Oil company wants to buy MY WATER to drill and frac

Oil company wanting to use water off of my property to drill and frac a well.... I know "fresh" water is going for .40 to .50 cents per bbl... this is probably not "fresh" water but good enough to frac with.... what would be a fair price to charge these folks per bbl???? Thanks for any help.

Midland County? 50 cents per barrel and up, even if brackish.

Thanks Wade, I do appreciate it.