Electrofacies Characterization and Core-Log Calibrations in Heterogeneous Bedded Salt Formations of the Delaware Basin: Significance for Hydrogen Storage

Salt formations offer large-scale subsurface hydrogen storage potential in the ongoing energy transition. However, heterogeneous bedded salt formations are mineralogically complex, influencing rock mechanics and differential dissolution, which potentially affects cavern integrity and stability. Limited access to core data presents additional challenges for detailed lithofacies characterization. Electrofacies models play a primary role in bridging this data gap, providing inter-well lithofacies predictions.

This study focuses on the Castile and Salado formations in the Delaware Basin, characterized by a diverse evaporite mineral composition. Our main goal is to build electrofacies models in multiple wells using unsupervised machine learning (k-means clustering) to unravel spatial and vertical lithofacies distribution within these bedded salt formations. Core-log data integration is essential to validate the models’ robustness.

The results provide insights into the lithological complexity of both formations. The Castile Formation exhibits relatively simpler mineralogy, featuring thick alternating anhydrite and halite members. In contrast, the Salado Formation presents a more complex mineralogical association, increasing geological heterogeneity. The higher halite proportion makes the Salado Formation an attractive candidate for hydrogen storage. However, non-salt rock interbedded layers introduce greater facies variation, posing challenges for safe cavern development. Furthermore, core-log data integration highlights well-log resolution limitations’ impact on electrofacies accuracy, such as the shoulder-bed effect, important in preventing misinterpretations.

Our integrated approach effectively captures the heterogeneous nature of the Castile and Salado formations at well-log scale. Electrofacies analysis improves geological assessment, especially in regions with limited core data, assisting decision-making for safe cavern development and hydrogen storage in bedded salts.