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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