## 1 Introduction  
Tight oil and gas, as crucial components for increasing petroleum resources [1; 2], are important resources in oil and gas exploration and development. However, the development of tight reservoirs is challenging due to their poor petrophysical properties, strong heterogeneity, and ultra-low permeability [3; 4]. The porosity, permeability, pore types and micro-pore structures in tight reservoirs play a crucial role in determining the fluid flow and storage capacity of a rock, which are critical factors in rock quality analysis [5; 6; 7]. These fundamental petrophysical studies are commonly conducted using the Winland method and its derivatives [8; 9]. Hence, an accurate understanding of the micro-pore and throat structures in tight reservoirs will benefit the study of their storage capacity and flow patterns. At present, micro-CT imaging [10; 11; 12], mercury injection capillary pressure (MICP) [13; 14; 15] and nuclear magnetic resonance (NMR) [16; 17; 18; 19] experiments, as methods capable of accurately reflecting micro-to-nano scale pore features, are extensively employed for microscopic porosity studies in tight reservoirs. All techniques have certain limitations. The micro-CT imaging method utilizes 2D CT scan data to construct 3D visualizations of pore structures within core samples. However, high-resolution CT equipment is expensive, and completing 3D imagingoften requires multiple scans, which will increase the cost and duration of research. The minimum throat radius measured using MICP is contingent upon the injection pressure; a heightened injection pressure allows for the measurement of a smaller throat radius. Additionally, the permeability of the core can also be predicted based on the capillary pressure curve obtained from MICP [20]. Yet, excessive injection pressure can easily damage the original pore structure of the sample. In addition, 100% mercury saturation is hard to reach since the mercury is not in the wetting phase [6; 21]. NMR experiments can effectively detect non-connected pores and nano-scale pores in core samples [22]. Analyzing the distribution and peak positions of the transverse relaxation time, T\({}_{2}\), enables the determination of pore types and their size distribution. Additionally, the continuity of NMR signals in the T\({}_{2}\) relaxation time distribution spectrum provides insights into the connectivity between pores and fractures [23; 24; 25]. However, NMR experiments cannot intuitively reflect pore diameter size. [PERSON] et al. amalgamated findings from NMR and MICP methods and uncovered that the relationships between NMR relaxation time T\({}_{2}\) and pore size are more in accordance with the power function relations than the linear relation [26]. [PERSON] and [PERSON] utilized accessibility functions for cubic lattices, combined with coordination numbers obtained from the MICP method, to determine surface relaxivity and percolating cluster size [27]. [PERSON] et al. identified a novel method that utilizes the transverse relaxation time value (T\({}_{2c}\)) of the right endpoint of negative intervals and the corresponding centrifugal radius (r\({}_{c}\)) to determine the coefficient C, enabling the conversion of NMR T\({}_{2}\) relaxation times into pore sizes [28]. Overall, integration with other experiments or the use of empirical parameters is necessary to convert the T\({}_{2}\) relaxation time distribution spectrum into a pore size distribution diagram. In comparative analyses conducted by some researchers on the curves obtained from MICP and NMR techniques, a degree of discrepancy between the two methods was observed, with the pore size distributions revealed by each not aligning perfectly. As shown in Table 1, researchers have observed in various porous media that there exists a crosspoint in the longer T\({}_{2}\) relaxation times when comparing NMR and MICP experimental methods. The MICP method tends to underestimate the proportion of macro-pores where T\({}_{2}\) is greater than the crosspoint, while it overestimates the proportion of mesopores.