Study On Mechanical Characteristics Of Suction?Sticking Drill And Prediction Of Impact Risk In Deep Gas Coal Seam

In recent years,China's coal mines have entered the deep mining.However,it is necessary to face the problem of large in-situ stress and gas pressure in deep coal mining.In the process of mining and drilling in this environment,the phenomenon of mine dynamic disasters often occurs,often causing casualties,large-scale equipment damage and property loss and other vicious events.In the mining process of deep coal seam with impact tendency,it is easy to cause rock burst dynamic disaster due to the large local coal stress.In the mining process of high gas coal seam,the phenomenon of coal and gas outburst dynamic disaster is easy to occur because of the high gas pressure.In the mining process of deep high gas coal seam with impact tendency,under the joint action of in-situ stress and gas pressure,rock burst,coal and gas outburst accidents may occur,and even lead to the occurrence of impact outburst composite dynamic disaster.The drilling cuttings method can be used to predict the risk of different degrees in the above three situations,and the dynamic phenomena of suction and sticking often appear in the process of prediction.However,for the deep coal seam with high gas content and impact tendency,the application of drilling cuttings method in risk prediction has many disadvantages,such as heavy workload,large error of drilling cuttings collection,and incomplete information collection due to discontinuous monitoring indicators.Therefore,based on the above factors and the situation that the coal stress and gas pressure have a great influence on the suction and sticking of the drill pipe,the research group uses the self-developed drilling multi parameter test system to carry out relevant drilling tests.Under the condition that the influence of the gas pressure on the effective stress of the coal body is proved,it is proposed to monitor the coal efficiently and accurately in combination with the dynamic phenomenon of the suction and sticking during the drilling process The method of volume effective stress is used to predict the impact risk of coal seam containing gas effectively.The research results have important theoretical value and practical guiding significance for accurately obtaining the prediction index and precursor information of gas bearing coal seam.According to the research content of this topic,the paper uses the method of theoretical analysis,laboratory test and field test to study the relationship between the parameters of drilling and the effective stress of coal body under the action of different gas pressure,and establishes the best drilling gas pressure value and the critical value of each parameter through the combination of drilling suction,sticking and data analysis.During the laboratory test,due to the limitation of the actual situation and simulation conditions,the accuracy of the relevant test data results isinsufficient,which leads to a slight bias in the conclusion.Therefore,in order to increase the accuracy and preciseness of the research results,it is necessary to verify and analyze the dynamic phenomena of suction drilling and stuck drilling in the process of downhole drilling.The research results show that the influence mechanism and effect of gas pressure on the effective stress of coal body are different.Under the optimal gas pressure value,the effective stress value of coal body is not only small,but also the peak value of stress is relatively far away from the front of the working face,so as to minimize the risk of coal seam impact.Therefore,the actual theoretical value,the data of drill pipe thrust,drill pipe torque and drilling cuttings amount should be strictly controlled in the process of borehole prediction The change characteristics can represent the effective stress of coal body and have a positive correlation with it.The change rules of these three parameters in the process of coal bed drilling can be used to predict the effective stress of coal body in front of the working face and its distribution.The phenomenon of drilling suction and sticking in the field has obvious characteristics of drilling parameters.During drilling suction,the thrust value of drill pipe is obviously reduced,when sticking,the torque value of drill pipe increases several times sharply;the suction and sticking points and the peak area of effective stress of coal body are gradually transferred to the depth of coal wall with the increase of gas pressure,and have a good consistent relationship.This thesis has 34 figures,10 tables and 66 references.