New insights into application of nanoparticles for water-based enhanced oil recovery in carbonate reservoirs

Abstract

Crude oil, water and rock (CWR) surface chemistry is a key parameter in oil and gas recovery from hydrocarbon reservoirs. This paper presents the chemistry of CWR interaction in presence of two water soluble nanoparticles for carbonate rocks. Two most common nanoparticles of aluminium oxide (Al2O3) and silica (SiO2) were selected and utilised for this study. Calcite was first modified to an oil-wet system to resemble the reservoir wetting condition then treated with nano-fluids containing under study nanoparticles at different concentrations. Alteration of wettability was then quantified using contact angle measurements, and zeta potential analysis. The change in fluid chemistry of the water due to presence of nanoparticles was also monitored before and after treatment of carbonate rock. The results show that after treatment of the oil-wet samples with nano-fluids, the solution’s pH decreased for SiO2 while it increased slightly for Al2O3. The contact angle results show a decrease trend for both nanoparticles but more pronounced for Al2O3. These results are in line with zeta potential results in which very negative surface charge for an oil-wet rock was converted to less negative or even positive for certain concentrations of nano-particles. Floating phenomenon also applied to calculate the level of water percentage between floated and sank powder for the modified calcite where amount of water level increased significantly when nanoparticles added to water solutions. Comparison of all tests show that silica nano-fluid with concentration between 0.1 and 2 wt % can be efficient EOR agent. High salinity is definitely not a good option to formulate nano-fluids such as alumina and silica at high concentrations showing inverse effects.