1. Fault-Fracture charachterization in OpendTect
Version 5.0
OpendTect Master Class
June 15, 2014

2. Outline Introduction Automatic Fault Extraction
Algorithm
Interface
Examples
New Fracture Attributes
Overview

3. Introduction This presentation covers the concepts/workflows for
Automatic fault extraction in OpendTect
Two new fracture related attributes
System Requirements:
For visualization, a good system is required.
Multicore processor
RAM 8GB or higher, and a good graphics card (>1GB)
Licence Requirements
Automatic Fault Extraction Dip-Steering LICENSE
New Fracture Attributes Dip-Steering LICENSE

4. Outline Introduction Automatic Fault Extraction
Algorithm
Interface
Examples
New Fracture Attributes
Overview

5. Finger Vein Pattern Technique Introduction
Used typically for fingerprint data processing
Biomedical technique extended to seismic

6. Finger Vein Pattern Technique Algorithm for automatically tracking faults
Input: A discontinuity volume with an enhanced fault pattern (e.g. Coherence or Similarity)
Curvature based score calculation for 2D profiles oriented along various azimuths (per Z-slice)
Extract connected components on each 2D profile (per Z-slice)
Apply thinning, merging algorithms on each connected component to form sticks
Sort and group sticks
Output a set of faults or a fault stick-set

7. Compute Score which includes both magnitude and width of fault anomaly
Finger Vein Pattern Technique Algorithm for automatically tracking faults
Z-slice through a discontinuity volume, e.g. Coherence
Compute Curvature of the discontinuity attribute, along a 2-D profile (AA`) oriented along azimuth ‘j’
Compute Score which includes both magnitude and width of fault anomaly
Assign Score to the 2-D profile AA`

8. Finger Vein Pattern Technique Algorithm for automatically tracking faults
Compute scores for all 2-D profiles along ‘4’ azimuths to get a “Capability slice” V(x, y)
Compute “Confidence slices” along different azimuths and choose the one with max value.
Move to next Z-slice

9. Outline Introduction Automatic Fault Extraction
Algorithm
Interface
Examples
New Fracture Attributes
Overview

10. Fault Extraction Start Position
Fault extraction produces two sets of outputs:
Volumes: fault scores, dip and azimuth
Faults: sticks or planes
Volumes launch:
Processing ->Create Seismic Output->Volume Builder
Faults launch:
Processing->Fault Extraction
Volume Builder UI

11. Fault Auto Extraction Fault Planes User Interface
The new Fault Auto Extraction tool is under the Processing menu
General threshold parameter (0)
Vertical parameters: Min sticks per fault (1) and Min vertical overlap rate (3)
Horizontal (per Z-slice) parameters: Min fault length (4), Search step-out (2) and optionally Merging faults (5) 1 2 3 4 7

12. Fault Auto Extraction Interface: Parameter explanation
Example Z-slice through a similarity volume. Note the faults lineaments with low similarity values (black).
The “Minimum Fault Length per Z-slice” is the horizontal length of the fault on any Z-slice. 4
The “Minimum Number of Sticks” is the min number of Z-slices
a fault must pass through, defines min vertical extent of fault 1

13. Fault Auto Extraction Interface: Parameter explanation
The “Search stepout between Z-slices” is the the horizontal displacement of the searching window over the inline/crossline direction when extracting the fault surfaces Zslice-by-Zslice 2
The “Min vertical overlap rate” defines the minimum overlap between anomalies on adjacent Z-slices, in order for them to be considered part of one single fault. 3

14. Fault Auto Extraction Interface: Parameter explanation
Z-Slice 1 1 1
Z-Slice 5
The “Minimum sticks per fault” is the min number of Z-slices a fault must pass through, i.e. it defines min vertical extent of fault.

15. Fault Auto Extraction Interface: Parameter explanation
Z-Slice 1 2 1 2
Z-Slice 5
The “Search stepout between Z-slices” is the horizontal displacement of the searching window over the inline/crossline direction when extracting the fault surfaces Zslice-by-Zslice

16. Fault Auto Extraction Interface: Parameter explanation
Z-Slice 1 1 2 3 3
Z-Slice 5
The “Min vertical overlap rate” defines the minimum overlap between anomalies on adjacent Z-slices, in order for them to be considered part of one single fault.

