subsurface-Imaging/Ocean-Bottom-Seismic
Hydrophone Geophone
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Geostreamer (PGS) or Isometrix (WGC)
Page 55
Air-GunMulti-component Cable8m
Sea Floor
Hydrophone (Pressure)
Geophone (VY & VZ)
CGG BroadSeis achieves a similar result with a tilted single-component cable
“Broadband High-Density Development Wide Azimuth – Application in the Gulf of Mexico” J. Hembd (CGG), A. Alcocer, M. Garcia, M. Vidal (Pemex), T. Goss, C. Ting (CGG), June 2013, EAGE
Z
X
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Receiver-side ghost (P-wave)Z = 0m
Z = 9 m (receiver)
Sea-surface (R = -1)
Time-delayed by 12ms Primary (up-going)
Ghost (down-going)
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Receiver ghost (rec. depth = 9m)
FAR-FIELD SIGNATURE
RECEIVER-SIDE GHOST
TIME-SERIES AMPLITUDE SPECTRUM Freq (Hz)
Freq (Hz)
Freq (Hz)
dB
dB
dB
RECORDED WAVELET
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Principle of deghost
Page 58
+1-1 R
0
12ms
P-WAVE GHOST OPERATOR
+1-1 R
12ms
VZ GHOST OPERATOR
+1-1 R
DEGHOSTED
0 0
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Makes convenient a deep tow - 18.75m
Page 59
Hydrophone
Geophone
http://www.geoexpro.com/articles/2013/08/broadband-seismic-technology-and-beyond-part-ii-exorcizing-seismic-ghosts
Towing deeper helps to dampen acquisition noise, reducing the need for reshoots,improving acquisition efficiency.
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Benefits of Broadband
Page 60
Conventional Broadband
The benefits of GeoStreamer ® broadband technology through the exploration & production life-cycle Anders Jakobsen Regional President Imaging Asia Pacific, Petroleum Geo-Services (2014)
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Synthetic Reservoir model
Page 61
Gas
Water
Oil
Sandstone
Sandstone
Shale
Sandstone Sandstone Sandstone
Shale
0km
3km
Dep
th
0km 6km
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Depth migration of Synthetic data
Page 62
Water-bottom
above reservoir interval
gas pocket
oil-bearingsands
gasshadow
below reservoir interval
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Hoover Madison Marshall
Page 63
4D in the Deepwater Gulf of Mexico: Hoover, Madison, and Marshall fields, The Leading Edge 30(9):1008 - 1018, September 2011, Michael B. Helgerud, Alisa C. Miller, David H. Johnston, Michael S. Udoh, Bill G. Jardine, Chad Harris, Neil Aubuchon, ExxonMobil
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The Value of 3D seismic
• Images the sub-surface of the earth.
• Possible to distinguish gas and oil reservoirs from surrounding events.
• Best imaged by depth migration.
• Best method to estimate the volume of oil reserves.
Page 64
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Lifetime of a field• Initial 2D acquisition, to identify regional trends.
• Large area 3D exploration survey, probably NAZ (Baseline).
• Initial processing and migration, no well information available.
• Identify prospects, bid on blocks from BOEM.
• Exploration wells.
• Move platform onto site.
• Production wells, water-injection wells.
• Update velocity model based upon well logs, new migration
Page 65
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OVERVIEW
•SEISMIC IMAGING GEOPHYSICS
•OFFSHORE IS RELEVANT
•THE ROLE OF SEISMIC
•MARINE SEISMIC ACQUISITION
•RESERVOIR MONITORING (4D)
Page 66
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Time-lapse (4D) Seismic
Page 67
https://www.pinterest.com/explore/time-lapse-photography/
Time-lapse photography takes a Picture of an event that is changing.
Ideally, the camera stays at the same angle, the only thing that changes is the item of interest.
Since seismic is another method ofimaging, the same principles apply.
The time-lapse seismic survey repeats an earlier seismic survey, in as similar a manner as possible.
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Page 68
West Africa
$36
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Page 69
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Page 70
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Coverage matching
Page 71
Baseline survey
Reservoir
Monitor survey
ONLY THE AREA COMMON TO BOTH BASELINE & MONITOR SURVEYS CAN BE USEDAS INPUT TO MIGRATION FOR 4D.
