Research On Gas Drainage Technology Of Ground Directional Drilling

Today people pay more attention to air pollution control, and in the face of non-renewable energy consumption in an increasingly tense situation, the safety situation of coal mine is still grim, it is an effective way to solve the problem to pull out enough coal seam gas. Can not only draw a large amount of gas to use, but also to reduce the gas pressure or content to solve the problem of gas overrun and coal and gas outburst in the process of mining. The gas drainage method that larger to reduce coal seam gas pressure than the traditional method for mine safety production play a more effective role, the technology of the surface directional drilling is a worth studying of gas extraction method.This paper first analyzed the occurrence state of the gas and the gas desorption characteristics of occurrence regularity, and then from the gas pressure, the content and permeability of coal seam gas flow influence factors extended to coal seam gas seepage theory. The coal seam as an ideal uniform distribution of virtual continuum, on the basis of the darcy’s law, that the gas in the flow field around borehole radial flow is linear seepage flow, based on several related equation of gas flow in coal seam gas migration control equation is established.This paper expounds the key technology of the surface directional drilling, directional drilling deflection control technology and branch hole sidetrack drilling construction technology in the process of drilling. On the basis of theoretical analysis, the mathematical model and the borehole geometry model are deduced, the computer technology is introduced into whole architecture, using numerical simulation software, three kinds of drilling extraction method to carry on the extraction effect simulation. Simulation results show that the single span bedding vertical borehole drilling and fracturing without extraction range is not as good as the scope of multi-branch horizontal hole extraction. On the extraction effect of multi-branch horizontal hole simulation, set up the extraction time, extraction aperture and negative pressure, contrasted three kinds of factors under various conditions on drainage radius.Group of pore distribution in the coal seam extraction ability, the longer drilling extraction time, the greater the radius of influence, extraction time and gas extraction radius of influence positively correlated relationship. The extraction aperture and influence range is positively proportional relationship, under the condition of the coal seam and drilling equipment to allow, as far as possible to adopt large aperture drilling extraction from the gas. Extraction negative pressure has the most reasonable value, below this value, the influence radius increases with the increase of negative pressure, make the best possible use of the performance of the pumping equipment to the most reasonable extraction of negative pressure drainage gas.