On a completely technical noteThe Reeves and Ungani zones are...

On a completely technical note
The Reeves and Ungani zones are fundamentally different.
Reeves is a sandstone - in this case, think glacial riverbeds choked with sands left behind by retreating glacier
Ungani is a dolomite - a carbonate deposited as limestone and then chemically changed through time to a dolomite - poorly understood since you cannot study a 'modern' dolomite and the chemistry is dependent is highly contested in academic literature. You could make a full career in trying to understand even one dolomite field.

Having potential is both is superior to only one but geos and especially engineers prefer sandstones.
Without boring readers, sandstones are layered, have relatively predictable parallel beds and the detailed knowledge measured in well-bores is more easily extrapolated to the rest of the field. The reservoir engineering algorithms were calibrated on sandstones. Dolomites are a pain in the ass but can be lucrative (very very lucrative in some cases). Typically the magic pudding way of developing them takes time and experimentation.

Likely there are more than a few Buruites that hope and pray the Reeves works again and again so the exploitation of the field is less problematic.