Characteristics and control mechanisms of coalbed permeability change in various gas production stages

• Published in: Petroleum science 2015-11, Vol.12 (4), p.684-691
• Main Authors: Tang, Da-Zhen, Deng, Chun-Miao, Meng, Yan-Jun, Li, Zhi-Ping, Xu, Hao, Tao, Shu, Li, Song
• Format: Article
• Language: English
• Subjects: Earth and Environmental Science; Earth Sciences; Economics and Management; Energy Policy; Industrial and Production Engineering; Industrial Chemistry/Chemical Engineering; Mineral Resources; Original Paper; 天然气产量; 机制; 煤层气井; 煤层渗透率; 物质平衡方法; 特征; 生产阶段; 直接控制
• ISSN: 1672-5107; 1995-8226
• DOI: 10.1007/s12182-015-0054-5

According to dimensionless analysis of the coalbed methane （CBM） production data of Fanzhuang block in southern Qinshui basin, the dimensionless gas production rate is calculated to quantitatively divide the CBM well production process into four stages, i.e., drai- nage stage, unstable gas production stage, stable gas pro- duction stage, and gas production decline stage. By the material balance method, the coal reservoir permeability change in different stages is quantitatively characterized. The characteristics and control mechanisms of change in coalbed permeability （CICP） during different production stages are concluded on five aspects, i.e., permeability trend variation, controlling mechanism, system energy, phase state compositions, and production performance. The study reveals that CICP is characterized by first decline, then recovery, and finally by increase and is controlled directly by effective stress and matrix shrinkage effects. Further, the duration and intensity of the matrix shrinkage effect are inherently controlled by adsorption and desorp- tion features.