Nuclear magnetic resonance (NMR) relaxometry typically involves the analysis of a relaxation time distribution. The surface relaxivity ($\rho$) is the key parameter that relates the relaxation time to the pore radius. Only a good estimate of the surface relaxivity enables a reliable determination of the pore radius distribution in a rock or sediment sample. A wide variety of approaches for the estimation of $\rho$ has been proposed; however, the accuracy of $\rho$ determination approaches has rarely been checked. We have compared different approaches of $\rho$ determination for a set of Eocene sandstone samples. Most approaches based on a weighted logarithmic mean of relaxation times or the peak relaxation time result in significant underestimation of $\rho$. However, the correct weighting of the set of relaxation times has proven to be a crucial approach in $\rho$ determination. The consequent application of geometric rules suggests the application of the weighted harmonic mean ($T_{hm}$). The specific surface area per unit pore volume ($S_{\text{por}}$), which results from the gas adsorption method, is another crucial parameter in most approaches for $\rho$ estimation. The quantities $T_{hm}$ and $S_{\text{por}}$ depend on the resolution of the used method. Applying the fractal theory, we adopt an approach that performs an upscaling of $S_{\text{por}}$ to the resolution of the NMR relaxometry. Using equal resolution for $T_{hm}$ and $S_{\text{por}}$, we obtain more reliable $\rho$ estimates. The resulting $\rho$ values are comparable with the ones determined by using the median relaxation time from NMR and the median pore-throat radius from the mercury injection capillary pressure method.

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估算始新世砂岩的核磁共振表面弛豫度：不同方法的比较

核磁共振（NMR）弛豫法通常涉及弛豫时间分布的分析。表面松弛度$\rho$）是将弛豫时间与孔半径相关联的关键参数。仅对表面弛豫度进行良好的估算，才能可靠地确定岩石或沉积物样品中的孔半径分布。各种各样的估算方法$\rho$已经提出；但是，准确性$\rho$确定方法很少被检查。我们比较了不同的方法$\rho$测定一套始新世砂岩样品。大多数基于弛豫时间或峰值弛豫时间的加权对数平均值的方法会导致对$\rho$。但是，事实证明，正确设置松弛时间的权重是解决这一问题的关键方法。$\rho$决心。几何规则的后续应用建议加权谐波均值（${Ť}_{H米}$）。单位孔体积的比表面积（${\mathrm{小号}}_{\text{波尔}}$气体吸附法产生的）是大多数方法中的另一个关键参数 $\rho$估计。数量${Ť}_{H米}$ 和 ${\mathrm{小号}}_{\text{波尔}}$取决于所用方法的分辨率。应用分形理论，我们采用了对${\mathrm{小号}}_{\text{波尔}}$核磁共振弛豫的分辨率。使用相同的分辨率${Ť}_{H米}$ 和 ${\mathrm{小号}}_{\text{波尔}}$，我们获得更可靠的 $\rho$估计。所结果的$\rho$ 该值与通过使用NMR中值弛豫时间和汞注入毛细管压力法中孔喉半径中值确定的值相当。