低渗透油藏提高原油采收率的生物化学基础研究

The low permeability oil &gas reservoirs are one of the most important oil &gas reservoir types in the world. 70% of the domestic newly increased oil and gas reserves and more than 70% of the new production are both from low permeability reservoirs. The proposal will investigate the low permeability reservoirs and the critical scientific issues they are facing, namely low permeability, the high pressure and insufficient injection of water injection wells due to the blockage of pore throats caused by clay swelling, and the low productivity and low efficiency of oil production wells. The proposal will characterize the types, abundance, and distribution of the anaerobic and/or facultative anaerobic microorganisms affecting the seepage of reservoirs and drag reduction, such as biosurfactant- producing bacteria, hydrophobic bacteria and bacteria which suppress clay swelling. The effects of the functional microorganisms and their metabolites on the seepage of reservoirs and drag reduction will be studied. The biological nano-materials will be produced as displacement agents that are based on the environmentally friendly microbial metabolites such as lipopeptide and/or glycolipid biosurfactants. The interaction of the agents with sandstone, oil and water and the influences of the agents on reservoir wettability, interfacial tension, seepage of reservoirs, and drag reduction will be examined. The fundamental understanding of the mechanisms in suppressing clay swelling, improving seepage, reducing flow resistance, and decreasing injection pressure by functional microorganisms in low permeability reservoirs will be established. The proposal can generate new technology of enhanced oil recovery in low permeability reservoirs and new biochemical principle in the seepage of reservoirs and drag reduction. The outcomes of the proposal will extend the life of the low permeability reservoirs by recovering more residual oil. Therefore, this proposal will have very important significance and a broad application prospect.

低渗透油气田是世界上重要的油气田类型之一，国内新增油气储量的70%、新增产量的70%以上为低渗与特低渗油气藏。除岩石致密渗透率低外，低渗透油藏还存在粘土膨胀造成孔喉堵塞导致注水井高压欠注与生产井低产低效等生产瓶颈问题。针对上述开发难点，本课题首先研究孔道减阻的厌氧或兼性厌氧功能微生物菌，如代谢生物表活剂菌，疏水功能菌，抑制粘土膨胀菌等。同时考察上述菌种的类型、丰度及其分布特征，掌握功能菌及其代谢产物对石油储层渗流与通道减阻的作用规律。采用脂肽类或糖脂类生物表活剂，制备生物基纳米材料驱替液，研究其对岩、油与水界面的作用特性及其对岩心微通道渗流与孔道减阻的影响。最终揭示低渗透油藏功能微生物抑制粘土膨胀、改善渗流、减少流体阻力、降低注水压力的生物化学原理，提出低渗透油藏提高原油采收率的新方法。本课题对于延长低渗透油藏的开发寿命与增加低渗透油藏的产量，具有非常重要的意义与广阔的应用前景。

低渗透油气田是世界上重要的油气田类型之一，国内新增油气储量的70%、新增产量的70%以上为低渗与特低渗油气藏。除岩石致密渗透率低外，低渗透油藏还存在粘土膨胀造成孔喉堵塞导致注水井高压欠注与生产井低产低效等生产瓶颈问题。构建了生物表活剂与纳米SiO2生物基纳米流体驱油体系，探讨了其对岩石润湿性、岩心驱油效果以及多孔介质油水分布的影响，解析了其提高低渗透储层原油采收率的机理。另一方面，采用高通量测序技术研究了低渗透油藏内微生物群落结构的多样性及特征，筛选分离出了四株高效Fe(III)还原菌，研究了其与储层不同粘土矿物的相互作用机制，揭示了低渗透油藏储层渗流与孔道减阻生物化学原理。.采用生物表活剂修饰纳米二氧化硅颗粒制备出了性能稳定的纳米流体。当其浓度保持在临界胶束浓度时，纳米流体稳定。SiO2纳米颗粒的浓度控制在1000mg/L以下。纳米流体使岩石表面润湿性趋向于亲水润湿，提高注水驱替的波及面积。物理模拟岩心驱替实验表明，50mD左右的低渗岩心，水驱采油率为46%左右，注入纳米流体后，采收率提高了4-18%，10mD左右的特低渗岩心，水驱采油率为26%左右，颗粒浓度为100mg/L的纳米流体，原油回收率提高了22%。1mD左右的超低渗岩心，水驱油率仅为13%左右，注入鼠李糖脂溶液之后，几乎没有作用。注入纳米流体后，采收率提高了22%。Fe(III)还原功能菌均能在兼性厌氧条件下代谢产生大量的生物有机酸，并能够高效的还原蒙脱石矿物中的Fe3+为Fe2+。四株Fe(III)还原功能菌，作用后蒙脱石特征峰强度降低且半峰宽数值增加，矿物物相发生转变，生成伊利石等新的次生矿物。抑制了粘土矿物水化膨胀，其抑制膨胀率分别为45.65%、48.91%、35.87%和40.22%。在克拉玛依油田开展了微生物驱油与缩膨增注的矿场试验，取得了显著的增油效果，这将成为油田采油的一项新技术。