Influencing factors and parameter optimization of staged fracturing in thin and medium coal seam group in Songhe mine in western Guizhou

At present, the CBM wells in thin and medium coal seam group show commonly the characteristics of "high production capacity but short period, fast attenuation and large attenuation amplitude in the early stage, difficult recovery in the late stage". Aiming at this phenomenon, Songhe mine in western Guizhou was taken as example to conduct comparative analysis of the engineering effect of demonstrative well group from the characteristics of coal reservoir occurrence, the reformative effect and influencing factors of staged fracturing, optimization of the construction parameters and engineering tests were carried out. The analysis showed that the staged fracturing of the combined layers is the main way for CBM development in multi-seam, the reformative effect is influenced by interlayer compatibility and development mode; ball sealer staged fracturing is affected greatly by interlayer span, effective perforation thickness, construction parameters and cementing quality. Based on the analysis of influencing factors, measures for optimization of construction parameters were proposed, that is:construction displacement of 6-8 m³/min, prepad liquid proportion of 40%-50%, single hole flow of 0.2 to 0.3 m³/min, sand plug of front segment, the optimization scheme has been proved to have good trial effect by later engineering, it has good reference significance for parameter optimization of staged fracturing for CBM development in similar geological condition of thin and medium coal seam group.