Design And Calculation Analysis Of Downhole Drainage Pumps For Natural Gas Wells

Aiming at the costs reduction of operation and the inadequacies of technique,further meet the needs of drainage gas recovery in low pressure and production natural gas well.A new type of drainage gas recovery pump is proposed,which drive powered using wellbore gas and apply for the vertical,deviated and horizontal well.Based on principle of pneumatic pressurization,a reciprocal pump mechanism which for pumping fluids from the wellbore to the ground and under the control of mechanical closed-loop can be driven by times power cylinder.The main results of the research work in the following areas:(1)On the premise of fully investigating the present situation of natural gas well drainage and gas recovery technology at home and abroad,a downhole drainage pump is proposed based on the principle of pneumatic supercharging.Combined with the actual situation of the West Sichuan gas field,the technical index of underground drainage pump is determined.(2)The structural composition,working principle,control loop and basic parameters of underground drainage pump are analyzed and calculated preliminarily.On the premise of reasonable assumption and properly simplified,the mathematical model of the dynamic system of the drainage gas pump is established by using the continuity equation,the energy conservation equation,the dynamic equation and the gas state equation.(3)The simulation model of drainage pump was constructed in the environment of MATLAB/Simulink.The influence of main structural parameters such as the diameter of the driving cylinder,the stroke of the piston and the diameter of the airway on the system's dynamic performance is discussed through dynamic simulation and the values of the main structural parameters are determined.Through the simulation,the frequency,flow,power and efficiency characteristics of the downhole drainage gas pump are studied.It is proved that the performance of the downhole drainage gas pump meets the technical requirements.(4)The overall structure design of underground drainage and gas pump is completed through the structural parameters determined by simulation.The finite element analysis software ABAQUS is used to analyze the pneumatic seals used in the driving cylinder module of underground drainage pump.Based on the established 2D axisymmetric model,the effects of geometric parameters and working parameters on the static sealing and reciprocating seal properties were investigated.Based on 3D finite element model,the influence of circumferential contact stress distribution and radial eccentricity of piston to the sealing performance was analyzed.The performance of the new type of underground drainage gas pump designed in this paper can meet the requirements of drainage and gas production in low pressure and low production gas wells.The pump has improved the shortage of existing drainage gas production equipment,and has good practical value.