Hydrophobic Silica with Potential for Water-Injection Augmentation of a Low-Permeability Reservoir: Drag Reduction and Self-Cleaning Ability in Relation to Interfacial Interactions

Abstract

An aqueous nanofluid containing superhydrophobic silica nanoparticles with a high surface activity and an average size of 7 nm was used to enhance the water injection of a low-permeability well. The mechanism for the aqueous nanofluid to enhance water injection was discussed. Findings indicate that the silica aqueous nanofluid can greatly increase the effective water permeability even after injecting water for 2100 pore volumes. This is because the hydrophobic silica nanoparticles can be well adsorbed onto the surface of the porous channels to cause hydrophilic to hydrophobic transformation. Both the hydrophobic capillary force and adhesion work contribute to increasing water injection; and in particular, there is a critical point in the pressure-permeability curves for the rock cores with different wettabilities. Only above the critical point, the hydrophobic rock core exhibits a higher effective water permeability than that of the hydrophilic one, which is imperative for drag reduction. Moreover, the hydrophobic rock core surface has a remarkable self-cleaning ability and can reduce the expansion ratio of clay and inhibit the formation of scale in association with the increase of effective porosity via decreasing the hydration film amount. This approach, highlighting the important role of wettability alteration in increasing water injection, could potentially promote the application of a silica aqueous nanofluid in enhanced oil recovery.

Functional Janus-SiO2 Nanoparticles Prepared by a Novel “Cut the Gordian Knot” Method and Their Potential Application for Enhanced Oil Recovery

“…The injection pressure and water permeability were measured with the method reported in an earlier work . In addition, the enhanced oil recovery (EOR) performance of the NPs-1 Janus-SiO 2 nanofluid and the NPs-2x Janus-SiO 2 /HPAM dispersion was also sequentially tested with the previously reported method . Here, the oil sands with 13.6% (mass fraction) oil were prepared from quartz sands with a size of 250–300 mesh and simulated oil [the mixture of the as-received crude oil (viscosity at 25 °C: 479.8 mPa·s) and diesel oil with a volume ratio of 1:1].…”

“…With the bidirectional regulation, the Janus-SiO 2 dispersion could act as the modifier to alter the hydrophilic porous channels of ultralow permeability reservoirs to hydrophobic ones. Because of the remarkable drag reduction and self-cleaning ability of a hydrophobic porous surface (Figure S8), 27 the water injection pressure greatly decreases (by 33.3∼50.0%), whereas the water permeability significantly increases (by 56.6∼98.7%). Both results were obtained under different injection flow rates from 1 to 5 mL/min (Figure 3g).…”

Nanoparticles as Depressurization and Augmented Injection Agents to Facilitate Low Permeability Reservoir Exploitation: Potentials and Risks

“…In Wuqi Oilfield, polysilicon adsorption decreased the thickness of water film, and the effective porosity increased from 22.22 to 37.14% (Qi, 2014). Moreover, acidification pretreatment is conducive to NPs performance, with which effective water permeability increases by 458.3%, comparing to that of 160.0% without pretreatment (Liu et al, 2019).…”

Mechanism of Nano-depressurization and Injection-Augmenting Technology and Its Application in China’s Oilfields: Recent Advances and Perspectives

“…Nanomaterials have attracted extensive attention in recent years. − Nanotechnology has been used to enhance oil recovery and to improve drilling fluid properties and depressurization and injection-augmenting in water injection wells to achieve more efficient development. − The application of nanoinjection-augmenting technology in oilfields has achieved excellent development effects. However, this technology has not been widely promoted, and most reports are limited to laboratory studies.…”