Research on lift pressure system with combined pipeline and intensive drill-hole gas drainage along the layer in low permeability coal seam

Abstract

Aiming at the problem of gas pre-drainage in high gas and low permeability coal seam,the strengthen technology of coal seam gas extraction was put forward which is the system of combined pipeline to lift the negative pressure and intensive large diameter drill-hole along seam.The extraction principle of realizing the permeable increasing in all zone by intensive large diameter drill-hole along seam was explained.According to the continuity liquid flow equation and energy equation,the expression of liquid energy changes was established to get liquid energy gradient lines in section competent pipeline.Combined with the “negative pressure-flow” characteristic curve of pre-drainage gas drill-hole,the mechanism of increase the negative pressure and extraction scalar through combined pipeline was clarified and the parameters of strengthen extraction technology in coal seam was confirmed by practical experience.The practice showed that this technical effect on governance gas was remarkable,the gas extraction rate in working face was above 55% and the production capacity increased from 1.2 Mt/a to 1.8 Mt/a.The upper corner gas concentration was under the safety standard,and thus the safety and efficiently mining in complicated geological conditions was realized.

Keywords

• low permeability
• pre-drainage in coal seam
• intensive drill-hole along seam
• energy gradient lines
• lift pressure system with combined pipeline