Adsorption Characteristics and Main Controlling Factors of Coalbed Methane in the Southeastern Ordos Basin

The adsorption characteristics of coalbed methane serve as a critical geological parameter that governs the enrichment, accumulation, and resource evaluation of coalbed gas. These characteristics hold substantial guiding significance for predicting reservoir producibility and optimizing development strategies. In this study, 20 representative coal rock samples were systematically collected and screened from the Baode–Jixian–Huangling–Hancheng mining area located on the southeastern margin of the Ordos Basin. Comprehensive analyses were conducted, including quantitative determination of coal petrographic components, industrial property testing, and isothermal methane adsorption experiments. Single-factor and multi-factor analytical approaches were employed to identify the dominant factors influencing methane adsorption behavior. The results indicate significant heterogeneity in the microscopic composition of coal rocks within the study area. Vitrinite (2.31−77%) and inertinite (4.67−64.35%) are the predominant maceral groups, followed by liptinite (<5.7%) and mineral matter (1.17−45.09%). The Langmuir volume (V_L = 10.14−24.85 m³/t) exhibits a strong positive correlation with vitrinite content, maximum vitrinite reflectance (0.67−2.60%), and carbon content (72.7−91.34%), whereas it shows a negative correlation with ash yield, volatile matter, inertinite, liptinite, mineral components, hydrogen content, and oxygen content. Sensitivity analysis based on multiple linear regression further identifies fixed carbon content (30.42−80.76%) and hydrogen content (3.04−5.37%) as the primary controlling parameters influencing methane adsorption capacity. Empirical models for predicting methane adsorption capacity and selecting favorable exploration zones were established: V_L = 0.284FC_d + 0.578 and P_L = 0.631H_daf − 0.896, both demonstrating statistically significant correlations. These findings provide a robust scientific foundation for the identification and prioritization of prospective coalbed methane exploration targets.