Investigation on Preparation and Profile Control Mechanisms of the Dispersed Particle Gels (DPG) Formed from Phenol–Formaldehyde Cross-linked Polymer Gel

To achieve in-depth profile control and further improve oil recovery, a new profile control agent, termed a dispersed particle gel (DPG), has been developed and reported. In this paper, the DPG particles with sizes ranging from submicrometer to micrometer are prepared successfully from phenol–formaldehyde cross-linked polymer gel by the high speed shearing method. The preparation method is convenient and easy to scale up for the field application. The microscopic characteristics of the DPG have been investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Parallel sandpack tests and microscopic visualization tests have been conducted to gain insights into the profile control mechanism. Additionally, scanning electron microscope (SEM) has been used to study the distribution of DPG particles in porous media. The results show that the DPG particles can block the high permeability layers by accumulating in large pore spaces or by directly plugging small pore throats. Meanwhile, the viscoelastic DPG particles can achieve in-depth profile control due to the elastic deformation and migration into the porous media of the reservoir. Moreover, the oil displacement tests show that the DPG can increase the sweep efficiency and effectively enhance oil recovery.