Investigation of the enhanced oil recovery mechanism of CO2 synergistically with nanofluid in tight glutenite

Huff-n-puff methods using nanofluid and/or CO 2 are most promising methods for enhancing oil recovery in the Mahu Oilfield, Xinjiang, China. Six tight glutenite reservoir samples were conducted the huff-n-puff experiment using different displacement fluids (i.e. D 2 O, supercritical CO 2 and nanofluid) following saturation with oil. The results of T 2 NMR spectra of the samples show that D 2 O can readily enter the larger pores stripping the oil with smaller pores remaining relatively untouched. Furthermore, the oil recovery was initially fast before quickly tapering with the final average oil recovery over samples using D 2 O huff-n-puff alone being only 14.89%. However, CO 2 could effectively enter both small and large pores with the oil recovery efficiency from small pores being greater than 20% and from the large pores being even higher with the final average recovery over two samples using CO 2 huff-n-puff alone being 40.44%. Relative to D 2 O alone, the nanofluid improved the oil recovery in small pores by more than 10%. There appears to be a synergistic effect combining CO 2 and nanofluid huff-n-puff; both CO 2 followed by nanofluid huff-n-puff or nanofluid followed by CO 2 huff-n-puff achieved similar final recoveries close to 50% of the overall oil.