煤储层孔隙结构多重分形特征控制着煤层气的运移和可持续产出，直接决定了煤层气的开采效率，对煤层气开采具有重要意义。为了研究中−高阶煤孔隙结构多重分形特征及其在煤化作用过程中的演化趋势，针对取自沁水煤田生产矿井的中−高阶煤样，整合高压压汞、低温氮气吸附实验和二氧化碳吸附实验，结合多重分形理论，表征并探究了中−高阶煤储层宏孔(> 50 nm)、介孔(2～50 nm)和微孔(< 2 nm)的多重分形特征在煤化作用过程中的演化趋势及其影响因素。结果表明，中−高阶煤宏孔、介孔和微孔的广义维数谱(D_q−q)和多重分形奇异谱(f(α)−α)均满足多重分形特征，这意味着中−高阶煤宏孔、介孔和微孔均表现出多重分形行为。相对于宏孔和介孔，微孔表现出更大的奇异性指数α₀和谱宽(∆D)值与较小的赫斯特指数(Hurst，H)值，即微孔具有更强的非均质性和更差的孔隙连通性。煤化作用促进了煤中大分子的聚合，使煤储层由宏孔优势型和宏孔−微孔并存型储层转变为更为致密的微孔优势型储层，煤中不同尺度孔隙孔径分布趋于均质化，导致中−高阶煤储层孔隙结构均质性的增强和孔隙连通性的改善。宏孔和微孔体积分数对其相应孔径范围内孔隙结构非均质性分别存在积极和消极的影响，而介孔体积分数并不是介孔孔隙孔径分布非均质性的有效约束。镜质组和惰质组对孔隙孔径分布非均质性表现出相反的影响，镜惰比(V/I)与H之间存在正相关性，与α₀之间呈负相关性，富镜质组煤发育更多的微孔从而表现出更强的孔隙结构均质性和较好的孔隙连通性。

Multifractal features of the pore structures of coal reservoirs control the transport and sustainable production of coalbed methane (CBM), which directly determines the efficiency of CBM extraction and is of great importance for CBM extraction. In order to investigate the multifractal characteristics of the pore structures of medium-high rank coals and their evolutionary trends during coalification, the medium-high rank coal samples from production mines in the Qinshui coal field were collected to investigate the evolution of the multiple fractal characteristics of medium-high rank coals macropores (> 50 nm), mesopores (2−50 nm) and micropores (< 2 nm) during coalification and their influencing factors by using multifractal theories and integrating the mercury intrusion porosimetry, low temperature nitrogen gas adsorption and low temperature carbon dioxide adsorption experiments, respectively. The results show that the generalized dimensional spectrum (D_q−q) and the multifractal singular spectrum (f(α)−α) of macro-, meso- and micropores of medium-high rank coals both satisfy the multifractal characteristics, which implies that the macro-, meso- and micropores of medium-high rank coals all exhibit multifractal behavior. Compared with macropores and mesopores, micropores have stronger non-homogeneity and lower pore connectivity exhibiting larger α₀ and ∆D values and smaller H values. Coalification promotes the aggregation of macromolecules in coal, which changes the coal reservoir type from macropores dominant reservoir and macropores-micropores coexisting reservoir to micropores dominant reservoir, and the pore size distribution of different scales in coal tends to be homogenized, leading to the improvement of pore structure homogeneity and pore connectivity in medium-high rank coal reservoirs. Macropore and micropore volume fractions have positive and negative effects on pore structure heterogeneity in their respective pore size ranges, while mesopore volume fraction is not an effective constraint on mesopore pore size distribution heterogeneity. The vitrinite and inertinite groups show opposite effects on the heterogeneity of pore size distribution, with a positive correlation between V/I and H values and a negative correlation with α₀. Vitrinite-rich coals develop more micropores and thus showing stronger pore structure homogeneity and better pore connectivity.