Corrosion Fatigue Performance of High Strength Drill Pipe in Sour Environments

Increasing demand for oil and gas has lead to exploration and drilling conditions get harsher and there is a greater demand for high strength materials to increase the strength to weight ratio, there have been developments in the area of low alloy steels with strengths as high as 165ksi.  The combination of fatigue stresses in the presence of sour conditions clearly has an important effect on the design and operating regimes of the drill pipes.  This paper discusses the impact of pH, H₂S concentration and temperature on the fatigue crack growth behavior of a high strength steel UD-165 used for drill pipes.  The fatigue crack growth measured at a constant DK and at varying frequencies from 1Hz to 1mHz will be presented.  The data obtained will be modeled using the principal of superposition for fatigue crack growth.