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The Chang 8 sandstone reservoir in the Pingliang North area of Changqing Oilfield presents challenges in oil utilization due to its heterogeneity and intricate oil-water relationships. Following fracturing production using the guar system, some wells exhibit minimal oil flow or even only water production. To investigate the root causes, rock cores, oil, and water samples are analyzed to understand their properties. Cores from oil-producing and water-producing wells are compared to simulate wettability under original sedimentary and reservoir conditions through oil and salt-washing treatments. Wettability assessments, including wetting angle and saturation imbibition methods, are conducted, and nuclear magnetic resonance (NMR) analysis reveals fluid distribution in the cores pre and post-treatment. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and fourier transform infrared spectrometer (FTIR) are used to examine substances extracted during washing. The study uncovers the reservoir’s complex wettability, showing mixed wet characteristics after imbibition. NMR data indicates fluid preference in different pore sizes. Wettability shifts post-treatment, possibly influenced by clay and iron mineral content. Increased core permeability post-washing suggests adsorbed substances. Analysis of washed substances identifies organic wax and inorganic salts impacting wettability by enhancing water or oil affinity. Organic matter and inorganic salts are highlighted as crucial factors affecting wettability, emphasizing the need for potent cleaning agents to restore the reservoir’s original state and improve oil recovery from tight sandstone reservoirs.

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Research on Difficulty in Utilizing Crude Oil in Complex Reservoirs and Seepage Mechanisms

  • 会议论文

  • 发表日期：

    2025年

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  • Xiaoyong Wen,
  • Hao Bai,
  • Zhiwen Li,
  • Hongtao Fei,
  • Chengwang Wang,
  • Xinlei Liu,
  • Xiaogang Yang,
  • Erdong Yao,
  • Fujian Zhou

摘要

The Chang 8 sandstone reservoir in the Pingliang North area of Changqing Oilfield presents challenges in oil utilization due to its heterogeneity and intricate oil-water relationships. Following fracturing production using the guar system, some wells exhibit minimal oil flow or even only water production. To investigate the root causes, rock cores, oil, and water samples are analyzed to understand their properties. Cores from oil-producing and water-producing wells are compared to simulate wettability under original sedimentary and reservoir conditions through oil and salt-washing treatments. Wettability assessments, including wetting angle and saturation imbibition methods, are conducted, and nuclear magnetic resonance (NMR) analysis reveals fluid distribution in the cores pre and post-treatment. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and fourier transform infrared spectrometer (FTIR) are used to examine substances extracted during washing. The study uncovers the reservoir’s complex wettability, showing mixed wet characteristics after imbibition. NMR data indicates fluid preference in different pore sizes. Wettability shifts post-treatment, possibly influenced by clay and iron mineral content. Increased core permeability post-washing suggests adsorbed substances. Analysis of washed substances identifies organic wax and inorganic salts impacting wettability by enhancing water or oil affinity. Organic matter and inorganic salts are highlighted as crucial factors affecting wettability, emphasizing the need for potent cleaning agents to restore the reservoir’s original state and improve oil recovery from tight sandstone reservoirs.