Setting aside DHIs where bright and flat spots can be interpreted as direct indicators, seismic doesn't really send back signals when it hits oil or gas, more sends back signals of the reservoir rock. Which, without nearby control, can be out. However in this case I would think it's less about seismic correlation and more about the complexity of the trap. It's not a simple trap like an anticline which is a little like an upside down teacup that collects all the oil migrating upwards.. HTDs can be very vertical reservoirs with highly erratic distribution based on the faulting, shearing, fluid pulses, facies distribution, brecciation etc etc etc. You look at 10 different diagrams and they'll all be different shapes:
And within those structures you have to find rock in the right phase of mineralisation. It can be underdone or overdone..
Only Buru will be able to say for sure but if it's more prospective deeper in the prospect then it's going to be some dynamic based on the the type of rock at the top of the Nullara vs the type of rock at the bottom and how exposed each were to the HTD processes. It could be the top was less exposed due to the exact nature of the upper facies and fractures/permeability to allow exposure to basinal brines or perhaps that they were over exposed compared to the bottom. And really top and bottom is almost the wrong way to think about it. Given you need to find the reservoir in the "just right" stage of mineralisation it's also looking at distance from faulting. Maybe as the drill was going deeper it was gradually intersecting more and more of a variably porous section between the leached halo and the over dolomitised/saddlerised dolomite.
Hopefully you can see from these diagrams that no one is really going to have a good answer right now. Very encouraging that they're back on the tools though.
