Reservoir characteristics and development control factors of Benxi Formation bauxite in Linxing area of Ordos Basin

In recent years, the bauxite gas exploration of Taiyuan Formation in Longdong area of Ordos Basin has made a major breakthrough, which has attracted wide attention at home and abroad. In the same period, the bauxite rock gas of Benxi Formation in Linxing area has also made some progress, but the characteristics and controlling factors of bauxite reservoir in this area are unclear, which restrict the exploration process. [Objective]In order to identify the reservoir characteristics and control factors of Benxi Formation bauxite in Linxing area, [Methods]The paper carried out XRD, casting sheet image, SEM-EDS, mercury intrusion porosimetry, nitrogen adsorption, carbon dioxide adsorption, routine porosity detection and other analysis methods. The mineral composition, pore structure and physical properties of the bauxite reservoir are characterized, and the controlling factors of the development of the bauxite reservoir are discussed based on seismic logging data. [Conclusion]The results show that the aluminum-bearing minerals in the bauxite of Benxi Formation in Linxing area are mainly diaspore, and the pore types are mainly intra granular pores, intergranular pores, matrix pores, intergranular pores and micro-cracks, and occasionally organic pores. In addition, the pore volume of bauxite rocks is mainly provided by mesoporous and macroporous pores, and the distribution range of pore peaks is mainly 30-70 nm, 80-130 nm and 4-13 μm. Thirdly, the physical property conditions of the bauxite reservoir are general, with an average porosity of 3.28% and an average permeability of 1.398×10-3 μm2, but the upper section with higher content of diaspore at the bottom still has better physical property conditions. Finally, the development of bauxite reservoir in Linxing area is controlled by palaeo-geomorphology, palaeo-sedimentary environment and diagenesis. Among them, The accumulation and distribution of bauxite are controlled by the paleogeomorphology of depressions and troughs and the enclosed and semi-enclosed intermittent swamps and lagoons sedimentary environment, while diagenesis controls the reservoir space type and physical property conditions of bauxite reservoirs based on the sedimentary environment.