石油储层微通道形成纳米减阻边界层的内在机理研究

The purpose of this project is to solve some key theory issues of reducing resistance mechanism by nanomaterial and improves the success rate and effective time of the technology of depressurization and augmented injection by nanomaterial. Theoretical research and experiment method are used to mainly investigate the inner mechanism of forming nanomaterial boundary layer in reservoir core microchannels, and master the adsorption capacity of nanomaterial with different kinds reservoir core. The contents are as the following:.To establish the mathematic computation model of the interaction of nano-particles with reservoir core, and study model Parameters and their computation method, and to test basic parameters of different oil reservoir core and compute micro forces, and then to illustrate the interaction mechanism on the formation of nano-particles boundary layer. .The various factors' influence on adsorption effect will be studied by adsorption test and microstructure performance test technology. The evaluation method of adsorption strength will be investigated, and a washing out experiment device of adsorption layer will be tried to produce and the factors and characters of influencing adsorption strength are going to be stuied. Considering the invisible characteristic of core, the magnetic resonance imaging technology is used to observe and test flow path, distributional pattern and core microchannels wettability， and study variation characteristics of core microchannel boundary layer before and after nano-treatment..The research results will provide theory evidence for selecting well and improving process, and increase success rate and effective rate of the technology. It also promotes the development of reducing resistance technology with nanomaterial and provides reference to increase oil recovery by nanotechnology.

本项目旨在解决纳米减阻机理中的一些关键理论问题，提高纳米降压增注技术的施工成功率和有效期。拟采用理论研究和实验测试的方法，重点研究储层微通道形成纳米减阻边界层的内在机理，掌握纳米材料与不同类型储层的吸附能力，包括：建立纳米颗粒与储层岩心的微观作用数学计算模型，研究模型参数及计算方法，测试不同类型油层岩心的模型参数，计算微观作用力，阐述形成纳米颗粒边界层的力学机制。通过纳米吸附实验与表面微结构等性能检测技术，研究多种因素对吸附效果的影响；研究吸附强度的评价方法，试制吸附层冲涮实验装置，研究影响吸附强度的因素与规律；针对岩心不可视的特性，采用核磁共振成像分析技术观察和测试纳米处理前后水流路径与形态分布、岩心的润湿性，研究岩心微通道边界层性能的变化。研究成果将为优选井层提供理论依据，为改进工艺提供指导，提高措施成功率和有效期，促进纳米减阻技术的发展，也为纳米驱油提高原油采收率起到借鉴作用。

本项目针对储层微通道形成纳米减阻边界层的内在机理进行了研究。重点研究了纳米液滴和纳米颗粒的微观受力特征，建立了多孔介质中水基纳米流体的微观作用计算模型和纳米流体的水流滑移模型；开展了纳米流体和储层岩心的特性实验研究，进行了模型参数的分析与计算；阐述了水基纳米流体吸附边界层的形成机制。自主研制了具有知识产权的冲刷实验装置，开展了吸附实验、冲刷实验、微观形貌和润湿性检测实验，研究多种因素对吸附效果的影响；采用核磁共振技术结合岩心驱替实验，研究了纳米流体处理岩心前后的水流减阻特征和润湿性反转的特性。研究结果显示：国内十余个油田岩心在不同盐度和酸碱性条件下的Zeta电位（ZP）大约在-14mV~-46.4mV；纳米流体的电位与粒径随浓度变化，0.2%以内ZP大约在-27mV~-378mV，粒径为40nm~170nm；纳米颗粒、纳米液滴和表面活性剂及水与孔壁在近壁处的作用能级分别为10-18J、10-17~19J、10-20J和10-21J左右，纳米颗粒依靠疏水作用力靠近孔壁，形成了“纳米颗粒+表面活性剂”的双重吸附机制，润湿性呈现“内疏外亲”的特征；若干岩心的吸附和冲刷特征显示，冲刷过程中润湿性反转，由亲水到超亲水再向疏水转化，与吸附机制的理论分析结论一致，验证了双重吸附机制。基于核磁共振技术开展了岩心驱替实验，成功表征了水基纳米流体驱替岩心的润湿性变化，T2截止值变大，润湿性变为强疏水，渗透率增加了33%以上，三者结果一致，初步形成了基于核磁共振技术的岩心润湿性变化的快速、无损的测试方法。项目成果对纳米减阻应用效果起到了一定的促进作用，2013年以来与2012年相比，水基纳米减阻技术在江苏油田应用中效果明显提高，平均有效期提高了6个月，有效率提高36.7%，单井累计增注量增加了120%。