高温高盐环境中纳米纤维素/有机碱杂化体系的构建及油水界面行为研究

SP and ASP flooding techniques have been considered as the predominant EOR methods in China and successfully implemented in oilfields. However, due to the technical issues of hydrolysis, salting-out, scaling, etc., of polyacrylamide based polymers, anionic surfactants and inorganic alkalis, the above recognized techniques can't be used in high temperature and salinity reservoirs. For the intent of promoting the temperature and salinity tolerance of flooding systems and their oil displacement efficiencies in harsh condition reservoirs, a complex chemical system consisting of functional NFC and organic alkali is formulated in this work. Emphasis is devoted to the interfacial behaviors between this system and crude oil in high temperature and salinity environment. Direct measurements of IFT and interfacial dilational rheology are conducted to understand the ad- and de-sorption behaviors of NFC and organic alkali at oil water interface and the structure of the interfacial film. Moreover, the emulsifying behaviors of the evaluated system and emulsion dispersion/coalescence are thoroughly examined to reveal the interaction and synergism between NFC and organic alkali at oil water interface, and thus elucidating the influences of harsh conditions and functional groups of NFC on the oil water interfacial behaviors. Eventually, on the basis of the established oil water relative permeability curves, the relationship between interfacial behaviors, synergistic effect and seepage characteristics of the fluids in porous media is tentatively presented, and thus optimizing the formulation of the system. It is hoped that these findings can provide a chemical flooding system for high temperature and salinity reservoirs, add insight into the investigations of oil recovery mechanisms and seepage law, and direct the development of harsh condition reservoirs.

聚-表二元和聚-表-碱三元复合驱技术已在我国油田取得巨大成功，但丙烯酰胺类聚合物、阴离子表面活性剂和无机碱由于水解、盐析、结垢等问题，不能满足高温高盐油藏化学驱的技术要求。为改善化学驱体系的耐温耐盐性能，提高高温高盐油藏化学驱效率，本项目拟通过高稳定性功能化纤维素（NFC）和有机碱分子间的协同作用构建一种化学驱杂化体系，重点探讨其在高温高盐环境中的油水界面行为。测定油水界面张力和界面扩张流变性，明确NFC/有机碱的界面吸附-解吸行为和界面膜结构；表征乳化和液滴分散-聚并行为，揭示界面上分子间的相互作用机制和构效关系，阐明高温高盐环境和NFC功能基团对油水界面行为的影响规律；建立油水两相相渗曲线，初步探索NFC/有机碱油水界面行为、协同作用和渗流特征的关系，进而提出组成优化思路。研究成果可望为高温高盐油藏化学驱提供一种体系，为驱油机理和渗流规律研究提供理论依据，为苛刻油藏开发提供参考。

高温高盐油藏是我国大庆、胜利、渤海等主力油田的压舱石，也是我国原油增储、稳产、上产的重要保证。化学驱是提高此类苛刻油藏采收率的主体技术和现实途径，虽然聚-表二元和聚-表-碱三元复合化学驱技术在我国油田取得巨大成功，但受制于丙烯酰胺类聚合物、阴离子表面活性剂和无机碱等水解、盐析和结垢等突出问题，传统化学驱体系已无法满足高温高盐油藏的技术需求，亟待研制新型耐温抗盐化学驱体系并明确其油水界面行为及驱油机理。该项目首次提出并构建出纳米纤维素/有机碱杂化化学驱体系，建立了原油与碱反应的动力学模式，阐明了原油中活性组分及亚组分；明确了纳米纤维素（NFC）在油水界面的分布模式及与乳液稳定性的关系，揭示了NFC吸附行为、微观渗流规律和驱油机理；构建了三种功能化NFC/有机碱复合驱体系，研究了高温高盐条件下复合驱的驱油效率，明晰了NFC表面结构和驱油效率的关系；通过稳态法建立化学驱过程油水相渗曲线，对比分析了NFC/有机碱驱和水驱的渗流特征，阐明了高温高盐环境中油水相渗变化规律，为揭示NFC/有机碱复合驱油机理提供理论指导。本项目相关成果在Soft Matter、Fuel等国际权威期刊发表学术论文7篇，授权中国发明专利1件，被连续两届SPE International Conference on Oilfield Chemistry（2019和2021年）遴选为大会报告。本项目重点研究和开发的纳米纤维材料已在长庆油田、塔河油田探索应用，初步取得成效。本项目首次将绿色纳米纤维材料引入油田化学领域，推动了我国油田化学学科向绿色、低碳、可循环方向发展，在石油领域引起广泛关注，引领了本领域国内外多个课题组、石油公司的实验和理论跟踪研究，包括加拿大卡尔加里大学Ian Gates组、挪威科技大学Ole Torsaeter组、Shell等。