Study On The Geological Characteristics And Control Mining Technology Of Coalbed Methane In Wudong Mine

The gas explosion and coal and gas outburst in Wudong coal mine seriously threaten the safety of mine production.The study of the geological characteristics of coalbed methane and related control mining technology in this area can provide support for reducing the hidden danger of gas accident and efficient utilization of coalbed methane resources,which has important practical application value.Based on the comprehensive analysis of the regional geological background,occurrence and output characteristics of coalbed methane and the prediction of gas emission in Wudong coal mine,this paper demonstrates the necessity and feasibility of gas drainage,carries out the optimization of coalbed methane control mining technology,the control mining scheme,the process design and application,and cooperates with the coal seam permeability enhancement technology,achieving good results.The main achievements of this paper are as follows:(1)The coal bearing stratum of Wudong coal mine is Xishanyao Formation of Middle Jurassic,with a large number of coal seams,including 54 coal seams and 30 minable coal seams,with a total thickness of 169.81m and a buried depth of less than 1000m.The main coal seams B1-2(45#)and B3-6(43#)are mined,with an average coal thickness of 27.88m.The coal seams gradually become thicker from west to East,and the coal seam structure tends to be complex.The coal rank is dominated by long flame coal,weakly sticky coal and gas coal.The gas content of B1-2(45#)and B3-6(43#)coal seams is 1.20-2.83 m3/T and 2.13-3.37 m3/T,respectively.The main component is methane,with the content of 34.10%-78.98%,followed by carbon dioxide,with a small amount of nitrogen,belonging to nitrogen methane zone.The main source of mine gas is goaf gas,the absolute gas emission value is 26.01m3/min,the absolute carbon dioxide emission value is 37.64m3/min,which is a high gas mine.The permeability coefficient of coal seam is 0.35 and 0.10 m2/Mpa2.d respectively.The reserves of coalbed methane resources are 16.7 × 104Mm3,and the actual pumping capacity is expected to reach 5.02 × 104Mm3.(2)According to the prediction of the mathematical model,the gas emission of the 45#(B1-2)coal seam with the mining elevation of+500m in the north mining area of Wudong coal mine is 2.82m3/t,the gas emission of the comprehensive mining face is 0.97m3/min,and the corresponding mining level of 43#(B3-6)coal seam is 3.50m3/t and 1.50m3/min respectively.The high negative pressure gas extraction system and the low negative pressure gas extraction system are respectively used to pre extract the gas in the coal seam and the goaf,with the negative pressure greater than 13Kpa and 5Kpa respectively.The methods of pre extraction before excavation,pre extraction before mining,high-level hole drainage,lower layer interception gas extraction,extraction while mining during mining,and pre buried pipeline drainage in the goaf are comprehensively adopted,together with the hydraulic fracturing of drainage hole and proppant There are coal seam permeability increasing technologies such as controlled fracture blasting,and two sets of permanent gas drainage systems are established on the ground,forming a comprehensive coal seam gas control mining technology suitable for Wudong coal mine.(3)Through the application of coalbed methane control mining technology,in 2018,the accumulated gas drainage of Wudong coal mine reached 3.275 million M3,the comprehensive mining face drainage rate reached 59%,the driving face mining rate reached 45%,making the desorbable gas content of+500m level 45%coal seam West Wing working face sampling measurement 0.7?3.13m3/t,with an average of 1.40m3/t,all less than the evaluation value of 5.5m3/t,meeting the requirements of coal mine gas drainage,gas prevention and control effect The fruit is remarkable.