Seismic Attribute Mapping of Structure and Stratigraphy Kurt J. Marfurt (University of Oklahoma)
Attribute Expression of Tectonic Deformation
6a-1
Course Outline Introduction Complex Trace, Horizon, and Formation Attributes Multiattribute Display Spectral Decomposition Geometric Attributes Attribute Expression of Geology Impact of Acquisition and Processing on Attributes Attributes Applied to Offset- and Azimuth-Limited Volumes Structure-Oriented Filtering and Image Enhancement Inversion for Acoustic and Elastic Impedance Multiattribute Analysis Tools Reservoir Characterization Workflows 3D Texture Analysis 6a-2
Attribute expression of tectonic deformation After this section you should be able to: • Use coherence to accelerate the interpretation of faults on 3-D volumes, • Use volumetric attributes to provide a preliminary interpretation across multiple surveys having different amplitude and phase, • Identify the appearance and structural style of salt and shale diapirs on geometric attributes, • Use curvature to define axial planes, and • Use coherence and curvature as an aid to predicting fractures.
6a-3
N
Growth faults, Gulf of Mexico
E
W S Moderate West dip Gentle North dip
Gentle South Dip
Moderate Southeast dip Northeast dip
West 6a-4
East
N
Growth faults, Gulf of Mexico 0
E
W S
Time (s)
2
4
6 6a-5
Identification of faults (Gulf of Mexico, USA)
Salt
Salt
6a-6
Identification of faults (Alberta, Canada)
6a-7
Identification of faults and stratigraphy (Gulf of Mexico, USA) 1.0
1.0
2.0 1.0
3.0
0.0
Time (s)
Time (s)
0.0
2.0 1.0
3.0 2.0
4.0
2.0
4.0 3.0 5 km
5 km
3.0
Seismic
‘Ban ding ’
Coherence Faults ‘Stratigraphy’
6a-8
Attribute imaging of faults and flexures
6a-9
Idealized growth fault
Fault seen on curvature. Seen on coherence. 6a-10
Idealized strike-slip fault
Fault not seen on curvature. Seen on coherence.
Fault with minimal offset
Fault seen on curvature. Not seen on coherence. 6a-11
Fault with finite offset
Fault seen on coherence. Not seen on curvature.
Folds and flexures
‘Fault’ seen on curvature. Not seen on coherence. 6a-12
Infilled grabens
Fault seen on coherence at depth. Infill/collapse seen on curvature shallow.
Basinwide Regional Interpretation across Heterogeneous Seismic Surveys
6a-13
Time/structure map of heterogeneous surveys
10 km N
Time (s) 0.8 1.0 1.2 1.4 1.6
Central Basin Platform, Texas, USA Top Devonian
6a-14
Coherence time slice on heterogeneous surveys
10 km
Coh 1.0
N
0.8
Central Basin Platform, Texas, USA t=1.0 s
6a-15
(Data courtesy of BP, OXY, Burlington)
A large regional survey Texas
Louisiana
East Cameron West Cameron
Eugene Island Vermillion South Marsh Island
Ship Shoal
Vermillion South
Gulf of Mexico 6a-16
(Biles et al, 2003).
Use of coherence to interpreter a large regional survey Texas
Louisiana
‘Coherence’ at 3.0 s Gulf of Mexico 6a-17
(Biles et al, 2003).
Interpretation Workflows
6a-18
Workflow#1: Using attribute to delineate limits of fault zones 2 km
N
W
low coh E
S N
W
mid coh
E
S N
W
high coh
E
S
6a-19
(Data courtesy of OXY)
Workflow#2: Using attribute time slices to help correlate horizons across faults 5 km B′′
Salt
N
C A
Pick an arbitrary line that runs around faults
A′′
Coherence time slice. T=2.7 s (Green Canyon, GOM, USA)
6a-20
B
Time (s)
2.0
A
4 km
A′′
B
B′′
2.5
3.0
Time (s)
C 2.0
C
Seismic ‘traverse’ chosen to avoid major faults
2.5 C 3.0
6a-21
(Data courtesy of BP)
Workflow #3: Using attributes to help fault naming and correlation
N 3 km
t=2.6 s
t=2.6 s
coherence
seismic
Northwest Louisiana, USA 6a-22
(Data courtesy of Seitel)
1) Pick on coherence using seismic time slice as a guide. Try to avoid stratigraphic discontinuities and unconformities
N N 3 km
3 km t=2.6 s
coherence
6a-23
t=2.6 s
seismic
(Data courtesy of Seitel)
A
A′′
N 3 km
n otto C Top alley V
2.5
t=2.6 s
coherence
6a-24
3.0
Bo tto m
Co tt
on V
a ll
ey
A′′
Time (s)
A
2.0
2) Choose a seismic line perpendicular to the fault traces. Pick and assign faults as you normally would.
seismic
(Data courtesy of Seitel)
B
B′′
3) Choose a 2nd EW seismic line further down the fault trace to begin forming a coarse fault grid.
2.0
B′′
A
A′′
Time (s)
B
2.5
t=2.6 s
coherence
6a-25
3.0
seismic
(Data courtesy of Seitel)
C
C
C′′
4) Pick a NS line and continue the process. If subtle discontinuities seen to be faults on seismic, track them on coherence.
N
2.0
Time (s)
3 km
2.5
C′′
t=2.6 s
coherence
6a-26
3.0
seismic
(Data courtesy of Seitel)
D
D
D′′
5) Pick additional NS lines and continue the process, forming a coarse grid.
