Production of Seamless Steel Pipe for Oil and Gas Extraction in Challenging Conditions

Abstract

Trends in pipe-steel development, smelting technologies, and hot-rolling and heat-treatment methods are reviewed, in the context of growing requirements on seamless pipe for oil and gas extraction in challenging conditions. As new resources become available, PAO Gazprom is developing appropriate requirements on high-strength, low-temperature borehole pipe and pump and compressor pipe that is resistant to H2S and CO2 corrosion. In the present work, metallurgical principles are outlined for the development of new grades of high-quality steel with minimum content of sulfur, phosphorus, and dissolved gas and corresponding treatment conditions. This involves the selection of the chemical composition so that martensite structure is formed on quenching and subsequent high-tempering, thereby ensuring the required combination of strength and ductility. It is shown that the optimal combination of strength and ductility may be attained at–60°C if chromium–molybdenum steel containing around 0.25 wt % C is alloyed with vanadium and niobium, which readily form carbides. Resistance to sulfide stress cracking may be afforded by microalloying of the steel so as to decrease the initial austenite grain size and by calibrating the content of molybdenum, which ensures high hardenability and slows softening on tempering. New compositions for martensitic stainless steel with 13% Cr are developed. That ensures the required resistance to CO2 corrosion and improves the strength and cold strength in comparison with the basic composition of 20X13 steel. Reconstruction of the electrosmelting and rolling systems at OAO Volzhskii Trubnyi Zavod (VTZ) ensures the required quality of the new products, from continuous-cast steel billet to the final pipe.