Seismic Attributes - Tectonics

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

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Identification of faults (Alberta, Canada)

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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’

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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

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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

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Coherence time slice on heterogeneous surveys

10 km

Coh 1.0

N

0.8

Central Basin Platform, Texas, USA t=1.0 s

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(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

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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

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t=2.7 s

coherence

(Data courtesy of Seitel)

Structural Deformation

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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

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High

(Chopra and Marfurt, 2007b)

Coherence Strat Slices

Line 1

Line 2

Line 3

Line 4

Line 5 Line 6

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(Chopra and Marfurt, 2007b)

Most-Positive Curvature Strat Slices

Line 1

Line 2

Line 3

Line 4

Line 5 Line 6

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(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

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1600 ms

Line 5

(Chopra and Marfurt, 2007b)

Line 6

Salt and Shale Diapirism

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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

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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

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(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

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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

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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?

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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