Improvement of Transient Interfacial Tension and Displacement Efficiency with Enzyme: An Application of Enzyme on the Heavy Oil Recovery

Abstract

Enzymatic enhanced oil recovery (EEOR), as an emerging technology stemmed from biotechnology, has been reported as an effective and environmentally friendly method for improving the recovery factor (R.F.) of conventional oil in both lab-scale and field-scale. Meanwhile, the exploration of the next-generation heavy oil recovery technique featured by low energy cost and low greenhouse gas emission has been of the great interests to the researchers because of the increasing requirement of the environmental protection in the recent years. As such, this study firstly conducted the work to systematically investigate the effects of enzyme on the transient interfacial tension (IFT) between the enzyme solution and heavy oil, and further the ability of unlocking remaining heavy oil of enzyme solution under different conditions. First, the transient IFTs between the enzyme solution and heavy oil are comprehensively measured with a high-temperature high-pressure (HTHP) pendant-drop tensiometer. The influences of the factors that possibly affects the transient IFTs, including pressure, temperature, concentration of enzyme solution and the contacting time of enzyme solution and heavy oil, were systematically examined and analyzed. Then, the enzyme solution flooding after a water (brine) flooding were carried out in the sandpack to probe the potential of enzyme solution to enhance the R.F. of heavy oil at high water-cut stage. The numerical simulation was also implemented to find the underlying mechanisms accounting for the flow behavior of the enzyme solution flooding. The results of the IFT measurements showed that except for the pressure, the other three factors, i.e., temperature, concentration of enzyme solution and contacting time, can impose great impacts on the transient IFTs. A high temperature and concentration of enzyme as well as a long contacting time was found to be beneficial to the decrease in IFTs. However, an optimal concentration of enzyme was still observed and recommended since a dramatic decrease in IFTs cannot be obtained once the concentration is larger than the recommended value. Meanwhile, all three tests of enzyme flooding with different enzyme concentrations presented a better recovery performance in comparison to the pure water flooding and validate the ability of enzyme to boost the heavy oil production. The modification of the relative permeability curves is found to be the main reason being responsible for such improvement of the migration of the residual heavy oil based on the numerical simulation.