The southern Junggar Basin in Xinjiang is rich in coalbed methane (CBM) resources. Large-scale development is underway in the Sigong River block (SGR block) of the Fukang West Block. Based on an integrated analysis of geological and hydrogeochemical characteristics, this study clarifies the key factors affecting CBM well productivity in the SGR block. Based on gas and water production performance, four distinct productivity types of CBM wells are identified, which are jointly controlled by burial depth, local structural and hydraulic disturbance, and also governed by synergistic interplay between gas content and permeability. The optimal geological combination—comprising the 700–1000 m burial depth, syncline core structure, stagnant hydrodynamic conditions, relatively high gas content, and favorable permeability—collectively contributes to the high-productivity Type I wells with low water production. In contrast, deep coal seams (>1400 m), characterized by reduced gas content and extremely low permeability, correspond to Type IV wells, which exhibit low gas and water production. Type II wells, located in the 1000–1400 m interval, exhibit moderate and variable productivity controlled by the interplay between high gas content and a wide range of permeability. Shallow margins (<700 m) affected by coal combustion and surface water influx produce high-water and low-gas wells (Type III). Geochemical signatures effectively differentiate between these types: closed, stagnant environments (Types I/II) are marked by a Na-Cl-HCO₃/Na-HCO₃-Cl water type, moderate total dissolved solids, and low sodium chloride coefficients, while open hydrodynamic conditions (Type III) are indicated by Na-SO₄-HCO₃ water with high sodium chloride coefficients. A δD-H₂O/δ¹⁸O-H₂O ratio of 7–9, combined with favorable TDS and water type, is identified as a key indicator of high productivity. Based on these relationships, a productivity response index model incorporating critical geological and geochemical parameters was developed. This model provides a practical tool for predicting CBM well performance and targeting sweet spots, offering significant value for exploring geologically and hydrologically complex basins.

No. 5 and No. 8 coal seams in the Yichuan area, Ordos Basin, are primary targets for coalbed methane (CBM) development, yet their pore structure differences and controlling factors remain poorly understood. This study integrates CO₂ adsorption, low-temperature N₂ adsorption, and mercury intrusion porosimetry to characterize the pore structure across the full pore-size range, with fractal dimensions quantified by V-S, FHH, and J-function models. The results show that the No. 8 coal has greater CO₂-accessible specific surface area and micropore volume, with micropores (50 nm: 31–48%) proportions, along with higher porosity and permeability, and better pore openness and connectivity. Fractal analysis indicates that the No. 5 coal has higher V-S and FHH fractal dimensions, suggesting greater micropore–mesopore structural complexity, while the No. 8 coal exhibits a higher J-function fractal dimension, reflecting stronger pore throat heterogeneity. Correlation analysis further indicates that micropore development is closely associated with coalification degree and vitrinite content; mesopore characteristics are associated with mineral matter and show a non-monotonic relationship with ash yield; and macropore–fracture systems are related to depositional setting and burial depth. The delta-plain-sourced No. 5 coal, with shallower burial and greater lithological heterogeneity, appears to retain better-developed seepage pathways, whereas the marine–continental transitional No. 8 coal, buried deeper and more compacted, is characterized by a dominance of adsorption space with limited connectivity. Accordingly, the pore structure of the No. 5 coal appears more favorable for gas seepage, while that of the No. 8 coal appears more favorable for gas adsorption. These pore-structure-based interpretations may provide a basis for differentiated CBM development strategies in the study area, although they should be regarded as preliminary pending validation with production data.