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<p>In order to further study the pore structure characteristics of mixed-sediments reservoir and the fractal characteristics of pores at different scales, 6 rock samples of mixed-sediments reservoir in Upper Youshashan Formation of NYS oilfield were selected. Based on rock physical properties, X-ray diffraction, low temperature CO<sub>2</sub>/N<sub>2</sub> adsorption and high pressure mercury injection experiments, the fractal theory was applied to characterize the pore structure of mixed-sediments reservoir and establish the pore division criteria. The relationship between pore fractal dimension and permeability, pore structure parameters and mineral component content was analyzed. The results show that the pore diameter distribution of the mixed-sediments reservoir is multi-peak, and the pores have obvious multi-scale fractal characteristics. The reservoir space is divided into micropores, mesoporous pores and macropores with the boundary of 1.1&#xa0;nm and 50&#xa0;nm. The fractal dimension of pores at different scales is different, and the fractal dimension of micropores (D<sub>C</sub>) &gt; mesoporous fractal dimension (D<sub>N</sub>) &gt; macropore fractal dimension (D<sub>Hg</sub>). There is a significant linear positive correlation between the fractal dimension of macropores and the comprehensive fractal dimension of pores (R<sup>2</sup> = 0.9488). Macropores are the main carrier of the complexity of reservoir space and pore structure in this mixed-sediments reservoir. The fractal dimension of macropores has a strong positive correlation with permeability (R<sup>2</sup> = 0.8942), and the heterogeneity of macropores controls the seepage capacity of the mixed-sediments reservoir. The pore volume of micropores and mesoporous pores has a good positive correlation with clay minerals (R<sup>2</sup> = 0.5257, R<sup>2</sup> = 0.5782), and clay minerals are conducive to the development of micropores and mesoporous pores in the reservoir to a certain extent. The fractal dimension of mesoporous pores was positively correlated with pore volume and clay mineral content (R<sup>2</sup> = 0.8089, R<sup>2</sup> = 0.4009). The pore volume of macropore is positively correlated with that of dolomite (R<sup>2</sup> = 0.4208), and dolomite is beneficial to the development of macropore volume. There was a strong negative correlation between mesoporous pore volume and calcite content (R<sup>2</sup> = 0.6555). The research results are of great significance for the quantitative characterization of the pore structure of the mixed-sediments reservoir in this area.</p>

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Study of the pore structure and fractal characteristics of mixed-sediments reservoirs based on low-temperature gas adsorption and high-pressure mercury injection

  • 期刊论文

  • 发表日期：

    2025年4月17日

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  • Fengjuan Dong,
  • Chao Zhou,
  • Jiayi Zhou,
  • Xiaojun Ding,
  • Jun Sheng,
  • Kunkun Li,
  • Dazhong Ren,
  • Xuefei Lu

摘要

In order to further study the pore structure characteristics of mixed-sediments reservoir and the fractal characteristics of pores at different scales, 6 rock samples of mixed-sediments reservoir in Upper Youshashan Formation of NYS oilfield were selected. Based on rock physical properties, X-ray diffraction, low temperature CO2/N2 adsorption and high pressure mercury injection experiments, the fractal theory was applied to characterize the pore structure of mixed-sediments reservoir and establish the pore division criteria. The relationship between pore fractal dimension and permeability, pore structure parameters and mineral component content was analyzed. The results show that the pore diameter distribution of the mixed-sediments reservoir is multi-peak, and the pores have obvious multi-scale fractal characteristics. The reservoir space is divided into micropores, mesoporous pores and macropores with the boundary of 1.1 nm and 50 nm. The fractal dimension of pores at different scales is different, and the fractal dimension of micropores (DC) > mesoporous fractal dimension (DN) > macropore fractal dimension (DHg). There is a significant linear positive correlation between the fractal dimension of macropores and the comprehensive fractal dimension of pores (R2 = 0.9488). Macropores are the main carrier of the complexity of reservoir space and pore structure in this mixed-sediments reservoir. The fractal dimension of macropores has a strong positive correlation with permeability (R2 = 0.8942), and the heterogeneity of macropores controls the seepage capacity of the mixed-sediments reservoir. The pore volume of micropores and mesoporous pores has a good positive correlation with clay minerals (R2 = 0.5257, R2 = 0.5782), and clay minerals are conducive to the development of micropores and mesoporous pores in the reservoir to a certain extent. The fractal dimension of mesoporous pores was positively correlated with pore volume and clay mineral content (R2 = 0.8089, R2 = 0.4009). The pore volume of macropore is positively correlated with that of dolomite (R2 = 0.4208), and dolomite is beneficial to the development of macropore volume. There was a strong negative correlation between mesoporous pore volume and calcite content (R2 = 0.6555). The research results are of great significance for the quantitative characterization of the pore structure of the mixed-sediments reservoir in this area.