Yao Peng, Zhang Junjian, Qin Zhenyuan, Fan Aiping, Feng Guangjun, Vandeginste Veerle, Zhang Pengfei, Zhang Xiaoyang
College of Earth Sciences & Engineering, Shandong University of Science and Technology, Qingdao 266590, China.
School of Resources and Earth Science, China University of Mining and Technology, Xuzhou 221116, China.
ACS Omega. 2024 May 23;9(22):23339-23354. doi: 10.1021/acsomega.3c09957. eCollection 2024 Jun 4.
Pore structure heterogeneity affects sandstone porosity and permeability and thus sandstone gas productivity. A total of 17 sandstone samples collected from the northwestern margin of the Junggar Basin in Xinjiang Province are investigated in this study. The pore-fracture system distribution of target sandstones is studied by high-pressure mercury injection tests. On this basis, single- and multi-fractal models are used to characterize pore structure heterogeneity, and the applicability of four models ( model, model, model, multifractal model) to characterize pore and fracture distribution heterogeneity are discussed. Moreover, a correlation between fractal dimension, pore structure parameters, and variation coefficient of porosity-permeability is discussed based on overburden permeability test results. The results are as follows. (1) (fractal dimension of model) shows a significant correlation with pore volume percentage, so the Sierpinski model could better characterize fracture distribution heterogeneity quantitatively. Multifractal dimensions are consistent with those of Sierpinski and Thermodynamic models, which indicates that the single- and multiple-fractal models are consistent. (2) The porosity and permeability decrease as a power function with higher confining pressure. The porosity and permeability behavior changes at a critical conversion pressure value. For a confining pressure lower than this critical value, the porosity and permeability decrease largely. For confining pressures higher than this critical value, the porosity and permeability vary less. In contrast, permeability has a larger variation rate and is more obviously affected by confining pressure. (3) Pore compression space is affected by the permeability variation coefficient. Compressibility, porosity, and permeability variation coefficient have no relationship with pore structure parameters since compressibility is affected by pore structure, mineral composition, and other factors in sandstone samples.
孔隙结构非均质性影响砂岩孔隙度和渗透率，进而影响砂岩气产能。本研究对取自新疆准噶尔盆地西北缘的17块砂岩样品进行了研究。通过高压压汞试验研究了目标砂岩的孔隙 - 裂缝系统分布。在此基础上，采用单分形和多重分形模型表征孔隙结构非均质性，并讨论了四种模型（模型、模型、模型、多重分形模型）对孔隙和裂缝分布非均质性的适用性。此外，基于上覆岩层渗透率测试结果，讨论了分形维数、孔隙结构参数与孔隙度 - 渗透率变异系数之间的相关性。结果如下：（1）（模型的分形维数）与孔隙体积百分比呈显著相关，因此谢尔宾斯基模型能更好地定量表征裂缝分布非均质性。多重分形维数与谢尔宾斯基模型和热力学模型的分形维数一致，这表明单分形和多重分形模型具有一致性。（2）孔隙度和渗透率随围压呈幂函数降低。在临界转换压力值处，孔隙度和渗透率行为发生变化。对于低于该临界值的围压，孔隙度和渗透率大幅降低。对于高于该临界值的围压，孔隙度和渗透率变化较小。相比之下，渗透率变化率更大，受围压影响更明显。（3）孔隙压缩空间受渗透率变异系数影响。压缩性、孔隙度和渗透率变异系数与孔隙结构参数无关，因为压缩性受砂岩样品中的孔隙结构、矿物成分等因素影响。
