Schlumberger Private

Offshore Seismic ExplorationPresented to:

BC Seafood Alliance February 17, 2004

Doug BogstieMarketing ManagerWesternGeco

Schlumberger Private

GECO DIAMOND

Schlumberger Private

Presentation Outline

•Seismic Acquisition Fundamentals

•Acquisition Footprint

•Seismic Data

•Marine Seismic Source

•Streamers

•Mackenzie River 2002 Test

•Mitigation Measures

•Questions

Schlumberger Private

Marine Acquisition System

Sea bed

Boat

Cable with hydrophones

Sea Surface

Source

Sedimentary Layers

Incidentwaves Reflected

waves

Schlumberger Private

MARINE ACQUISITION

Sea bottom

Subsurface interface

Common Shot gather

Schlumberger Private

MARINE ACQUISITION

Sea bottom

Subsurface interface

Schlumberger Private

MARINE ACQUISITION

Common Mid Point (CMP) gather

Schlumberger Private

COMMON MID POINT GATHER

Common Mid Point (CMP) gather

“Primary” reflections

Schlumberger Private

COMMON SHOT GATHER

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Two-

Way

Tim

e, s

econ

dsOffset

Direct Arrival

Sea bottom reflection

Swell noise

Sea bottom multiple

Schlumberger Private

2D vs 3D Marine Seismic

Schlumberger Private

Presentation Outline

•Seismic Acquisition Fundamentals

•Acquisition Footprint

•Seismic Data

•Marine Seismic Source

•Streamers

•Mackenzie River 2002 Test

•Mitigation Measures

•Questions

Schlumberger Private

Aerial View of Seismic Vessel in Operation

~ 100 m ~ 20m x 20m~ 200 m

~ 600 m

Schlumberger Private

VESSEL “FOOTPRINT” CONCEPT

Schlumberger Private

Presentation Outline

•Seismic Acquisition Fundamentals

•Acquisition Footprint

•Seismic Data

•Marine Seismic Source

•Streamers

•Mackenzie River 2002 Test

•Mitigation Measures

•Questions

Schlumberger Private

Constituents of Seismic Data

SchlumbergerGeco-PraklaSmall Throws

Thin Beds

Steep DipsLateral Variation

Fresnel Zone

Surface Waves

Interbed Multiples

Losses

Surface Ghosts

Receiver Array

Scattering

Reverberations

Source Array

uneven seabed

overburden

Schlumberger Private

STANDARD SEISMIC DATA 3D PROCESSING

Schlumberger Private

Presentation Outline

•Seismic Acquisition Fundamentals

•Acquisition Footprint

•Seismic Data

•Marine Seismic Source

•Streamers

•Mackenzie River 2002 Test

•Mitigation Measures

•Questions

Schlumberger Private

Dual source

300% door20 m 2200 litre float

10.5 m Tow Point to CoS9m

12 m

100 m190 m185 m

185 m 10.5 m Tow Point to CoS190 m100 m

250 m 12 m

9m

20 m300% door

2200 litre float

120 m

6 m

6 m6 m

6 m

6 m

6 m

250 m

.

Vessel

= CoS

= SPU

Sub-array

Array

Schlumberger Private

3397 Airgun Array Output(6 Meter Tow Depth)

0 100 200 300 400 500Time (msec)

55

33

11

-11

-33

-55

Aco

ustic

Pre

ssur

eB

ar-M

eter

s

Tow Depth = 6 mPeak Amp = 50.9 Bar-m

Am

plitu

de S

pect

rum

dB re

1µP

a/H

z at

1m198.8

186.8

174.8

162.8

150.8

210.8

Frequency (hz)0 50 100 150 200

Schlumberger Private

Peak to Peak pressure in the horizontal plane at 10m depth, far field.

10 m

500 m radius

Center of source

Schlumberger Private

Peak to Peak pressure in the vertical plane

500 m radius

Center of source

Schlumberger Private

Presentation Outline

•Seismic Acquisition Fundamentals

•Acquisition Footprint

•Seismic Data

•Marine Seismic Source

•Streamers

•Mackenzie River 2002 Test

•Mitigation Measures

•Questions

Schlumberger Private

Nessie 4 Streamer•High vessel efficiency through minimal technical down-time•High strength for increased streamer lengths•Contains foam and ISOPAR M

Cross-section cartoon of streamer:

Kevlar stress members

Hydrophones and wires

Polyurethane jacket

Schlumberger Private

Monowing Towing Technology

0.0020.0040.0060.0080.00

100.00120.00140.00

0 5 10 15

Std. Deflectors Monow ings.

Monowings

Total Drag (t) for N Streamers (6000 m, ∆ y = 100 m)

Conventional Towing

Number of streamers

Typical Pulling Limitation

Schlumberger Private

3D Seismic Surveys: Shot Zamboni or Race Track Style

At Least As Long As The Streamer:In The GoM, At Least 6 Km.

Turns Take At Least 2.5 Hours

Area To Be Surveyed

Schlumberger Private

Horizontal & vertical streamer steering

Q Fin

Schlumberger Private

Streamer Steering

Schlumberger Private

Presentation Outline

•Seismic Acquisition Fundamentals

•Acquisition Footprint

•Seismic Data

•Marine Seismic Source

•Streamers

•Mackenzie River 2002 Test

•Mitigation Measures

•Questions

Schlumberger Private

Acoustic Testing from Mackenzie River 2002 Project

• The Objectives

• Record seismic source levels• Record ambient and back

ground noise• Record sound attenuation

over distance

Graphic

Schlumberger Private

Positioning of the cages

Schlumberger Private

Caged Fish Assessment Result

• Test located in backwaters at Norman Wells• Sound level was 220 db at 2 m from airguns• 4 fish out of 196 died (no large fish mortalities)• Examinations show that these fish did not die from exposure

to airguns, but died as a result of handling induced stress.

Schlumberger Private

Presentation Outline

•Seismic Acquisition Fundamentals

•Acquisition Footprint

•Seismic Data

•Marine Seismic Source

•Streamers

•Mackenzie River 2002 Test

•Mitigation Measures

•Questions

Schlumberger Private

WesternGeco Mitigation Measures

•Ramped Start-up•Source Shutdown•Documentation & Reporting•Trained Mammal Observers•Passive Acoustic Monitoring

Bottlenose Whales

Schlumberger Private

Questions

MV Geco SnapperBeaufort Sea 2001-2002