Evaluation of the synergistic effect of a complex enzyme–formulated nano oil displacement agent to enhance low–permeability heavy oil recovery

Enzyme–enhanced oil recovery is an emerging technology; however, the underlying mechanisms governing this process remain incompletely elucidated. In this paper, an enzyme nano–oil displacement agent has been formulated by combining enzymes (lipase, cellulase, esterase, and protease) with our previously formulated composite nano–oil displacement agent to evaluate oil displacement efficiency. The following results were obtained: (1) enzymes addition could change the wettability to a more water–wet state with increasing magnitude of 3.6 % than nano–oil displacing agent, and which is not a significant mechanism for oil displacement; (2) enzyme addition resulted in a further reduction in interfacial tension, with a magnitude 13.4% lower than that of the nano–oil displacing agent, and which is also not a significant mechanism for oil displacement; (3) additional oil could be recovered by adding enzymes through syringe flooding experiments; (4) Core displacement experiments have confirmed that enzymes added can increase tertiary oil recovery by 5.5 % (average 35.4 %) compared with nano–oil displacing agent (average 29.9 %); (5) enzymes added could enhance imbibition efficiency with increasing magnitude of 4.1% than nano–oil displacing agent; and (6) the fundamental mechanism underlying the enhanced oil flowability lies in the degradation of long–chain alkanes into shorter–chain alkanes and functionalized metabolites. This paper presents a promising solution for tertiary oil recovery by integrating enzymes, biopolymers, nanoparticles, and surfactants to enhance low–permeability (< 50 mD) heavy oil (< 500 mPa. s) recovery.