Experimental investigation on migration and retention mechanisms of elastic gel particles (EGPs) in pore-throats using multidimensional visualized models

Abstract

Knowledge of migration and retention mechanisms of elastic gel particles (EGPs) in pore-throats is essential for the effective application of EGPs as a smart sweep improvement and profile control agent for enhanced oil recovery (EOR). The matching coefficient (defined as the ratio of particle size to pore-throat size) is used to investigate its influence on migration, retention and profile control performance of EGPs. A 1-D continuous pore-throat visualization model (PTVM), a 2-D heterogeneous PTVM and a 3-D heterogeneous core model were constructed and used to investigate pore-scale migration, retention and controlling mechanism of migration and retention characteristics on EGPs profile control. The results of the 1-D continuous PTVM indicated that while the matching coefficient was in the optimal range (i.e., 0.20–0.32), the EGPs could not only smoothly migrate to the deeper pore-throats, but also form stable retention in the pores to resist the erosion of injected water, which was conducive to the effective in-depth profile control. The results of the 2-D heterogeneous PTVM verified that the sweep efficiency in low-permeability regions could be significantly improved by in-depth migration and stable retention of EGPs in the pore-throats with an optimal matching coefficient (0.29), which was much better than that in cases with a smaller matching coefficient (0.17) or an excessive matching coefficient (0.39). Moreover, the NMR displacement experiments of 3-D heterogeneous cores were carried out to simulate the EGPs profile control in actual reservoir porous media. Saturation images and T2 spectrum curves of crude oil showed that EOR in the low-permeability layer was highest (56.1%) using EGPs profile control with an optimal matching coefficient, attributing to the in-depth migration and stable retention of EGPs.