ABSTRACT

Well overpressure, if not adequately anticipated can cause several mishaps such as blow outs, oil spills, which can lead to loss of lives, properties and rig time. This study analyzes two wells obtained from the field X in offshore Niger Delta to estimate pore pressures, and determine if the formation is overpressured. To accomplish this, Gamma Ray, Neutron Porosity and Density, and Resistivity logs were first, used to identify possible pay zones. Overburden pressure, shale volume and Normal Compaction Trend (NCT) were then calculated from density log, gamma ray log and sonic velocity logs respectively using Ikon Science’s Rokdoc software. Finally, the pore pressure was predicted with the same software, making use of Bower’s model for pore pressure prediction.

From zonation, three zones of interest were identified in well A at 3753m-3840m, 4156m-4185m and 4032m-4058m. Four zones of interest were identified in well B at 3342m-3356m, 3500m-3518m, 3558m-3612m and 3827m-3925m. Observing the pore pressure values in all zones, it was observed that all identified pay zones are overpressured. Cross plots of Sonic velocity against depth, resistivity against depth and Density against depth for both wells were used to confirm overpressure at the said depths.