Evaluation Of Cleaning Effect Of Online Tubing Cleaning Device For Workover Operations And Optimization Of Nozzle Structure

During the development of the oil field,it is an important process to guarantee the normal and safe working of oil wells and ensure stable and highly efficient production of oil fields by performing well repair operations.As an important Part of workover operations,the effect and efficiency of tubing cleaning has a direct effect on whether follow-up inspections and rePair work can be performed smoothly.It is also an important prerequisite for safe and economical exploitation of oil wells.However,the commonly used methods of cleaning oil pipelines have problems such as large occupied area,low cleaning efficiency,large manpower consumption,and environmental pollution,which seriously affect the safety,economy,and environmental protection of workover operations.In view of the above problems,an efficient and environmentally friendly tubing on-line cleaning device is proposed.Besides,the cleaning effect evaluation and nozzle structure optimization of the on-line cleaning device of workover oil tubing is carried out.The specific research contents and achievements are as follows:(1)A study on the evaluation criteria for the cleaning effect of the tubing on-line cleaning device is carried out.According to the requirements of workover operations and the characteristics of the dirt layer of the oil pipe,it is determined that the wax in the soil layer is cleaned.And combined wth jet structure and Parameters,the evaluation index system for the oil pipe online cleaning device is established as:①The temperature of the jet acting on the surface of the dirt layer is higher than the melting point of the dirt,and the higher the temperature,the better the cleaning effect.②The greater the area of the steam jet acting on the surface of the dirt layer,the faster the cleaning efficiency.③The higher the jet velocity and dynamic pressure acting on the surface of the dirt layer,the greater the jet striking force and the better the cleaning effect of the device.(2)A comparative analysis of the cleaning effect of the on-line cleaning device of four different nozzle structures(cylindrical,conical-contracting,conical-straight I,conical-straight II)is conducted with Fluent software.And the nozzle structure with the best cleaning effect is selected by the evaluation criteria.The results shows that the conical straight I nozzle has the best cleaning effect,and is preferably used as the nozzle structure of the device.(3)The optimization study of the nozzle geometric parameters of the tubing on-line cleaning device is carried out.Orthogonal experiment is used to study the variation of the cleaning effect of nozzles with different geometric parameters(outlet diameter,length-diameter ratio,shrinkage angle).The research shows that the optimal geometric parameters combination of nozzle is that the nozzle outlet diameter is 4.5mm,the aspect ratio is 2.5,and the shrinkage angle is 30°.The cleaning effect of the device before and after nozzle optimization is compared and analyzed.After the nozzle optimization,the cleaning effect of the tubing on-line cleaning device is significantly improved.(4)The effect of tubing lift speed on the on-line cleaning effect is studied.Combining the theory of phase change and heat transfer,the effect of lifting speed on the on-line cleaning effect was quantitatively compared and analyzed by quantitatively comparing the cleaning rate of the wax tubing with the same cleaning time.The results show that when the tubing lifting speed is 0.16 m/s,the cleaning rate is 67.9%.The device has the best cleaning effect on the wax-lined tubing,and it also satisfies the working requirements of the online cleaning and workover operations.(5)The study on the effect of the number of nozzles on the cleaning effect of online operations is carried out.The results show that the increase of the number of nozzles makes the total area of steam effect increase,and the cleaning effect increases.However,too many nozzles cause the temperature,velocity and dynamic pressure of the jet at the wall of the wax layer to decrease,which leads to a decrease in the cleaning effect.When the number of nozzles is 10,the entire tubing on-line cleaning operation works best.