INTRODUCTION TO SEISMIC INTERPRETATION IN PETREL
These notes provide a quick introduction to the user interface and seismic interpretation
tools in Petrel, as well as the data set that you will be using during this course. More
detailed descriptions of Petrel’s functionality can be found in the Petrel help file.
By the end of the first session of this course you should be able to find your way around
the data set in Petrel, and be able to interpret horizons and faults on 2D seismic data. We
will go into more detail on some of the more advanced seismic interpretation tools later
in the course.
Layout and Functionality
Opening a project
The first and second Petrel explorers
Creating new windows
Accessing detailed menu options
Settings menu / changing appearance of objects
Accessing the help file
Well section Window
Interpretting a horizon
Seeded 2D Autotracking
Turning off snap to features
Starting a new horizon
Continuing interpretation of an existing surface
1. Layout and Functionality
In order to view all the menu options in Petrel, you first need to open the project from the
file menu. The overall layout of the menu system in Petrel is similar to most windows
based programs, with icons arranged within folders in a tree view in the Input tab of the
first Petrel Explorer.
The various parts of the Petrel user interface are described below:
Title bar - The file name (project name) and location is displayed in the Title bar. Press
and drag the Title bar to move the Petrel screen on your desktop.
Menu bar – (Top) Click on any of the Menu bar headings to access a list of dialog
boxes, pop-up menus, commands and features.
Toolbar - (Top) Tools for commonly accessed commands. These tools are useful
shortcuts for items that can also be found by accessing the Menu bar.
Function bar - (Right) Process specific functionality. These tools change as different
processes are selected in the Process diagram. Note that there can be two Function bars –
one on the right hand side and one below the Display window.
Petrel Explorer – (Left) A file manager for optimizing all related model data. Consists
of three tabs.
Process diagram - (Left) Four tabs process diagram (access to the process in petrel),
process manager (automate processes) and the windows tab (control the plots and
windows in the project.
Display window - Checked items in Petrel Explorer will be displayed in the active
Message bar - (bottom left) Information on processes will be displayed here.
Info Bar - (bottom right) Shows information of the selected item in the active window.
An hourglass is displayed when a process is running.
The first Petrel Explorer contains four tabs for different types of data , however, only the
first one (Input) will be used for the majority of this course.
Input – imported data such as lines, points, gridded surfaces and SEG-Y data is stored
here. Output data of the same kind is put here as well, e.g. if a set of internally modeled
faults are converted to polygons, the generated polygons will automatically be put here.
Model – internally created data connected with a 3D model (such as faults, trends and 3D
grids) is stored here. Imported grids (3D models or parts of models) and properties will
also be put here.
Results – the numerical results of volume calculations and simulations are held on this
tab such that they can be browsed and any reports made.
Templates – color tables and all the different templates are stored under this tab.
Basic display options.
First Petrel Explorer.
Second Petrel Explorer.
The second Petrel Explorer (also called the Process dialog) also contains four tabs with
links to different types of information. Again we will mostly only use the first one.
Process diagram – a list of all the process steps available in Petrel. Some process steps
may be inactive – if they are not licensed. These are marked with a No parking sign.
Some process steps will be grayed i.e. inaccessible in the early stages of building a
model. It implies that data for these steps is inadequate. These process steps will become
available as soon as data required to use them is generated.
Cases – cases are the input to a volume calculation or a simulation. They represent one
possible representation of reality i.e. they contain a grid, a single property model etc. etc.
Each time either a simulation or a volume calculation is created, a new node will appear
here. These act as filters for the display of results.
Workflow – Workflows generated in the project for automating mapping tasks or
rebuilding model grids are held here.
Windows – a list of all windows in use in the project. This is the place for deleting a
window permanently or to turn off a window for later use. Each window will have a list
of related tools like axis, legends e.g.
In order to view the detailed options available for each process in Petrel, you need to
open a window from the Window menu. Open a 2D window to begin with. Now when
you click on each of the processes in the first tab of the second Petrel Explorer, you will
see a different series of icons appear along the right hand side of the screen. When you
move the mouse over each icon you will see a description of what it does.
Further options related to each of the objects in the Input tab of the first Petrel Explorer
can be accessed by either double clicking on them or by right clicking and selecting
settings. The settings window that appears allows you to change the display style of the
object, view statistics related to it and to perform various operations on the object.
By clicking on the tick boxes next to each object in the First Petrel Explorer, you can turn
them on and off in the display window. General objects, such as the North arrow, legend,
grid lines etc can be turned on and off from the display toolbar that runs along the top of
the screen. Move the mouse over each icon to see description of what it does.
Further descriptions on the user interface (and functionality) of Petrel can be found in the
Html help file that can be accessed through the Help menu. It is a good idea to keep this
open whilst you are learning your way around Petrel.
2. The Spitsbergen Dataset
The dataset for this course is taken from the Isfjorden area in Spitsbergen. The main data
types available to you are listed below:
Cultural Data – This folder contains a series of polygons that define the water depth.
Seismic Surveys – This folder contains the 2D seismic lines that will be your main
dataset for this course.
