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<p>Shunbei Oilfield are characterized by ultra-deep (exceeding 8000&#xa0;m) and ultra-high temperatures (surpassing 150&#xa0;°C). Conventional chemical agents struggle to achieve efficient oil displacement under such extreme temperature conditions. It holds significant importance to search for chemicals that can be effectively used in harsh environments for the efficient development. This study focuses on the chemical agents commonly used in oilfields. Through experiments including high-temperature behavior, interfacial properties, emulsification characteristics, instability dynamics of oil-in-water (O/W) emulsions, and oil-washing efficiency, to elucidate how the type and structure of chemical agents influence chemical flooding. The high-temperature resistance of sodium alpha-olefin sulfonate (AOS) is only around 155&#xa0;°C. In contrast, non-ionic surfactants include fatty alcohol polyoxyethylene ethers (AEO-9) exhibits higher than 200&#xa0;°C. All six chemical agents tested are effective in significantly reducing the interfacial tension (IFT). However, AOS exhibited a relatively poor ability to alter oil-water interfacial properties. Consequently, the O/W emulsions formed by AOS have larger droplet sizes and weaker stability, with a dewatering rate exceeding 50% within just 50&#xa0;min. Moreover, as the number of ethylene oxide (EO) groups added increases, the adsorption layer of chemical agents AEO series and castor oil polyoxyethylene ethers (EL) series at oil-water interface becomes more stable. This results in O/W emulsions with smaller droplet sizes, higher sphericity, and stronger stability. Given that the molecules in EL series are larger compared to those in AEO series, they form a thicker layer at oil-water interface. Consequently, O/W emulsions they formed do not have extremely small droplet sizes, nor do they exhibit very low viscosity. AOS demonstrates the lowest oil-washing efficiency (20.75%). AEO-9 achieves an impressive oil-washing efficiency of 78.29%, while EL-80 also performs well with an efficiency of 73.71%. The same pattern can also be observed when considering the imbibition recovery. The findings of this research can serve as a valuable guide for the screening and optimization of chemical flooding systems in ultra-high-temperature reservoirs.</p>

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Strategy for optimizing chemical systems for ultra-high-temperature reservoirs of Shunbei oilfield

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月15日

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  • Yaoyu Liu,
  • Jiang Tian,
  • Zhirong Feng,
  • Yao Wang,
  • Jia Gao,
  • Mengfan Ding,
  • Xin Chen,
  • Shun Liu,
  • Jianbin Liu

摘要

Shunbei Oilfield are characterized by ultra-deep (exceeding 8000 m) and ultra-high temperatures (surpassing 150 °C). Conventional chemical agents struggle to achieve efficient oil displacement under such extreme temperature conditions. It holds significant importance to search for chemicals that can be effectively used in harsh environments for the efficient development. This study focuses on the chemical agents commonly used in oilfields. Through experiments including high-temperature behavior, interfacial properties, emulsification characteristics, instability dynamics of oil-in-water (O/W) emulsions, and oil-washing efficiency, to elucidate how the type and structure of chemical agents influence chemical flooding. The high-temperature resistance of sodium alpha-olefin sulfonate (AOS) is only around 155 °C. In contrast, non-ionic surfactants include fatty alcohol polyoxyethylene ethers (AEO-9) exhibits higher than 200 °C. All six chemical agents tested are effective in significantly reducing the interfacial tension (IFT). However, AOS exhibited a relatively poor ability to alter oil-water interfacial properties. Consequently, the O/W emulsions formed by AOS have larger droplet sizes and weaker stability, with a dewatering rate exceeding 50% within just 50 min. Moreover, as the number of ethylene oxide (EO) groups added increases, the adsorption layer of chemical agents AEO series and castor oil polyoxyethylene ethers (EL) series at oil-water interface becomes more stable. This results in O/W emulsions with smaller droplet sizes, higher sphericity, and stronger stability. Given that the molecules in EL series are larger compared to those in AEO series, they form a thicker layer at oil-water interface. Consequently, O/W emulsions they formed do not have extremely small droplet sizes, nor do they exhibit very low viscosity. AOS demonstrates the lowest oil-washing efficiency (20.75%). AEO-9 achieves an impressive oil-washing efficiency of 78.29%, while EL-80 also performs well with an efficiency of 73.71%. The same pattern can also be observed when considering the imbibition recovery. The findings of this research can serve as a valuable guide for the screening and optimization of chemical flooding systems in ultra-high-temperature reservoirs.