High-mature organic-rich shale (HMORS) has substantial resource potential, and its reservoir heterogeneity is essential for shale gas resource evaluation and exploration. In this research, to characterize quantitatively the complex pore structure of HMORS in detail, we conducted monofractal and multifractal analyses using N₂ adsorption–desorption data from the Lower Permian (LP) HMORS in the Lower Yangtze South Yellow Sea, which is a prospective target for shale gas exploration. We also aimed to discuss the correlation, controlling factors, and application effects, to provide a new scientific analytical tool for characterizing the pore structure heterogeneity (PSH) of HMORS. The upper, middle, and lower sublayers of the LP are dominated by siliceous shale, clay shale (ClS), and clay shale and clay-mixed shale (ClS–ClMS), respectively. The monofractal dimensions D1 and D2 calculated by the Frenkel–Halsey–Hill model were not notably correlated, indicating that they are independent. The D1 of H3-type HMORS was significantly higher than its D2, while D1 and D2 of the H2 type were similar, indicating that slit-shaped pores have higher surface roughness than the internal structural complexity, whereas ink-bottle pores do not differ substantially. The monofractal study revealed that the overall PSH of HMORS is controlled primarily by calcareous minerals, and that of the ClS is also influenced by total organic carbon. The multifractal analysis revealed that the low-probability measure areas controlled the full-size pore size distribution heterogeneity of HMORS. The monofractal model can characterize ClS–ClMS with ink-bottle pores, and the multifractal model can characterize ClS with slit-shaped pores. In addition, D1 and the multifractal parameters were not significantly correlated [a_-10- a₁₀, Hurst index (H), a₀- a₁₀ and a_-10- a₀], whereas D2 correlated negatively with a₀-a₁₀, which had opposite a_-10-a₀ and H, indicating that the pore connectivity of the internal PSH of HMORS can be improved. Compared to monofractal analysis, the multifractal model has enhanced applicability in characterizing the PSH of HMORS quantitatively, which is of great significance for the study of widely developed HMORS with huge shale gas exploration potential in South China.

高成熟有机物富页岩 （HMORS） 具有巨大的资源潜力，其储层非均质性对于页岩气资源评价和勘探至关重要。在这项研究中，为了定量详细表征 HMORS 的复杂孔隙结构，我们使用来自长江南南海下游二叠统 （LP） HMORS 的 N₂ 吸附-脱附数据进行了单分形和多分形分析，这是页岩气勘探的前瞻性目标。我们还旨在讨论相关性、控制因素和应用效应，为表征 HMORS 的孔结构异质性 （PSH） 提供一种新的科学分析工具。LP 的上、中、下亚层分别以硅质页岩、粘土页岩 （ClS） 和粘土页岩和粘土混合页岩 （ClS-ClMS） 为主。由 Frenkel-Halsey-Hill 模型计算的单分形维度 D1 和 D2 没有显著相关性，表明它们是独立的。H3型HMORS的D1显著高于D2，而H2型的D1和D2相似，表明狭缝状孔隙的表面粗糙度高于内部结构复杂性，而墨水瓶状孔隙没有显著差异。单分形研究表明，HMORS 的整体 PSH 主要受钙质矿物控制，ClS 的 PSH 也受总有机碳的影响。多重分形分析显示，低概率测量区域控制了 HMORS 的全尺寸孔径分布异质性。单分形模型可以表征具有墨水瓶孔隙的 ClS–ClMS，多重分形模型可以表征具有狭缝形孔隙的 ClS。 此外，D1 和多重分形参数不显著相关 [_a-10- a_10，Hurst 指数 （H），a₀- a₁₀ 和 _a-10- _{a 0}]，而 D2 与 _{0-a 10} 呈负相关，其中 _{a-10-a 0} 和 H 相对，表明 HMORS 内部 PSH 的孔连接性有待改善。与单分形分析相比，多重分形模型在定量表征 HMORS PSH 方面具有更强的适用性，对华南地区广泛开发、具有巨大页岩气勘探潜力的 HMORS 的研究具有重要意义。