Study Of The Coal-seam Permeability Impact On The Accuracy Of The Manometry Results Of Active And Passive Gas Pressure Measurement Method

The coal seam gas pressure serves as one of the most important fundamentalparameter in studying on gas issues.The accurate determination of coal seam gaspressure is particularly important.However,there are some certain errors of pressureresults measured by active and passive method and the real value in the actualmeasurement process.There are many factors affecting the error,coal seampermeability coefficient is one of the main factors influencing the accurate results ofgas pressure measurement by active and passive method,there is no research on it.Firstly,based on the Darcy’s law,to establish the drilling gas radial flow modeland boundary conditions through the theoretical hypothesis,Geting the amount of gasemitted from the coal wall of the effective influenced radius’boundary line of pressurehole.Obtained a stabilization time of gas pressure under the conditions of natural gaspressure boost and inflation.Secondly combined with the similarity theory,similarstudies carried out on laboratory and field measurement of gas pressureprocess.Finally, designing and processing of a gas pressure measuring analoginstruments,and conducting laboratory simulation tests.Nearly three months of experimental studies have shown that,when the coal seampermeability coefficient unchanged,the gas in the coal seam in the unidirectional orradial flow,Error results() of gas pressure measurement and gas pressure meetlogarithmic relationship,namely: A ln p B;The balancing time of gas pressuremeasurement and gas pressure meet power relationship,namely:h A pB(A and Bare constants).Error manometry results and the balancing time of gas pressuremeasurement decreas with increasing pressure.when the coal seam permeabilitycoefficient changed,error manometry results decreases with the increase of its.Whenthe coefficient of permeability is generally greater than10m2/M Pa2d,errormanometry results with its small change.On the contrary,error manometry results withseam permeability coefficient obvious changes.The balancing time of gas pressuremeasurement decreases with increasing coal seam permeability coefficient.When thecoefficient of permeability is generally greater than20m2/M Pa2d,small changesin the balance of time.On the contrary,The balancing time of gas pressuremeasurement results with seam permeability coefficient obvious changes.