Study On Multi-stage Fracturing Optimization Of CBM Horizontal Well In Qiyuan Mining Area

The 15~# seam in Qiyuan Area is mainly dominated by high-rank coal,which has the characteristics of thin coal seam,low porosity,low permeability and remarkable anisotropy,heterogeneity.Various stimulation technologies were applied to increase gas production,however,most production wells are characterized by low gas production,large water production capacity,or even no gas production.Therefore,it is necessary to optimize and research the horizontal well fracturing to improve the CBM production.Under the premise of mastering the basic characteristics of the target coal seam,combined with the experimental results,the damage mechanism of high-rank coal by different types of fracturing fluids was analyzed,and then developed a low damage fracturing fluid system;Fracture parameters and construction parameters of horizontal well multi-stage fracturing are optimized by using numerical simulation.The research results indicate that the CF-1 cleaning fracturing fluid has good performance to high-rank coal fracturing.The best production capacity can be obtained when the fracture parameters are half-length of fracture 120m,conductivity 10~15D·cm,number of cracks 5~7.The optimal construction parameters are as follows:liquid volume 300~350m3,pre-liquid ratio 20%,displacement 3~5m3/min and sand ratio about 15%.Through field applications,QY-XH well production reaches 7000m~3/d,which is a significant yield increase.This study results provides theoretical guidance for multi-stage fracturing stimulation of high-rank coal seam.