驱油用可控降解链球型纳米流体：制备-构像-综合性能平衡性调控机制研究

50% or even more of the original in-place oil reserves is not currently recoverable by conventional enhanced flooding methods. Studying higher efficient recovery technology is needed to power the future. Nanoflooding techniques, as strategic alternatives, have advantages over conventional techniques for oil emulsification, wettability alteration and unique mechanisms for oil displacement. However, some key and basic issues must be addressed. In this project, degradable organic silicone will be used to prepare surface-activated and degradable nanoparticles through a modified one-step Stöber method. Then by molecular design, end-capped polymer chains will be grafted to the degradable nanoparticles, and the self-dispersion oil-displacing agents (PND) with diverse conformation will be synthesized. By regulating conformation, degradation behavior of PND can be under the control, with a tradeoff properties between stabilities over a long enough period and complete degradation ultimately and combined with controlling the nano-size of PND, requirements of flow assurance would be expected to meet, avoiding the formation plugging. Based on overall property evaluation and deep research into the influence of conformance on interfacial properties of oil/water/solid multi-phase systems, regulation mechanism of balanced performance will be understood and used to overcome the obstacles that restrict one agent into oilfield, which will be profitable to develop nanoflooding technology for higher hydrocarbon production recovery.

油田水驱与常规强化采油技术之后，仍有50%甚至以上的原油残留地下，难以有效开采，需研究进一步大幅提高采收率的新技术，来保障国家能源安全。纳米驱因其原油乳化、润湿性改变等特殊性质，可被视为常规化学驱的战略接替技术。然而要将纳米技术成功应用于油田提高采收率领域，尚有关键基础与理论问题需要研究。本项目以可降解有机硅桥段为功能单体，采用一步法制备表面官能化的纳米粒子，然后接枝上聚合物链制备得到不同构像的纳米流体（PND），来实现纳米粒子自分散稳定性；调控PND构像来调节降解行为，赋予其中长期稳定，但终极可降解能力，并调控PND尺寸使其在储层内可安全运移，从而消除储层堵塞风险；基于PND构像与油/水/固多相体系界面性质响应规律的研究，通过构像调控，平衡其剥离油膜、乳化、分散、暂堵、调剖多重功效与油水多相体系破乳间的性质矛盾，解决新型驱油剂潜在应用的瓶颈难题，并为纳米驱技术发展奠定理论基础。

本课题以可降解有机硅桥段为功能单体，采用一步法制备了表面官能化的纳米粒子，然后接枝上聚合物链制备得到12种不同构象（链球型、两亲性链球型、两亲性Janus）的球状硅基纳米材料，并将其分别分散在水中得到驱油纳米流体（PND）。研究发现，硅基纳米颗粒具有较好的长期稳定性，在加入两性离子高分子型稳定剂PSPA后其能在高矿化度水中高分散稳定。硅基纳米颗粒可以显著降低油水界面张力及改变亲油岩心表面的润湿性，在100mg/L时，油水界面张力即可降至30mN/m以下。通过研究驱油纳米流体的注入性得到了岩心渗透率与纳米颗粒粒径之间的匹配关系，结合驱油实验发现：岩心平均渗透率与纳米驱油体系尺寸匹配时，纳米驱油体系具有较好的提高采收率效果（浓度为100mg/L时，提高采收率可达11.81%）；匹配关系较差时，通过改变体系浓度或者与不同化学药剂交替注入的方式，以得到更高的提高采收率幅度。通过对纳米流体采出液的研究发现该类乳化液可通过高频/高压脉冲交流电场进行破乳。.本课题研制的驱油纳米流体在具有剥离油膜、乳化、分散、暂堵、调剖多重功效的同时，也具有可在储层内安全运移、油水多相体系易破乳的性质，为纳米驱油技术发展及应用奠定了基础。该研究成果将依托中国海油“十四五”重大科技项目开展纳米驱油体系矿场试验。