An improved capillary pressure model using fractal geometry for coal rock

Based on fractal geometry and the “matchstick” tubes model, an improved capillary pressure model was theoretically derived to assess capillary pressure data for coal. The model was based on fractal geometry and the “matchstick” tubes model. Our improved model can be simplified as Li model and Brooks-Corey (B-C) model when the fractal dimension and tortuosity parameter take specific values in coal porous media. Furthermore, the capillary pressure data of different coals samples collected in the LZ Coal Mine in China were measured employing mercury intrusion method, and the heterogeneity of typical coal samples were evaluated using the pore volumetric percent curves and SEM images. The matching results of the B-C model, Van Genuchten (V-G) model, Li model, and our improved model were assessed in comparison with the test data. The comparison indicated that our improved model had better agreement with the test data relative to the conventional models.