Han Changcheng, Li Guan, Dan Shunhua, Yang Yi, He Xudong, Qi Ming, Liu Geng
Xinjiang Key Laboratory for Geodynamic Processes and Metallogenic Prognosis of the Central Asian Orogenic Belt, Urumqi 830047, China.
College of Geology and Mining Engineering, Xinjiang University, Urumqi 830047, China.
ACS Omega. 2022 Aug 23;7(35):31352-31366. doi: 10.1021/acsomega.2c03717. eCollection 2022 Sep 6.
The primary factor impacting the tight sandstone reservoirs and fluid flow capacity represents the pore-throat structure. On the basis of petrophysical characteristics test, scanning electron microscopy (SEM), and casting thin-section examination of tight sandstone reservoir specimens from the Permian Lucaogou Formation in Jimsar Sag, Junggar Basin., the full-size pore-throat parameters and distribution characteristics were determined by constant-rate mercury injection (CRMI) analysis. Using fractal theory and multifractal theory, the pore architectures of sandstone pores are analyzed. Mercury intrusion capillary pressure (MICP) is used to compute the dimensions of fractals using various fractal models and multifractal characteristics. Analysis is done on the relationships between tight sandstone pore architectures and fractal and multifractal characteristics. According to the research, a network of tightly packed sandstone pores may be assessed using the dimensions of fractals computed from a 3D capillary model. When displacement pressure is increased, the dimensions of fractals rise; when permeability, pore-throat diameter, and variable coefficient are increased, it falls. Tight sandstone pores exhibit multifractal features, according to the multifractal analysis, and multifractal parameters may depict the size, concentration, and asymmetry of the pore size distribution (PSD). Sandstone's PSD is comparable when its multifractal parameters (Δα, Δ, α, α, α) are identical. Pore diameters of tight sandstone are positively connected with information dimensions and correlation dimensions , and information dimensions have a greater impact on PSD than correlation dimensions . Additionally, the 3D capillary model's dimensions of fractals and exhibit a substantial negative association. These findings play a significant guiding role in the quantitative characterization of unconventional reservoir pore structures. The multifractal technique is effective to define the heterogeneity of the sandstone pore system and to differentiate between distinct PSD in heterogeneity.
影响致密砂岩储层和流体流动能力的主要因素是孔隙结构。通过对准噶尔盆地吉木萨尔凹陷二叠系芦草沟组致密砂岩储层岩心进行岩石物理特性测试、扫描电子显微镜（SEM）分析以及铸体薄片观察，利用恒速压汞（CRMI）分析法确定了全尺寸孔隙结构参数和分布特征。运用分形理论和多重分形理论，对砂岩孔隙结构进行了分析。利用汞侵入毛细管压力（MICP），通过不同的分形模型和多重分形特征来计算分形维数。分析了致密砂岩孔隙结构与分形及多重分形特征之间的关系。研究表明，利用三维毛细管模型计算出的分形维数可以对致密砂岩孔隙网络进行评价。驱替压力增大时，分形维数增大；渗透率、孔隙直径和变异系数增大时，分形维数减小。多重分形分析表明，致密砂岩孔隙具有多重分形特征，多重分形参数可以描述孔隙尺寸分布（PSD）的大小、浓度和不对称性。当多重分形参数（Δα、Δ、α、α、α）相同时，砂岩的PSD具有可比性。致密砂岩孔隙直径与信息维数和关联维数呈正相关，信息维数对PSD的影响大于关联维数。此外，三维毛细管模型的分形维数和呈显著负相关。这些研究结果对非常规储层孔隙结构的定量表征具有重要的指导意义。多重分形技术在定义砂岩孔隙系统的非均质性以及区分非均质性中不同的PSD方面是有效的。
