Effective extraction radius of gas drilling in coal seam

Abstract

In order to predict effective extraction radius of drilling hole in gas control of coal mineꎬ taking No. 6 coal seam of Sijichun mine in Guizhou Province as an exampleꎬ a gas seepage model of surrounding units of boreholes was established. Thenꎬ gas pressure distribution cloud chart along radial direction at different drilling time was obtained through Comsol numerical simulation. Finallyꎬ effective extraction radius was determined based on theoretical derivation and numerical simulation data while considering critical gas pressure (0􀆰 5 MPa)ꎬ and verification was made with on ̄site test. The results show that relative error rate of theoretical and simulated effective extraction radius is less than 10%ꎬ verifying accuracy of both calculation results. Effective radius is linearly dependent on extraction time. Considering its complexity to measure effective radius on siteꎬ it can be obtained through theoretical and numerical simulation methods used in this paperꎬ which provides a theoretical basis for underground gas control.