I think the normal average ratio for failure/success in this situation is in the ball-park of 3:1, which is a huge improvement on the results of random selection of a drill target.
However, given the amount of data/3D previous drill by BHP etc that ratio could easily be reversed 1:3 in favour of success (maybe even higher).
I have a simplistic mental model, that it's a bit like a game of battleships, all information gained from the first strike or miss greatly determines/improves the odds for subsequent drill results (this of course disregards gas/oil quality).
NEN Price at posting:
34.5¢ Sentiment: Buy Disclosure: Held
