Fractal characterisation of pore structure of Longmaxi Formation shale in northern Guizhou using NMR

This study focuses on the fractal characterisation of pore structure of the core samples from the Longmaxi Formation in northern Guizhou utilising scanning electron microscopy, mineral composition analysis and NMR. The permeability is calculated by using the improved SDR model proposed by Zhou et al., followed by an analysis of the impact of rock physical properties and mineral composition on pore structure. The results reveal that the samples exhibit a multi-fractal structure and the NMR-derived fractal dimensions are primarily distributed between 2.70 and 2.87, with an average of 2.77, indicating a higher degree of complexity compared to that observed in the Sichuan Basin. The fractal dimensions show a negative correlation with porosity, and the influence of larger pores on porosity is greater than that of smaller pores. Furthermore, a negative correlation is observed between permeability and fractal dimensions. Quartz content and calcite content are inversely related to pore structure complexity. In contrast, the presence of clay minerals contributes to increased pore complexity as their content rises. [Received: November 15, 2023; Accepted: March 10, 2025]