In this work, Total organic content (TOC) was computed, based on the Passey Δ log R technique, for Pologbene-1 and pologbene-2, and the computed values were compared with TOC values obtained from geochemical logs spanning the same depth in the two wells.
The Passeys Δ log R method employs the overlying of properly scaled porosity log (generally the sonic transit time curve) on a resistivity log (preferably from a deep reading tool). In water-bearing, organic –clean rocks, the curves track each other. In hydrocarbon- bearing reservoir rocks or organic-rich non-reservoir rocks, a separation between the curves occurs. The magnitude of the separation in organic-rich rock source rock is influenced by the level of organic maturity (LOM). The LOM, when used in combination with the magnitude of the log separation, can lead to the determination of TOC.
A major challenge in the use of the Passey’s method in the determination of the TOC is the computation of the LOM. In this work, LOM was computed from Vitrinite reflection data obtained in the Pologbene field from a previous published work.
Comparison of TOC values obtained from the Passey’s Δ log R method to the TOC obtained from a geochemical log from the same well shows good agreement in the TOC values. The Δ log R method presented is important because it confirms that organic richness can be assessed in the absence of geochemical data in the Niger Delta.