In recent years, several innovative techniques that seek to maximize total reservoir recovery have gained great interest and attention worldwide. Nanoparticles have been developed for various applications in reservoir engineering and EOR fields. Using nanoparticles for these applications refers to their small size compared to the pore throat sizes; therefore they could easily move into porous rocks without severe influence on permeability.
Nanofluids; Nanoparticles Colloidal Dispersions, have been investigated as an enhanced oil recovery method. The nanoparticles, present in the three phase contact region of rock, hydrocarbon and the nanofluid, tend to form a self-assembled wedge-shaped film and force themselves between the discontinuous phase and the substrate. This wedge film acts to remove the hydrocarbon from the formation surface, which results in increasing the recovered oil much more than other conventional EOR methods.
Although most of recent studies concluded that using silica nanoparticles dispersed in water results in decreased residual oil saturation after water-flooding and subsequently incremental ultimate oil recovery, the oil displacement mechanism using nanoparticles is not clearly understood yet. The focus of this study is to investigate the probable mechanism of nanoparticles dispersions to improve the recovery.
In this study, silica nanoparticles dispersions were used in core flooding experiments using plugs from Bahariya formation; Egyptian sandstone formation, to evaluate the effect of four different sizes of hydrophilic silica nanoparticles with diameters range from 5 to 60 nm and concentrations range from 0.01 wt.% to 3 wt.%. Results obtained from the experiments indicate that 15–20 nm silica particles 3% wt. dispersions are highly recommended to be used as advanced EOR method as the recovered oil was more than 65% of the IOIP, just at the breakthrough point, compared with 36% recovered by water flooding.
Unlike the traditional displacement mechanisms, focus on three forces: capillary, viscous and gravity, nanotechnology focuses on nano-scale forces such as disjoining force. Analysis and interpretation of the results showed that the main energies, driving the disjoining pressure mechanism, are Brownian motion and electrostatic repulsion between the nanoparticles. Particle size affects the strength of this disjoining force: the smaller the particle size, the higher the charge density, and the larger the electrostatic repulsion between particles. When this force is confined to the vertex of the discontinuous phases, displacement occurs in an attempt to regain equilibrium. These results indicate that nanofluids are expected as a future promising EOR method.
This paper also summarizes the mechanism of preparing the nanofluids and the ability of exploiting Egyptian resources of pure silica sand to produce nanosilica particles with a simple and cheap method. Trial experiments have been done to prepare the nanosilica particles mechanically and the results are illustrated.