Fractal characteristics of micropore structure of Taiyuan Formation bauxite reservoir in Longdong area of Ordos Basin.

This article focuses on the geological and reservoir characteristics of the Taiyuan Formation bauxite gas reservoirs in the Longdong area of the Ordos Basin, China. It identifies the bauxite reservoirs as sedimentary formations with distinct logging features—high natural gamma ray readings (around 500 API) and low acoustic wave time differences—and classifies them based on diaspore mineral content into bauxite, argillaceous bauxite, and aluminous mudstone. The reservoir pores mainly consist of dissolution pores within particles, intergranular pores, and microcracks, with an average porosity of 8.49% and low permeability averaging 0.261 × 10⁻³ μm². Using high-pressure mercury injection and low-temperature nitrogen adsorption experiments, fractal dimensions were calculated to evaluate pore structure, leading to a classification system where Type I reservoirs (D1 fractal dimension 2.2–2.6) represent high-quality targets for exploration. The study highlights the significance of micro ancient landforms, especially buried pits, in influencing bauxite thickness and reservoir quality.