The pore structure of marine-continental transitional shales from the Longtan Formation in Guizhou, China, was investigated using fractal dimensions calculated by the FHH (Frenkel-Halsey-Hill) model based on low-temperature N₂ adsorption data. Results show that the overall (fractal dimension under low relative pressure, ) and (fractal dimension under high relative pressure, ) values of Longtan shales were relatively large, with average values of 2.7426 and 2.7838, respectively, indicating a strong adsorption and storage capacity and complex pore structure. The correlation analysis of fractal dimensions with specific surface area, average pore size, and maximum gas absorption volume indicates that can comprehensively characterize the adsorption and storage capacity of shales, while can effectively characterize the pore structure complexity. Further correlation among pore fractal dimension, shale organic geochemical parameters, and mineral composition parameters shows that there is a significant positive correlation between fractal dimensions and organic matter abundance as well as a complex correlation between fractal dimension and organic matter maturity. Fractal dimensions increase with an increase in clay mineral content and pyrite content but decrease with an increase in quartz content. Considering the actual geological evaluation and shale gas exploitation characteristics, a lower limit for and upper limit for should be set as evaluation criteria for favorable reservoirs. Combined with the shale gas-bearing property test results of Longtan shales in Guizhou, the favorable reservoir evaluation criteria are set as and . When is less than 2.60, the storage capacity of the shales is insufficient. When is greater than 2.85, the shale pore structure is too complicated, resulting in poor permeability and difficult exploitation.

中文翻译：

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贵州龙潭页岩毛孔分形特征

利用FHH（Frenkel-Halsey-Hill）模型基于低温N ₂吸附数据计算的分形维数，研究了贵州龙潭组海相陆相过渡页岩的孔隙结构。结果表明，总体（低相对压力下的分形维数，）和（高相对压力下的分形维数，）龙潭页岩的值相对较大，平均值分别为2.7426和2.7838，表明其强大的吸附和储存能力以及复杂的孔隙结构。分形维数与比表面积，平均孔径和最大气体吸收量的相关分析表明，它可以全面表征页岩的吸附和储藏能力，而可以有效地表征孔隙结构的复杂性。孔隙分形维数，页岩有机地球化学参数和矿物组成参数之间的进一步相关性表明，分形维数与有机质丰度之间存在显着的正相关，并且分形维数与有机质成熟度之间具有复杂的相关性。分形尺寸随粘土矿物含量和黄铁矿含量的增加而增加，但随石英含量的增加而减小。考虑到实际的地质评价和页岩气的开采特征，下限和上限应设置为有利储层的评价标准。结合贵州龙潭页岩的页岩含气性试验结果，确定了有利的储层评价标准为 和 。当小于2.60时，页岩的储存容量不足。当大于2.85时，页岩孔隙结构太复杂，导致渗透性差并且难以开采。