3. Window Types
The Window menu allows you to open various different types of display window. The
four that you will use during this course are listed below, along with a description of the
mouse button controls for each window type. Try to open each window type in turn and
then turn on some data objects and practice the mouse controls.
If you set both the main Petrel window and the individual windows
within it to Restore (as opposed to Maximise) you can drag the main
window across both of your screens in order to give you enough space
to view at least two windows at the same time.
2D Window – Used for viewing the position of data objects in map view. In this window
holding down the left mouse button will allow you to zoom in and out, whilst holding
down the middle button (wheel) will allow you to pan the view.
3D Window – Used for viewing the position of data objects in 3D space, this view can be
very useful for understanding how your well, seismic and surface data relate to each
other. In his view the holding down the left mouse button will allow you to rotate your
objects in 3D space, the middle button (wheel) allows you to pan, whilst holding down
them both together will allow you to zoom in and out.
Interpretation Window – Used for viewing seismic and well data in a vertical 2D
display, and for interpreting surfaces and faults from the seismic. In this display the left
mouse button allows you to pan the display, whilst moving (not holding) the mouse
wheel allows you to zoom in and out.
Well Section Window – This window type allows you to view and correlate well data and
well tops in a vertical 2D display.
4. Seismic Interpretation
Open a new Interpretation window and turn on a 2D seismic line. Take some time to look
at the character of each surface in the seismic and see if you can trace them across the
basin between the two wells. You can also turn on the two regional surfaces to help you
get your eye into the stratigraphy.
If you want to change the colour of the seismic
display, you can do this by going into the settings
for the line you are looking at, and selecting a
different colour template from the drop down menu
on the Info tab. If you want to fine tune the colour /
adjust the contrast etc, you can do this by clicking
on Colors tab. The top right icon on this tab (the
white piece of paper icon) will return the settings to
default if you don’t want to keep the changes you
Once you have oriented yourself with the seismic
interpretation window, you can start to interpret
your first horizons and faults. In order to bring up
the seismic interpretation options you need to have
a seismic interpretation window as your active
window, and also highlight the Seismic
Interpretation process under Geophysics section in
the second Petrel Explorer. If you have done this
correctly you should now see the following icons along the right hand side of your
screen. The main functions you will use during the first part of this course are highlighted
To begin interpreting a horizon you need to click on the Activate Horizon Interpretation
icon and select the interpretation mode you will use by clicking on one of the icons under
the Activate Horizon Interpretation icon. The three options for 2D data are listed below:
2D Autotracking – Petrel will attempt to automatically interpret a horizon for you when
you place a “seed point” by clicking on a point somewhere along a seismic reflector. This
option works ok for surfaces which are very laterally consistent (e.g. the seabed) but does
not work so well for more complex or faulted reflectors.
Guided Autotracking – Petrel will try to autotrack between seed points that you create by
clicking along a reflector. This provides more control than full 2D autotracking, but may
also have problems when interpreting complex surfaces.
Manual Tracking – This option is similar to the guided autotracking function, but will
try to link your points together with straighter lines. For some complex surfaces even this
option may be too sensitive, in which case you will need to activate the full manual
option by turning off the snap to features function on the Autotracking tab of the settings
for the horizon that you are working on (see also below).
When you place your first point on the seismic you will notice that Petrel creates a new
Horizon Interpretation under a folder called Interpretation folder in the Input tab of the
first Petrel Explorer, you can double click on this to access the Autotracking tab
mentioned above, as well as changing the display style and name of the horizon.
Take some time to practice with all three interpretation modes. If you want to delete some
of the points that you have interpreted or Petrel as autotracked, click on the Eraser icon in
the seismic toolbar (right hand side of your screen) and then click on the points you wish
to delete. You will need to click on Activate Horizon Interpretation again to go back to
interpretation mode again.
When you have finished interpreting your first horizon and want to start a second one,
click on the Deactivate Current Interpretation icon in the seismic toolbar. When you next
click on the seismic section Petrel will automatically start a new interpretation for you
and add it to the interpretation folder. You will notice that the new surface is highlighted
in bold, whereas your first surface will be in normal text – this indicates which horizon is
If you click on the first one again it will become bold and you will be able to add more
points to it by clicking in the interpretation window. This system allows you to alternate
between as many horizons as you want, and to add points interpreted on different seismic
lines to the same interpretation. To see how this works, turn on a different seismic line in
your interpretation window and interpret the same surface. When you turn on your
interpretation in a 2D or 3D window you will see that it contains points that have been
interpreted on both lines
If you accidentally interpret a surface as two separate interpretations on different lines,
you can merge them back into one by going to the Operations tab on the settings box for
one of the interpretations and using the “Append Points” operation, which can be found
under the Common Operations folder. Highlight the interpretation you wish to merge in
the first Petrel Explorer and then click on the blue arrow next to Points to append: then
click Apply or OK. All the points will then be held as a single interpretation again.
The process for interpreting faults is very similar but more simple than for horizons.
Click on the Activate Fault Interpretation icon to begin, and then click on the seismic
section to interpret your fault. The system for deleting points, starting a new
interpretation and continuing an existing interpretation is the same as for horizons.