Introduction of Corrosion resistant oil well seamless steel pipe

Oil Wells and gas Wells steel pipes include the drill pipe for mining, well wall protection pipe inserted inside the well to prevent formation collapse and pipeline system hanged inside the wall protection tube for production.Based on security considerations, oil well pipe generally adopts seamless steel pipe.As a result of the oil well and gas well mining depth deepening year by year, such high strength oil well pipes as N80 (yield strength 551 MPa grade) and P110 (yield strength 758 MPa) are developed, these pipes have reached the American petroleum institute standards.However, the sulfide stress cracking accident happened in the 50s in Canada, so sulfide corrosive environment sulfide stress cracking of high strength steel aroused people's concern.Sulfide stress cracking of low alloy steel is a kind of form of hydrogen embrittlement, the production fluid with the system of hydrogen sulfide inhibits corrosion reaction in the process of hydrogen produced by dissipation, to invade the significantly increased the amount of hydrogen in steel. The higher the strength of steel, the greater the sensitivity of sulfide stress cracking, so good to sulfide stress cracking resistance of high strength steel for development.The sulfide stress cracking resistance of steel is associated with the microstructure of steel.From martensite phase organization view shows the following measures is effective: adding Nb and quenching tempering heat treatment can form fine grain structure; Reduce the intergranular segregation elements such as P and Mn can prevent the grain boundary cracks; Increasing tempering temperature can reduce the internal strain, etc.Since the 60s have developed resistance to sulfide stress cracking of low alloy oil well drill pipe, and has made steady development.In the deep well, due to the high bottom hole temperature (5000m class well, downhole temperature about 250 e), so the corrosion environment is very serious.In oil Wells in severe corrosion environment, usually to inject steel rust preventer protection, but no matter technically, or from an economic point of view, anticorrosive agent application is very difficult, therefore developed suitable for all kinds of corrosive environment, without injecting antifushiji the corrosion resistance of alloy steel.From the perspective of corrosion resistance, corrosion resistant alloy steel can be roughly divided into system of martensite stainless steel, duplex stainless steel and austenite system high Ni alloy three kinds. The CO2 corrosion environment is often referred to as low sulfur corrosion environment. CO2 and H2S production fluid with together, but can form weak acid after CO2 dissolved in water, can be used as consumption due to steel corrosion reaction of the source of H + ions, so compared with the same acid aqueous solution pH, the corrosion rate of carbon steel. To reduce under the environment of CO2 corrosion rate, effective solution is to add Cr, now good to under the environment of CO2 corrosion resistance and economy of 13 Cr steel (AISI420) demand increased rapidly.However, because of 13 Cr steel under the temperature of more than 150e, corrosion speed will increase, and the traces of H2S environment with sulfide stress cracking sensitivity, thus developed a new type of 13 Cr steel, namely by lowering the content of C, inhibition of Cr carbide precipitation, ensuring effective amount of Cr, which can improve the application of the critical temperature in CO2 environment. In addition, add the Mo can make in the trace H2S environment passivity oxide film stability, inhibition of hydrogen in the steel. Especially under the environment of high temperature, duplex stainless steel containing 22% ~ 25% Cr can be used.In oil Wells and gas Wells with plenty of H2S, can use the austenite high Ni alloy with good corrosion resistance.Its critical temperature and corrosion resistant alloy elements of the content of Mo and W, depending on the use environment, has developed a Mo and W content different alloy series.