Design And Performance Research Of Downhole Throttle In Gas Well Without Wire Rope Fishing

In the process of natural gas exploitation,the phenomenon of gas hydrate clogging the pipeline often happens,which brings a lot of inconvenience to the management and production of gas wells.Compared with traditional methods of hydrate prevention and control,the downhole throttling technology is more effective,more reliable and more cost-effective.Region in a gas well,the author of this thesis use traditional choke auxiliary operation need wire rope,complex operation and so on,puts forward a free scoop structure features of wire rope for choke solution,changqing oilfield has been put into use in some gas wells the choke,and preliminary application effect is good,but there is also a small amount of gas wells using the choke production can not meet the expected demand,etc.In this thesis,with the support of the project commissioned by Changqing Oilfield,the design improvement and performance research of the downhole throttle without wire rope is carried out,which provides theoretical basis and reference for its further application.The main work is as follows:(1)This thesis starts with the downhole throttling mechanism,analyzes the distribution of physical parameters around the gas nozzle before and after the fluid throttling,establishes a mathematical model of the critical flow regime under working conditions,and clarifies the critical flow state judgment method.Based on the laws of thermodynamics,the thermodynamic model followed in the throttling process is deduced,and the difference between ground throttling and downhole throttling is analyzed.(2)This thesis introduces the structure and working process of the preset throttle and the rear throttle,and analyzes the common problems encountered when the traditional throttle is put into production.On the basis of the existing choke theory,a downhole choke without wire rope fishing was proposed,and its structure,composition and working process were clarified.Workbench software was used to check the strength of the key parts of the choke.(3)Analyze the influence of the choke depth and gas nozzle size on the throttling production of gas wells on the theoretical basis of the main process parameters of the choke.And through the use of PIPESIM software to simulate the impact of choke entry depth,gas nozzle size,natural gas water-gas ratio and other parameters on throttling production.(4)This thesis studies the choke performance of the downhole choke without wire rope fishing.Through the use of Fluent fluid analysis software,the gas-liquid two-phase flow is used to simulate the fluid flow around the gas nozzle,and the changes of pressure,temperature,density,velocity and other parameters before and after the throttling of the downhole choke without wire rope fishing are analyzed.Finally,a control group was set up to compare and analyze the throttling performance of the downhole choke without wire rope fishing and the traditional choke.Through the above analysis,the following conclusions are drawn: The key components of the downhole choke for gas wells without wire rope fishing meet the strength requirements;by adjusting the depth of the choke,it is found that the deeper the choke is,the harder it is to produce hydrate,But the pressure difference borne by the throttle will gradually increase with the increase in the depth of entry,which will affect the service life of the throttle;when other conditions are fixed,the diameter of the gas nozzle determines the daily gas output.The larger the gas nozzle,The higher the daily gas production rate;combined with the actual engineering experience and requirements,the choke depth is determined to be 1500m;the simulation results of Fluent show that the choke performance of the gas well free wire rope fishing choke is higher than that of the traditional choke Throttling performance;...