Marine Seismic Acquisition

RECENT NATIONAL SEISMIC FACILITIES

P.Farcy, B. Marsset, H. Nouze

IFREMER

Introduction

Conventional Multichannel Seismic Equipment (SMT)

- Technical description
- Examples

High Resolution (2D/3D) Seismic Equipment (HR)

- Technical description
- Examples

High speed Seismic Equipment (SISRAP)

- Technical description

On-going developments and conclusion

Discussion

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
INTRODUCTION (1/6)

« Conventionnal » seismic
Target depth ≅ X 1000 m
Target size ≅ X 100 m
Deep scientific / industrial exploration

High Resolution
Target depth ≅ X 100 m
Target size ≅ X 10 m
Fluid escape, gaz hydrates,
reservoir modelling

Very High Resolution

Target depth ≅ X 10 m
Target size ≅ X 1 m
Site survey, sedimentary models, reservoir
modelling

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
INTRODUCTION (2/6)

Penetration and Vertical Resolution as a function of Frequency

Log10 (FHertz)
-2 -1 0 1 2 3 4
7 Natural seismicity

5 « Conventionnal » seismic
Log10 (Métres)

4
HR seismic
3
VHR seismic

-1

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 Marine Seismic Acquisition
INTRODUCTION (3/6)

Seismic source frequency content

Log10 (FHertz)
-2 -1 0 1 2 3 4

Natural seismicity
Explosives
Air guns
Water guns
« Conventionnal » seismic
Sparkers
HR seismic
Electro-acoustic transducers

Boomers
VHR seismic

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 Marine Seismic Acquisition
INTRODUCTION (4/6)

CONVENTIONNAL MULTICHANNEL SEISMIC EQUIPMENT (SMT)

¾ 1994 : Technical report

¾ 1997 : Scientific report :

- Need of a longer streamer
- Need for positioning
- Development of Ocean Bottom seismometers
- Development of a 3D approach
- Outline of the processing aspect
¾ 1998 : Decision is made for a new development
¾ 1999 : Technical processing choice (Géovecteur 2D)
¾ 1999 : Sea trials (ESSER 1 2 3 4)
¾ 2000 : First scientific application

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 Marine Seismic Acquisition
INTRODUCTION (5/6)

HIGH RESOLUTION (2D/3D) SEISMIC EQUIPMENT (HR)

¾ 2000 : Technical specification

¾ 2001 : Early sea trials, operational specification

¾ 2002 : First scientific application (N/O Le Suroît 2D/3D)
¾ 2003 : Coastal application (N/O L’Europe 2D)
¾ 2003 : Transfer to GENAVIR
¾ 2004 : First operational application (January 2004, N/O L’Atalante 2D)

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 Marine Seismic Acquisition
INTRODUCTION (6/6)

HIGH SPEED (8 knots) SEISMIC EQUIPMENT (SISRAP)

¾ 2003 : Decision is made for a new development

- Obsolete equipment
- Unique acquisition system
¾ 2004 : Development, sea trials (July 2004) and transfer to GENAVIR (October 2004)

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
MULTICHANNEL SEISMIC EQUIPMENT

Digital streamer layout

¾ 4500 metres (360 traces @ 12.25 m)

¾ 12 depth controllers (@ 300m)

¾ Tail buoy (RGPS, radar transponder)

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 Marine Seismic Acquisition
MULTICHANNEL SEISMIC EQUIPMENT

Air delivery

¾ 4 * 300 m3/h
¾ 1 * 660 m3/h

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 Marine Seismic Acquisition
MULTICHANNEL SEISMIC EQUIPMENT

Seismic source

¾ Bubble-cancelled airguns (GI guns)

¾ Air guns (G guns, Bolt)

Array capacity up to 18 guns

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 Marine Seismic Acquisition
MULTICHANNEL SEISMIC EQUIPMENT

Acquisition system

¾ SERCEL SEAL (Seismic acquisition)

