maruja 2 update..., page-6

keep it simple and it's not too difficult to understand.
Oil floats on water (due to density contrast).

Maruja 1 found a thin reservoir with oil that flowed at good rates, but NO water or water contact was seen at this well location.... in other words it is oil on rock and they dont know where the water contact is (at that time).
Maruja 2 -both wells found good reservoir but which also found water, hence no oil.

So they know how far down they have water, but updip (beacuse oil is above water in the same horizon) there must be a contact. An oil-water contact will give them the oil column and from that they can calculate how much is likely (always as a range due to uncertainties).

So they may need another well to find out. The question (and risk) is do they think they have enough remaining potnetial to warrant another well.
The assumption is that the reservoir unit is continuous which is not always the case. It could be discontinous (i.e. a stratigraphic limitation) which complicates things. So there still could be potential. They are saying that they need more time to evaluate the results.

Never a slam dunk in this business.