Unloading Mechanism: An indication of Overpressure in niger Delta (‘X’-Field) Using Cross Plots of Rock properties

This study has investigated the unloading mechanism causes of overpressure and delineated the overpressure zones in X-field Niger Delta. The Niger Delta basin has many overpressure zones with different origins and depositional environments. This research used well log data from four (4) wells in X-Field Niger Delta. The logs include Gamma ray log, deep induction log, Density log, and sonic log. Densities and p-wave velocities derived from sonic log were cross plotted using the E log modelling tool embedded within Hampson-Russel software application. The crossplots were subjected to over pressure analysis. The results obtained revealed Unloading mechanism from 5341ft (1627.9m) to 6448ft (1965.4m) and overpressure zones from 4234ft (1290.5m) to 4788ft (1459.4m) about 168.86m thick within well 01, Unloading mechanism from 2289.5m to 2298.3m and overpressure zones from 2280.7m to 2285.1m within well 02, also Unloading mechanism from 3246m to 3335m and overpressure zones observed from 3157m to 3201m within well 03, and finally Unloading mechanism observed from 5970ft (1819.7m) to 6677ft (2035.1m) and overpressure zones observed from 4554ft (1388.1m) to 5262ft (1603.8m) (about 215.79m thick) within well 04. The results obtained in the over-pressured zones occurred in similar depths in parts of the Niger Delta Basin. The areas identified as overpressure zones should be critically examined prior to drilling to avoid blowout. This study has delineated overpressure zones and unloading intervals in the study area using well logs and crossplots.