Research On Continuous Conversion Device Design Of Sucker Rod Pump And Velocity String In Coalbed Methane Wells

The thesis was supported by the National Science and Technology Major Project(No.2016ZX05066)which are ‘Demonstration Project for Combined Production of CBM,Tight Gas,and Shale Gas in Coal Measures in Linxing-Shenfu Area’.This research is based on the characteristics of CBM drainage and gas production and the law of water and gas production in CBM reservoirs.The velocity string technology is introduced into the production of CBM wells.In order to realize the continuous and efficient drainage of CBM wells,a method is proposed.Continuous Conversion technology of Sucker Rod Pump and Velocity String in Coalbed Methane Wells is proposed.This research provides a design scheme for the selection of pipe string suitable for the requirements of continuous conversion and extraction of coalbed methane wells,and a continuous conversion scheme for CBM wells from three-drainage extraction to speed string extraction.This drainage technology can effectively prolong the high and stable production time of coalbed methane wells and improve the development benefits of coalbed methane.The main research progress is as follows:First of all,this article introduces the production characteristics of coalbed methane wells at various stages,and analyzes the reasons why high production t ime is short and stable production is difficult to sustain for a long time.Summarizing and analyzing the application and effect of velocity string technology in conventional gas wells,it is proposed to apply velocity string technology to coalbed methane wells.Combining the reservoir characteristics and drainage characteristics of coalbed methane wells,a scheme of three-drainage production-velocity string continuous conversion drainage for coalbed methane wel s is proposed.Secondly,in view of the fact that the velocity pipe string carries out gas and water-carrying production in the middle and late stages of coalbed methane production,the production conditions of the velocity pipe string gas and liquid production are analyzed.Conventional gas wells have studied the necessary conditions for gas-carrying liquid.Because conventional gas wells produce large gas and have less liquid accumulation,they can carry liquids.However,coalbed methane wells produce less gas.In addition to studying the critical gas production rate of gas-carrying liquids,it is also necessary The study of the amount of air-carrying liquid gives the sufficient conditions for the production of the gas-carrying liquid of the velocity string.By analyzing the working conditions of the three-pumping equipment and the speed string,the continuous conversion conditions are given.Combined with the production data of coalbed methane wells,the production conditions of the velocity string were analyzed by an example.Thirdly,in view of the proposed overall scheme of continuous conversion of three-drainage equipment-velocity string,the design of continuous conversion of three-drainage equipment-velocity string was carried out,and the specific process flow was given.Through the analysis of the production conditions of the rod pump and the speed pipe string,combined with the production characteristics of coalbed methane,the conversion conditions of the two processes are given.According to the scheme design and combined with the field application,the design check of the continuous conversion device and other key parts was completed,and the analysis and calculation of the opening conditions of the continuous conversion device were performed.Then,for the three-pump production-velocity string continuous conversion drainage technology,the selection method of rod pump and tubing was established based on the water production of the gas well;from the rod string strength,the critical liquid carrying condition,the erosion phenomenon,and the string pressure Starting from the four aspects of loss,a method for selecting the speed string was established.Aiming at the critical liquid-carrying conditions,a nomogram for the selection of the speed string is designed for easy reading.Analyze and study the pressure loss calculation model of gas-liquid two-phase vertical pipe flow,give the calculation method of the production pressure loss of the velocity string of coalbed methane wells,use MATLAB to compile the calculation program,and give the change law of the velocity string pressure loss.Finally,according to the three-pumping equipment-speed pipe string continuous conversion drainage plan,the start-up conditions of the velocity pipe string production were analyzed,the design of the continuo us conversion drainage pump was completed,and the prototype manufacturing was finally completed.The extraction and extraction equipment and technology proposed in this paper realize the continuous conversion of coalbed methane wells from three extraction extraction to velocity string extraction extraction,and realize water-carrying production by relying on the energy of the gas itself.This not only changes the defect of existing equipment in CBM extraction,but also greatly reduces the damage to the reservoir caused by workover operations,which is of great significance for realizing the continuous and efficient extraction of CBM wells.