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Obstructions affecting monitor acquisition
Page 72
Reservoir
Monitor survey
Exclusion zone
4D in the Deepwater Gulf of Mexico: Hoover, Madison, and Marshall fields, The Leading Edge 30(9):1008 - 1018, September 2011 Michael B. Helgerud, Alisa C. Miller, David H. Johnston, Michael S. Udoh, Bill G. Jardine, Chad Harris, Neil Aubuchon, ExxonMobil
Platform
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Undershoot acquisition
Page 73
Platform
Source vessel
Recording vessel
Cannot acquire near offsets this way!
Recording vessel exclusion
Source vessel exclusion
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Planning the monitor survey
Page 74
BASELINE NAZ (E-W)
E-W WAZ, PROBABLY NOT THE BEST MONITOR
NAZ AT 90 DEG (N-S) NOT A GOOD MONITOR
MATCH OR EXCEED IF POSSIBLE EVERYACQUISITION PARAMETER OF THE BASELINESURVEY, EVERY SHOT & RECEIVER POSITION
WAZ SHOT SPACING IS MUCH LARGER THEN NAZ
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Example Baseline & Monitor
Page 75
4D in the Deepwater Gulf of Mexico: Hoover, Madison, and Marshall fields, The Leading Edge 30(9):1008 - 1018, September 2011 Michael B. Helgerud, Alisa C. Miller, David H. Johnston, Michael S. Udoh, Bill G. Jardine, Chad Harris, Neil Aubuchon, ExxonMobil
>
<<
=
=<
>
=
==
<
<>
=
BASELINEMONITOR
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4D Co-Binning of Baseline & Monitor
R’ S’M’
R1
S1
M1
dRR’dMID dSS’
BASELINE
MONITOR
AZ (S’-R’)
Page 76
3 Binning Criteria Options:1. minimum dSR = |dRR’|+|dSS’|2. minimum dAZ (fold to 0o - 90o)3. minimum dMID
R2
S2
M2
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dSR dAZ (deg) dMID
dS
R b
ind
AZ
bin
dM
IDb
in
Best overall
Average over all offsets
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Receiver motion correction
Page 78
Assume a boat-speed of 2.5m/s (a typical number)
50m shot spacing, 25m receiver-group spacing, 10 second record time.
After 10 seconds, boat and cable has moved 25m, or 1 receiver-group spacing
Position at time shot fired
Position at time 10s after shot fired
Important to apply if: Baseline & Monitor boat speeds differ, sailing direction ofBaseline & Monitor are reversed, or Monitor is OBC but Baseline is towed streamer.
R1 R2 R3 R4 R5
R1 R2 R3 R4
S
S
25m
25m
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Receiver motion correction
Page 79
BEFORE REC. MOTION CORR. AFTER REC. MOTION CORR.1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
Tim
e (s
)
Tim
e (s
)
Chan # Chan #
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4D –Change in material properties
Page 80
Material Density (kg/m3) Vp (m/s) Impedance Z = rv
Shale 2400 - 2800 1800 - 5000 4.5x106 – 1.3x107
Sandstone 2200 - 2800 1500 - 4500 3.8x106 – 1.1x107
Oil (40 API) 830 1226 1.0x106
Water (brine) 1030 1507 1.6x106
Gas 1.225 343 420
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Water Flood
Page 81
Oil
Sandstone
Shale
Shale
BASELINE MONITOR
Oil
Sandstone
Shale
Shale
vwater > voil
rwater > roil
Water
OWC
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Gas Cap Expansion
Page 82
Oil
Sandstone
Shale
Shale
MONITOR
Oil
Sandstone
Shale
Shale
voil >> vgas
roil >> rgas
Gas
GOC
BASELINE
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Fluid substitution effects
Page 83
BASELINEWATER FLOOD
GAS EXPANDOR
MIG
RAT
ED S
TAC
KIN
DEP
THN
MO
’D C
MP
GA
THER
IN T
WT
100m Offset 3200m 100m Offset 3200m 100m Offset 3200m
vwater > voil >> vgas
OWC
GOC
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Fluid substitution summary
• Water-Flood - if water replaces oil the monitor data is shifted to shallower times relative to the baseline, and is dimmer, and gathers curve up relative to the baseline.
• Gas-Cap Expansion - if gas replaces oil, the monitor data is shifted to deeper times relative to the baseline, and is brighter, and gathers curve down relative to the baseline.
• The time-lapse effect of gas-cap expansion is larger and easier to detect. Page
84
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85
BASELINE DATA
Typical 4D processing flow
NOISE ATTENUATIONDESIGNATUREGUN-CABLE DATUM/3D STATICS
DEMULTIPLE
CO-BINNING BASE & MONNOISE ATTENUATIONTRACE-INTERP./Q-CORR.
