Petrel F 5 horizon interpretation 2018 v1.0

Schlumberger-Private
Module 5: Horizon Interpretation
Petrel 2018 Geophysics
Seismic Visualization and Interpretation

Exercise 1: Overview

Horizon interpretation techniques
Horizon interpretation is a combination of manual and automated
interpretation techniques.
1 Manual interpretation
2 Guided autotracking
3 Seeded 2D autotracking
4 Seeded 3D autotracking
5 Autotrack inside polygon
6 Active box autotracking
7 Paintbrush autotracking
1
2 3 4 5
6
7

Interpret a seismic horizon (1)
1. Open a new Interpretation window. Display a seismic section, for instance Inline 575.
Display the color bar thru right-click on the seismic and select Color legend. Right-click
on the legend and select Settings. Adjust the display.
2. Click Select on the Window toolbar (icon ).
3. Right-click the seismic section and click New seismic horizon ( ) on the mini toolbar .
A new seismic horizon appears
in the active Horizon Interpretation folder
of the Input pane.

There are two other ways to insert a
new seismic horizon:
 Insert a horizon from the 2D/3D
interpretation group on the Seismic
Interpretation domain tab.
 Right-click the Interpretation folder
and select New seismic horizon.

4. Identify a horizon you want to track. Check for its polarity (Peak or Through) via the color bar.
Then do:
a. Right-click the seismic horizon in the Input pane.
b. Navigate to the Settings dialog box and click the Autotracking tab.
c. Select Peaks or Throughs depending what horizon you want to track

5. Click Tool Palette on the Home tab. Or else: right-click on the seismic section and
select Tool Palette (icon ) from the mini-toolbar.
6. Open the seismic interpretation Tool Palette.
7. Select a method of horizon interpretation.
Begin to digitize the seismic event.
If you use guided or manual interpretation:
a. Hold down the left mouse button and
move the cursor in the direction of
interpretation.
a. Press N or double-click to break
the pick.

9. To erase all or part of the horizon on the seismic section, click Interactive eraser on
the Seismic interpretation Tool Palette.

10. Continue interpretation. Use the Tool Palette to display every 10th inline and crossline for
interpretation. To view your progress, open a 2D window and display it next to the
Interpretation window. Display the horizon in these windows.

Interpret seismic horizon (6)
11. Click Ghost curve. Use the Ghost
to correlate the horizons across a fault
in order to avoid mis-picks.

Exercise 2: Autotracking

Autotracking
Autotracking is a powerful tool for horizon interpretation, particularly in
areas with good reflector continuity, signal strength, and data quality.
There are three main types of horizon autotracking:
 Guided Autotracking
 Seeded 2D Autotracking
 Seeded 3D Autotracking

Guided autotracking (1)
Digitize two or more points, and the tracking connects the seeds
following the seismic peak/through.
This option gives a high degree of control over the interpretation
and should be used in areas of low S/N or several faults.

1. In an Interpretation or a 3D window, activate and display the seismic
line for Guided Autotracking.
a. Right-click the seismic section to
insert a new horizon and click the
Select option on the Window toolbar.
b. Select New seismic horizon from the mini toolbar.
c. Goto Settings/Info of the horizon and change the name to
Autotrack.
2. From Home tab > View group, click Tool
palette.

4. From the Tool Palette, click the Seismic Interpretation option.
5. On the seismic interpretation Tool Palette, click Guided
autotracking.

6. Click on a reflector to select the start and end points. The
interpretation follows the seismic event between the two seed points.
7. Double-click, or press the N or H key to end an interpretation segment
and break the pick.

Seeded 2D autotracking (1)
Seeded 2D autotracking uses a single digitized (seed) point to
track the horizon of the displayed intersection based on the
autotracking parameters.
The horizon continues tracking until the tracked event no
longer meets the defined tracking parameters due to a fault,
amplitude decay, or reverse polarity.