17. Fault Auto Extraction Interface: Parameter explanation
Z-Slice 1 4 1 2 3 4
Z-Slice 5
The “Minimum fault Length per Z-slice” is the minimum horizontal length of the fault on any Z-slice.

18. Fault Auto Extraction Interface: Parameter explanation5

19. Fault Auto Extraction Interface: Parameter explanation
Either a “Fault Stick Set” or individual “Faults” can be outputted. 6 1 2
The “Number of top faults” is the maximum number of tracked faults on any Z-slice. In case of noisy data, use of a small number here may be helpful. 3 7 4 5 6 7

20. Outline Introduction Automatic Fault Extraction
Algorithm
Interface
Examples
New Fracture Attributes
Overview

21. Fault tracker similarity Fault score Fault azimuth grey
Biggest fault sticks
All faults
Volume components
similarity
Fault score
Fault azimuth grey
Binary faults 90%
Binary faults 95%
Fault azimuth color
Volume components
Biggest fault sticks
All faults
Sponsored by:

22. Fault Auto Extraction Example: Gulf of Mexico
Inline showing stacked seismic data after Fault Enhancement Filter application.
A min similarity volume, computed from this fault enhanced seismic volume, is used as input for Auto Fault Extraction algorithm.

23. Fault Auto Extraction Example: Gulf of Mexico
Inline showing stacked seismic data after Fault Enhancement Filter application with automatically extracted faults on top.
Fault points

24. Fault Auto Extraction Example: Gulf of Mexico
Z-slice at 400ms showing stacked seismic data after Fault Enhancement Filter application.

25. Fault Auto Extraction Example: Gulf of Mexico
Z-slice at 400ms showing Min Similarity computed from fault enhanced seismic.

26. Fault Auto Extraction Example: Gulf of Mexico
Z-slice at 400 ms showing Min Similarity computed from fault enhanced seismic with automatically extracted faults.

27. Outline Introduction Automatic Fault Extraction
Algorithm
Interface
Examples
New Fracture Attributes
Overview

28. New Fracture Attributes Overview
Two new qualitative fracture characterization attributes, Fracture Proximity and Fracture Density, are going to be available in OpendTect v5.0
Fracture Proximity improves visualization of potential fracture anomalies.
It computes the lateral distance (i.e. along Z-slice) from a trace location classified as a fracture.
Whether a particular trace can be defined as being part of a fracture, is determined by a user-specified threshold, on various curvature/coherence related attributes such as Max Curvature.
Fracture Density attribute is useful in pin-pointing locations with maximum fracture activity, within a user-defined radius.
This “radius” can for example be linked to fracking radius for drilling.
It computes the ratio of “number of traces classified as being fractures” to the “total number of traces present”, in a circle of given radius along Z-slices.

29. Outline Introduction Automatic Fault Extraction
Algorithm
Interface
Examples
New Fracture Attributes
Overview

30. New Fracture Attributes Interface
Input data should be a discontinuity attribute, e.g. Similarity & Curvature 1
Threshold value of input discontinuity attribute above which a fracture anomaly is expected 1 2 2 3
Choose to output either “Fracture Proximity” or “Fracture Density” 3
For “Fracture Density” a radius for scanning and computing the density of fracture anomalies, is also required. 4 4

31. Outline Introduction Automatic Fault Extraction
Algorithm
Interface
Examples
New Fracture Attributes
Overview

32. New dip-steered attributes Example: Gulf of Mexico
Max curvature is a possible input for Fracture Proximity and Density attributes.
Input: Maximum curvature
Inl/Crl stepout: 2
Steering input : Detailed steering
Z-slice at 400 ms

33. New Fracture Attributes Example: Gulf of Mexico
Max curvature value of more than denotes a possible fracture.
The distance from all those traces where max curvature is higher than the threshold is computed by the Fracture Proximity attribute.
Fracture Proximity
Input: Maximum curvature
Fracture threshold: 0.004
Z-slice at 400 ms
Colorbar unit = Meters

34. New Fracture Attributes Example: Gulf of Mexico
Max curvature value of more than denotes a possible fracture.
The ratio of all those traces where max curvature is higher than the threshold to the total number of traces, present in a circle of radius 400m, is computed by the Fracture Density attribute.
Fracture Density
Input: Maximum curvature
Fracture threshold: 0.004
Radius: 400 m
Z-slice at 400 ms