Because of the following two reasons, you cannot directly create a lithology log from an LAS file:
- Lithology and zone bar logs need to have interval-based data, not depth-based data.
- You need some sort of text keyword describing the lithology.
However, there are three methods you can use to modify the LAS data so that you can create a lithology log or zone bar log:
- 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 Table command. This will create an interval table that you can use to create a zone bar, however, the interval may be very small depending on the spacing of data in the LAS file. You will need to update the To depth column to use the From depth value for the next row, and you will need to add a new column of data (Data | Edit | Append) and enter a lithology keyword for each interval. If there are many rows of data, this may not be viable.
- Create a lithology table by clicking Home | New | Table and type in the data yourself. You would add the Hole ID (the same for all rows), the From and To depths for each interval, and the lithology keyword. This way, you could divide the depth 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 have relatively few intervals, this method would be the easiest of the three. Then create a lithology log from this lithology table.
- 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 to sort it by the variable used to determine the lithology. Once it is sorted, click Data | Transform and enter your lithology for the given rows. For example, if GR between 50 and 75 is sandstone, and that interval is in rows 1-100, enter D="sandstone" and specify rows 1-100. Repeat for all lithologies. When you are finished, re-sort the data based on the From column so that the data is in depth order again. Create the zone bar log from this table. After creating the log, select it and make sure Merge intervals in the Property Manager is set to True.
Updated: June 30, 2016