Depends on what your lease has for liquidated damages (most leases are $2,500.00/acre) The most I've heard people being paid is $5K/per acre plus FMV for timber. Most pads are now in the 4-5 acre range since the permitting is easier on a smaller pad. It is an intersting thing though people are getting paid more then their lease requires for liquidated damages.
adubu,
One more thing to think about... Aside from giving up the land for the pad site, it may be that the remaining well depreciates the vaule of your remaining land. I know people who allowed a pumping station on their lakefront land 50 years ago for $1000. It is still there today and they cannot get rid of the eyesore. It really detracts from what is an otherwise absolutely beautiful property.
I'm not saying you shouldn't let them drill -- they have to drill somewhere. But consider writing the contract with enough protections that the well (and fence, and road, and electrical lines) won't diminish the rest of your property for the next 100 years.