物理化学学报

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一种新型CO2/原油助混剂CAA8-X的应用与助混机理

马骋, 窦翔宇, 刘泽宇, 廖培龙, 朱志扬, 刘卡尔顿, 黄建滨   

  1. 北京分子科学国家研究中心, 分子动态与稳态结构国家重点实验室, 北京大学化学与分子工程学院, 北京 100871
  • 收稿日期:2020-12-08 修回日期:2021-01-05 录用日期:2021-01-06 发布日期:2021-01-08
  • 通讯作者: 黄建滨 E-mail:JBHuang@pku.edu.cn
  • 基金资助:
    国家油气重大专项(2016ZX05016-001)资助项目

Application and Mechanism of a Novel CO2-Oil Miscible Flooding Agent, CAA8-X

Cheng Ma, Xiangyu Dou, Zeyu Liu, Peilong Liao, Zhiyang Zhu, Kaerdun Liu, Jianbin Huang   

  1. Beijing National Laboratory for Molecular Sciences(BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
  • Received:2020-12-08 Revised:2021-01-05 Accepted:2021-01-06 Published:2021-01-08
  • Supported by:
    The project was supported by the National Oil and Gas Major Project (2016ZX05016-001).

摘要: CO2驱是一种具有广阔前景的提高油藏采收率的方法。其中,降低CO2与原油的最低混相压力以实现混相驱是增强CO2驱效果的重要手段。由此我们设计了由亲油基团十六烷基和亲CO2基团全乙酰蔗糖酯基结合的新型“亲油-亲CO2助混分子”十六酸全乙酰基蔗糖酯CAA8-X,研究发现,CAA8-X对超临界CO2流体和不同油相的煤油、白油以及长庆原油有优异的助混效果,界面张力消失法和细管实验法测定结果表明,CAA8-X可以将超临界CO2/长庆原油的最低混相压力降低20.5%。用分子动力学模拟计算了CO2分子与全乙酰蔗糖酯基的亲和能力,研究了这类新型“亲油-亲CO2助混分子”通过多酯头基降低与CO2亲和势能而降低油/CO2界面能的助混机理。

关键词: 烷基蔗糖酯, 超临界CO2, 两亲分子, 分子动力学, 提高采收率, 混相压力

Abstract: Surfactants are widely applied for promoting miscibility and reducing interfacial tension between oil and water phases because of their remarkable amphiphilic morphology. Along with development and popularization of tertiary oil recovery techniques, surfactants play a significant role in crude oil exploitation. Among the various tertiary oil recovery techniques, supercritical CO2-enhanced oil recovery is a promising method for improving oil recovery. However, the establishment of CO2-enhanced oil recovery brought new requirements and challenges to traditional surfactant research and development, especially for molecular design. In this method, the reduction of the minimum miscibility pressure between supercritical CO2 and crude oil is required to achieve miscible flooding-an important means to enhance oil recovery. Therefore, a novel miscible flooding agent that exhibits oil-water miscibility analogous to conventional surfactants is desirable for this method. Meanwhile, a conspicuous difference of polarity matching the high polarity of H2O molecule against low polarity of alkane molecule, which is the essential feature of traditional surfactant, won't suit this case well due to a medium polarity of CO2 molecule. According to previous work done in our laboratory, surfactants with multiple ester groups considerably reduce the minimum miscibility pressure between supercritical CO2 and crude oil. Therefore, inspired by the "oil-water-amphiphilic molecules" design, herein, we replaced the hydrophilic moiety with multiple ester groups and designed a new type of "oil-CO2 amphiphilic molecule" as a miscible flooding agent, which is composed of an alkane tail and multiple ester groups as the lipophilic and CO2-philic groups, respectively. In the strategy based on the proposed agent, the number of ester groups and the length of the alkane tail are the main parameters. In addition, we optimized the molecular structure of the proposed agent, CAA8-X, which comprises cetyl and acetyl sucrose esters as the lipophilic and CO2-philic groups, respectively. We verified that the as-synthesized agent can remarkably reduce the minimum miscibility pressure between supercritical CO2 and various types of oil samples, including kerosene, white oil, and crude oil from the Changqing region. The crude oil-CO2 minimum miscibility pressure reduction ratio was 20.5% as measured by the vanishing interfacial tension method and the slim tube test. In this study, we also established a method called the rising height method to measure the minimum miscibility pressure with significantly reduced time and equipment cost. Furthermore, to demonstrate the mechanism of this miscible flooding agent for CO2-enhanced oil recovery, the affinity between the CO2-philic group and molecular CO2 was investigated via molecular dynamics simulation. The results indicated that the "oil-CO2 amphiphilic molecule" can reduce oil-CO2 interfacial tension because of lower affinity potential energy between the CO2-philic group and molecular CO2.

Key words: Alky sucrose ester, Supercritical-CO2, Amphiphile, Molecular dynamics, Enhanced oil recovery, Miscible pressure

MSC2000: 

  • O648