Optimization Of Screen Completion Technology In Broken Soft Coal Seams

The coal seam gas outburst seriously restricts the safe mining of coal mine,and the gas pre-drainage is the necessary condition to ensure the safe production of coal mine,and the drilling technology is an important means to solve the gas pre-drainage.Due to the soft texture and high pressure of soft outburst coal seam,hole wall collapse and channel deformation are caused after drilling construction,resulting in poor gas flow,blocking screen tube down,and unable to efficiently extract and utilize gas.Taking Sijiazhuang Coal Mine as the engineering background,this paper optimizes the screen completion technology of broken soft coal seam in order to achieve the purpose of efficient gas extraction.This paper analyzed the factors influencing the drilling quality of the underground broken soft coal seam according to the geological conditions of the study area by the research methods of field data analysis,theoretical analysis and indoor design calculation.On this basis,it optimized the drilling process,screen tube lowering process and supporting equipment.Based on previous studies on the sand control and compression performance of the screen tube,FLUENT software was used to simulate the flow field inside the screen tube.By analyzing the flow field characteristics inside the screen tube,the shape and arrangement of the screen holes were optimized.Finally,the optimized screen completion technology was used in Sijiazhuang Coal Mine to carry out drilling tests.The results show that the coal seam firmness coefficient of Sijiazhuang mining area is less than 1,which belongs to broken soft broken coal seam.The main factors affecting the quality of drilling include geological factors,technological factors and equipment factors.In the study area,the coal seam hardness coefficient,fault and collapse column are the main factors affecting the quality of drilling.The creep characteristics of coal rock containing gas will lead to the collapse and deformation of drilling holes,which will decrease the quality of drilling holes.The process and equipment can be optimized according to the mining conditions to improve the quality of drilling.The optimized drilling process is air screw drilling,which reduces the influence of drilling process on drilling quality.To optimize the screen tube lowering process,the drill pipe is used as the wall casing to lower the screen tube,which can effectively prevent the obstruction caused by the hole collapse to lower the screen tube.The simulation analysis shows that under the same conditions,the circular hole screen with phase difference of 90° has smaller eddy current reduction zone and convection reduction zone,the energy consumption in the screen is the minimum,and the weighted average velocity at the outlet is 34.5m/s.The field monitoring results demonstrate that the gas extraction effect is improved by 20%,and the screen tube discharge rate is 97%,which indicates that the optimized process and equipment have improved the gas extraction efficiency,verifies the reliability of the research results,and provides an example for similar research areas.