Controlling factors and development patterns of cleats in No.8 coal seam in the central-eastern Ordos Basin

Huang Daojun; Xu Hao; Hu Jianling; Wu Xiaozhuo; Jiao Pengshuai; Chen Shida; Wang Yanqing; Dong Yu; Dai Xianduo; Wu Heng

doi:10.16186/j.cnki.1673-9787.2025060006

Abstract：Objectives Cleats serve as the primary conduits for fluid production and the key storage spaces for free gas in deep coal seams.Their characteristics directly influence methane occurrence state and flow capacity.Methods Through detailed drill core descriptions and CT scanning,cleats in the deep coal seams of the central-eastern Ordos Basin were systematically characterized.By integrating analyses of coal macroli-thotypes,mineral content,and vitrinite reflectance(Ro),formation mechanisms and main controlling fac-tors of cleats were comprehensively investigated.Results The results indicate that cleat development is con-trolled by macrolithotypes,mineral content,and coal metamorphism degree.Cleat frequency decreases pro-gressively from bright to dull coal,with cleats most developed in bright coal(averaging 19.7 cleats per 5 cm)and largely absent in dull coal.Cleats are confined to vitrinite and do not penetrate other components.An increase in mineral content gradually reduces cleat development.Cleats are most developed when the vi-trinite reflectance(Ro)ranges between 1.2%and 1.8%.Based on temporal matching analysis and the stress field evolution during major tectonic events,it is inferred that the face cleats in the study area trend NW-SE.Spatial distribution of these controlling factors was used to delineate cleat development zones,showing most intensive development in the central study area.Conclusions This study clarifies controlling factors and spatial distribution patterns of cleats in deep coal seams,confirming the dominant influence of coal macrolithotypes,mineral content,and metamorphism degree on cleat development.The findings provide a scientific basis for deep resource exploration and development.