Unsupervised Electrofacies Classification and Porosity Characterization in the Offshore Keta Basin Using Wireline Logs

TL;DR

This paper introduces an unsupervised machine learning workflow using wireline logs for electrofacies classification and porosity analysis in the offshore Keta Basin, aiding early formation evaluation.

Contribution

It develops a reproducible, log-only clustering method with quantitative validation for subsurface characterization in data-scarce offshore environments.

Findings

Four electrofacies clusters identified with moderate separation.

Depth-continuous patterns linked to clay content and porosity.

Workflow provides a practical tool for frontier offshore basin analysis.

Abstract

This study presents an unsupervised machine learning workflow for electrofacies analysis in the offshore Keta Basin, Ghana, where core data are scarce. Six standard wireline logs from Well~C were analysed over a depth interval comprising approximately $11{,}195$ samples. K-means clustering was applied in multivariate log space, with the clustering structure evaluated using inertia and silhouette diagnostics. Four clusters were identified, supported by an average silhouette coefficient of approximately $0.50$, indicating moderate but meaningful separation. The resulting electrofacies exhibit systematic, depth-continuous patterns associated with variations in clay content, porosity, and rock framework properties, forming a geological continuum from shale-dominated to cleaner sandstone-dominated units. The results demonstrate that log-only, unsupervised clustering supported by quantitative metrics provides a robust and reproducible framework for subsurface characterisation. The proposed workflow offers a practical tool for early-stage formation evaluation in frontier offshore basins and a foundation for future integrated studies.