Experimental Investigation of Stability of Silica Nanoparticles at Reservoir Conditions for Enhanced Oil-Recovery Applications.

Shidong Li,Yeap Hung Ng,Ole Torsæter,Hon Chung Lau,Ludger P Stubbs

doi:10.3390/nano10081522

Abstract

To be effective enhanced oil-recovery (EOR) agents, nanoparticles must be stable and be transported through a reservoir. However, the stability of a nanoparticle suspension at reservoir salinity and temperature is still a challenge and how it is affected by reservoir rocks and crude oils is not well understood. In this work, for the first time, the effect of several nanoparticle treatment approaches on the stability of silica nanoparticles at reservoir conditions (in the presence of reservoir rock and crude oil) was investigated for EOR applications. The stability of nanoparticle suspensions was screened in test tubes at 70 °C and 3.8 wt. % NaCl in the presence of reservoir rock and crude oil. Fumed silica nanoparticles in suspension with hydrochloric acid (HCl), polymer-modified fumed nanoparticles and amide-functionalized silica colloidal nanoparticles were studied. The size and pH of nanoparticle suspension in contact with rock samples were measured to determine the mechanism for stabilization or destabilization of nanoparticles. A turbidity scanner was used to quantify the stability of the nanoparticle suspension. Results showed that both HCl and polymer surface modification can improve nanoparticle stability under synthetic seawater salinity and 70 °C. Suspensions of polymer-modified nanoparticles were stable for months. It was found that pH is a key parameter influencing nanoparticle stability. Rock samples containing carbonate minerals destabilized unmodified nanoparticles. Crude oil had limited effect on nanoparticle stability. Some components of crude oil migrated into the aqueous phase consisting of amide-functionalized silica colloidal nanoparticles suspension. Nanoparticles modification or/and stabilizer are necessary for nanoparticle EOR application.

Highlights

In recent years, nanotechnology research on enhanced oil recovery (EOR) has shown promising results in the laboratory
Stability screening tests were performed for a range of unmodified and surface-modified silica nanoparticles, as well as silica nanoparticles with hydrochloric acid (HCl) as stabilizer by using methods of stability visualization and turbidity scanning
The results showed that surface modification with polymer and addition of HCl can improve stability of fumed silica nanoparticles under high-temperature and high-salinity conditions remarkably

Summary

Introduction

Nanotechnology research on enhanced oil recovery (EOR) has shown promising results in the laboratory. Some EOR experiments with silica nanoparticles have been performed and showed positive results in increasing oil recovery [1,2,3,4]. The proposed EOR mechanisms for silica nanoparticles include interfacial tension reduction, wettability alteration, plugging of pore channels, disjoining pressure and emulsification [5,6,7,8]. The prerequisite of these mechanisms working well in the reservoir is that nanoparticles are stable at reservoir conditions so that they can maintain their surface activities for EOR. The settling velocity of small spherical particles in a suspension follows Stokes law [9]: V=

Methods

Results

Conclusion