Low-permeability reservoirs have become increasingly important targets for hydrocarbon exploration in lacustrine basins. However, complex pore-throat structures and the influence of diagenesis may impede our understanding of reservoir quality. Additionally, due to their similarly low permeability and porosity, identifying different types of low-permeability reservoirs—especially common beach-bar and turbidite deposits in lacustrine basins—is challenging. In this study, we applied an explainable machine learning (ML) model using mercury injection parameters of beach-bar and turbidite sandstone deposits in the Dongying Depression, Bohai Bay Basin, China, to classify the two groups of sandstone deposits and investigate the most influential factors in classifying them. Unlike conventional statistical or “black-box” ML approaches, our method integrates the full suite of pore-throat parameters while identifying the most influential features for classification. The model achieved an overall accuracy of 80 % in classifying the two deposit types. It shows that turbidite deposits have higher porosity and permeability than beach-bar deposits, mainly due to lower cementation and increased dissolution. This higher porosity and permeability in turbidite sandstones is likely caused by the release of organic acids from surrounding organic-rich source rocks, which promote dissolution, and by the infilling of organic matter that hinders cementation. In addition to permeability and porosity, our study finds that specific surface area is a key parameter for differentiating the two deposit types. A smaller specific surface area indicates higher macro-porosity, which benefits permeability. Overall, our explainable ML model not only accurately classifies beach-bar and turbidite sandstone reservoirs but also identifies the factors that control reservoir quality.
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