¾ SERCEL SEAPRO QC (Real-time seismic Quality Control)

¾ ECOS (Integrated navigation system)

Acquisition and operating laboratory (container 20”)

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 Marine Seismic Acquisition
MULTICHANNEL SEISMIC EQUIPMENT

SERCEL SEAL (seismic acquisition)

¾ Acquisition management
- Sampling rate : 4ms, 2 ms, 1 ms, 0.5 ms
- Data format SEGD 2
- Storage media : DLT

¾ Streamer control

Streamer control units

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 Marine Seismic Acquisition
MULTICHANNEL SEISMIC EQUIPMENT

SERCEL SEAPRO QC (Real-time seismic Quality Control)

¾ Ambient noise monitoring

¾ Frequency (F) and Frequency – Wavenumber (FK) analysis
¾ Common shot gather
¾ Common receiver gather

Local and remote QC workstations

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 Marine Seismic Acquisition
MULTICHANNEL SEISMIC EQUIPMENT

ECOS (Integrated navigation system)

¾ Depth controllers handling (depth, heading)

¾ Vessel navigation (GPS / DGPS)
¾ Tail buoy navigation (RGPS)
¾ Layout visualisation

ECOS workstation

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 Marine Seismic Acquisition
MULTICHANNEL SEISMIC EQUIPMENT

On board processing facilities (GEOVECTEUR 2D)

¾ SUN Ultra 60

¾ Storage media :
- DLT
- 70 Gb hard disks

¾ OYO 24” thermal plotter

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 Marine Seismic Acquisition
« Conventionnal » seismic data examples

N/O NADIR

Deep structure of the Angolan Margin : “Source and acquisition design for deep imaging”
¾ The “monobulle” source : ”bubble” tuning versus “peak” tuning
¾ Acquisition configuration : combined seismic reflection and refraction (OBS) studies

Gas hydrates studies in the Nankai Trough : “What long offsets can bring us”
¾ Amplitude variations with offsets and AVA analysis

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
« Conventionnal » seismic data examples

Deep structure of the Angolan Margin

“Source and acquisition design for deep imaging”

¾ The “monobulle” source : ”bubble” tuning versus “peak” tuning

¾ Acquisition configuration

¾ Zaiango study location map

¾ Subsalt imaging

¾ Combined reflection (MCS) and refraction (OBS) studies

¾ Processing

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 Marine Seismic Acquisition
« Conventionnal » seismic data examples

Deep structure of the Angolan Margin : The “monobulle” source

Amplitude

Amplitude
Time Time

Amplitude

Amplitude
The « monobulle » source consists in
tuning the different guns on the main
Time Time
bubble instead of on the first peak, thus
allowing to increase low frequency
acoustic level. 50 50
dB

dB
30 30

10 10
0 50 100 Hz 0 50 100 Hz
Frequency Frequency

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 Marine Seismic Acquisition
« Conventionnal » seismic data examples

Deep structure of the Angolan Margin : Acquisition configuration

4500 metres
Seismic reflection
• Source : 4802 inch3
• Shot spacing : 100 m
• Air delivery : 992m3/h

75 inch3 9L 9L 9L 9L Seismic refraction

• Source : 3155 inch3
• Shot spacing : 75 m
• Air delivery : 1300 m3/h

75 inch3 9L 9L 9L 9L

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 Marine Seismic Acquisition
« Conventionnal » seismic data examples

Deep structure of the Angolan Margin : Zaïango study location map

from Maryline Moulin,

Thèse Univ. Brest, 2003

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 Marine Seismic Acquisition
« Conventionnal » seismic data examples

Deep structure of the Angolan Margin : Subsalt imaging

Monobulle section
Bassin du Bas Congo

5 s Twt
Corresponding composite oil exploration section
Bassin du Bas Congo
Bassin du Kwanza

