This TIPS&TRICKS illustrates the process of importing and geo‐referencing map and seismic data bitmap images, and how they can be used in interpretation workflows. This type of data is easily obtained from professional society and other technical publications, or from a corporate archive database. It can be used to fill gaps in the existing project data or incorporate the results of previous studies in the current interpretation. Image data must be loaded and geo‐referenced properly before being used in Petrel. They can be positioned either horizontally as a slice, or vertically as a profile.
Map images oriented as a slice can be used to guide the creation of contours, and cultural data, as well as draped on existing surface interpretations to enhance visualization and control quality. Seismic data and geologic cross section images can be obtained from literature and loaded as profiles to guide interpretation.
Import
Right‐click on a folder in the Input pane and choose Import (on selected)… Images are easily imported to Petrel using the Bitmap image (BMP,JPG,TIFF,GIF,PNG) file type option in the import window.
Petrel is sensitive to the image file size. Large image files may not load. In this case the file needs to be rescaled outside of Petrel to a smaller size for import. Cropping the image outside of Petrel to remove any unnecessary data will further reduce the file size and make positioning easier.
Once the file is imported, it must be located correctly in the world, or geo‐referenced, for use in interpretation. This requires that several points, whose locations are known, are loaded into the project and also exist in the image for reference. The accuracy of positioning images in Petrel is limited by constraints imposed by the software. Images are positioned using only 3 points corresponding to corners of the image. Reference points other than 3 corners of the image must be tied visually by trial and error adjustment of the X, Y, and Z coordinate of one or all of the three corners in a display window. Further limits on the accuracy of positioning are imposed by the fact that the image can only have 4 sides or borders, no hinge lines are allowed, and opposite sides must be parallel. This impacts the positioning of 2D seismic profile images the most due to the fact that 2D seismic lines are rarely if ever straight. Therefore, irregularly shaped or hinged 2D seismic profile images may not be appropriate for interpreting in this manner. 3D seismic inline and crossline profiles are straight by design and are more suitable for this type of interpretation.
Map Data
Images must be located, or geo‐referenced, correctly in the world before interpretation begins. The image can easily be given a general location initially by using data already in the Petrel project.
1. Open the Settings of the image by double clicking on it in the Input pane.
2. Select an object in the Input pane you want to use as reference and make it active. An active object has bold font in the Input pane.
3. Press Set from selected to get the location limits from the existing object.
The positioning of the image must then be fine‐tuned using known locations and reference points on the image. Petrel allows you to adjust the X, Y, and Z coordinates of three corners of the image. This is an iterative process. Start by adjusting the coordinates to large whole numbers to make it easier in the beginning. Continually check opposite corners of the image for a tie to the reference points after each adjustment. Substantial shifts in the ties may occur on the opposite corner of the image after coordinate adjustment, especially if there is a large distance between the reference point and the edge of the image due to stretching or squeezing.
1. Display the image and reference objects in a 2D window.
2. Position the image as accurately as possible using the Orthonormal method. This method allows you to adjust the X and Y of the origin location, the Y location of one adjacent corner, and the X location of the other adjacent corner, maintaining the aspect ratio of the preliminary coordinates. Be sure to uncheck the Relative to selected “Origin” box at the top.
3. Change the method to Independent edges and fine‐tune the position by adjusting the X and Y coordinates to align reference points common to both the project data and the image. Reference data commonly used are well locations and property boundaries. Skewed, distorted, or otherwise poorly produced images will be difficult to position accurately.
Once the image is positioned correctly it can be used to enhance visualization of an existing surface.
1. Open the Settings dialogue window for the surface you want to enhance.
2. Go to the Style tab.
3. In the Solid subtab, change the color option to Textured.
4. Use the blue arrow to enter the image file as input in the box that appears.
12. Enter a z value you want to assign to a contour.
13. Click on the Select and edit line icon , select the line you want to adjust, and click on the
to set the z value for the contour.
The digitized contours and faults can be used as input in the Make/edit surface process.
Seismic Data
Seismic profile images can play an important role in Petrel interpretation workflows. Useful images are often included in technical reports and publications and can be used to provide insight or guide an interpretation. They must have features that enable them to be accurately geo‐referenced with objects already loaded to the project. Features like IL/XL or CDP/SP annotations are required to accurately orient the image geographically. You will also need time/depth annotations to properly scale the image.
The following example uses images from a publication to help guide a new interpretation in the same area. The seismic profile image does not have IL/XL annotations. Another image shows the location of the seismic profile image in relation to a known reference. The seismic profile image will be positioned in map view based on this and then fine‐tuned and adjusted in depth to existing seismic data.
1. Import the base map image showing the seismic profile image location.
2. Geo‐reference the base map image with the field boundary polygon that has been loaded to the project.
3. Create a polygon that represents the line of section for the seismic profile image. Make sure that the template of the polygon matches the domain of the seismic.
4. Copy the line of section polygon 3 times and set the Z value of each to match one of the depth annotations on the image (‐500, ‐1000,‐1500) to be used as reference.
5. Import the seismic profile image. Use the line of section polygon to initially position the image.
Project reference data Base map image Seismic profile image
8. Adjust the Z coordinates until a visual match is established with the reference polygons.
9. Create a vertical intersection from the line of section polygon by right clicking on it and selecting Create vertical intersection.
10. Display the project seismic data in the vertical intersection by clicking on the blue button or using the keyboard shortcut Ctrl B and selecting the volume to display from the input tab.
11. Make a copy of the line of section polygon and use the Equal space operation to insert points at regular intervals to use in positioning the profile image.
12. Adjust the X and Y coordinates of one side to closely match the project seismic displayed in the vertical intersection using the points created in the previous step as reference.
13. Display a seismic line from the project that intersects the image and fine‐tune the image Z coordinates to obtain a visual tie. Differences in the data used in the image and the seismic in the project may prevent an exact tie.
NOTE: Images in Petrel are restricted to the depth domain. It cannot be changed by the interpreter. In order to display with time domain seismic you must set the domain of the display to Any. This is just a technicality because the image is referenced to the scale of the project seismic data, regardless of the domain.
