Study on Applicability of Ball-and-Stick Model in Reservoir Pore-Throat Network Simulation

At present, the ball-and-stick model is widely used to simulate the reservoir pore-throat network. However, due to the large span of reservoir pore-throats, there is still a lack of effective verification on whether the ball-stick model is fully applicable. The configuration analysis of a constant velocity mercury injection curve is carried out by using configuration theory and the hierarchical analysis method. The applicability of the ball-and-stick model in a reservoir pore-throat network simulation is discussed by interpreting the reservoir pore-throat structure information behind the configuration. The results show that there are two configuration regions, A and B, in the constant velocity mercury injection curve. In configuration region A, the mercury saturation of pores, the pore channel and the throats increase monotonically with the increase in mercury inlet pressure, indicating that pore channels and throats coexist in this configuration region, the pore-throat ratio is greater than one, and the ball-and-stick model is applicable. In the B configuration region, mercury saturation in pores and throats increases monotonically with the increase of mercury inlet pressure, while mercury saturation in the pore channel remains unchanged, indicating that this configuration region is basically throat with a porethroat ratio of one. The ball-and-stick model is no longer applicable, and the capillary model is more suitable. The ball-and-stick model combined with the capillary model can simulate the full-scale pore throat network of the reservoir. This study provides a method to calibrate the application zone of ball-stick model and capillary model by using constant velocity mercury injection curve configuration, which has important guiding significance for the simulation of the reservoir pore-throat network and the study of the seepage law.