Aqueous Nanobubble Dispersion of CO2 for Enhanced Oil Recovery – Coreflooding and Huff-n-Puff Experiments

Abstract

Abstract This paper presents an experimental study of aqueous nanobubble dispersion of carbon dioxide (CO2-NB) for enhanced oil recovery. CO2-NB was compared with brine and slightly supersaturated carbonated water (eCW) in corefloods with Berea sandstone cores and dead oil at room temperature. CO2-NB was also compared with a mixture of CO2 and brine with no NB in high-pressure high-temperature huff-n-puff experiments with live oil-saturated tight Kentucky sandstone cores using three different fracture-matrix configurations. Coreflooding results showed that the displacement of oil by CO2-NB yielded a delayed breakthrough, in which the oil recovery factor at breakthrough (RFBT) was 9.1% original-oil-in-place (OOIP) greater than RFBT in the brine case. The displacement of oil by eCW did not show such an increase in RFBT, but showed a long-term gradual increase in oil recovery after the breakthrough. The increased RFBT by CO2-NB can be attributed to the nucleation of a CO2-rich phase near the displacement fronts, where the metastable aqueous phase releases CO2 to the oleic phase while the nanobubbles of CO2 with capillary pressure release CO2 to the surrounding aqueous phase. That is, the partially miscible displacement of dead oil by the in-situ generated CO2-rich phase could have enhanced RFBT by CO2-NB in comparison to the immiscible oil displacement by water in the brine case. Huff-n-puff experimental results showed a systematic increase in oil recovery by using CO2-NB in comparison to CO2-brine (with no NB). In the CO2-NB case, the annular, artificial, and combination fractures had oil recoveries of 34%, 36%, and 39% OOIP, respectively. In the CO2-brine case, they were 245, 22%, and 28% OOIP, respectively.