5 s Twt
from Maryline Moulin,
Thèse Univ. Brest, 2003

Albian Cretaceaous Aptian (salt)

salt) Eocene

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 Marine Seismic Acquisition

Deep structure of the

Angolan Margin :
Combined studies
from I. Contrucci et al.,
G.J.I. in press

Refraction data

Reflection data

Gravimetry data
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 Marine Seismic Acquisition
« Conventionnal » seismic data examples

Deep structure of the Angolan Margin : Processing

¾ on board processing (Geovecteur) : Up to constant velocity post stack migrated sections
¾ Advanced processing : Deconvolution, Pre-stack migration and migration velocity analyses

from R. Bartolome et al.,

Submitted to J. Applied Geophys.
EGU - Nice, France, 25-30 April 2004
 Marine Seismic Acquisition
« Conventionnal » seismic data examples

Gas hydrates studies in the Nankai Trough

“what long offsets can bring us”

¾ Study location map

¾ Seismic line SFJHR01

¾ Amplitude variations with offsets and AVA analysis modelling results

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
« Conventionnal » seismic data examples

Gas hydrates studies in the Nankai Trough : Location map

from H. Nouzé et al.,

Submitted to GRL

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
« Conventionnal » seismic data examples

Gas hydrates studies in the Nankai Trough : Seismic line SFJHR01

0 10 20 30 km

500

1000

from H. Nouzé et al.,

Submitted to GRL

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
« Conventionnal » seismic data examples

Gas hydrates studies in the Nankai Trough : Amplitude Versus Offset anomalies

Distance (km) Offset (m)

0 10 0 2000
500 800

Twt (ms)
Depth (m)

1600
1000

Common Receiver gather Common Depth Point

from H. Nouzé et al.,

Submitted to GRL

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
« Conventionnal » seismic data examples

Gas hydrates studies in the Nankai Trough : Amplitude Versus Angle anomalies

0.9
0.8
Reflection coefficient

0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.
0 10 20 30 40 50 60

Incidence angle (degrees)

from H. Nouzé et al.,
Submitted to GRL

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
HIGH RESOLUTION PROJECT (2001 – 2003)

Frequency bandwidth - resolution

¾ frequency bandwidth: 40-500 Hz
¾ vertical resolution 1 - 2 m
¾ lateral resolution 5 m
¾ several 100 m of penetration in sediments

Application fields: from continental shelf to slope

¾ sedimentary process
¾ paleo-climatology, sea level variations
¾ slope stability, landslide, seismicity
¾ shallow gas, fluid escape structure, gas hydrate
3D ¾ hydrocarbon reservoir study

Breakthroughs
¾ 2D High Resolution seismic exploration / 3D detailed survey
¾ kinematics processing / amplitude processing and inversion
¾ multidisciplinary studies
¾ multi-frequency and multi-scale studies

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 Marine Seismic Acquisition
HIGH RESOLUTION PROJECT (2001 – 2003)
Objectives

¾ 2D and 3D seismic acquisition tailored to high resolution seismic imaging:

sources, acquisition geometry, positioning,...

¾ Operational system

¾ Amplitude control

⇒ kinematic imaging + preserved amplitude processing / inversion

Milestones

¾End-user requirement

¾State of the art technology

¾Academic and industrial partnerships

¾ Link with other field of current research :

- Methodology : Sea-floor characterisation
- Technology : Development of sediment echo-sounder and deep-towed seismic

⇒ Integrated approach
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 Marine Seismic Acquisition
2D HR seismic layout

¾ One array of sources (up to 6 air guns)

¾ One streamer of 72 traces @ 6.25 metres, 4 depth controllers

¾ Acquisition speed: 4 to 5 knots

¾ Streamer/source immersion: 1.5 to 3 metres
¾ Shooting rate up to 5 s

¾Operating vessel: open-sea R/V

Add-on: HR 2D seismic on-board costal vessel

¾ Source: Sparker
¾ Operating vessel: N/O L’Europe

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 Marine Seismic Acquisition
3D HR seismic layout