Time (s)
2.0
2.5
D′′
t=2.6 s
coherence
6a-27
3.0
seismic
(Data courtesy of Seitel)
6) Pick a new time slice through the coherence volume
t=2.5 s
coherence
6a-28
t=2.7 s
coherence
(Data courtesy of Seitel)
7) Use the crossposted fault picks from the vertical seismic to guide your interpretation on the seismic coherence slices
t=2.5 s
coherence
6a-29
t=2.7 s
coherence
(Data courtesy of Seitel)
Structural Deformation
6a-30
Offshore Trinidad Time Slice (t=1.2 s) N
Galeota Ridge
Complex faulting difficult to detect on seismic
Coherence shows lateral continuity of faults
2 km
2 km
Seismic 6a-31
Coherence (Gersztenkorn et al., 1999)
Coherence Time Slice (1.1 s)
W
N
N
2 km
E′
E
D′
6a-32
E
S
D
Dip / Azimuth Time Slice (1.1 s)
D
E′
E
D′
(Gersztenkorn et al., 1999)
Seismic Data D
2 km
D′
Time (s)
0.9
1.1 1.3
Time (s)
0.7
E
E′
1.1 1.5
6a-33
(Gersztenkorn et al., 1999)
Teapot Dome (WY, USA) R′′
R’
R′′
Q
Q
Q
P′′
P Coh 1.0
P’
P′′
P R
P Curv neg
R
R
0 Q′′
Q′′
pos
0.8
Coherence
6a-34
Q′′
Most Positive Curvature
Most Negative Curvature
Teapot Dome (WY, USA)
Time (s)
0.5 P
P′′ R
R′′
Q
Q′′
1.0
1.5
6a-35
(Data courtesy of RMTOC)
Reverse Faulting (Alberta, Canada) A
A’ A
A’
Neg
0
Pos
Low
6a-36
High
(Chopra and Marfurt, 2007b)
Coherence Strat Slices
Line 1
Line 2
Line 3
Line 4
Line 5 Line 6
6a-37
(Chopra and Marfurt, 2007b)
Most-Positive Curvature Strat Slices
Line 1
Line 2
Line 3
Line 4
Line 5 Line 6
6a-38
(Chopra and Marfurt, 2007b)
Most-Negative Curvature Strat Slices
Line 1
Line 2
Line 3
Line 4
Line 5 Line 6
6a-39
(Chopra and Marfurt, 2007b)
1000 ms
1600 ms
Line 1 1000 ms
Line 2
Line 3
Line 4 Faults that appear as discontinuities (seen on both coherence and curvature horizon slices)
Neg
0
Pos Flexures seen on most positive curvature horizon slice that do not appear coherence slice
6a-40
1600 ms
Line 5
(Chopra and Marfurt, 2007b)
Line 6
Salt and Shale Diapirism
6a-41
Vertical seismic section through the La Rue salt dome, East Texas, USA 3 mi
PECAN GAP 1.0
AUSTIN CHALK
4350
BUDA LIME
Time (s)
JA ME S
JAMES LIME
LIM E
11300
COTTO N 3.0 6a-42
Depth (ft)
La Rue Salt Dome
2.0
CHALK
LOUANN SALT
VALLEY
.
SALT WELD
LIME 20900
(Maione, 2001)
Isochron contour map of the interval between the James and Buda Limestones >1300 ms
SALT WITHDRAWAL BASIN
~ 600 ms
8 km 1.4 s 1.9 s 6a-43
(Maione, 2001).
Time slice through La Rue Salt Dome, East Texas, USA
6a-44
Ring faults difficult to see on seismic data, easier to see on coherence
(Maione, 2001).
Time slice through coherence volume Time slice at 1.232 s
La Rue Salt Dome
Salt Dome
Salt Dome 8 km
6a-45
(Maione, 2001).
Time slice through coherence volume Time slice at 1.400 s
La Rue Salt Dome
Salt Dome
Salt Dome 8 km
6a-46
(Maione, 2001).
Time slice through coherence volume Time slice at 1.636 s
La Rue Salt Dome
Salt Dome
Salt Dome 8 km
6a-47
(Maione, 2001).
Coherence volume, looking South, showing concentric ring fault patterns and stratigraphic thickening N
La Rue Salt Dome 8k m
6a-48
(Maione, 2001).
Vertical section between two salt withdrawal basins 3 km 1.0
1.5
2.0
Seismic 6a-49
Coherence (Maione, 2001).
Mapping Folds and Flexures
6a-50
Central Basin Platform, Texas, USA high
low
0
Seismic amplitude
5 km
high
Coherence high
Horizon slices along Devonian 0
Most positive curvature 6a-51
(Blumentritt et al., 2006)
Methodology
Pick lineaments seen on curvature high
0
2 km
6a-52
(Blumentritt et al., 2006)
Interpretation of Lineaments Red and Blue lines: Readily observable faults
Green lines: Subtle geologic features
6a-53
Deformation model
(Blumentritt et al., 2006)
Application
What is the geologic explanation of these lineaments?
2 km
6a-54
(Blumentritt et al., 2006)
Buckling in Competent Rocks?
6a-55
Application
(Blumentritt et al., 2006)
Structural Deformation In Summary: • In general, time slices show better fault images (with less interpreter bias) than horizon slices. • Geometric attributes are relatively insensitive to the seismic source wavelet, such that they are useful in visualizing geologic features that span surveys subjected to different acquisition and processing. • Geometric attributes allow us to quickly define and name a coarse fault network. • Volumetric curvature allows us to map subtle folds and flexures associated with tectonic deformation. • Volumetric curvature also illuminates faults that are inaccurately imaged or have small vertical throw. • Geometric attributes allow us to visualize plastic deformation in ductile shales and brittle deformation in more competent carbonates and sandstones. 6a-56
