Study On Corrosion Of Wellbore Materials In High Pressure Gas Wells

The natural gas extraction environment is developing from conventional gas wells to"ultra-deep,ultra-high temperature,and ultra-high pressure"(ie,"three super" gas wells)gas wells."Three-super" gas wells generally refer to natural gas wells with ultra-deep depth(≥6000m),ultra-high temperature(≥177℃),and ultra-high pressure(≥105MPa).At present,the failure of "three super" gas wells often occurs in the western region,and the key factor affecting the failure of wellbore integrity is the corrosion resistance of wellbore materials.Therefore,in this paper,combined with the complex working conditions of an oil and gas field in the western region,such as ultra-high temperature,ultra-high pressure,high CO2 content,high Cl-content,acidification,acid fracturing and other factors,the stainless steel wellbore materials under the "three super" working conditions are mainly studied in the same environment,the corrosion resistance was evaluated based on the whole life cycle of gas wells.The test results show that the main cause of tubing coupling failure is stress corrosion cracking,The main reason for a large number of pitting corrosion pits on the inner wall of the tubing is that the fresh acid acidification process is the cause.There is a certain pitting corrosion phenomenon on the inner wall of the tubing during the residual acid flowback process of super 13Cr compared with 15Cr,but the pitting corrosion degree is relatively light during the fresh acid acidification process;the four test tubes are slightly corroded in the formation water,but all of them have different degrees of pitting corrosion;Under the condition of three working conditions of formation water,JFE13Cr has the best corrosion resistance,and the pitting tendency of super 13Cr and 15Cr is serious.During the process of connecting and detaching BT-S13Cr110 BGT1 tubing with two specifications,the copper plating layer generally fell off and slightly glued.Under the condition of ISO 13679 system B test,the tubing joint failed to pass the evaluation of ISO 13679 class Ⅳ test.