Research And Application On Pressure Relief And Permeability Increasing In Low Permeability Coal Seam By Hydraulic Fracturing In Wu Yang Coal Mine

Coal seams in China have low permeability generally. Because of this, gas extraction isinefficient and safety production is affected seriously. According to gas extraction problem inhigh gassy and low permeability coal seam of Wu Yang Coal Mine, the hydraulic fracturing isproposed. Based on theoretical analysis, experiment analysis and numerical simulation,fracture initiation, propagation mechanism and effects of pressure relief and permeabilityincreasing were analyzed. Combined with field test, the parameters were determined. Thisresearch will provide theoretical basis and technical support for gas extraction in lowpermeability coal seam of Wu Yang Coal Mine.Through hydraulic fracturing theory analyzing, theoretical calculation model of fracturingpressure and fracture length were got and combined with experiment of permeability incomplete stress-strain process, the effect of pressure relief and permeability increasing wasalso studied. Using RFPA numerical simulation software, behavior of fracturing pressure andpropagation extension changing with ground stress deviation and consistent coefficient wereresearched. In addition, the field test locations were chose based on geological condition ofWu Yang Coal Mine and hydraulic fracturing program were designed. Then, hydraulicfracturing parameters were also determined including injection pressure, injection time, holesealing method and sealing depth based on both theoretical calculation formula model andnumerical simulation results. In the end, by filed test, the program was verified and theextraction effect was investigated.Field test results indicated coal permeability increased obviously after hydraulicfracturing and gas extraction concentration and flow improved significantly. The hydraulicfracturing was suitable to high gassy and low permeability coal seam of Wu Yang Coal Mine. Based on theoretical analysis, numerical simulation and field test, the main parameters ofhydraulic fracturing technology suitable to Wu Yang Coal Mine were concluded.