Research On Application Of Cathodic Protection Technology For Anticorrosion Of Tubing String In Oil And Gas Wells

Tubing corrosion in oil and gas wells is one of the main reasons for frequent work-over operations,and how to solve it has become the primary issue in protecting oil and gas well production.Therefore,this paper analyzes the factors that affect the corrosion prevention of pipe strings,determines external current cathodic protection technology as a means of pipe string corrosion prevention,and establishes a model of the cathodic protection system for oil and gas well pipe string corrosion prevention.Firstly,a study was conducted on the corrosion of coalbed methane well tubing in Xinzhou City,Shanxi Province.Temperature was selected as the main influencing factor for coalbed methane well tubing corrosion,and the weight loss method was used to compare the corrosion rate changes of coalbed methane well tubing materials under natural corrosion conditions and external current cathodic protection conditions at different temperatures.Secondly,based on different underground environmental temperatures,electrochemical experiments and potential testing were used to study the performance of coalbed methane well tubing materials.The corrosion current density,corrosion potential,and minimum protection potential required for cathodic protection of the tubing materials were determined at different temperatures.Once again,in order to ensure the normal operation of the cathodic protection system for the coalbed methane well string,combined with existing well equipment,insulation design was carried out for the wellhead hanger and smooth rod hanger through three-dimensional modeling,and stress simulation analysis was conducted on their models.Finally,based on the experimental parameters and insulation equipment simulation results,on-site experiments were conducted to study the feasibility and accuracy of the cathodic protection system for coalbed methane well tubing.Research has shown that through the weightlessness method experiment,it is found that the uniform corrosion rate of natural corrosion of hanging pieces is between 0.8565mm/a and1.8970mm/a in different underground environmental temperatures,and the uniform corrosion rate of cathodic protection is between 0.1003mm/a and 0.1155mm/a.As the underground temperature increases,the corrosion rate of the pipe string becomes faster.By adopting external current cathodic protection measures,the protection degree of the pipe string material has increased by 88.29%～93.97% compared to the natural corrosion state.Through electrochemical experiments,the minimum protective potential required for the coalbed methane well string was determined to be-742.33 m V(CSE).By conducting insulation design and stress simulation on existing well equipment,the simulation results can meet the application requirements of coalbed methane wells,and have certain practical significance for achieving the application of cathodic protection technology for oil and gas well strings.