the value proposition of 3d and 4d marine seismic data

The Value Proposition of 3D and 4D MarineSeismic Data

May 10 2017

By Dr. Taylor Goss

https://www.linkedin.com/in/taylor-goss/

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

OVERVIEW

•SEISMIC IMAGING GEOPHYSICS

•OFFSHORE IS RELEVANT

•THE ROLE OF SEISMIC

•MARINE SEISMIC ACQUISITION

•RESERVOIR MONITORING (4D)

Seismic Imaging is Upstream

http://www.slideshare.net/UPES_Dehradun/financing-of-downstream-projects-in-oil-gas-sector

Active Seismic & Passive

S R R

S

Reflection Seismic & Borehole

S R S

R

Land Seismic & Marine

S

R

S R

OVERVIEW






Offshore and Onshore

http://www.ogfj.com/articles/print/volume-12/issue-4/features/offshore-vs-shale.html

Break-even Oil price

http://www.resilience.willis.com/articles/2015/01/07/impact-oil-prices-energy-sector/

My Offshore projects

Canada

West Africa

Brazil

Trinidad

Australia

Northern& Southern GOM

$35

$36

$36 $40

$20 ??

$41

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.

OVERVIEW






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

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

Seismic to reduce Risk

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

Cost: Rig vs Seismic Acquisition

$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

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

http://www.colorado.edu/physics/phys2900/homepages/Marianne.Hogan/waves.html

VP > VS

Seismic is imaging by sound

Nankai data (Prof. Greg Moore, U. of Hawaii)

Seismic can see below the surface

Imaging using sound

• Seismic data is acquired using sound, which is vibrations that travel through a material. The speed of sound varies by material:

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

Reflection at an interface

R = Z2 - Z1

Z2 + Z1

Reflection coefficient

T = 2Z1

Z2 + Z1

Transmission coefficient

Z1=r1v1

Z2=r2v2

T + R = 1

Imaging the Reservoir

Shale

Oil

Shale

Gas

Water

rshale > rwater > roil > rgas

Sandstone

Bright spot indicators

R +1-1

Reflectivity series

OWC

GOC

OVERVIEW






Marine Seismic Boat & Towed Streamer

Air-GunHydrophone Streamer8m 9m

3.6km

Sea Floor

Air-gun array

http://www.geoexpro.com/articles/2010/01/marine-seismic-sources-part-I

Numbers are gun volumes in in3

24 air-guns in total

Hydrophone Streamer

http://www.sercel.com/products/Pages/sentinel-rd.aspx

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.

https://en.wikipedia.org/wiki/Hydrophonehttp://www.geol.lsu.edu/jlorenzo/ReflectSeismol03/Geophones_files/geophones.htm

Seismic Cable Bird

http://www.geospace.com/product-listings/marine-seismic-products/https://www.km.kongsberg.com/ks/web/nokbg0238.nsf/AllWeb/1C507A27559FD548C12578410035F8C7?OpenDocument

Sub-surface grid = 0.5 x surface grid

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

Offset spacing = 2 x shot spacing

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

2D Seismic Acquisition

• 1 air-gun array, 1 streamer cable

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

CGG 2D multi-client offshore Namibia

http://www.cgg.com/en/What-We-Do/Multi-Client-Data/Seismic/Africa-ME-and-Kazakhstan/Namibia

2D line from offshore Namibia

http://www.cgg.com/en/What-We-Do/Multi-Client-Data/Seismic/Africa-ME-and-Kazakhstan/Namibia

50m

3D Narrow Azimuth Seismic• 2 air-gun arrays (flip-flop), 4 streamer cables

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

Netherlands Offshore F3 Block

Inline View Crossline View

Time Slice

https://www.opendtect.org/osr/pmwiki.php/Main/NetherlandsOffshoreF3BlockComplete4GB

Inline (sailing direction)

CrosslineTime

Efficiency in 3D acquisition

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

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)

104m

70mBattleship Texas (BB-35): 175m long, but only 29m wide!

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)

5 Dimensions of 3D acquisition

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

Wide Azimuth Fleet Config.

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

Each shot-point is acquired 4 times

+/-4200m

Rose Diagrams for NAZ & WAZ

+ 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

Significant improvement in image

NAZ WAZ

http://www.spgindia.org/geohorizon/july2009/andrew.pdf

Imaging Challenge & Acquisition

WATER

SALT BODY

Narrow Azimuth

Wide Azimuth

Full Azimuth

StagSeis (CGG) – Full Az to 9km

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

Traditional race-track acquisition

SAILING STRAIGHT, SHOOTING, MAKING $

TURNING, NOT SHOOTING, COSTING $

Dual Coil (WGC) – Full Azimuth

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 $

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.

http://www.colorado.edu/physics/phys2900/homepages/Marianne.Hogan/waves.html

VP > VS

Towed Streamer & Ocean Bottom

S R SR

Marine Seismic & Ocean Bottom Cable

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

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

200m

Y

RecordingVessel

SourceVessel

Geophone vs Hydrophone imaging

http://www.cgg.com/en/What-We-Do/Subsurface-Imaging/Ocean-Bottom-Seismic

Hydrophone Geophone

Geostreamer (PGS) or Isometrix (WGC)

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

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)

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

Principle of deghost

+1-1 R

0

12ms

P-WAVE GHOST OPERATOR

+1-1 R

12ms

VZ GHOST OPERATOR

+1-1 R

DEGHOSTED

0 0

Makes convenient a deep tow - 18.75m

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.