MIGRATION (BASELINE VEL.)RESID. MATCH FILTER TO MONBASE RESID. MOVE-OUT CORR.STACK
MONITOR DATA
NOISE ATTENUATIONDESIGNATUREGUN-CABLE DATUM/4D STATICS
DEMULTIPLE
CO-BINNING BASE & MONNOISE ATTENUTATIONTRACE-INTERP./ Q-CORR.
MIGRATION (BASELINE VEL.)BASE RESID. MOVE-OUT CORR.STACK
REC. MOTION CORRECTIONMATCH FILTER TO BASELINE
REC. MOTION CORRECTION
COST OF 4D PROCESSING IS 2x SINGLE 3D SURVEY (3x IF MONITOR HI-RES)
HI-RES MONITOR3D PROCESSING
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Normalized Root-Mean Square
• NRMS = RMS (MON - BASE)AVG RMS(BASE,MON)
• Range: 0 – 2. Smaller is better.
Page 86
4D in the Deepwater Gulf of Mexico: Hoover, Madison, and Marshall fields, The Leading Edge 30(9):1008 - 1018, September 2011 Michael B. Helgerud, Alisa C. Miller, David H. Johnston, Michael S. Udoh, Bill G. Jardine, Chad Harris, Neil Aubuchon, ExxonMobil
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Hoover Madison Marshall
Page 87
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Hoover Madison Marshall
Page 88
4D in the Deepwater Gulf of Mexico: Hoover, Madison, and Marshall fields, The Leading Edge 30(9):1008 - 1018, September 2011 Michael B. Helgerud, Alisa C. Miller, David H. Johnston, Michael S. Udoh, Bill G. Jardine, Chad Harris, Neil Aubuchon, ExxonMobil
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Monitor acquisition by OBC
• It is possible to acquire Monitor data by OBC, even though Baseline data was towed streamer.
• Plan that Monitor receivers will replicate Baseline shots, and vice-versa.
Page 89
4D acquisition and processing of streamer and OBC data in West Africa: A case history to demonstrate how survey planning and advanced processing techniques improve repeatability for reservoir monitoring.” Steve Knapp*, Dan Maguire, Xiaoguang Meng, and Surinder Sahai Sep. 2014, SEG
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Monitor acquisition by OBC
Page 90
4D acquisition and processing of streamer and OBC data in West Africa: A case history to demonstrate how survey planning and advanced processing techniques improve repeatability for reservoir monitoring.” Steve Knapp*, Dan Maguire, Xiaoguang Meng, and Surinder Sahai Sep. 2014, SEG
Ray-trace receiver-side of monitor data from floating water-bottom datum.Source-side of monitor and both sides of baseline ray-trace from z=0.
Baseline Sources
Monitor Receivers
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OBC vs Streamer ray-path
Page 91
R
Reservoir
Water
S
Sediment
R’
DIFFERENCE DECREASES AS WATER GETS SHALLOWER
DIFFERENCE DECREASES AS RESERVOIR GETS DEEPER
S’
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4D Co-Binning of Baseline & Monitor
R’ S’M’
S1
R1
M1
dSR’dMID dRS’
BASELINE
MONITOR
AZ (S’-R’)
Page 92
3 Binning Criteria Options:1. minimum dSR = |dSR’|+|dRS’|2. minimum dAZ (fold to 0o - 90o)3. minimum dMID
S2
R2
M2
(Modified for Monitor OBC)
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Results from 4D OBC project
Page 93
0 2 0 2 0 2 0 2
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Lifetime of a field (continued)• Initial 2D acquisition, to identify regional trends.• Large area 3D exploration survey, probably NAZ (Baseline).
• Initial processing and migration, no well information available.• Identify prospects, bid on blocks from BOEM.• Exploration wells.• Move platform onto site.• Development wells, water-injection wells.
• Update velocity model based upon well logs, new migration• Several years of production.
• Begin plans for 1st Monitor survey.• Monitor survey acquisition.
• Co-processing of Baseline & Monitor survey, optimal for 4D results.• Separate 3D processing of Monitor data to optimize 3D image.
• Drill new development wells informed by 4D results.• Several more years of production.
• Ready for 2nd Monitor, etc.Page
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The Value of 4D seismic
• Images the change in the reservoir.
• Best way to know how the reservoir is changing, plan for new wells, estimate remaining reserves.
Page 95