Experimental study on foamy viscosity by analysing CO2 micro-bubbles in hexadecane

Continuous desorbing gas in the heavy oil generates lower viscosity with dispersing gas micro-bubbles. In this study, laboratory experiments were carried out to measure the viscosity of foamy hexadecane, typical component of heavy oil, and to investigate the CO2 gas micro-bubbles at ranged temperature of 20 – 50 °C and depressurization pressure of 1.0 – 6.0 MPa. Apparently, hexadecane mobility increases with increasing foam swelling. The viscosity ratio of foam vs. original hexadecane showed 0.90 – 0.70 with increasing foam swelling in the swelling range of 3.0 – 4.8%. The foam swelling is caused by dispersed gas micro-bubbles, and its viscosity was more reducible at either low temperature or high foam swelling based on present measurement results. The bubble distribution showed the large bubbles (approximately 50 µm in diameter) were coalesced but the micro-bubbles (approximately 5 µm in diameter) were stable under the shear of 1575 s-1, within 3 minutes of measuring. It shows that the micro-bubbles in smaller diameter have higher stability against the high shear rate. Therefore, generating foam by creating CO2 micro-bubbles is capable to make flow through the pore throats with viscosity reduction and improves oil recovery from non-mobile domain, such as aggregate and fine pores, by its swelling.