Constructing the pore-throat capillary bundle model using MICP data

Knowledge of the pore structure of rocks is very important for the evaluation and exploitation of oil and gas reservoir. For the low-permeability sandstone reservoirs, it is very difficult to study the pore structure of rock accurately due to the complexity, irregularity, and heterogeneity. In this paper, we proposed a method to describe the pore structure by means of injection and the withdrawal curve created by MICP test. The mercury volume and size frequency distribution of both pores and throats ranging from micropores to macropores were obtained by MICP data. Furthermore, a pore network model, called pore-throat capillary bundle model, was proposed based on MICP data, which consist of spherical pore and cylindric throat. All the important parameters for describing the features of pore-throat capillary bundle model, such as throat/pore radius, average pore-to-throat size ratio, tortuosity, length of throat-unit, and the total number of pores and throats, were calculated. Moreover, the mathematical model for calculations of porosity, permeability, and permeability contribution by the capillary tubes was derived in this study. A total of 14 sets of core samples were taken as examples to verify the availability of the pore-throat capillary bundle model. The results revealed that there is a good agreement between the predicted and experimental results. This would indicate that the pore-throat capillary bundle model is properly modeling actual porous media. This work gives insight into the pore structure by application of MICP data and has great significance for the study of single-phase or multiphase fluid seepage based on the pore-throat capillary bundle model in the future.