Aadland Reidun C, Akarri Salem, Heggset Ellinor B, Syverud Kristin, Torsæter Ole
PoreLab Center of Excellence, Department of Geoscience and Petroleum, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway.
RISE PFI, N-7491 Trondheim, Norway.
Nanomaterials (Basel). 2020 Jul 1;10(7):1296. doi: 10.3390/nano10071296.
Cellulose nanocrystals (CNCs) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (T-CNFs) were tested as enhanced oil recovery (EOR) agents through core floods and microfluidic experiments. Both particles were mixed with low salinity water (LSW). The core floods were grouped into three parts based on the research objectives. In Part 1, secondary core flood using CNCs was compared to regular water flooding at fixed conditions, by reusing the same core plug to maintain the same pore structure. CNCs produced 5.8% of original oil in place (OOIP) more oil than LSW. For Part 2, the effect of injection scheme, temperature, and rock wettability was investigated using CNCs. The same trend was observed for the secondary floods, with CNCs performing better than their parallel experiment using LSW. Furthermore, the particles seemed to perform better under mixed-wet conditions. Additional oil (2.9-15.7% of OOIP) was produced when CNCs were injected as a tertiary EOR agent, with more incremental oil produced at high temperature. In the final part, the effect of particle type was studied. T-CNFs produced significantly more oil compared to CNCs. However, the injection of T-CNF particles resulted in a steep increase in pressure, which never stabilized. Furthermore, a filter cake was observed at the core face after the experiment was completed. Microfluidic experiments showed that both T-CNF and CNC nanofluids led to a better sweep efficiency compared to low salinity water flooding. T-CNF particles showed the ability to enhance the oil recovery by breaking up events and reducing the trapping efficiency of the porous medium. A higher flow rate resulted in lower oil recovery factors and higher remaining oil connectivity. Contact angle and interfacial tension measurements were conducted to understand the oil recovery mechanisms. CNCs altered the interfacial tension the most, while T-CNFs had the largest effect on the contact angle. However, the changes were not significant enough for them to be considered primary EOR mechanisms.
通过岩心驱替实验和微流控实验，对纤维素纳米晶体（CNCs）和2,2,6,6 - 四甲基哌啶 - 1 - 氧基（TEMPO）氧化纤维素纳米纤维（T - CNFs）作为强化采油（EOR）剂进行了测试。两种颗粒均与低矿化度水（LSW）混合。根据研究目标，岩心驱替实验分为三个部分。在第1部分中，通过重复使用相同的岩心柱塞以保持相同的孔隙结构，在固定条件下将使用CNCs的二次岩心驱替与常规水驱进行比较。CNCs比LSW多采出了5.8%的原始地质储量（OOIP）原油。对于第2部分，使用CNCs研究了注入方案、温度和岩石润湿性的影响。二次驱替观察到相同的趋势，CNCs的表现优于其使用LSW的平行实验。此外，颗粒在混合润湿性条件下似乎表现更好。当CNCs作为三次采油剂注入时，额外采出了2.9 - 15.7%的OOIP原油，高温下产生的增量油更多。在最后一部分中，研究了颗粒类型的影响。与CNCs相比，T - CNFs采出的油显著更多。然而，注入T - CNF颗粒导致压力急剧上升，且从未稳定下来。此外，实验完成后在岩心表面观察到了滤饼。微流控实验表明，与低矿化度水驱相比，T - CNF和CNC纳米流体均导致了更好的波及效率。T - CNF颗粒显示出通过破碎事件和降低多孔介质的捕集效率来提高采油率的能力。较高的流速导致较低的采油率和较高的剩余油连通性。进行了接触角和界面张力测量以了解采油机理。CNCs对界面张力的改变最大，而T - CNFs对接触角的影响最大。然而，这些变化不足以使其被视为主要的强化采油机理。
