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Role of Polymer-Based Nanofluids on Asphaltene Adsorption during Carbon Dioxide (CO2) Injection
Energy & Fuels ( IF 5.3 ) Pub Date : 2021-08-31 , DOI: 10.1021/acs.energyfuels.1c02333
Ronald Nguele 1 , Hikaru Hirota 1 , Yuichi Sugai 1 , Kyuro Sasaki 1, 2
Affiliation  

As part as efforts to prevent or to delay asphaltene adsorption during carbon dioxide (CO2) oil recovery, the role of polymer-based nanofluid on asphaltene kinetics and adsorption mechanisms was studied. The model crude oil was an asphaltene solution obtained after mixing of 1 g of asphaltenes (extracted using n-heptane) in 100 g of pure toluene. In the absence of sorbent (Berea sandstone), injecting CO2 decreased the concentration of asphaltene in the equilibrium at the rate of −0.01 mg·g–1·MPa–1 until 5 MPa, beyond which the decrease was −0.04 mg·g–1·MPa–1. The model oil in contact with sandstone wetted with formation water (0.5 wt %NaCl) prompted an asphaltene adsorption, which increased with CO2 solubility and was as high as 58 μg/g-rock. Under the same conditions, the adsorption was 3-fold lower when the wetting fluid was a nanofluid (0.05 g of alumina oxide nanoparticles into 100 g of aqueous poly(vinyl alcohol), PVOH). The measurements of interfacial tension (IFT) between the asphaltene solution and the investigated wetting fluids at different CO2 injections, showed that IFT reduction depends on CO2 solubility and the nature of wetting fluids. IFT reduction was more pronounced for water compared to nanofluid or PVOH alone. A Ward–Tordai short time approximation was employed to estimate the kinetics of asphaltene at the interface with the water, the PVOH, and the nanofluid. The estimated diffusion coefficients of asphaltenes were found within the range of ∼10–12 m2/s for water-wet sandstone and ∼10–18m2/s for PVOH-wet and nanofluid-wet sandstones, suggesting that adsorption of asphaltenes was not diffusion-controlled. Rather, it pertained to ability of the wetting fluid to provide a steric hindrance. The combined analysis of the Langmuir adsorption isotherm and the solid–liquid equilibrium model revealed that CO2 altered rather the affinity of the wetting fluid toward the asphaltenes in suspension, which defined in turn the amount of asphaltene adsorbed. A series of dynamic adsorption replicating CO2 oil recovery showed that nanofluid injected ahead of CO2 could desorb up to 35% of adsorbed asphaltene owing to a steric hindrance and the preferential affinity of alumina nanoparticles with the asphaltenes irrespective of CO2 injection pressure.

中文翻译:

聚合物纳米流体对二氧化碳 (CO2) 注入过程中沥青质吸附的作用

作为在二氧化碳 (CO 2 ) 采油过程中防止或延迟沥青质吸附的努力的一部分,研究了基于聚合物的纳米流体对沥青质动力学和吸附机制的作用。模型原油是将 1 g 沥青质(使用庚烷提取)与 100 g 纯甲苯混合后获得的沥青质溶液。在没有吸附剂(Berea 砂岩)的情况下,注入 CO 2使平衡中的沥青质浓度以 -0.01 mg·g –1 ·MPa –1的速率降低至 5 MPa,超过此降低为 -0.04 mg·g –1 ·MPa –1. 与被地层水(0.5 wt %NaCl)润湿的砂岩接触的模型油促使沥青质吸附,随着CO 2溶解度的增加而增加,高达58 μg/g-rock。在相同条件下,当润湿液为纳米流体(0.05 克氧化铝纳米颗粒进入 100 克水性聚乙烯醇,PVOH)时,吸附量降低 3 倍。在不同的 CO 2注入下沥青质溶液和研究的润湿液之间的界面张力 (IFT) 的测量表明,IFT 的减少取决于 CO 2溶解度和润湿液的性质。与单独的纳米流体或 PVOH 相比,水的 IFT 降低更为明显。使用 Ward-Tordai 短时间近似来估计沥青质在与水、PVOH 和纳米流体界面处的动力学。沥青质的估计扩散系数在水湿砂岩的约 10 –12 m 2 /s 和PVOH 湿和纳米流体湿砂岩的约 10 –18 m 2 /s范围内发现,表明沥青质的吸附是不受扩散控制。相反,它与润湿液提供空间位阻的能力有关。Langmuir 吸附等温线和固液平衡模型的综合分析表明,CO 2而是改变了润湿液对悬浮液中沥青质的亲和力,这反过来又定义了吸附的沥青质量。一系列动态吸附复制的CO 2的油回收表明,纳米流体喷射提前CO的2可以解吸到由于空间位阻和氧化铝纳米颗粒与沥青质无关CO的优先亲和力吸附沥青质的35%2的喷射压力。
更新日期:2021-09-16
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