Water Saturation from Wire-Line Logs, Niger Delta Nigeria

Well log data from eight wells located in the X fields of the Niger Delta Basin were used in the determination of some petrophysical characteristics of the reservoir sands. Well log data were obtained from sonic, gamma-ray, matrix density and resistivity logs. The petrophysical characteristics investigated were porosity, water saturation, tortuosity and permeability. The results of the analysis revealed the presence of different sand and shale units. The thickness of each sand unit was highly variable, ranging between 6.1 and 21.5 m. Average porosities vary between 25.0 and 72.0 percent and generally decreasing with depth. A modeled water saturation showed a better value for water saturation (calculation) for non-Archie media. The correlation between the modeled water saturation method (using a different value of cementation factor m and tortuosity a as given by some literature) gives a weaker correlation for the non-Archie media while the Archie media gives a stronger correlation when compared with the Archie equation. The average water saturation of these units varied between 5.0 and 64.0 percent. These values are generally high for the sand units in varying wells.