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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