The Failure Analysis Of Austenitic Stainless Steel Coiled Tubing In Oil Wells

Coiled tubing is a kind of hydraulic pressure drive equipment, mainly used in oil fieldand so on. The operation of coiled tubing system including the small diameter coiledtubing continuous down into the well to proceed the special work, and not interfere withthe existing coiled tubing. When the work is finished, small diameter coiled tubing isrecovered from wells, coiling around a large scroll to transport easily.In this paper the research mainly discussed the failure analysis situation of coiledtubing in oil wells. In today’s production of the engineering, coiled tubing can bringconsiderable economic benefits and environmental benefits. However, because of thedifferent work environment and condition, The coiled tubing can craze very easily, thus tobring huge economic losses. Therefore, the analysis and research about coiled tubingappears very important. In the trial, we should consider the work condition, state, and someother factors, so as far as possible through the work environment to create similarcondition for this test, this needs to know the condition of oil well clearly, containing thebrine strength, the temperature under oil well and the stress at work, try to reach the similarenvironment.Through the methods of the macroscopic observation, metallographic analysis, SEMand EDAX to analyse the causes of the crack failure of coiled tubing. And used the316Laustenitic stainless steel as test material for the stress corrosion cracking tests.After manytests, it turned out that：(1)Because of the high Cl-concentration, stress and hightemperature, these result in the SCC of coiled tubing.（2）With the increase of stress, thetime of stress corrosion will get shorter. which increase the crack growth rate and greatlyaccelerate the breakdown of the material.（3）With the increase of temperature andconcentration of magnesium chloride solution, the time of stress corrosion will get shorter.（4）For solution treatment sample, its resistance to stress corrosion cracking performanceis significantly better than the sample without any processing through.