微生物原位产铁基纳米颗粒提高原油采收率

Iron nano-particles produced by microorganisms in situ enhance oil recovery

摘要:

【背景】 基于微生物原位产纳米可产生驱油用纳米流体设想。【目的】 将微生物产纳米能力与纳米流体提高原油采收率技术相结合，进行微生物原位产铁基纳米颗粒提高原油采收率研究。【方法】 从页岩岩屑获取实验所用菌株，经基因组测序分析对菌株进行鉴定，建立邻菲罗啉法Fe(II)浓度标准曲线测定菌株的Fe(III)还原能力，通过扫描电镜(scanning electron microscopy, SEM)、透射电镜(transmission electron microscopy, TEM)、Zeta电位分析对菌株与赤铁矿(Fe₂O₃)作用产纳米颗粒形态与粒径进行表征，通过油/水/岩界面动态润湿角测定与油滴剥离及运移实验对微生物产纳米进行驱油性能分析，最后探究微生物产纳米颗粒提高原油采收率的能力。【结果】 经鉴定分离的菌株为吉尔卡湖希瓦氏菌(Shewanella chilikensis)，编号为FR1；菌株FR1能使赤铁矿(Fe₂O₃)快速还原，铁还原率达到65.26%；与赤铁矿(Fe₂O₃)作用10 d经显微电镜观察显示：在细菌细胞壁上、细胞内部及细菌蚕食的赤铁矿表面都附着大量的球状纳米颗粒；通过粒径分析表明未接菌的空白对照粒径>1 000 nm的颗粒含量达到88.05%，接菌后主要转化为尺寸在10−1 000 nm的纳米级颗粒；这些纳米颗粒作用于原油和岩石界面能明显改变油润湿界面的润湿性，并且对固体界面上的原油进行有效剥离；通过FR1原位产生的纳米流进行岩心驱替，排出液水相表面张力下降到27.9−28.6 mN/m，提高原油采收率为16.38%−17.76%。【结论】 研究结果为微生物提高原油采收率提供了一种新的技术思路。

Abstract:

[Background] Nano-particles produced by microorganisms in situ can enhance oil recovery. [Objective] To study the effects of iron nano-particles produced by microorganisms in situ on oil recovery by combining microbial production of nanoparticles with the technology of nano-fluids enhancing oil recovery. [Methods] We isolated the strains from shale rock debris and identified the strains by genome sequencing. Subsequently, we established the standard curve of Fe(II) concentration by the o-phenanthroline method to determine the Fe(III) reduction ability of the strain, and characterized the morphology and particle size of nano-particles produced by strain interaction with hematite (Fe₂O₃) by scanning electron microscopy, transmission electron microscopy, and Zeta potential analysis. Finally, we investigated the ability of the nano-particles to enhance oil recovery by determining the dynamic wetting angle at oil/water/rock interface and conducting oil droplet stripping and transport experiments. [Results] The isolated strain was identified as Shewanella chilikensis FR1. FR1 could rapidly reduce Fe₂O₃, with the iron reduction rate reaching 65.26%. After the strain was interacted with Fe₂O₃ for 10 days, a large number of spherical nano-particles were observed on the surface of hematite on the bacterial cell walls, inside of the cells, and eaten by bacteria. The particles with the size >1 000 nm accounted for 88.05% in the blank control without strain inoculation, and those in the bacterial inoculation group mainly had the size of 10–1 000 nm. The nanoparticles in the oil-rock interface could obviously change the wettability of oil-wetted interfaces and effectively strip crude oil on the solid interface. The nano-particles generated by FR1 in situ could be used for core flooding, decreasing the surface tension of the aqueous phase of the discharged fluid to 27.9–28.6 mN/m and increasing the oil recovery to 16.38%–17.76%. [Conclusion] The results of this study provide a new technical idea for microbial enhanced oil recovery (MEOR).