Category Archives: Geology

Compare lists from text files using Matlab – an application for resource exploration

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INTRODUCTION

With today’s post I would like to share a Matlab script I used often to compare lists of ID numbers stored in separate text files. The ID numbers can be of anything: oil and gas wells, mining diamond drill hole locations, gravity or resistivity measurement stations, outcrop locations, you name it. And the script will handle any combination of ASCII characters (numbers, letters, etcetera).

I included below here some test files for you to try with the code, which is in the next section. Please refer to the comment section in the code for usage and file description. Have fun, and if you try it on your lists, let me know how it works for you.

TEST FILES

These files are in doc format; they need to be downloaded and saved as plain txt files. Test1 and Test2 contain 2 short lists of (fake) Canadian Oil and Gas wells; the former is the result of a search using a criterion (wells inside a polygonal area), the latter is a list of wells that have digital wireline logs. Test3 and Test4 are short lists of (fake) diamond drill holes.

*** Notice that script is setup to compare list in Test2.txt against list in Test1.txt and not the other way around. If using this on your own lists, you will have to decide in advance which subset of wells you are interested in.

Test1

Test2

Test3

Test4

THE SCRIPT

Here is the code:

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Image processing tips for geoscientists – 1

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Today I would like to show a way to quickly create a pseudo-3D display from this map:

Original image

The map is a screen capture of a meandering river near Galena, Alaska, taken in Google Earth. I love this image; it is one of my favorite maps for several reasons. First of all it is just plainly and simply a stunningly beautiful image. Secondly, and more practically, the meanders look not too dissimilar to what they would appear on a 3D seismic time slice displayed in grayscale density which is great because it is difficult to get good 3D seismic examples to work with. Finally, this is a good test image from the filtering standpoint as it has a number of linear and curved features of different sizes, scales, and orientation.The method I will use to enhance the display is the shift and subtract operation illustrated in The Scientist and Engineer’s Guide to Digital Signal Processing along with other 3×3 edge modification methods. The idea is quite simple, and yet extremely effective – we convolve the input image with a filter like this one:

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