The impact of salinity, alkalinity and nanoparticle concentration on zeta-potential of sand minerals and their implication on sand production

Abstract

The effect of brine salinity, cation type, pH, and produced sand on zeta potential (ZP) measurements with and without the presence of silica nanoparticles is investigated through pH measurement, static tests for sand and ZP measurements as well as Field Emission Scanning Electron Microscope (FESEM) analyses. Three important factors were investigated: composition of the injected brine, surface charge and pH. Their influence on stability of nanoparticles in the injected brine and amount of sand segregation was determined and the analysis of the new outcomes based on rock/brine ZP measurements was reported. The results show that the use of silica nanoparticles with high pH helps in preventing sand production and that pH has a main effect on the surface charge of the sand particle released, affecting the ZP of the solution. Nanoparticles can be active as a coating on sand grains and prevent sand segregation during water flooding. Divalent cations have been found to acquire a more substantial impact on neutralizing the negative charge of the sand particles than monovalent cations at the same concentration and pH conditions at 25 ℃. The value of ZP becomes of higher negative value with the decrease of brine salinity. The effectiveness of SiO2 nanoparticles is quite different for soft water and smart water. For soft water, the nanoparticles work more effective at pH higher than 8; and for smart water, the nanoparticles perform better at pH lower than 8. To reduce sand production with the use of silica nanoparticles, it is highly suggested to increase pH, as pH and sand production mechanisms were observed to be inversely related.