Li Guanlin, Guo Yinghai, Wang Huaichang, Yang Xiaokai, Hou Yundong, Ye Shiyue, Zhang Kunzhe
School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China.
Key Laboratory of Coalbed Methane Resources & Reservoir Formation Process, Ministry of Education, Xuzhou 221008, China.
ACS Omega. 2023 Feb 27;8(10):9499-9510. doi: 10.1021/acsomega.2c08189. eCollection 2023 Mar 14.
In this study, the pore-throat structure and lithological and fractal characteristics of fine-grained sandstone reservoirs of Permian Shanxi Formation in Ordos Basin are investigated using various experiments, including casting thin section, scanning electron microscopy (SEM), high-pressure mercury injection (HPMI), and nuclear magnetic resonance (NMR). The relation between rock type difference and pore structure difference is explored, and the controlling effect of pore-throat structure on physical properties of fine-grained sandstone reservoir is studied. The results show that the sandstone sample can be categorized into quartz arenites, sublitharenite, and lithic sandstone. The average porosity and permeability are, respectively, 4.46% and 0.129 mD. The pores are mainly of intergranular and intercrystalline types, and the throats are lamellar and tubular types. Furthermore, the fine-grained sandstone is typically characterized by a binary pore structure. Micropore-throat, as the main reservoir space, is the dominant factor of the reservoir physical property difference. In addition, the correlation between fractal dimension and rock composition is studied with pore-throat morphology being comprehensively analyzed. The results indicate that the quartz arenite is dominated by quartz intergranular lamellar throats, and there are numerous intergranular pores and tubular throats connecting them in litharenite and sublitharenite. Moreover, the content of pores and throats play major roles in the change of fractal dimension. The characteristics, causes, and main controlling factors of micropore and throat types should be emphatically analyzed to predict the physical properties of fine-grained sandstone.
本研究采用铸体薄片、扫描电子显微镜（SEM）、高压压汞（HPMI）和核磁共振（NMR）等多种实验手段，对鄂尔多斯盆地二叠系山西组细粒砂岩储层的孔喉结构、岩性及分形特征进行了研究。探讨了岩石类型差异与孔隙结构差异之间的关系，研究了孔喉结构对细粒砂岩储层物性的控制作用。结果表明，砂岩样品可分为石英砂岩、亚岩屑砂岩和岩屑砂岩。平均孔隙度和渗透率分别为4.46%和0.129 mD。孔隙主要为粒间孔和晶间孔，喉道为片状和管状。此外，细粒砂岩具有典型的二元孔隙结构。微孔喉作为主要储集空间，是储层物性差异的主导因素。另外，结合孔喉形态，研究了分形维数与岩石组成之间的相关性。结果表明，石英砂岩以石英粒间片状喉道为主，岩屑砂岩和亚岩屑砂岩中存在大量粒间孔和连接它们的管状喉道。而且，孔隙和喉道的含量在分形维数变化中起主要作用。应着重分析微孔喉类型的特征、成因及主要控制因素，以预测细粒砂岩的物性。
