The Study On The Continuous Drainage Equipment Of The Mechanical Lifting-velocity String For CBM Wells

The thesis was supported by the projects which are “Research on High Efficient Dewatering Gas Production Technology for CBM Wells on Liu Lin Demonstration Area(No.2011ZX05062-004)” and “Research on the Design of Bottom-Hole Pump Technology for the Drainage of CBM Wells(No.51174224)”.With the analysis of the characteristics of CBM drainage and the laws of the water production and gas production of CBM reservoir,based on velocity string method and the conventional beam pumping drainage equipment,the integrated continuous drainage project was presented which means the method of mechanically artificial lifting-velocity string,according to the requirements of Energy saving,continuity,stability in CBM drainage.This Study provided a design of velocity string which is applicable to the drainage of the CBM wells and a scheme of continuous switch that is from artificial lifting to velocity string lifting.This study lay the groundwork for the continuous high efficient drainage of CBM wells.With this device applied,the time when the CBM wells keeps high and stable production can be extended.And the development efficiency of CBM can be improved.Firstly,this thesis introduced the different stages of in the CBM drainage gas production,and analyzed the reasons that the time is short when the production is high,and the difficulties in stable production.By the analysis and summary of the conventional water producing gas well production and operation process,a design of production process technology was presented which can be applicable in CBM velocity string drainage gas production.Secondly,combined with the actual situation of production of CBM wells,according to the analysis of velocity string selection method in the conventional gas wells,the selection method of velocity string was presented where hollow rod and continuous tube used as velocity string.According to the analysis of methods of pressure drop of gas water two-phase flow in vertical circular tube and the production conditions of CBM wells by velocity string,the calculation results of press drop with velocity string was presented.Combined with the actual data of CBM wells,the analysis of velocity string selection design example was presented.Thirdly,in the light of the design scheme of machinery lifting-velocity string drainage device,the method and devices was presented that the artificial beam pumping unit swifts into velocity string continuously.The changes of horse head load also was presented,and the basis for the selection of related equipment provided.The scheme and structure design of key parts was completed,including cover of traveling valve,joint,switch,etc.According to the basic principle of impact dynamics,the design principle of switch component was presented.With LS-DYNA,the switch process was simulated by the method of SPH-FEM.Similarly,according to the working principle of ground driving screw pump and electric submersible pump using as the conventional drainage devices,the structure and process schemes were designed which they can continuously swift to velocity string.The swift scheme was also provided.By the mechanical principles and SPH-FEM method,the load and deformation of the key components were analyzed in the continuously swift process.Finally,the design of supporting system of velocity string production process was presented,including the wellhead equipment,the selection and design method of the gas water separator,etc.With the device and method of drainage mentioned in this thesis,the continuous switch process can be completed in which the CBM wells can be switched from artificial lifting to velocity string by using the energy of gas comes from the coal reservoir.This device and method not only meet the requirements of low and discontinuous water production,but also realized the CBM drainage with no energy consumption and no relative motion components.This can significantly improve the cycle of failure-free operation,also reduce the frequency of the workover operations in CBM wells.This can avoid the damage to the CBM reservoirs.This design made a difference in extending high and stable production time.