Seeded 2D autotracking (2)
1. Open an active interpretation or a 3D window and insert a new seismic horizon.
2. On the seismic interpretation Tool Palette, click Seeded 2D autotracking.
3. Click once along a seismic event. The interpretation follows the event to each side of
the point selected, and stops when an abrupt change in an amplitude value occurs.
4. Repeat the procedure for the segment across the fault and other lines.

Seeded 3D autotracking
 Works only for 3D seismic data. Seeded 3D autotracking parameters
are defined in the Autotracking tab of the horizon Settings dialog box.
 Choose one or multiple seed points. The horizon is tracked outward in
all directions from these points.
 When the reflectors are of good quality, this method is an efficient way
of interpreting through the seismic cube.

Perform seeded 3D autotracking (1)
1. Open an Interpretation window and insert a new horizon.
2. On the seismic interpretation Tool Palette, click the Seeded 3D autotracking
option.
3. Click once on the seismic event to be autotracked. The interpretation expands
over the entire cube while the seismic event characteristics of the first seed
point are obtained.

Perform seeded 3D autotracking (2)
4. Open a 3D window and display the
horizon you 3D autotracked.
Depending on the strength of the
reflector, some areas of the horizon were
not autotracked.
5. Right-click on the horizon and select
Delete content…
6. Open Settings/Autotracking of the
horizon. Uncheck Use wavelet tracking.
7. Redo the autotracking.

Perform seeded 3D autotracking – different approach
(1)
Perform a 3D autotrack:
a. In the 3D Window display Inline 575.
b. Create a new horizon.
c. Using 2D Autotrack track the positive event at
around 635ms.
d. Open Settings/Autotracking of the horizon.
e. Click on button 3D Track to autotrack the
horizon
f. Push the icon Instant undo and track
g. Change a tracking parameter and observe
the automatic update of the interpretation
based on the new parameters.

Paintbrush autotracking
 In Paintbrush autotracking, points are tracked within a user
defined area.
 Drag the cursor to track a horizon interpretation that follows the
cursor path.
 This tool works in both 2D and 3D windows, however it is mostly
used in the 2D Window.

Active box autotracking (1)
1. In a 2D window, activate the seismic
volume and partially interpreted
seismic horizon from the Input pane.
2. Access the seismic interpretation Tool
Palette.
3. Click Active box autotracking.

4. Use the cursor to draw a box
over the area you want to
autotrack.
The box must include some
existing interpretation.

5. Paint the horizon interpretation outwards using Paintbrush
autotracking.
6. Continue the active box autotracking over the entire area and QC the
results in an Interpretation window and a 3D window. Check where
the horizon is tracking the wrong seismic event!

The following slides explain the individual autotrack
parameters
Go quickly thru the slides if there is some time. There are no exercises provided
discussing the parameters in detail.
The next exercises start with slide 42

Click the Autotracking tab to control the way in which your horizons are
autotracked.
Autotracking settings

Autotracking tab: General section
Make these selections in the general area of the Autotracking tab:
 Seismic volume for autotracking
 Priority
 Quality
 Signal feature

Autotracking tab: Seismic volume
The activated seismic cube is picked up automatically. Use the blue arrow
to change the seismic cube.

Autotracking tab: Priority
Original Seeds Amplitude
ProximityAmplitude & Proximity
Comparison of tracking results using
three seed priority methods.
Priority regulates the priority queue of available seed points for the
expansion process.

Autotracking tab: Quality
Seed Point
Potential child points
Accepted child picks from
phase 1 and 2
Basic 3x3 Validated 3x3
Validated 5x5
The Quality option on the Autotracking tab controls
how stringently each seed point is checked before it is
expanded.

Autotracking tab: Signal feature (1)
Signal feature
controls the feature
to be tracked.

Autotracking tab: Signal feature (2)
Trace features in Petrel:
Z-crossings (blue)
S-crossings (green).
The illustration shows what non-zero centric means.
A time-based SEG-Y plots along the time axis. A zero
crossing for this represents a local minimum or local
maximum in the non-zero centric world.
A peak in the zero-centric seismic represents an
S-increasing feature, while a trough represents a
Z-increasing feature.
1
2

Autotracking tab: Parameters subtab - Seed confidence
Specifies the minimum value for the seismic amplitude as a
percentage of the seed point.
The confidence level determines how much slack the tracker
applies to seed values when determining whether to accept or
reject expansion points.

