The Numerical Simulation Research For The Parameters Of Pre-pumping Coal Seam Gas In Hebi Third Mine

Gas extraction is the main technical measures of prevention and control of coal and gas disasters and accidents, and reasonable extraction parameters can improve the extraction efficiency and reduces the risk of gas accidents. This paper analyzes the main factors influencing the extraction, and the diffusion – seepage equation is built based on the theory of gas flow and storage in coal seams, which is used to analyses the relation between the effective radius of extraction and the extraction time, drilling diameter, extraction negative pressure and the hole spacing, by using comsol simulation software to simulate. 0.74 MPa is used on the standard for defining the effective radius of extraction.Both the crossing hole and the hole drilled along seam are simulated, and the simulation results are shown below. The effective extraction radius increases over time,the drilling gas flow decreases over time and tends to be stable. The relationship between effective extraction radius and drilling diameter is analyzed by simulating four different drilling diameters, and 94 mm drilling diameter is proved to be the best drilling diameter by considering the effective extraction increment caused by the unit drilling diameters. Four different extraction negative pressure of 14.76 kPa,25kPa,35 kPa and 45 kPa is used to simulate the relationship between the effective extraction radius and extraction negative pressure, about 25 kPa is proved to be the best extraction negative pressure for the crossing hole, and 14.76 kPa is suitable for the hole drilled along seam. Rensonable hole spacing is simulated to proved that it can completely eliminate gas extraction with blank between the two drillings, so based on the effective extraction radius with the pre-draining time in half a year, the crossing hole spacing is 3.73 m, and the hole spacing drilled along seam is 2.66 m.The simulation results are in conformity with the test by contrasting each other,and the preliminary design scheme of the crossing hole and hole drilled along seam for 4101 working face are made.