Benchmarking water saturation models for the Mishrif formation using dean–stark data
摘要
Accurate estimation of water saturation (Sw) is essential for reservoir characterization and reliable calculation of hydrocarbons in place. This study presents the first systematic benchmarking a total of 83 water-saturation models for the Mishrif Formation in southern Iraq. This includes 64 Archie-based formulations employing Indonesian, Dual Water, Waxman–Smits, Simandoux and Juhasz models along with 19 data-driven models including combinations of Random Forest, Light Gradient-Boosting Machine (LGBM) and Self-Organizing Maps (SOM) clustering approaches. The analysis integrates conditioned well-log data with 131 depth-matched core samples from three wells (A–C). Dean–Stark water-saturation measurements were used as ground-truth calibration for quantitative benchmarking. Model performance was evaluated using four complementary metrics: mean squared error (MSE), concordance correlation coefficient (CCC), Pearson correlation coefficient (R) and coefficient of determination (R2). To resolve inconsistencies among individual metrics, two dual-ranking algorithms combining these measures were implemented, enabling robust model selection. Results indicate that among the Archie-based models, the Borai Dual-Water Linear model outperforms all others, while Random Forest model ranks highest among data-driven approaches. Overall, advanced machine learning models-based models consistently outperform Archie-based counterparts in the studied shaly carbonate reservoir. Probabilistic uncertainty analysis confirms acceptable reliability for volumetric applications (|error|≤ 0.20). The proposed benchmarking workflow reduces model-selection ambiguity and is methodologically transferable to similar shaly carbonate reservoirs worldwide.