Autotracking tab: Parameters subtab - Value range
Allows you to specify a minimum and maximum amplitude
value seismic attribute to be tracked.
Picks outside these amplitude limits are rejected.

Autotracking tab: Parameters subtab - Doublet/Tracking
rule
Specifies which part of a doublet the tracker follows.

Autotracking tab: Parameters subtab - Dip/Wavelet
Dip: Optimize the autotracking
parameters for dipping reflectors.
Wavelet: Test the potential
expansion points using the
correlation of a seismic trace
window.

Autotracking tab: Constraints subtab (1)
Lateral limits: Limit the autotracking horizontally.
Vertical limits: Constrain the autotracking vertically.

Autotracking tab: Constraints subtab (2)
Using co-volume: If selected, the autotracking uses two seismic
inputs instead of one.
Seed/Locking: Choose what to do with an existing interpretation.

Exercise 3: Horizon Edits and Manipulation

Display and annotate horizon: Interpretation window (1)
1. Display the horizon interpretation in the Interpretation window.
2. With the Select option on the Window toolbar, right-click the horizon
and click Horizon settings on the mini toolbar.
1
2

Display and annotate horizon: Interpretation window (2)
3. On the Style tab in the Settings for Seismic
horizon dialog box, set the display style for
2D/3D interpretation and crossing points.
4. To aid during interpretation and to know
where you picked the horizon on the previous
or next intersection, click Neighbor
sections.
(This option is available only for 3D data.)
5. (Optional) In the Annotation section, choose
to display the name of the horizon on the
section.

Display and annotate horizon: 3D window
1. Display the horizon in a 3D window.
1 2
3 4
2. Set the display style for 2D interpretation.
3. Set the display for 3D interpretation.
4. Manipulate the resolution slider bar.
2
3
4

Edit and manipulate using the seismic interpretation
Tool Palette
1
2 3
4
5
6
7
1 Undo (Ctrl + Z) / Redo (Ctrl + Y)
2 Interactive Eraser
3 Delete
4 Paintbrush
5 Polygon
6 Bounding box
7 Single point

Deletion of mis-picks
1. Open a 3D window and display an 3D Autotracked horizon from the
Input pane.
2. Highlight the misinterpreted using one of the tools of Tool Palette:
Polygon – Bounding box – Single point
3. Once highlighted push the ‘Delete’ – button
of the keyboard..

Parent-child editing
The autotracking uses a trace-to-trace method to verify and
expand the seed point.
When a point or a selection of points is accepted, it becomes
a parent to other potential child points that are picked from
neighboring traces.

Edit parent and child points in an interpretation (1)
1. Open a 3D window and display an 3D Autotracked horizon from the
Input pane.
2. Select Bounding box from the Tool Palette.

3. Click Select parent points from the Manipulate group on the Tools
contextual tab.
4. Click a misinterpreted point; the path back to its original seed point
turns yellow.

5. Click Select child point from the Manipulate group on the Tools
contextual tab.
6. Click the first wrongly tracked point on the path; all points that originate
from it turn yellow.
7. Push the ‘Delete’-key of
the keyboard to delete the
highlighted points.

Horizon flattening
 Flatten individual lines on an interpreted horizon in the
Interpretation window.
 The interpreted horizon does not have to be consistent over
the entire line. Petrel allows for gaps in the interpretation,
such as breaks over faults.
 The gaps are interpolated linearly; you can interpret on the
flattened sections.

