Study on the stimulation technologies for low-yield CBM wells in Zhengzhuang Block

After years' development, CBM production is currently taking shape in Zhengzhuang Block, the Qinshui Basin, Shanxi.As the drainage gas recovery continues, however, the production rate of some production wells presents the obvious decline trend. In this paper, the reasons for the low production rate of drainage wells were analyzed deeply from the aspects of geological structure (fault and collapse column) and engineering construction (fracturing fuid and fracturing parameters). In order to realize the desired reservoir stimulation effect, it was proposed to adopt active water fracturing fuid and variable displacement construction technology in construction sites, and especially to apply the fracturing technology of "high liquid rate, high sand rate and variable displacement" in low-yield wells which are deep with extra low permeability. Production decline is caused by coal bed blockage, so it was recommended to take the blockage removing measure of secondary hydraulic fracturing. And microbial blockage removing technology was, for the frst time, experimentally implemented in Zhengzhuang Block to explore its effectiveness in treating the low-yield wells in this block.