Brad Artman

• undergraduate: Colorado School of Mines, Geophysical Engineer

• graduate: Stanford University, Ph.D. candidate

• work experience:

– Western Atlas Logging Services, Junior Engineer

– U.S. Geological Survey, Visiting Scientist

– Shell Deepwater Development Inc., Petrophysicist & Exploration Geophysicist

passive seismic imaging at ValhallBrad Artman, Stanford Exploration Project – Advanced imaging team

Monday, September 27

multiple modeling in the image-spaceBrad Artman, Stanford Exploration Project – Advanced Imaging Team

Ken Matson, Advanced Imaging Team

Monday, September 27

passive seismic imaging at ValhallBrad Artman, Stanford Exploration Project – Advanced imaging team

Monday, September 27

passive seismology

• not event location

• structural imaging

– reflection seismology: subsurface investigation from the time-delayed reflections of sound off of geologic variations.

– passive imaging: with no application of controlled experimental sources, a relationship between a recorded transmission wavefield and reflection wavefields is required.

• requires: stationary seismometers, lots of disk space

crustal scale exploration

earthquake energy

capitalizing on ambient noise

• earthquake arrivals

• ocean waves

• wind vibrations coupled with foundations

• cultural activity

– vehicle and boat traffic

– drilling noise

– nearby seismic acquisition

Valhall

VALHALL

STAVANGER

0 100 km

UNITEDKINGDOM

NOR WAY

GERMANY

DENMARK

UNITEDKINGDOM

GERMANY

DENMARK

NORWAY

0 100 km

HOD

• one of the North sea giant fields

• partners Amerada Hess, Shell and Total

• reservoir highly porous chalk

• first production 1982

• field life 2028

• field production 90,000 bpd/day

• expected ultimate recovery 1,050 mm stb oil

• produced to date (01.01.2003) 500 mm stb oil • remaining reserves 540 mm stb oil

• high activity level – new wells & well work

Valhall Life of Field Seismic (LoFS)

• Permanent field wide seismic array installed at Valhall during 2003

– 120 km seismic cables

– 2414 groups of 4C sensors

– Covers 45sq km

– 3 seismic surveys acquired, 4th to be acquired mid-September

operations

• state of the art airgun array carried by stand-by boat – 53,000 shots per survey

• ~1/2 cost of LoFS installations related to the source

• passive seismology by correlation

• why image?

– linearity of wavefield extrapolation

• application to Valhall LoFS

• why try passive seismic imaging?

• future plans

transmission wavefield

time (s)

dep

th (m

)

position(m) position(m)

ambient noise

r1 r2

t

r1 r2

ambient noise

r1 r2

t

r1 r2

ambient noise

r1 r2

t

r1 r2

ambient noise

r1 r2

t

r1 r1 r1 r2

lag

r1 r2

ambient noise

r1 r2

t

r1 r1 r1 r2

twt

r1 r2

0 1200600 position(m)

20 2

5 3

0tim

e(s)

5 1

0

0 200100

lag

(s)0

0.1

0.3

400300offset(m)

0 1200600 position(m)

20 2

5 3

0tim

e(s)

5 1

0

0-100 200100

lag

(s)0

0.1

0.3

offset(m)300

0 1200600 position(m)

20 2

5 3

0tim

e(s)

5 1

0

0-100-200

200100

lag

(s)0

0.1

0.3

offset(m)

0 1200600 position(m)

20 2

5 3

0tim

e(s)

5 1

0

0-100-200

100

lag

(s)0

0.1

0.3

offset(m)-

300

n long traces n short traces2

• passive seismology by correlation

• why image?

– linearity of wavefield extrapolation

• application to Valhall LoFS

• why try passive seismic imaging?

• future plans

why image?signal/noise enhancement

one correlated shot gather migrated image

flow model

T= Transmission wavefieldD= Source wavefield (down-going)U= Receiver wavefield (up-going)R= Total reflection data

Rz+1

Tz TzRz

+

Uz Dz

Uz+1 Dz+1

+ -

Tz+1 Tz+1

+ -

correlation extrapolation

SR Migration

flow model

T= Transmission wavefieldD= Source wavefield (down-going)U= Receiver wavefield (up-going)R= Total reflection data

Rz+1

Tz TzRz

+

Uz Dz

Uz+1 Dz+1

+ -

Tz+1 Tz+1

+ -

correlation extrapolation

CMP Migration

flow model

T= Transmission wavefieldD= Source wavefield (down-going)U= Receiver wavefield (up-going)R= Total reflection data

Rz+1

Tz TzRz

+

Uz Dz

Uz+1 Dz+1

+ -

Tz+1 Tz+1

+ -

correlation extrapolation

Passive Migration

flow model

T= Transmission wavefieldD= Source wavefield (down-going)U= Receiver wavefield (up-going)R= Total reflection data

Rz+1

Tz TzRz

+

Uz Dz

Uz+1 Dz+1

+ -

Tz+1 Tz+1

+ -

correlation extrapolation

imaging advantages• poor data quality mandates imaging

• transformation from transmission to reflection wavefield can be accomplished along the way

• saves time

– n instead of n2 traces

– removes IFFT of n2 (long) traces

– trace length difference ~cancels strict compute cost savings

– file i/o provides big savings

• 1 shot of n traces vs. n shots of n traces

• multiple image-space summations

synthetic proof of concept

reflection gather active migration

synthetic proof of concept

correlated passive gather passive migration

• passive seismology by correlation

• why image?