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwi_g7z_4IzQAhVH0iYKHWRrCEkQjRwIBw&url=http://www.geoexpro.com/articles/2013/08/broadband-seismic-technology-and-beyond-part-ii-exorcizing-seismic-ghosts&psig=AFQjCNGjp77Yph7UAt2bVnC-LNUDk9yhKQ&ust=1478268310281422

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwi_g7z_4IzQAhVH0iYKHWRrCEkQjRwIBw&url=http://www.geoexpro.com/articles/2013/08/broadband-seismic-technology-and-beyond-part-ii-exorcizing-seismic-ghosts&psig=AFQjCNGjp77Yph7UAt2bVnC-LNUDk9yhKQ&ust=1478268310281422

Benefits of Broadband

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)

Synthetic Reservoir model

Gas

Water

Oil

Sandstone

Sandstone

Shale

Sandstone Sandstone Sandstone

Shale

0km

3km

Dep

th

0km 6km

Depth migration of Synthetic data

Water-bottom

above reservoir interval

gas pocket

oil-bearingsands

gasshadow

below reservoir interval

Hoover Madison Marshall

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

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.

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

OVERVIEW






Time-lapse (4D) Seismic

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.

West Africa

$36

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=0ahUKEwjq-629zvbPAhWFSiYKHekUAqoQjRwIBw&url=http://www.lahistoriaconmapas.com/atlas/country-map04/equatorial-guinea-offshore-oil-map.htm&psig=AFQjCNG-LcefOKKZ1S3qXBwCx9c0BSOm4A&ust=1477507368687838






Coverage matching

Baseline survey

Reservoir

Monitor survey

ONLY THE AREA COMMON TO BOTH BASELINE & MONITOR SURVEYS CAN BE USEDAS INPUT TO MIGRATION FOR 4D.

Obstructions affecting monitor acquisition

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

Undershoot acquisition

Platform

Source vessel

Recording vessel

Cannot acquire near offsets this way!

Recording vessel exclusion

Source vessel exclusion

Planning the monitor survey

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

Example Baseline & Monitor


>

<<

=

=<

>

=

==

<

<>

=

BASELINEMONITOR

4D Co-Binning of Baseline & Monitor

R’ S’M’

R1

S1

M1

dRR’dMID dSS’

BASELINE

MONITOR

AZ (S’-R’)

3 Binning Criteria Options:1. minimum dSR = |dRR’|+|dSS’|2. minimum dAZ (fold to 0o - 90o)3. minimum dMID

R2

S2

M2

dSR dAZ (deg) dMID

dS

R b

ind

AZ

bin

dM

IDb

in

Best overall

Average over all offsets

Receiver motion correction

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

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=0ahUKEwjy2bDuxvnPAhUE6SYKHRc7C5MQjRwIBw&url=http://stackoverflow.com/questions/33651243/plotting-seismic-wiggle-traces-using-matplotlib&psig=AFQjCNGOjlvIiYHhc-5AjlCsh02Ntztm9g&ust=1477608522662089




Receiver motion correction

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 #

4D –Change in material properties

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

Water Flood

Oil

Sandstone

Shale

Shale

BASELINE MONITOR

Oil

Sandstone

Shale

Shale

vwater > voil

rwater > roil

Water

OWC

Gas Cap Expansion

Oil

Sandstone

Shale

Shale

MONITOR

Oil

Sandstone

Shale

Shale

voil >> vgas

roil >> rgas

Gas

GOC

BASELINE

Fluid substitution effects

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

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

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

Normalized Root-Mean Square

• NRMS = RMS (MON - BASE)AVG RMS(BASE,MON)

• Range: 0 – 2. Smaller is better.


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.

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

Monitor acquisition by OBC

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

OBC vs Streamer ray-path

R

Reservoir

Water

S

Sediment

R’

DIFFERENCE DECREASES AS WATER GETS SHALLOWER

DIFFERENCE DECREASES AS RESERVOIR GETS DEEPER

S’

4D Co-Binning of Baseline & Monitor

R’ S’M’

S1

R1

M1

dSR’dMID dRS’

BASELINE

MONITOR

AZ (S’-R’)

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)

Results from 4D OBC project

0 2 0 2 0 2 0 2

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

94

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.

the value proposition of 3d and 4d marine seismic data

Engineering