采用自制纳米流体SNF-SL,开展了系列原位渗吸成像实验,研究了特低渗岩心纳米流体的渗吸效果和排油成像特征.基于纳米流体对岩心润湿性、油水界面张力与黏度等因素的影响,分析了纳米流体对渗吸动力与阻力的协同作用,阐述了纳米强化渗吸的力学机制.结果显示:特低渗裂缝岩心中纳米流体的渗吸采收率比重水高2.63%和5.75%;质量百分比为0.15%和0.3%的纳米流体可使油水界面张力下降59%和65%,岩心表面接触角由73.8-降低至9.5-和6.6-,降粘率达39%和48%,从而使渗吸毛管力提高了24%和44.6%,原油粘附功下降了99.2%和99.7%,内摩擦阻力下降了39%和48%.结果表明:竖直裂缝的渗吸效果最好,水平裂缝次之,且均高于基质岩心的采收率,原因是裂缝增加了纳米流体与岩心的作用面积,缩短了横向渗吸排油距离,同时竖直缝基于重力分异作用加快了排油速度;纳米流体的质量百分比或温度越高,渗吸排油效率也就越高,原因是纳米流体通过对岩心和原油的双重作用,产生了提高渗吸动力,减小内外摩擦阻力的协同效应,提升了渗吸排油效果,体现了纳米流体强化渗吸的力学机制.
A series of in situ imbibition imaging experiments were carried out by using the self-developed nanofluid SNF-SL to study the imbibition effects and oil drainage imaging characteristics of nanofluids in ultra-low permeability core. Based on the influence of nanofluids on factors such as core wettability, oil-water interfacial tension, and viscosity, the synergistic effects of nanofluids on the power and resistance of imbibition were analyzed, and the mechanical mechanism of nano-enhanced imbibition was expounded. The results showed that the imbibition recovery rate of nanofluids in fractured cores with ultra-low permeability was 2.63% and 5.75% higher than that of nanofluids in hydrophilic cores. Nanofluid with concentration ranging from 0.15% and 0.3% could reduce the oil-water interfacial tension by 59% and 65% and the contact angle of the core surface from 73.8- to 9.5- and 6.6-, and the reduction rate of viscosity could reach 39% and 48%. Therefore, the capillary force of imbibition was increased by 24% and 44.6%. The adhesion work of crude oil was reduced by 99.2% and 99.7%. The internal friction resistance was reduced by 39% and 48%. The results demonstrated that the vertical fractures had the best imbibition effect, followed by the horizontal fractures, which were higher than the recovery rate of the matrix core. The reason lay in the fact that the fractures increased the action area between the nanofluid and the core and shortened the oil drainage distance of transverse imbibition, and the oil drainage speed was accelerated by the vertical fractures based on gravity differentiation. The higher concentration or temperature of the nanofluid led to a higher oil drainage efficiency of imbibition. The synergistic effects of improving the power of imbibition and reducing the internal and external friction resistance occured through the dual action of the nanofluid on the core and crude oil, improving the oil drainage effects of imbibition, which reflected the mechanical mechanism of the nanofluid to enhance imbibition.
[1] 邹才能, 邱振. 中国非常规油气沉积学新进展: \非常规油气沉积学" 专辑前言[J]. 沉积学报, 2021, 39(1): 1-9.
[2] 杨勇, 张世明, 曹小朋, 等. 胜利油田低渗透油藏压驱开发技术实践与认识[J]. 油气地质与采收率,
[13] Wang Q, Zhao J Z, Hu Y Q, et al. Numerical simulation of static spontaneous imbibition at the core scale [J]. Acta Petrolei Sinica, 2022, 43(6): 860-870.
[14] Shabina A Jyoti P. A generalized model for spontaneous imbibition in a horizontal, multilayered porous medium [J]. Chemical Engineering Science, 2019, 209: 115175.
[15] Zhao M W, Song X G, Lv W J, et al. The preparation and spontaneous imbibition of carbonbased nanofluid for enhanced oil recovery in tight reservoirs [J]. Journal of Molecular Liquids, 2020, 313: 113564.
[16] Wei Q, Li Z P, Wang X Z, et al. Mechanism and influence factors of imbibition in fractured tight sandstone reservoir: an example from Chang8 reservoir of Wuqi area in Ordos Basin [J]. Petroleum Geology and Recovery E-ciency, 2016, 23(4): 102-107.
