Abstract: Coalbed methane (CBM) is an environmentally friendly unconventional natural gas resource, and its genesis types and distribution patterns are closely linked with the basin structure. Based on gas composition and stable isotope data from 2 422 CBM samples collected from 17 typical coal-bearing basins in China, this study analyzes the genetic types, distribution patterns, and enrichment models of CBM in different types of coal-bearing basins CBM mainly includes biogenic gas, thermogenic gas, and mixed gas. Biogenic CBM is primarily distributed in shallow zones along the margins of cratonic basins or near fault zones within rift basins, with maximum burial depths of less than 1 800 m and vitrinite reflectance (R_o) values below 0.5%. Thermogenic CBM is mainly found in deep zones of craton basin or in the middle-to-deep structural units of foreland basin, characterized by maximum burial depths exceeding 3 600 m and R_o values greater than 1.5%. Mixed CBM is widely distributed in the middle-to-shallow zones of various types of basins, with maximum burial depths ranging from 1 800 m to 3 600 m and Ro values between 0.5%and 1.5%. By integrating the distribution patterns of different genetic types of CBM with the tectonic evolution of various basins, enrichment models for different types of basins were established. (1) In craton basin, hydrocarbons accumulate in depression centers, slope belts, and marginal thrust-nappe structures. (2) In foreland basin, the enrichment areas include the lower plate of thrust faults in thrust belt, shallow slope zones in foredeep, and traps within foreland uplift zone. (3) In rift basin, hydrocarbons are enriched in trough areas and slope zones. Based on basin types and CBM genetic mechanisms, differentiated exploration and development strategies are proposed. (1) For enrichment zones of biogenic or mixed CBM in low-rank coals, such as shallow slope belts in foreland basin and trough or slope areas in rift basin, microbial stimulation techniques or optimized water-injection processes may be explored. (2) For enrichment zones of deep thermogenic CBM in the depression centers of craton basin, high-efficiency stimulation technologies such as supercritical CO₂ fracturing are recommended. These findings provide significant guidance and reference for CBM resource evaluation and development deployment across different geological settings.

Key words: coal-bearing basin, coalbed methane, genesis type, distribution pattern, exploration strategy, geological control

摘要： 煤层气是一种环境友好型非常规天然气资源,其成因类型及分布规律与盆地构造类型密切相关。基于中国17个典型含煤盆地2 422件煤层气样品的气体组分和稳定同位素组成特征,分析了不同含煤盆地煤层气的成因类型、分布规律和富集模式。煤层气主要包括生物成因气、热成因气和混合成因气3种成因类型。生物成因型煤层气主要分布在克拉通盆地边缘的浅层区域或断陷盆地的断裂带附近,其最大埋深小于1 800 m,煤岩镜质体反射率(R_o)小于0.5%;热成因型煤层气主要分布在克拉通盆地深部或前陆盆地的中—深部构造单元,其最大埋深超过3 600 m,煤岩R_o大于1.5%;混合成因型煤层气广泛分布于各类盆地的中—浅部,其最大埋深为1 800~3 600 m,煤岩R_o为0.5%~1.5%。综合不同成因类型煤层气的分布规律和不同盆地的构造演化背景,建立了不同盆地类型的煤层气富集模式:①在克拉通盆地建立了凹陷中心、斜坡带、边缘逆冲推覆构造的煤层气富集模式;②在前陆盆地建立了冲断带断层下盘、前渊斜坡带浅层、前缘隆起带圈闭的煤层气富集模式;③在断陷盆地建立了洼槽区和斜坡区的煤层气富集模式。基于盆地类型与煤层气成因机制提出了煤层气差异化勘探与开发策略:①针对前陆盆地浅层斜坡带和断陷盆地洼槽区与斜坡区的低阶煤生物成因型煤层气或混合成因型煤层气富集区,可探索微生物增产技术或注水工艺优化;②针对克拉通盆地凹陷中心的深部热成因型煤层气富集区,宜采用超临界CO₂压裂等高效改造技术。研究认识对于不同地质背景下煤层气的资源评价与开发部署具有重要指导与参考意义。

关键词: 含煤盆地, 煤层气, 成因类型, 分布规律, 勘探策略, 地质控制