Laboratory Study and Field Test of Bio-Nano Oil Displacement System in Offshore Low Permeability Reservoirs

At present, some low permeability reservoirs in offshore oil fields have small pores and complex structures. When the fluid flows through them, it is strongly affected by the phase interface, resulting in high water injection pressure, low oil recovery and poor development effects. In this paper, the laboratory research of bio-nano oil displacement system that is suitable for low permeability reservoirs is carried out. The results show that the bio-nano oil displacement system can transform the oil wetting of rock interface into the water wetting, and effectively reduce the oil-water interfacial tension to 10–3 mN/m. The bio-nano oil displacement system, liquid wax and kerosene system can form stable emulsion with an emulsification index of about 0.5. Oil washing efficiency of the bio-nano system can reach 70%, and the viscosity reduction rate of heavy oil can reach more than 90%. Compared with conventional water driving, bio-nano driving has no obvious pressure rise and good injection performance. Oil recovery of cores with different permeability is significantly improved after treatment with bio-nano system. Composite biological nano oil displacement system has obvious effects on improving oil recovery, which is 9.35% higher than that of single active nano oil displacement agent. The biological nano oil displacement effect of well S17 is good. By the end of June 2022, the injection pressure of well S17 is 9.0 MPa, its comprehensive water content is reduced from 84% to 79%, the accumulated oil production is 18081 m3 with its effective period of 215 days. This study will provide a set of environmentally friendly bio-nano oil displacement solution for solving the problems of poor physical properties, low sweep efficiency, and prominent plane conflicts in low permeability reservoirs.