Changing down-hole conditions observed during hydrocarbon exploration can be
divers. Some desired ones concern oil/gas shows while others may vary from
borehole/drilling fluid association and pressure situations. Managing pressure variations
and geopressure zones while drilling has been an issue of concern which has yield generic
positive results over the years. However pre-pressure zones (i.e. zones above pressure
zones), can display characteristics that are worthy of note in view of the underlying rock
potential. Pore pressure and fracture pressure has been evaluated using Eaton’s equations
amongst others on data for some reservoir of Agbada formation in the petroliferous Niger
Delta. This is in view of knowing the potential of this pre-pressured zone with effective
porosity and water saturation necessitated by production operations and well re-entry
processes. These computations adopted various pressure models and have yielded good
result presented as plots. It was observed that depth of rock units is the main indicator of
rock shrinkage leading to increase in fracture due to increase in production and hydraulic
fracturing. Adequate attention must be paid to the integrity (density) of the explored
formation as they become sandwiched with under-compacted argillaceous sediments