Flatten a seismic horizon in interpretation window (1)
1. Open an interpretation
window and display the
seismic horizon.
2. With the Select option on
the Window toolbar, right-
click the seismic horizon to
be flattened and select
Flatten horizon from the
context menu.
2
1

Flatten a seismic horizon in interpretation window (2)
4. Toggle OFF the interpretation (horizon, faults) in the Input pane to
improve the display.
5. To unflatten the horizon, right-click with the Select option and click
Flatten horizon.
3 4
5

Interpretation display filter
Filters related to interpretations
are located in the Seismic main
folder or you can find them under
each horizon interpretation object
in the Input pane.
In the Interp survey inclusion
filters folder, you can filter cells
belonging to the different surveys.

Horizon operations: Bulk shift (1)
1. In the Input pane, open the Settings dialog box for the horizon.
2. On the Operations tab, expand the
Arithmetic folder and select Z = Z + Constant.
3. Define the constant value and click Run.
The horizon shifts vertically.
2
3

Horizon operations: Bulk shift (2)
3
21

Horizon operations: Smoothing
Gaussian smooth
Median smooth
1. Expand the Seismic operations folder and select
Gaussian or Median smooth.
2. For Median smooth, set the number of Iterations
and Radius.

Lesson 4: Convert Horizon Interpretation
into Surfaces and Generating Surface
Attributes

Make surface process (1)
1. On the Seismic Interpretation domain tab, go to the Utilities group
and click Make surface.

2. From Main input, drop in the interpreted
horizon that you wish to convert into a
surface. You also can specify the name
of the output file by selecting Name and
writing the name.
3. Click Suggest settings from input.
Petrel suggests the gridding algorithm
based on the chosen input data.
4. On the Geometry tab, specify the
parameters as shown in the figure.

The surface will be automatically displayed in the active window.
Display the surface in a 2D window and adjust the colors: open
Settings of the surface and goto Colors.
Check on the highlighted check boxes
shown in the right figure.
Right-click on the surface and select Color legend.
Adjust the displayed color legend thru right-clicking on the
legend and selecting Settings.

Originally interpreted horizon
Surface created from horizon
interpretation

Surface operations: Smooth (1)
1. In the Surface operations folder on
the Operations tab of the Settings
dialog box for the Surface, select
Smooth.
2. Define Iterations and Filter width
parameters.
3. Click Run.
1
2
3

Surface operations: Smooth (2)
Original surface for smoothing. Surface after smoothing process.

Additional exercises (it time is left)
• Display Inline 555. Track the positive (red)
loop of the horizon around 1000ms.
• Using the Player select an increment of
10.
• Interpret every 10th inline and xline.
• Make a copy of the interpretation (Ctrl-C,
Ctrl-V).
• Apply 3D Autotrack on this seed grid
• Map the result

Useful information – discussed functions not covered in
this course

Flattened objects
 Interpretation objects can be converted in the flattened space.
These objects can be faults, horizons, surfaces, points, and grid
interpretations (which are subobjects of the horizon interpretation
associated with only one seismic survey).
 Create new interpretation objects (faults, horizons, and grid
interpretations) and interpret them directly in the flattened space.
 A history of the flattened objects is stored on the History tab in
the Settings dialog box.

Flatten 3D volumes (1)
1. On the Seismic Interpretation domain tab,
go to the Utilities group and click the Make
surface icon.
2. Using the Make/edit surface dialog, convert
the horizon interpretation to a surface.

3. To flatten a seismic cube:
a. Activate the seismic cube that
you wish to flatten.
b. Right-click the surface and
select Flatten cube.
c. In the Input pane, a virtual
flattened seismic volume
named Flattened 1 is created.
Also, a new folder named
Flattening surfaces is created.
Use this folder to track the
history of flattening operations.

d. In the Settings dialog box for
Flattened volume, click the Flattening
tab and insert a Reference surface for
flattening.

4. In the Input pane, make the Interpretation
folder bold and click the Flattening dialog
box to insert objects into the table. Click
Flatten and Apply.
The seismic volume is flattened on the
reference surface. All objects in the
Interpretation folder are flattened.

5. Open a 3D window and display Flattened 1 from the Input pane. You also
can insert individual objects.
6. Click Re-flatten, Un-flatten, and Flatten to flatten and unflatten the objects
in the list.

Petrel F 5 horizon interpretation 2018 v1.0

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