help me to calculate Shale volume

[Shakespear]

There is a simple answer but it does not always apply to every situation :-(

Use several equations for calculating shale content (word clay is also used here) ,Vshale, and use the minimum Vshale calculated.

However the local lithology and the tools you use influence Vshale values you will get.

For example, Gamma Ray Tool is popular as a basic Vshale indicator. However you will not be able to use it if there are radioactive sands in the zones of interest.

You take the value of GR in the nearest 100% shale, take the GR value where YOU thing you see 100 % sand. Using the simple ratio equation you calculate what fraction of sand-shale you have in the zone you are analyzing. Notice this is very SUBJECTIVE (you need to make a decision as to what is SHALE and what is CLEAN SAND, which may be off by say 10%) leading to potential errors. This is where experience comes !!!!

In Limestone/Dolomite environments GR maybe useless. Or if you have a mixture Limestone/Sandstone, GR is not good. What to do? You use X-plots and here you need to do a little reading and use a spreadsheet or a computer program :-)

The following book may help you out.

[link Point to another website Only the registered members can access]
Another POTENTIAL problem to remember is that the logging tools may not be calibrated correctly !!!! Then you calculation are completely suspect or useless. Here we need to look into Quality Control of the logs. You look at the log readings in same lithology zones in different wells and see if the log reading are similar. This is just one way of doing this. There are other things to look at.

Hope that helps

PS: Try not to make this too complicated. Read about it, try it out and then talk to a geologist or a log analyst for help. If possible that is.