强吸附-疏水性纳米聚硅微粒的制备及其在低渗油田微孔道固液界面的减阻增注行为研究

Low permeability oil fields contribute more than 60% of all the crude oil reserve discovered in China. In such oil fields strong seepage resistance caused by the micro-pore structure in ganisters leads to a under 30% low crude oil recovery rate by flooding. Current resistance reduction technologies relying on acidizing and fracturing have short efficacy span while cause serious harm to contingent geological structures. Studying the effect of the micro-pore inner surface's wettability on seepage resistance is critical in theory and practice to developing efficient resistance reduction and flooding enhancement technologies that are environment-friendly. This research chooses nano-polysilicon particles as the functional carriers for their similar chemical composition to oil reservior ganisters. By designing special molecular groups and adjusting their surface structure, it aims at synthesizing a family of super-hydrophobic composite nano-particles that show strong "anchoring" adsorptivity on the inner surface of micro-pore channels. These nano-particles can be used to creat stable water-base "nano-scrap" dispersion systems. In a low permeability oil field treated with such a system, adsorbing the nanoparticles modifies the micro-pore inner surface at no other cost to the reservior. This helps to reduce resistance and enhance water injection, thus improving oil recovery. This research will study the effect of surface modifiers on the properties of functional nanoparticles to design and prepare surface functionalized nanometer polysilicon; it will characterize the conditions for phase separation of the water-base nanopartcle dispersion system and the adsorping-wetting behavior of such nano-polysilicon on the micro-pore inner surface to construct hydrophobic micro-channel surfaces; it will explore the effect of the nano-polysilicon layer on the micro-pore inner surface on the seepage dynamics and tribology under low permeability and high pressure, to reveal the mechanism in reducing resistance and enhancing water injection of such nano-polysilicon materials. This research will provide essential data and theoretical basis for applying nano-polysilicon materials in oil recovery by flooding in low permeablity oil fields.

我国已探明石油储量的60%以上属低渗透油藏，由于岩隙孔道细小、渗流阻力大，原油采收率不足30%，且现有的酸化压裂减阻技术有效期短、对地层伤害严重。探索微孔道表面润湿特性对渗流阻力的影响规律，对开发高效环保减阻增注技术有重要的理论意义和应用价值。 .本项目拟采用与油藏砂岩有相似化学组成的纳米聚硅微粒为功能载体，通过分子设计和表面结构调控，合成在微孔道表面具有吸附"钉扎"作用的超疏水性复合纳米微粒，并制成稳定的水分散体系。通过对油藏微孔道表面无害吸附改性，实现减阻增注，提高原油采收率。 .研究表面修饰基团对纳米聚硅的吸附性、疏水性的影响，探索纳米聚硅水分散体系的相分离条件及其在微孔道表面的吸附-润湿行为，构建微孔道的疏水表面；通过研究低渗、高压下微孔道表面吸附层对渗流行为和固液摩擦学行为的影响，揭示纳米聚硅材料的减阻增注作用机理，为纳米材料在低渗透油田注采工艺中应用提供基础数据和理论依据。

低渗透油藏岩石由于孔道细小、渗透率低，注水开发过程中常存在喉道堵塞、注水压力过大、开发效率低等问题。利用疏水性纳米聚硅在岩石表面改性可显著降低注水阻力，增加注水量。但疏水纳米聚硅常以聚集体形式存在，且需要有机溶剂分散携带，造成适用范围较窄和资源浪费。本项目针对小尺寸、水分散性的疏水纳米聚硅开展了如下研究工作：.（1）以硅酸钠为前驱体，有机硅化合物为修饰剂，构建了强吸附-超疏水纳米聚硅微粒，并通过调整极性和吸附亲水性基团，获得了具有水分散性能的纳米聚硅；发现了“化学破碎”纳米聚硅方法，可使由粒径20nm左右纳米颗粒形成的聚集体（约1μm）解聚、并进一步破碎为小于10nm的碎片，适用于特、超低渗油藏的孔道改性。.（2）探索了修饰剂化学组成和空间位阻与纳米颗粒尺寸、表面微观结构的构效关系，掌握了纳米聚硅的结构和性能调控规律；研究了纳米颗粒与表面修饰剂反应的热力学和动力学规律；通过对反应介质、表面活性剂对聚集-解聚集状态的调控，实现对纳米颗粒的高效纯化。开发了规模化制备纳米聚硅的原位表面修饰技术。.（3）开发了纳米聚硅均匀可控的环境响应性相分散-分离工艺，以调控纳米颗粒在岩石表面的吸附-润湿性转变行为；研究了其对水/岩石界面和注入液流变学行为的影响，发展了纳米减阻增注作用机制。.（4）利用超疏水性纳米聚硅在石英砂表面构筑了超疏水性微纳结构，制备了物理化学性质稳定的超疏水支撑剂；构建了负载交联剂的纳米聚硅、负载长碳链化合物的纳米聚硅驱油剂。可用于压裂措施后注水通道减阻增注，调控油水流度比，调高采收率。.（5）开发了纳米聚硅减阻增注剂单釜2000L规模化制备工艺和油田现场施工工艺，在长庆、延长等油田进行了现场实验，累计增加注水9243m³，获得了很好的减阻增注效果。.本项目建立了多种低渗透油藏开采用纳米功能材料的结构调控及制备方法，发现了化学破碎纳米聚硅方法，阐明了作用机制，为低渗油田纳米材料的开发提供了理论依据和基础数据。