¾ Two arrays of sources (1 or 2 air gun(s) per array)

¾ Two streamers of 48 traces @ 6.25 metres, 25 meters apart , 6 depth controllers
¾ DGPS positioning of the sources

¾ Acquisition speed: 4 to 5 knots

¾ Distance between sailed lines: 25 m
¾ Streamer/source immersion: 1.5 to 3 metres
¾ Shooting rate up to 3 s

¾ Operating vessel: N/O Le Suroît

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
HIGH RESOLUTION SEISMIC

Equipment
¾ SEAL seismic acquisition system (SERCEL)
¾ Numerical streamers on two winches

¾ Swinging booms (3D, N/O Le Suroît)

¾ DGPS positioning of source arrays (3D)

¾ Shot control unit (bubble cancelled air guns, flip/flop shooting mode)
¾ Oiling system of guns for high shooting rate (< 5 s)

¾ ECOS HR control unit

¾ Recording unit (disc) and off-line archive unit (DVD)
¾ Streamer depth controllers

¾ Real time quality control (SeaProQC)

¾ Off-line quality control (dedicated software)

Integration
¾ 10" acquisition container remotely controlled
¾ Interface with on-board navigation system

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 Marine Seismic Acquisition
HIGH RESOLUTION EQUIPMENT

Depth controller

Mini-GI source array Streamer on winch

with DGPS positioning (3D)

Swinging booms on-board N/O Le Suroît (3D)

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 Marine Seismic Acquisition
HIGH RESOLUTION EQUIPMENT

¾ Stand-alone seismic laboratory

¾ Acquisition remote control (vessel electronic operating room)
¾ Interface with electronic equipment of the vessel

Remote operating room

Acquisition laboratory (container 10”)

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
Real Time HIGH RESOLUTION ACQUISITION AND QC
Real-time Off-line Navigation Seismic
Shot monitoring

Depth controller Processing sequence Quality control

monitoring
• Extraction of raw navigation data
• Raw navigation process • Display / QC
• (X,Y) inversion ( seismic gathers )
DVD

Navigation • Pre-processing
control unit • Automatic signal analysis
Archive

Fold map up-date (3D)

• NMO / Stack

Seismic
recording / QC
Bathymetry (3D)
3D stack
(X,Y) position + Z coordinate Navigation and
⇒ Navigation quality control seismic Quality
control
SEGD file

Acquisition Off-line Quality Control

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 Marine Seismic Acquisition
HIGH RESOLUTION ON-BOARD QUALITY CONTROL

Navigation Seismic

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 Marine Seismic Acquisition
HR seismic data examples
Open-sea vessel (N/O Le Suroît)
Mini-GI sources : 40 - 250 Hz

2D survey:
¾ one streamer of 120 traces
¾ one array of two mini-GI air guns
¾ shooting rate: 6 s
¾ source immersion: 1.5 m / streamer immersion: 3 m

3D survey:
¾ two streamers of 48 traces
¾ two arrays of one mini-GI air gun
¾ shooting rate: 3 s
¾ source immersion: 1.5 m / streamer immersion: 3 m

Coastal vessel (N/O L’Europe)

Sparker source : 60 - 350 Hz

2D survey:
¾ one streamer of 72 traces
¾ shooting rate: 3 s
¾ source immersion: surface / streamer immersion: 2 m
EGU - Nice, France, 25-30 April 2004
 Marine Seismic Acquisition
Hydratech cruise - 2D HR seismic

3D
1000 m

1500 m

Hydratech cruise (2002, N/O Le Suroît) :

¾ European projects: Hydratech, Costa
¾Data set : EM300 swath bathymetry, sediment profiler,
2D/3D High Resolution seismic

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
Hydratech cruise - 3D HR seismic
3D acquisition
Constraints
¾ Survey speed: 4.5 knots
¾ Turning duration: 30 to 45 '
¾ Sea conditions: up to 4-5 (Beaufort)

