Sonic Log Porosity

Calculating sonic log porosity

Common matrix travel times:
(microseconds per foot)
sandstone = 55.6
limestone = 47.5
dolomite = 43.5
anhydrite = 50
salt = 67
drilling fluid = 189

(multiply by 3.28 to get microseconds/meter)
This program calculates sonic log porosity, corrected for shale and uncompaction effects if desired. It can be used with either English or metric data.

If the shale travel times are greater than 100 microsec/foot, then the shales are probably uncompacted. The presence of hydrocarbons in uncompacted zones will make the porosity even higher.

Be careful choosing travel times in shales. If the hole is washed out, a high travel time may be due to cycle skipping. Keep in mind that there often is no satisfactory way to correct a sonic log, and watch out for older, non-compensated sonic logs that are overly affected by borehole conditions.


Do you want to save your calculations? The input box at the very bottom of the screen records all the inputs and outputs for each calculation run. To save this information, select all the text in the box and copy it, then open a spreadsheet and paste it in as comma-separated values. Each data type will land in its own column, and each calculation run, or depth, will occupy a row. Format the spreadsheet to separate rows into different geologic formations, and you're done. Isn't that easier than writing everything down?

Don't have a spreadsheet handy? If you are working on a phone or a tablet, you can still copy the text and paste it into a note or an email.

The Recording box will reset if you press the "Help" or "Reset" buttons, or if you navigate to a different page.