Low-Yield Genesis of Coalbed Methane Stripper Wells in China and Key Technologies for Increasing Gas Production

For the problem where numerous coalbed methane (CBM) stripper wells exist in China, this paper analyzes the genesis of the stripper wells from the aspects of geological conditions and development technologies combined with the CBM development of some typical blocks. A series of key secondary stimulation technologies for CBM stripper wells are put forward, including low-damage fracturing fluid for preventing reservoir damages, proppants with multigraded sizes for supporting multilevel fractures, large-scale fracture network stimulation (FNS) for improving reservoir permeability, and coal measure gas development for increasing the exploitable resources within a single well scope, as well as coordinated stimulation of parent-child wells for the overall production improvement of low-yield blocks. Also, it is pointed out that all types of stripper wells could adopt the low-damage fracturing fluid and multigraded proppant and optimize the drainage schedule to inhibit reservoir damage and promote the maintenance of fracture conductivity. For resource-controlled stripper wells, large-scale FNS of coal seams, coal measure gas development, and coordinated stimulation of parent-child wells could be adopted according to the differences in resource abundance and coal seam distribution. For the stripper wells controlled by the coal structure and ground stress, FNS of the surrounding rock could be conducted to construct stable and efficient channels for CBM migration. In addition, by conducting large-scale FNS, the stimulation effect of fracturing-controlled stripper wells improves, while after unblocking and reopening the existing reservoir fractures of the drainage-controlled stripper wells, an optimized drainage schedule could be adopted to prevent reservoir damages and promote the maintenance of fracture conductivity.