Research and Field Test on the Environmentally Friendly New Bio-Nano Oil Displacement System

With the advancement of green oilfield chemistry, offshore oilfields are increasingly emphasizing the environmental requirements of chemical flooding agents. Conventional polymer systems, such as high-molecular-weight polymers, are introducing new challenges, including organic blockage in production wells and difficulties in separating produced fluids, thereby affecting the operational efficiency and capacity building of oilfield development. To address these issues, this study developed an environmentally friendly bio-nanotechnology-based enhanced oil recovery (EOR) system. Laboratory performance evaluations and microscopic oil displacement experiments were conducted. The results demonstrated that the bio-nano EOR system could transform oil-wet rock interfaces into amphiphilic wetting interfaces and effectively reduce the oil-water interfacial tension to the level of 10−3 mN/m. The “small size” effect of nanomaterials allows them to penetrate micro-sized pores and throats, achieving a recovery rate of up to 50% after 20 h of nanocapillary imbibition. Additionally, the bio-nano EOR system exhibited excellent performance in degrading large crude oil molecules. Component analysis results showed that the heavy components of crude oil, such as resins, asphaltenes, and aromatics, decreased, while the content of saturated hydrocarbons increased, reaching a maximum proportion of 28.95%. Furthermore, the bio-nano EOR agent demonstrated favorable injectivity and oil-washing effects. The injection resistance factor was 1.4, and the residual resistance factor was 1.6. On the basis of a 58% waterflood oil recovery rate in simulated cores, the incremental oil recovery could reach up to 21.73%. Microscopic displacement simulations revealed that the oil recovery performance of the bio-nano EOR system is significantly influenced by the pore structure of the porous medium and fluid parameters. Specifically, the pore-throat ratio of the reservoir, fluid interfacial tension, and wetting angle show negative correlations with the EOR performance, while the reservoir coordination number and fluid viscosity exhibit positive correlations. Field test of this bio-nano EOR system have already been conducted. By December 2024, well group BH08 show a 14-percentage-point reduction in comprehensive water cut, 0.2% increase in recovery degree, and one cumulative oil increment of 9000 m3 with an effective period lasting up to 225 days. This research provides a novel solution for enhancing the recovery of offshore sandstone reservoirs in alignment with green oilfield chemistry principles, offering significant contributions to the development of environmentally friendly oil recovery agents.