The reservoir quality, pore spaces and pore size distributions of Bashijiqike sandstones in Kuqa depression were described by thin sections, SEM (scanning electron microscopy) analysis and nuclear magnetic resonance (NMR) tests. In order to quantitatively characterize the complexity of pore structure, NMR T₂ (transverse relaxation time) spectrum was used for fractal analysis. This study unravels the relationships between petrophysical parameters, NMR parameters and fractal dimension of the ultra-deep tight sandstones. Primary intergranular pores are the main component of pore spaces, followed by secondary dissolution pores and micropores, and there contain microfractures. The NMR T₂ spectra are either bi-modal or uni-modal distribution. The uni-modal T₂ spectrum reflects uniform pore spaces. The coexistence of intragranular pores and intergranular pores leads to the bi-modal T₂ spectrum. There is a positive correlation between fractal dimensions and T_2gm (geometric mean of the T₂ distribution). Consequently, four pore structure types are determined according to irreducible water content, T_2gm, RQI (reservoir quality index), and the characteristics of individual pore structure are summarized. Because of the uniform pore space, Type I and Type IV have the lowest fractal dimensions. The structure of Type II and Type III are most heterogeneous due to their combination of intergranular and intragranular pores. The results help clarify the internal relationships between petrophysical parameters and microstructure, and have implications for pore structure evaluation of ultra-deep sandstones worldwide.

通过薄片、SEM（扫描电镜）分析和核磁共振（NMR）测试描述了库车坳陷巴什吉奇克砂岩储层质量、孔隙空间和孔径分布。为了定量表征孔隙结构的复杂性，采用NMR T ₂（横向弛豫时间）谱进行分形分析。本研究揭示了超深致密砂岩的岩石物理参数、核磁共振参数和分形维数之间的关系。原生粒间孔是孔隙空间的主要组成部分，其次是次生溶蚀孔和微孔，并含有微裂缝。NMR T ₂光谱是双峰或单峰分布。单峰 T ₂光谱反映了均匀的孔隙空间。粒内孔和粒间孔共存导致双峰T ₂谱。_{分形维数和 T 2gm}（T ₂分布的几何平均值）之间存在正相关。因此，根据束缚水含量，T _{2gm确定了四种孔隙结构类型}，RQI（储层质量指数），以及单个孔隙结构的特征进行了总结。由于均匀的孔隙空间，I 型和 IV 型具有最低的分形维数。II型和III型的结构由于粒间孔和粒内孔的组合而最不均匀。该结果有助于阐明岩石物理参数与微观结构之间的内在关系，并对全球超深砂岩的孔隙结构评价具有重要意义。