Abstract To better evaluate the reservoir quality and optimize shale gas extraction, it is necessary to quantitatively characterize pore structure in shale reservoirs using complementary methods. Conventional tools that have been used extensively for pore characterization include gas physisorption, mercury injection capillary pressure (MICP), nuclear magnetic resonance (NMR). Small- and ultra-small-angle scattering (SAS and USAS) techniques use neutrons or X-ray beam to penetrate shales and obtain information on its pore structure by measuring the intensity of scattered radiation within a range of scattering angles. SAS and USAS measures total pores in a size range from 0.5 nm to 20 μm. The petrophysical parameters such as porosity, pore size distribution (PSD), fractal dimension, and pore connectivity of shale reservoirs can be obtained by analyzing the SAS/USAS data using recently established mythology. The difference in the results of porosity and PSD between the scattering technique and fluid intrusion or physisorption techniques can provide unique information on closed pores. As reported in the literature, contrast-matching small-angle neutron scattering (CM-SANS) experiments can effectively characterize the accessibility of pores to various fluids to assess the pore connectivity of shale reservoirs. Future perspectives of utilizing SAS/USAS techniques are also put forward in the review.

中文翻译：

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页岩孔隙特征：小角度散射技术综述

摘要 为了更好地评价储层质量，优化页岩气开采，需要采用互补方法定量表征页岩储层孔隙结构。已广泛用于孔隙表征的常规工具包括气体物理吸附、压汞毛细管压力 (MICP)、核磁共振 (NMR)。小角和超小角散射（SAS 和 USAS）技术使用中子或 X 射线束穿透页岩并通过测量散射角范围内的散射辐射强度来获取有关其孔隙结构的信息。SAS 和 USAS 可测量尺寸范围为 0.5 nm 至 20 μm 的总孔隙。岩石物理参数，如孔隙度、孔径分布 (PSD)、分形维数、页岩储层的孔隙连通性可以通过使用最近建立的神话分析 SAS/USAS 数据来获得。散射技术与流体侵入或物理吸附技术之间孔隙度和 PSD 结果的差异可以提供关于封闭孔隙的独特信息。正如文献报道的那样，对比匹配小角度中子散射 (CM-SANS) 实验可以有效地表征孔隙对各种流体的可及性，以评估页岩储层的孔隙连通性。审查中还提出了使用 SAS/USAS 技术的未来前景。散射技术与流体侵入或物理吸附技术之间孔隙度和 PSD 结果的差异可以提供关于封闭孔隙的独特信息。正如文献报道的那样，对比匹配小角度中子散射 (CM-SANS) 实验可以有效地表征孔隙对各种流体的可及性，以评估页岩储层的孔隙连通性。审查中还提出了使用 SAS/USAS 技术的未来前景。散射技术与流体侵入或物理吸附技术之间孔隙度和 PSD 结果的差异可以提供关于封闭孔隙的独特信息。正如文献报道的那样，对比匹配小角度中子散射 (CM-SANS) 实验可以有效地表征孔隙对各种流体的可及性，以评估页岩储层的孔隙连通性。审查中还提出了使用 SAS/USAS 技术的未来前景。