Estimation of Overpressures in Onshore Niger Delta Using Wire-Line Data

In this study, we have estimated overpressures using well logs from three wells in onshore Niger Delta Field. Key logs required for the prediction were conditioned and quality controlled to meet the standard required for reliable results. The overburden stress (or true vertical stress), normal compaction trends (NCT) and shale velocity trends were generated from the volume of shale, density, gamma, resistivity and sonic logs. Prediction points were picked at depths with thick shale and where there are no washouts (identified from caliper log). Pore pressures in the wells were then predicted using Eaton-s exponent of 5 and compared with measured pressures (RFT data). Overpressures were estimated by observing the deviations of the predicted fluid pressures from the hydrostatic pressure line. The results obtained from the analysis reveal that two of the three wells are mildly overpressured at all depths while one well (G-005) experiences hard overpressure at a depth of about 15400 ft. The predicted Pore Pressures also compares favorably with the measured pore pressures at the three well locations, indicating that the Pore Pressure Prediction model used in this work is suitable.