Experimental Investigation on Migration and Retention Mechanisms of Elastic Gel Particles (EGPs) in Pore-Throats using Multidimensional Visualized Models

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 T 2 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.