[17] Wang X G, Song X F, Jiang B Y, et al. Numerical simulation of low-permeability fractured reservoirs on imbibition [J]. Science Technology and Engineering, 2013, 13(7): 1952-1956.
[18] 王新科. 二氧化硅纳米流体制备及其在超低渗油藏渗吸排油规律研究[D]. 北京: 中国石油大学, 2018.
[19] 吕文娇. 表面活性剂对纳米SiO2的表面化学调控规律及渗吸机理研究[D]. 北京: 中国石油大学, 2019.
[20] Li R, Jiang P X, Gao C, et al. Experimental investigation of silica-based nanofluid enhanced oil recovery: the effect of wettability alteration [J]. Energy and Fuels, 2017, 31: 188-197.
[21] Xu D R, Bai B J, Wu H R, et al. Mechanisms of imbibition enhanced oil recovery in low permeability reservoirs effect of IFT reduction and wettability alteration [J]. Fuel, 2019, 244: 110-119.
[22] Zhang H, Nikolov A, Wasan D. Enhanced oil recovery (EOR) using nanoparticle dispersions: underlying mechanism and imbibition experiments [J]. Energy Fuels, 2014, 28: 3002-3009.
[23] 徐鹏, 张世阔, 方松, 等. SiO2纳米颗粒在碳酸盐岩储层中强化采油实验研究[J]. 化学工程师, 2018, 32(1): 15-17, 26.
[24] 白云, 蒲春生, 刘帅, 等. 双亲纳米SiO2颗粒的制备及提高渗吸采收率性能[J]. 精细化工, 2022, 39(4): 828-836.
[25] 周德胜, 师煜涵, 李鸣, 等. 基于核磁共振实验研究致密砂岩渗吸特征[J]. 西安石油大学学报(自然科学版), 2018, 33(2): 51-57.
[26] Zhou H D, Zhang Q S, Dai C L, et al. Experimental investigation of spontaneous imbibition process of nanofluid in ultralow permeable reservoir with nuclear magnetic resonance [J]. Chemical Engineering Science, 2019, 201: 212-221.
[27] Qiu R D, Gu C Y, Xue P Y, et al. Imbibition characteristics of sandstone cores with difierent permeabilities in nanofluids [J]. Petroleum Exploration and Development, 2022, 49(2): 330-337.
[28] 杨胜来, 魏俊之. 油层物理学[M]. 北京: 石油工业出版社, 2004. 2023, 30(6): 61-71.
[3] Andersen P S, Ahmed S. Simulation study of wettability alteration enhanced oil recovery during co-current spontaneous imbibition [J]. Journal of Petroleum Science and Engineering, 2021, 196: 107954.
[4] Zhao H, Yang H B, Kang X, et al. Study on the types and formation mechanisms of residual oil after two surfactant imbibition [J]. Journal of Petroleum Science and Engineering, 2020, 19: 107904.
[5] You L J, Cheng Q Y, Kang Y L, et al. Imbibition of oxidative fluid into organic-rich shale: implication for oxidizing stimulation [J]. Energy Fuels, 2018, 32: 10457-10468.
[6] Qin C Z, Brummelenc H. A dynamic pore-network model for spontaneous imbibition in porous media [J]. Advances in Water Resources, 2019, 133: 103420.
[7] Cheng H, Wang F Y. Mathematical model of the spontaneous imbibition of water into oilsaturated fractured porous media with gravity [J]. Chemical Engineering Science, 2021, 231: 1-11.
[8] Wang F Y, Zhao J Y. Mathematical model of liquid spontaneous imbibition into gas-saturated porous media with dynamic contact angle and gravity [J]. Chemical Engineering Science, 2021, 229: 116139.
[9] 孟庆帮, 刘慧卿, 王敬. 天然裂缝性油藏渗吸规律[J]. 断块油气田, 2014, 21(3): 330-334.
[10] 王敬, 刘慧卿, 夏静, 等. 裂缝性油藏渗吸采油机理数值模拟[J]. 石油勘探与开发, 2017, 44(5): 761-770.
[11] 王家禄, 刘玉章, 陈茂谦, 等. 低渗透油藏裂缝动态渗吸机理实验研究[J]. 石油勘探与开发, 2009, 36(1): 86-90.
[12] 李爱芬, 凡田友, 赵琳. 裂缝性油藏低渗透岩心自发渗吸实验研究[J]. 油气地质与采收率, 2011, 18(5): 67-69, 77, 115-116.
