Statistically if you take 10% chance of success across four...

Statistically if you take 10% chance of success across four holes then the way to calculate it is by saying that there is then 90% chance of failure on each of the four holes, so the chance of success in one of them out of four is:

0.9 * 0.9 *0.9 *0.9 = 65% chance of them all failing = 35% chance of success, where success is any one hole succeeding.

Chance of all four succeeding is

0.1 * 0.1 * 0.1 *0.1 = 0.01%.

Now this all assumes the chances of success in any hole is totally unrelated to any of the other holes, which is probably far from true due to them being in the same basin formation (as I understand it), but still gives you an idea.

I would think that based on information at hand 10% might be a little low, but just guessing.