Increasing demand for oil and gas has lead to exploration and drilling conditions getting 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 used for drill pipes. The
fatigue crack growth measured at a constant stress intensity factor (DK) and at varying frequencies from
1Hz to 1mHz is presented. The role of corrosion products in creating crack closure effects in
environments containing high H2S concentrations is discussed.