– linearity of wavefield extrapolation

• application to Valhall LoFS

• why try passive seismic imaging?

• future plans

Valhall data

Valhall data

Valhall data

trace #

Depth slice near 88m

energy localized around rig

moveout across traces suggests surface noise

Valhall data

Reflector?

mono-freq. boat noise

rig activity

Valhall pipe cut normalization

4km

12km

Valhall pipe cut image

4km

12km

Valhall pipe cut image

4km

12km

Valhall active seismic

4km

12km

• passive seismology by correlation

• why image?

– linearity of wavefield extrapolation

• application to Valhall LoFS

• why try passive seismic imaging?

• future plans

why try passive seismic imaging

• understand a completely undeveloped experiment

• capitalize on:

– existing hardware

– competitor’s sources

– teleseismic & local noise

• extend imaging bandwidth to lower frequencies

• imaging forward scattered modes

• passive seismology by correlation

• why image?

– linearity of wavefield extrapolation

• application to Valhall LoFS

• why try passive seismic imaging?

• future plans

future plans

• continued exploration of existing data

– multi-component experiments

– appropriate bandwidth parameterization

– time/energy requirements

– earthquake sources

• rig-site continuous correlation

• BP’s passive seismic imaging capabilities

– file-handling infrastructure

– native 3D imaging algorithms

Oyo-Geospace cable

multiple modeling in the image-spaceBrad Artman, Stanford Exploration Project – Advanced Imaging Team

Ken Matson, Advanced Imaging Team

Monday, September 27

• Surface Related Multiple Elimination (SRME)

– mechanics

– classic shortfall

– addressing the problem through imaging

• shot-record imaging

• multiple modeling at Maddog

• implications and status

*

=

=

* =

*

Surface Related Multiple Extraction

r

s

SRME

r

s

?

SRME

r

s

SRME

r

s

?

SRME

r

s

SRME

r

s ?

SRME

r

s

SRME

E

N

*

SRME

E

N

*

SRME

•Exact kinematic modeling•Linearly increasing amplitude error w/ order of multiples•Suffers when FULL acquisition not supplied

•co-located sources and receivers

… in the image space

•Exact kinematic modeling- independent of velocity•Same amplitude problems (requires adaptive subtraction)•Wavefront healingWavefront healing

SRME

z

x

wavefront healing

z

x

wavefront healing

z

x

wavefront healing

• Surface Related Multiple Extraction (SRME)

– mechanics

– classic shortfall

– addressing the problem through imaging

• shot-record imaging

• multiple modeling Maddog

• implications and status

flow model

T= Transmission wavefieldD= Source wavefield (down-going)U= Receiver wavefield (up-going)R= Total reflection data

Rz+1

Tz TzRz

+

Uz Dz

Uz+1 Dz+1

+ -

Tz+1 Tz+1

+ -

correlation extrapolation

flow model

M= Multiple modelU = Receiver wavefield (up-going)

Mz

Mo

+

Uo Uo

Uz Uz

+ -

convolution extrapolation

*

*

shot-record migration

image-space multiple model

• Surface Related Multiple Extraction (SRME)

– mechanics

– classic shortfall

– addressing the problem through imaging

• shot-record imaging

• multiple modeling Maddog

• implications and status

shot-record migration

image-space multiple model

migration

migration after subtraction

subtraction after migration

migration after subtraction

migration

• Surface Related Multiple Extraction (SRME)

– mechanics

– classic shortfall

– addressing the problem through imaging

• shot-record imaging

• multiple modeling Maddog

• implications and status

image space multiple modeling

• exact kinematics

– inexact dynamics requires adaptive subtraction

– 1-2 less dimensions makes subtraction less expensive

• velocity independent

• incremental expense (1.5x) to produce during shot-record migration

– direct extension to Common Image Gathers

– split-spread input data required

• less expensive than regularization + SRME + migration

status

• documented 2- and 3-D programs running

• suite of 2-D synthetic tests

• single shot 3-D synthetic test

– comprehensive testing will require significant resources

acknowledgements

Sverre Brandsberg-Dahl, Joe Dellinger, Valhall BU

Richard Clarke, John Etgen, Advanced Imaging Team

Phuong Vu, David Lewis, Keith Gray, Jerry Ehlers, Randy Selzer

Ken Matson, Gerchard Pfau

migrated conventional multiples

migrated image

image-space multiple model

migrated conventional multiples

migrated image