CAC, while I agree with you that there is a little bit of a Heisenberg cat in there (once discovered, the gas is no longer undiscovered), it really isn't custom to reward companies for undiscovered gas, and less so when the drilling of the first well are carried. Tot buys a stake in PRL 15 as a whole, but as a potential bonus, it rewards IOC for an additional find and even pays for the first well. It isn't that material when you compare it with InterOil's 30% stake in PRL 15 and the LNG plant, they're likely to make much more of any undiscovered gas (once discovered) in PRL 15, but it's a tacit acknowledgement from Total that there probably is a lot more in PRL 15 than just EA.
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I suppose this arrangement could provide a benefit (i.e. a "reward"
if IOC internally questioned whether they were going to be willing/able to spend their own money to ever "discover" the additional gas in those locations. Maybe they like Triceratops' potential better and knew internally that these other areas would just sit idle for a long time if they had to go it alone. Maybe they thought..."We don't feel super-confident that there's more gas there but if TOT wants to spend their money looking...we'll happily take what we can get if they find some"???