Interpretation of the rock-electric and seepage characteristics using the pore network model

Abstract

There always exists the configuration of pores and throats in real rocks, and a pore space may connect with several throats. The pore-throat configuration could lead to the complex pore structure, furthermore, it could greatly influence the rock physical properties such as rock-electric and seepage characteristics. Therefore, a simple pore network model is proposed to characterize the complex pore structure using the throat-pore radius ratio. On the one hand, a simple pore network model is used to study the effect of the pore-throat structure on rock-electric characteristics, on the other hand, it provides a new avenue to interpret the permeability property by introducing the pore network model into the NMR method. The simulation results demonstrate that the complex pore-throat structure not only leads to the non-Archie phenomena, but also results in the electrical anisotropy. Moreover, by combining NMR method with the pore network model, the inversion T2 spectrum could be further decomposed into pore and throat spectra, and the throat spectrum distribution are closely related to the seepage characteristics. Hence, it shows the potential to directly interpret the formation permeability on the basis of the throat spectrum. By comparing the distribution characteristics of throat spectrum to the measured permeabilities of cores, the results show that when the throat spectrum mainly distributes in the long relaxation time and the spectrum amplitude is strong, it is more likely to have good permeability. In addition, the well sections with long relaxation time and high amplitude of the throat spectrum correspond well to relatively high permeability zones in the field, which further verifies the effectiveness of the proposed method.