Import Uncalibrated Raster Logs

  

The Raster Calibration utility provides options for straightening, depth calibrating, and digitizing a raster image; you can also pick formation tops and pay intervals. It is a quick way to view a raster log without using the Cross Section Module.

To import un-calibrated raster logs:
  1. On the Main Module, select the Rasters tab.
  2. Click the “Calibrate…” button to open the “Calibrate Log Image” tool.
  3. Select the button on the toolbar.  Alternatively, select File > Open on the menu bar at the top of the screen.  Next, navigate to folder containing the images and select the desired image file.  By default, Petra will look in the the project’s IMAGES folder.
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It’s usually worthwhile to spend a few seconds scrolling up and down through the image to see what’s actually there.  Usually, raster images store a complete copy of the scanned paper log, which can contain the same log at different scales as well as repeat sections.
  1. A scanned log is just an image, so Petra needs a way to know how the image corresponds to depth.  Select the “Add” button on the right side of the screen; note that this turns the mouse pointer into a line.  Click right on the 1200’ marker, and enter in the depth.
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  1. Scroll down the image to 5400’MD, and add another depth calibration point.  Notice that Petra automatically extrapolates depths between two depth points, which are marked with thin black lines.  Commercially depth-calibrated logs often have dozens of calibration points, most of which are unnecessary.  Well-scanned logs that minimize image stretch really only need a few points.  In our case, the calibration is pretty good for most of the depth range, but could use improvement.  Add more depth calibration points where the calibration is off (around 2400’MD and 4900’MD).
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  1. Now that the top part of the well is calibrated, scroll to the 5” section, and add a calibration point just a little below the 5400’MD line.  Put the depth in as 5401’MD.
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  1. Add a point at the TD marker at 6424’MD and at a few more points to get a good calibration to the image.  Again, add depth calibration points where the black lines are off the 100’ intervals on the log.  Notice that Petra will add thick black lines in the correlation – these are actually the tops we imported earlier.
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  1. Select the “-“ button to zoom out on the section.  Right now, we have two sets of depth calibration points over the image: a shallow set over the 1” log, and a deeper set over the 5” log.  In between, there’s a lot of extraneous information that we’d rather just cut out.  Select CTRL and click somewhere in the region between the shallow and deep set of calibration points.  Notice that the section goes dark, signifying that it won’t display on cross sections.  In our case, this will just keep the entire section from being crammed into a tiny sliver between 5400’MD and 5401’MD, but this technique can be really useful to cut out other extraneous parts of an image.  This technique is also useful for cutting out a repeat section between one run and the next.
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  1. Select the “+” button to zoom back into the image.  The next step is to add scales.  Petra can draw both an upper scale and a lower scale on the same cross-section.  Scroll to the bottom of the depth calibration points.  On the “LwrScl” section, select the “Top” and “Bottom” buttons to set the boundaries of the upper scale marker.
    Next, scroll to the top of the image.  On the “UprScl” section, select the “Top” and “Bottom” buttons to set the boundaries of the upper scale marker.
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  1. Scroll to the very top of the image.  Add the top and bottom of the header with the “Top” and “Bottom” buttons in the “HDR” section.
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  1. The final step is to add a group name.  Group names usually describe the depth-calibrated part of the image – usually by describing the scaling or the curves.  Right now there’s only one group name – “DEFAULT.”  On the menu bar at the top of the screen, select Group>Add or Delete Groups.
From a user-perspective, group names are a way of comparing similar raster images from one well to another.  Though commercial vendors generate thousands of unique group names for every combination of tool and scale, it’s usually better to have fewer, more general group names rather than many excruciatingly exact ones.  In the Image Group Name entry, type in “Induction”, and select the Add button.
  1. Select the Done button.  Back in the Calibration tool, use the group name dropdown and select “Induction.”  Select the button to save the calibration to the group name.  Behind the scenes, Petra’s actually creating a LIC file that saves these calibration points – the location of which is shown in the “Save File As” window.