Performance of environmental friendly water-based calcium carbonate nanofluid as enhanced recovery agent for sandstone oil reservoirs

Abstract

Recent studies have demonstrated great potential of nanofluids as enhanced oil recovery (EOR) agent. Many mechanisms behind increasing oil recovery inducing alteration of surface wettability toward more water wet have been proposed when displacing oil by nanofluids. In this study, the effect of calcium carbonate nanofluid on wettability alteration of sandstone rock samples was studied. Nanoparticle was synthesized by chemical precipitation method and characterized by X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FE-SEM) and dynamic light scattering (DLS). The average particle size of nanoparticles was 55.4 nm. The rock samples were aged in oil to ensure desired oil-wet conditions. The effects of nanofluid concentration and temperature on wettability change were investigated and optimum concentration of calcium carbonate nanofluid was determined. Adsorption of nanoparticles on rock surface was characterized by FE-SEM. The wettability alteration was evaluated by measuring/calculating contact angle (static, advancing and receding), surface energy, liquid area fraction, and wettability index. 2-D oil-wet glass micromodel was used to compare the performance of optimum nanofluid concentration obtained from wettability tests against normal water flooding. Results showed alteration of wettability from oil-wet to water-wet for all nanofluid concentrations. More wettability alteration was observed at higher temperature (80 °C) than ambient conditions (25 °C). Optimum nanofluid concentration (0.025 wt%) was obtained that changed contact angle from 116.41° (non-treated surface) to 46.99° at 25 °C and 28.7° at 80 °C. Flooding oil-wet 2-D glass micromodel with optimum nanofluid concentration resulted in 20% additional ultimate recovery factor compares to normal water flooding.