Organic matter evaluation of the Nkporo Shale, Anambra basin, from wireline logs.

Abstract

A modified form of Schmoker's formation density log technique has been used in evaluating the total organic carbon content TOC of the continuous shale sections of the Nkporo Shale in three exploratory wells (Alade – 1, Anambra River – 1, and Anambra River – 3) in the Anambra Basin. Weight percent TOC was found to range from 0.2 – 4.9%; with an average of 2.8% in Alade – 1 well; 0.2 – 4.3%, with an average of 1.8% in the Anambra River – 1 well; and 0.2 – 5.3%, with an average of 3% in the Anambra River – 3 well. The average TOC values obtained in this study are similar to the average TOC values obtained from organic geochemical analysis of the Nkporo Shale in the Anambra Basin, the Afikpo Syncline, and the Calabar Flank.



Crossplots of the formation density and the gamma ray logs show a generally positive correlation between them; although a few intervals have high gamma ray values corresponding with low formation density. The positive correlation between the formation density and the gamma ray logs suggests a dominantly terrestrial source for the organic matter. Intervals with low formation density (high TOC) corresponding with high gamma ray values are interpreted as source beds with significant marine organic matter.

Global Journal of Pure and Applied Sciences Volume , No 1 January (2001) pp. 103-110



KEY WORDS:

Organic carbon, wireline logs, source rocks, shale, basins.