gas shale porosity calculation

[Anulacp]

Hello,
I need your help. I need to calculate porosity in shale (potentially gas/oil shale). Can I do it freely using sonic log (using Willy equation)? Is there anything against? I have no density log. Actually, I have neutron log, that could be better indicator of porosity, however it is not calibrated into porosity units, and I do not know how to do it with no software for log interpretation or petrophysical calculations. I have only logs on papersheet and a pen, and Exccel spreadsheet. Besides sonic log there are also GR log and laterolog curves at my disposal.
Thanks

[kochichiro]

I highly do not recommend to use sonic logs for porosity estimation in gas reservoirs, because of gas effect.
The best source of porosity data in gas shale is, of course, density tool.
In my opinion you have only two options to calculate porosity:
- first – to calibrate neutron logs with straight line method;
- second – to calculate sonic logs from resistivity data and calibrate real sonic log for gas effect.