Data set
¾ profile length: 8 km
¾ 173 recorded profiles, 12 days
¾ 7700 x 3400 m (25 km²), 150 Gb
sailed lines fold map

Cutaway view of a subset of the 3D cube

3D pre-stack depth imaging

EGU - Nice, France, 25-30 April 2004
 Marine Seismic Acquisition
Hydratech cruise - 3D HR seismic

3D seismic interpretation
800 m
fluid escape
1 km structure

seismic
horizon
1000 m
Depth

1200 m

BSR

1400 m fault

In-line interpretration – Sismage software courtesy of Total

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
Hydratech cruise - 3D HR seismic

Seismic facies analysis

undisturbed
sediments

disturbed
sediments

2 km

Detailed mapping of the most recent evidence of slope instability – Sismage software courtesy of Total

EGU - Nice, France, 25-30 April 2004

 Marine Seismic Acquisition
Hydratech cruise - 3D HR seismic

Seismic amplitude analysis : Preliminary attempts

Sea-bottom raw amplitude
3.5 km

7.5 km

Sea-bottom corrected amplitude

3.5 km

Integrated approach using sea-

sea-bottom
corrected amplitude and structural
interpretation
7.5 km

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 Marine Seismic Acquisition
East Corsica - 2D HR seismic

Seismic layout:
¾ Coastal vessel (N/O L’Europe)
¾ One streamer of 72 traces
¾ One Sparker source Bathymetry
(m)

¾ Water depth: from 100 to 800 metres Bastia

Performance:
¾ Vertical resolution 1 m
¾ Horizontal resolution 3 m

North

Geological settings
Extension of the Golo sedimentary system,
system, from
3D view of the bathymetry (EM300) A. Gervais and T. Mulder (University of Bordeaux)
Bordeaux)

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 Marine Seismic Acquisition
S
S N
400

340
Head of Golo canyon
2D Migrated section
(2001, N/O L’Europe)
415
depth (m)

490

565
3 km
W E
10 km
790

Sedimentary Golo fan

2D Migrated section 865

depth (m)
(2003, N/O L’Europe)

940

1015

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 Marine Seismic Acquisition
Conclusion (1/4)
Further technological evolution

CONVENTIONNAL MULTICHANNEL SEISMIC EQUIPMENT

¾Operating vessel : N/O L’Atalante

¾Increase in air delivery (one new compressor)
¾Increase in source quality (new air guns)
¾Increase source level (up to 18 guns)

Further evolution
¾Increase streamer length to 6000 meters

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 Marine Seismic Acquisition
Conclusion (2/4)
Further technological evolution

HIGH RESOLUTION (2D/3D) SEISMIC EQUIPMENT

¾Tail buoy
- Increase offset (800 metres)
- Positioning accuracy
¾ Additional active sections
- 2D (120 traces)
- 3D (2 * 72 traces)
¾Source monitoring (air pressure, calibrated hydrophones) for
amplitude processing

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 Marine Seismic Acquisition
Conclusion (3/4)
Further technological evolution

HIGH SPEED (8 knots) SEISMIC EQUIPMENT (SISRAP)

¾ New stand alone system

¾ New streamer for application using HR acquisition electronics
¾ Increase in air delivery (3 * 150 m3/h compressors)

Two SISRAP systems available in 2005 for simultaneous campaigns

Opportunity to operate SISRAP and High-Res equipments during the same campaign

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 Marine Seismic Acquisition
Conclusion (4/4)
Further evolution

Source monitoring
¾ Source modelling through near field measurements
¾ Gun control

Quality control
¾ Definition of a standard Quality Control sequence (SMT, HR, SISRAP)
¾ Development of Quality Control tools
- Navigation data
- Seismic data

Standard processing tools

¾ Definition of a standard processing sequence (to be discussed with end-users)
¾ Development of processing tools

EGU - Nice, France, 25-30 April 2004