三塘湖盆地条湖—马朗凹陷侏罗系西山窑组巨厚煤层孔隙多尺度联合表征

Combined multi-scale characterization of pores in ultra-thick coal seams of Jurassic Xishanyao Formation, Tiaohu-Malang sags, Santanghu Basin

陈跃 雷琪琪 马东民 王馨 王兴刚 黄蝶芳 荣高翔

CHEN Yue LEI Qiqi MA Dongmin WANG Xin WANG Xinggang HUANG Diefang RONG Gaoxiang

1. 西安科技大学 地质与环境学院, 西安 710054; 2. 中国石油 吐哈油田分公司 勘探开发研究院, 新疆 哈密 839009; 3. 西安荣翔精细化工有限责任公司, 西安 710000

1. College of Geology and Environment, Xi'an University of Science and Technology, Xi'an, Shaanxi 710054, China; 2. Research Institute of Exploration and Development, Tuha Oilfield Company, PetroChina, Hami, Xinjiang 839009, China; 3. Xi'an Rongxiang Fine Chemical Co. Ltd., Xi'an, Shaanxi 710000, China

三塘湖盆地侏罗系西山窑组中下部巨厚煤层分布广泛，然而目前对于巨厚煤层孔隙特征的研究较少。为精细表征盆地条湖—马朗凹陷煤储层孔隙特征，以西山窑组9-1和9-2煤为研究对象，通过高压压汞、低温液氮吸附、核磁共振、CT扫描、扫描电镜等实验手段和孔隙—裂隙分析系统(PCAS)探究其孔隙发育特征。结果表明，两煤分层煤样表面形貌差异较大，9-1煤表面含有大量矿物晶体颗粒，气孔、角砾孔、摩擦孔以及微裂隙发育，孔裂隙拓扑结构明显，9-2煤具有明显的原生纤维结构，裂隙规模小而分散。两煤层孔隙结构分形特征差异明显，9-1煤比9-2煤非均质性更强，液氮吸附曲线属于Ⅱ型，存在H4型曲线滞后环。9-2煤微孔和小孔分维值分别为2.53和2.63，复杂程度更高，渗流孔连通性更强。煤样多重分形特征表明，小孔径孔隙分布较集中，分布范围较小，该孔径段非均质性更强，其中9-1煤孔径分布集中性更强，孔径分布间隔相对更均匀。采用联合表征煤样全尺度孔径分布特征，9-2煤总孔容大于9-1煤，大孔体积占比最大，分别为47.97%和44.48%，其次为中孔和小孔，微孔占比最少；微孔对两煤层孔比表面积贡献最大，分别为62.67%和58.43%；9-1煤各孔径的孔容贡献率与孔径大小呈正相关，而孔比表面积与孔径大小呈负相关。

The ultra-thick coal seams in the middle and lower parts of the Jurassic Xishanyao Formation in the Santanghu Basin are widely distributed. However, research on the pore characteristics of these ultra-thick coal seams is limited. To accurately characterize the porosity features of these coal reservoirs in the Tiaohu-Malang sags of the Santanghu Basin, the study examined the 9-1 and 9-2 coal samples of the Xishanyao Formation. Techniques such as high-pressure mercury intrusion porosimetry, low-temperature liquid nitrogen adsorption, nuclear magnetic resonance (NMR), CT scanning, scanning electron microscopy (SEM), and the pore-crack analysis system (PCAS) were used to investigate pore development characteristics. The results show significant differences in surface morphology between the two coal seam samples. The surface of the 9-1 coal sample contains a large number of mineral crystal particles, with well-developed pores, breccia pores, friction holes, and micro-fractures, displaying a distinct pore-fracture topological structure. The 9-2 coal sample exhibits prominent primary fibrous structures, with smaller and more dispersed fractures. The fractal characteristics of the pore structures also differ significantly between the two coal seams, with the 9-1 coal sample showing stronger heterogeneity. Its liquid nitrogen adsorption curves correspond to type Ⅱ with a H4 hysteresis loop. For the 9-2 coal sample, the fractal dimensions of micropores and small pores are 2.53 and 2.63, respectively, indicating higher complexity and better permeability connectivity. Multifractal characteristics analysis shows that pores of small diameters exhibit a more concentrated distribution and a narrower range, with stronger heterogeneity. The pore distribution of 9-1 coal sample is more concentrated, with a relatively more uniform pore size distribution intervals. Using a combined full-scale characterization method, it is revealed that 9-2 coal sample has a higher total pore volume than 9-1. Macropores have the largest volume proportion, accounting for 47.97% and 44.48%, respectively, followed by mesopores and small pores, and the proportion of micropores is the smallest. Micropores contribute the most to the pore specific surface areas for both seams, which are 62.67% and 58.43%, respectively. For the 9-1 coal sample, the pore volume contribution positively correlates with pore size, while the specific surface area contribution negatively correlates with pore size.

国家自然科学基金项目(41902175)、中国石油科技攻关项目(2021DJ2306)和山西省科技厅揭榜招标项目(20201101002)联合资助。

https://doi.org/10.11781/sysydz2025010104