Study On Technology And Equipment Of Cleaning Wellbore In Coalbed Methane Well

CBM well drainage follows the principle of slow,continuous and stable.Discontinuous production and frequent workover operations will lead to the decline or even failure of CBM well production recovery,which will affect the development effect of CBM well.In recent years,workover problems such as pump sticking,low pump efficiency and suction port blockage caused by pulverized coal have become increasingly prominent,and have gradually become the main factors affecting the drainage and production continuity of coalbed methane wells.In order to solve the problem of workover caused by pulverized coal deposition,this paper studies as follows:Firstly,the hazards,causes and characteristics of pulverized coal are systematically summarized,and the source,causes and production process of pulverized coal are summarized from three aspects of geology,engineering and production.Based on the characteristics of pulverized coal content and particle size in the produced fluid,the regular characteristics of pulverized coal production in different production stages are analyzed,and the deposition position of pulverized coal from the formation into the wellbore and its influence on production are analyzed and summarized.Secondly,from the theory of pulverized coal settlement to the simulation analysis,the reasons and locations of pulverized coal deposition are systematically studied.Through theoretical calculation,the final settling velocity and critical carrying velocity of pulverized coal are obtained.Combined with the particle size characteristics of pulverized coal in different production stages,the reference value of daily water output of pulverized coal in different production stages is obtained.Aiming at the problem of pulverized coal deposition in different positions in the wellbore,the fluid simulation analysis is carried out by using the software,and the reasons for the deposition are clear.The ideas of improving the pump structure and the process of pulverized coal discharge in the wellbore are put forward.Thirdly,the paper puts forward the process plan of flushing shaft to discharge pulverized coal,designs the flushing pump and flushing bottom pipe string,calculates and analyzes the equipment selection,flushing displacement and construction pump pressure,and simulates the flushing process of the two sets of processes by using software,compares the changes of pulverized coal volume fraction before and after flushing,and evaluates the effect of discharging pulverized coal.According to the demand of slime washing,the optimization and compounding test of dispersant and suspending agent were carried out.A new type of well washing fluid with good dispersing effect and long suspension time was prepared,and the field application and effect evaluation were carried out.Finally,the design scheme of anti pulverized coal tubular pump is put forward,and the key parts of pulverized coal discharge,namely protective cover and pump barrel nipple,are designed and analyzed.The effect of pulverized coal discharge of the pump is simulated by using software,and two wells are selected for field application,with good effect.