Study On Condition Of Discharging Coal Dust From Annulus Between Rod And Tube In Coalbed Methan Wells

The paper analyzes the factor of the destroyed coal bed forming coal dust based on coal bed character and the process requirements of the Coalbed methan well discharge and production.In view of the coalbed methan well discharging coal dust and slight amount water, for avoidance the coal dust pumped to annulus between pumping rod and tubing sediment leading to stuck pump,the paper simulates and analyzes the coal dust's movements.According to the analytical results and N-S equation research the influence factor of the output of the coal dust and how to adjust the area of annulus between pumping rod and tubing.According to the features of the coalbed methan well discharging coal dust and slight amount water,the paper researchs the working system of intermittent pumping.Based on the condition of the coal skeleton destroyed,The paper researchs the intensity of discharge and production how to influence the pressure of the coal bed and the seepage discharge of the fluid by the way of hydrodynamics.By researching the coal dust particles'force condition,the movement condition of the coal dust particles in the coal bed pore and the relation between the seepage discharge of the coal bed fluid and the diameters and amount of the coal dust discharged are obtained.The software"fluent"is used to simulate the movement law of the coal dust particles in the annulus between pumping rod and tubing.The relation between the output of the coal dust and the fluid velocity in the annulus between pumping rod and tubing is obtained.Based on the force condition of the coal dust in the fluid,N-S equation is used to analyze the relation between the output of the coal dust and fluid delivery and discharge and production parameter.Based on the analytical results,the relation between the area of the annulus between pumping rod and tubing and the output of coal dust is obtained.At the same time,the paper optimizes the diameter of collar and develope the new structure of rod string.Based on the coal dust pumped to annulus between pumping rod and tubing sediment and the theory of rushing silt, the intermittent time of pumping is developed and the relation between the intermittent time and the diameter and concentration of the coal dust is obtained. Research find that increasing fluid delivery and decreasing the area of annulus between pumping rod and tubing can help to discharge coal dust and reduce stucking pump,which prolongs the repair cycle.