Heavy Wall Seamless Line Pipe X70–X80 for Sour Service Applications

Abstract

The continued shift of exploration and production to deep water fields will require the industry to develop alternative pipe solutions to cope with the challenging demands of these exploration regions. Because of the complexity of exploration conditions in deep water fields, e.g. high pressures, low temperature and sour reservoirs, higher grades and heavier wall thickness in combination with low temperature toughness and suitability for sour service are required. The Vallourec&Mannesmann Tubes’s alloying concept for line pipe steels based on low carbon concept [1] was extended to grades X70 and X80 with wall thicknesses up to 75mm. In this paper the latest results on industrial studies on high strength heavy-wall steels manufactured by seamless hot rolling and subsequent quench and temper treatment are presented. The work is a part of the development program for high performance heavy wall seamless pipes for special applications such as J-lay collars, buckle arrestors and risers. Mechanical properties, advanced metallographic examinations, results of the sour service resistance and weldability are reported.

Mechanical Characterization of Resistance-Welded and Seamless API 5L X52 Pipes: A Comparative Study

“…Stringer-shaped inclusions are known to cause anisotropy in mechanical properties such as tensile ductility and fracture toughness [26]. Variations in grain size and grain shape along different directions can also cause anisotropy [32]. Another study [46] suggested, based on an analysis of texture intensities, that the anisotropy of toughness at room temperature might be attributed to the variation in the volume fraction of the {110} plane, with an angle to the circumferential direction.…”

“…During plastic deformation due to cold or hot work, grains are elongated in the direction of the applied stress. Therefore, the ferrite grain size varies in different directions, resulting in anisotropy in mechanical properties [28,32]. It is observed that grains of perlite and ferrite are usually oriented in the directions of lamination.…”

“…SMLS pipes are used in different oil and gas installations, such as offshore, because they have excellent corrosive performance and low-temperature toughness for exploitation in deep-water oil and gas reservoirs [28]. Traditionally, seam-welded pipes have been used in offshore conditions for several years, and the pipes employed include the API 5L grades from X42 to X100 [30][31][32][33]. Different studies have been carried out to study their mechanical behaviors [34,35] and corrosive behaviors [5].…”