Experimental investigation of SiO2 nanoparticle–assisted CO2 flooding in carbonate saline aquifers

CO2 flooding is an important process for controlling plume migration and initial pore space utilization. However, the characteristics of nanoparticle–assisted CO2 flooding in carbonate saline aquifers are poorly understood. In this study, experiments were conducted on the effect of SiO2 nanoparticles (SNPs) on the characteristics of CO2 flooding in carbonate saline aquifers. Six experiments have been conducted on CO2 flooding, three on the influence of the injection rate, three on the influence of nanoparticles, and one on the T2 spectrum and core porosity. The results show that (1) the brine recovery efficiency of CO2 flooding and SNPs–assisted CO2 flooding decreases with increasing rate. SNPs can improve the water recovery efficiency of CO2 flooding; for this study, the injection rate decreased from 2.5 mL/min to 0.5 mL/min, and the increase in SNPs–assisted CO2 flooding increased from 13.04 % to 26.12 %. (2) The brine recovery efficiency of CO2 flooding and SNPs–assisted CO2 flooding also decreases correspondingly with increasing injection rate. (3) The change in porosity is greater after CO2 flooding than after SNPs–assisted CO2 flooding, although the change gradually decreases with increasing injection rate. (4) As the injection rate increases, the injection and production pressure differences increase. Injection–production pressure differences are lower for SNPs–assisted CO2 flooding than for CO2 flooding. This work provides a safe and efficient CO2 storage technology for carbonate saline aquifers.