Pore Pressure Evaluation and Prediction in Esenam Field Northern Depobelt, Niger Delta Nigeria

Abstract

Pore Pressure Predict ion is a co mmon pract ice before drilling operation in the oil and gas industry. This is very important to avoid surprises such as blowout. Indirect method of pore pressure evaluation and prediction was undertaken in Esenam Field located in the Northern Niger delta basin of Nigeria using wireline log data. The overpressure indicators used are the sonic, resistivity and bulk density logs fro m eight wells drilled in the field. It was revealed that the deeper part of Esenam field (Agbada Format ion) is overpressured. Inference fro m the analysis of sonic and density log data shows that overpressure in this field could primarily be generated by disequilib riu m co mpaction. The depth to the top of overpressure zone falls within the r ange of 2261±5 metres to 2280±10 metres subsea; this is based on the deviation from normal co mpaction trend curve. Pore pressures are accurately predicted using an Eaton exponent of 3.0 and 1.2 for wireline log data.