Ann: Alameda-1 Drilling Update, page-369

Great question. I asked myself the same.

Lots of reasons and even for them (theyre pretty smart folks make no mistake about it), there is still speculation. I suspect the pressure they hit was associated with a discontinuity/fault zone, which is fairly distinct. They know that imbricated formations/reverse faults are the order of the day here. These fault zones may be "compartmentalised" and have different permeability, fluid composition and pressure conditions to the surrounding reservoir. So they looked at the logs, and said where do the "normal" reservoir conditions persist to? OK, we will back off, drill sidetrack and test the reservoir zone, away from the potential influence of the high pressure/fault zone.

Herein, lies another clue as to the water intersected. The Marti did not hit water, based on the logs. So the presence of water in a zone of high pressure/deteriorating hole conditions, much higher than the recorded oil intersections in the Marti well further reinforces the interpretation of the Alameda well intersecting a faulted zone in the Marti sequence, mid way through the expected oil column as seen in the nearby Marti well. The Marti well drilled the same formation so we're not talking analogues here, we're talking direct correlation.

Like others inc @jakspara Id be happy to hear@VOGC and others take on this.
Still 300 posts to get though so maybe already answered by someone.