The Erdaoling Mining area, located in Inner Mongolia, NW China, is recognized for its considerable potential in coalbed methane (CBM) exploration and development. However, the complex structures in this region have significant influences on coal reservoir characteristics, particularly pore structure features. This study focuses on the No. 2 coal seam of the Middle Jurassic Yan’an Formation. Three structural patterns were classified based on the existing structural characteristics of the study area. Coal samples of No. 2 coal seam were collected from different structural positions, and were subjected to low-temperature CO₂ adsorption (LTCO₂A), low-temperature N₂ adsorption/desorption (LTN₂A), low-field nuclear magnetic resonance (LF-NMR), and scanning electron microscopy (SEM) experiments, so that the structural controlling effects on pore structure would be revealed. Quantitative analysis results indicate that in terms of asymmetric syncline, from the limb to the core, the total porosity and movable fluid porosity of the coal decreased by 1.47% and 0.31%, respectively, reaching their lowest values at the core. Meanwhile, the dominant pore type shifted from primarily one-end closed pores to “ink-bottle” pores, indicating increased pore complexity. In the fold-thrust structure, the micropore specific surface area, micropore volume, mesopore specific surface area, mesopore volume, and total porosity show clear correlations with variations in coal seam structure. These parameters all reach their maximum values in the fault-cut zone at the center of the syncline, measuring 268.26 m²/g, 0.082 cm³/g, 0.601 m²/g, 1.262 cm³/g, and 4.2%, respectively. Simple pore types, like gas pores and vesicular pores, were identified in the syncline limbs, while open pores, “ink-bottle” pores, and complex multiporous types were mainly developed at fault locations, indicating that faults significantly increase the complexity of coal reservoir pore types. For the broad and gentle syncline and small-scale reverse fault combination, porosity exhibits a decreasing trend from the syncline limbs toward the core. Specifically, the mesopore specific surface area and movable fluid porosity increased by 52.24% and 43.69%, respectively, though no significant effect on micropores was observed. The syncline core in this structural setting developed normal gas pore clusters and tissue pores, with no occurrence of highly complex or heterogeneous pore types, indicating that neither the broad gentle syncline nor the small-scale faulting significantly altered the pore morphology. Comparatively, the broad and gentle syncline and small-scale reverse fault combination was determined to exert the strongest modification on pore structures of coal reservoir, followed by the asymmetric syncline, while the broad syncline alone demonstrated minimal influence.

The study on the hydraulic fracturing potential of coalbed methane (CBM) reservoirs aims to assess the ability of coal seams to increase permeability and gas well productivity under the action of hydraulic fracturing. It provides a theoretical basis and technical support for optimizing reservoir fracturing design and improving the efficiency of CBM development, thereby addressing the issue of unstable production enhancement effects of the reservoirs. This review analyzes the primary factors influencing the hydro-fracturing potential of CBM reservoirs, taking into account both geological conditions and mechanical characteristics, and discusses the key physical and numerical simulation techniques for stimulating CBM reservoirs. Physical simulation techniques mainly focus on pore-fracture structure characterization, rock mechanics testing, logging interpretation, and injection falloff testing in the well. Numerical simulation technologies mainly focus on geomechanics simulation, digital core simulation, fracture propagation simulation, and fracturing operation simulation. There are many problems in the current research. The results of indoor tests differ significantly from the field application effects. The calculation accuracy of the evaluation parameters for the hydro-fracturing potential of CBM reservoirs is low. The construction of digital models is influenced by mathematical statistical methods, leading to the fallacy of equivalent cognition. The prediction of the fracturing improvement effect of CBM reservoirs faces systematic deviations in engineering applications. There is a lack of a comprehensive evaluation system that covers the coordination of multienergy systems, as well as environmental and economic factors. The analysis suggests that the breakthrough paths for future research should focus on the following aspects. Improve the physical compatibility between the experimental conditions and the actual reservoir environment. Innovate modeling methods that integrate geological measurement mechanisms and data-driven approaches. Establish a dynamic simulation system that covers the evolution of multi-scale fractures and the coupling of stress. Construct a multi-source dynamic evaluation system that integrates the goals of energy integration systems, environmental constraints, and economic benefits. This is to establish a geological-engineering collaborative research framework covering the entire time and space domain, thereby promoting the precise and efficient transformation of reservoirs and the efficient development of CBM.

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.