特低渗砂岩油藏CO2-低界面张力黏弹流体协同驱油机理研究

目的特低渗油藏储层物性差、层间非均质性强,造成CO₂驱易发生气窜,提高采收率效果欠佳,其中,CO₂水气交替驱作为结合CO₂驱和水驱优势的方法,具有较高的适用性。为进一步改善CO₂-水交替驱的开发效果,开展了CO₂-低界面张力黏弹流体协同驱油研究。 方法通过界面张力和润湿性能测试评价低界面张力黏弹流体基本性能,并利用微观可视化驱油实验及岩心驱油实验等,探究了不同驱替方式的驱油效果和CO₂-低界面张力黏弹流体协同驱油过程中二者之间的“协同作用”机理。 结果低界面张力黏弹流体具备良好的界面活性和改变岩石表面润湿性能力,水驱后开展CO₂驱、低界面张力黏弹流体驱、CO₂-低界面张力黏弹流体交替协同驱,采收率可在水驱基础上分别提高0.91%、10.66%、16.25%,其提高采收率机理包括降低界面张力、改善流度比、改变岩石表面润湿性及乳化作用的协同效应等。 结论CO₂-低界面张力黏弹流体协同驱既可有效增强非均质特低渗砂岩油藏注CO₂过程中气体流动性控制,又能够降低CO₂萃取轻烃导致重质组分沉积的影响,具有协同增效作用。      

Measuring the disparity among scientific disciplines using Library of Congress Subject Headings

Scientometrics - Examining the relationships among scientific disciplines is important today, but existing methods are limited by the contents and structure of their bibliographic databases. We...     

Flow field simulation and pressure drop modeling by a porous medium in PEM fuel cells

For proton-exchange membrane fuel cells, the distribution of reactant flow in the stack is critical to the fuel cell's efficiency. The uneven distribution of reactant flow in the stack may cause poor current density, low performance, and material degradation. To understand and accurately predict the flow field in the proton-exchange membrane fuel cell system, the present study aims to develop a simple correlation to analyze the pressure drop in fuel cell stacks. The flow channel in each cell of a stack is treated as a porous medium, and a power-law model is used to approximate the porous medium momentum source term. For the stacks with fewer cell numbers, namely, 1, 5, and 10 cells, the parameters in the power law are established based on the experimental data. Then, a correlation is developed to simulate the flow and predict the pressure drop in the stack with higher cell numbers (ie, 20 and 40 cells). The simulations show that the pressure drop in each cell of a stack is almost invariable, and the average pressure drop decreases with increasing the number of cells. The flow uniformity in the stacks with different cell numbers is evaluated using the dimensionless pressure drop and the pressure drop ratios. It suggests that the lower the cell number, the more uniform the pressure drop. The developed model is conducive to efficiently designing the flow channel for a fuel cell stack with large cell numbers.     

Ferulic acid and EGCG alter the structural characteristics of ovalbumin and its application in mineral loading

This study aims to fabricate mineral-loading nanocarriers using natural materials. The interaction patterns between ovalbumin (OVA) and four water-soluble polyphenols, namely ferulic acid (FA), (-)-Epigallo-catechin 3-gallate (EGCG), gallic acid (GA) and epicatechin (EC), were investigated. Results showed that the optimised conditions for preparing stable OVA–polyphenol complexes are at the OVA–polyphenol ratio of 4:1 at pH 6, under which OVA–FA and OVA–EGCG showed the highest stability and mineral-loading capacity among four OVA–polyphenol complexes. The fluorescence results indicated that the addition of EGCG and FA induced a significant fluorescence quenching to OVA. The interaction between OVA and polyphenols involved hydrogen bonding, hydrophobic interaction and electrostatic interaction. Fourier transform infrared spectroscopy (FTIR) analysis suggested that both FA and EGCG enhanced the stability and orderliness of the structure of OVA. The transmission electron microscopy images also exhibited the spherical structure of OVA after the addition of FA and EGCG. Furthermore, scanning electron microscope–energy dispersive X-ray spectrum results suggested that OVA–FA and OVA–EGCG complexes were better mineral carriers than OVA–GA and OVA–EC. This study may serve as the theoretical support for the promising application of OVA in the fabrication of mineral-loading nanocarriers in functional food and pharmaceutic.     

Stochastic Control of a Class of Dynamical Systems via Path Limits

Journal of Dynamical and Control Systems - Some limit theorems are derived for a class of controled Markov systems with small noises. The aim is to understand the effects of strategies of actions...     

ZnO·2.7Al2O3 nanocomposite with high optical transparency

Here we report a transparent dual-phase ZnO·2.7Al₂O₃ ceramic. The composite is pore-free and consists of thin nanosheets with a spinel phase and a hexagonal phase, while the two phases match closely in both lattice and refractive index. Such features result in excellent optical transmittance (maximum value >80% in the visible spectrum) at comparable phase volume. This work may provide a new thought for the rational structural design of optical nanocomposites.     

Alkylated lignin with graft copolymerization for enhancing toughness of PLA

Journal of Materials Science - A green modification method for effectively enhancing toughness of PLA was established. Herein, alkaline lignin (LG) was firstly alkylated with dodecane, and then...     

Substrate temperature-controlled precursor reaction mechanism of PEALD-deposited MoOx thin films

Journal of Materials Science - Molybdenum oxide (MoOx) films had been grown by using plasma-enhanced atomic layer deposition (PEALD) with Mo(CO)6 precursor and O2 plasma reactant in a substrate...