The traditional reservoir classification methods based on conventional well logging are inefficient for determining the properties, such as the porosity, shale volume, J function, and flow zone index, of the tight sandstone reservoirs because of their complex pore structure and large heterogeneity. Specifically, the method that is commonly used to characterize the reservoir pore structure is dependent on the nuclear magnetic resonance (NMR) transverse relaxation time (T2) distribution, which is closely related to the pore size distribution. Further, the pore structure parameters (displacement pressure, maximum pore-throat radius, and median pore-throat radius) can be determined and applied to reservoir classification based on the empirical linear or power function obtained from the NMR T2 distributions and the mercury intrusion capillary pressure curves. However, the effective generalization of these empirical functions is difficult because they differ according to the region and are limited by the representative samples of different regions. A lognormal distribution is commonly used to describe the pore size and particle size distributions of the rock and quantitatively characterize the reservoir pore structure based on the volume, mean radius, and standard deviation of the small and large pores. In this study, we obtain six parameters (the volume, mean radius, and standard deviation of the small and large pores) that represent the characteristics of pore distribution and rock heterogeneity, calculate the total porosity via NMR logging, and classify the reservoirs via cluster analysis by adopting a bimodal lognormal distribution to fit the NMR T2 spectrum. Finally, based on the data obtained from the core tests and the NMR logs, the proposed method, which is readily applicable, can effectively classify the tight sandstone reservoirs.

中文翻译：

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基于核磁共振测井的致密砂岩储层分类

传统的基于常规测井的储层分类方法由于致密的孔隙结构和较大的非均质性而无法有效地确定致密砂岩储层的孔隙度，页岩体积，J函数和流动带指数等性质。具体而言，通常用于表征储层孔隙结构的方法取决于核磁共振（NMR）横向弛豫时间（T2）分布，该分布与孔径分布密切相关。此外，孔结构参数（位移压力，最大孔喉半径，并根据NMR T2分布和汞侵入毛细管压力曲线获得的经验线性或幂函数，可以确定并应用到储层分类中。然而，这些经验函数的有效概括是困难的，因为它们根据区域而不同并且受到不同区域的代表性样本的限制。对数正态分布通常用于描述岩石的孔径和粒径分布，并根据大小，平均半径和小孔径和大孔径的标准偏差定量表征储层孔隙结构。在这项研究中，我们获得了六个参数（体积，平均半径，表示孔隙分布和岩石非均质性的特征，并通过NMR测井计算总孔隙度，并通过采用双峰对数正态分布拟合NMR T2光谱通过聚类分析对储层进行分类。最后，根据从岩心测试和核磁共振测井得到的数据，该方法易于应用，可以有效地对致密砂岩油藏进行分类。