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| How can I create a lithology log from an LAS file? |
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There are two problems with this creating a lithology log from an LAS file:
1. Lithology and zone bar logs need to have interval-based data, not depth-based data.
2. You need some sort of text describing the lithology (a keyword).
If you want just a simple lithology log, I suggest using a zone bar log for this. If you want a more complex log (including indents and indent line styles), then I suggest using the lithology log.
There are three methods you can use to modify the LAS file so that you can create a lithology or zone bar log from the data:
1. Load the LAS file into Strater's data table, and then convert the LAS data table to an interval table using the Table | Convert to Interval command. This will create an interval table that you can use to create a zone bar or lithology log. However, the interval may be very small depending on the spacing of data in the LAS file. You will need to add a new column of data (Edit | Append Column) and enter a lithology keyword for each interval. Since there are so many rows of data, this may not be viable.
2. Create an interval table (zone bar log) or a lithology table (lithology log) by going to File | New | Table and type in the data yourself. You would add the Hole ID (the same for all rows), the From and To data (for example, 2275 to 2355 could be the first interval, 2355 to 2365 the second, etc), and the lithology keyword. This way, you could divide the depth up into your own custom intervals. You may be able to determine the intervals you want by looking at a line log of the data in the LAS file. If you only have a relative few intervals, this would be the easiest. Then create a zone bar log (or lithology log) from this data table.
3. If the lithology is dependent on some other variable in the LAS file (ie. all the high GR values are one lithology, all the medium ones are another, and all the low GR values a third lithology), I suggest converting the LAS data table to an interval table (Table | Convert to Interval), then use Data | Sort and sort it by the variable used to determine the lithology. Once it is sorted, enter in the lithology keyword for the first cell in the range of values in a new column, and copy it throughout the entire range (ie. for the range where GR is 50-75 copy "sandstone" or whatever in a new column). Repeat for all lithologies. When you are finished, resort the data based on the From column so that the data is in depth order again. Create the zone bar log (or lithology log) from this table. When you create the log, select the log and make sure Merge Intervals in the Property Manager is set to True.
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