Adaptability Evaluation of Mathematical Model of Capillary Pressure for High-rank Coalbed Methane

We pick out 5 typical mathematical models of capillary pressure and propose a more convenient method for evaluating the applicability. Then, based on the mercury intrusion experiments in which the core samples adopted are from southern Qinshui Basin, the adaptability of the 5 capillary pressure mathematical models are evaluated. The results show that the capillary pressure curves for high-rank CBM formation are not in accordance with ether Corey model or Brooks-Corey model. Thomeer model is only adapted to the II-type formation with medium permeability and porosity and HE Chengzu model is only adapted to the I-type formation with relatively high permeability and porosity. While Li model is adapted to all type of CBM formation. The key parameters of b and λ can be calculated much more easily by equations(12)and(13), and the values calculated can fit the experimental data perfectly.