Environmentally Assisted Cracking of Subsea Pipelines in Oil & Gas Production Environments—Effect of Static Loading

Abstract

Fatigue crack growth rate of line pipe steels in sour environments typically exhibits a steady-state value at low frequencies. However, in highly inhibited sour environments, there is no evidence of a steady-state fatigue crack growth at low frequencies. This is likely a result of static crack growth rate at K max . Stable static crack growth measured under constant stress intensity factor (K) conditions in inhibited sour environments was in the range of 10 −7 mm/s to 10 −8 mm/s. The crack growth rate in inhibited sour environments is likely associated with crack tip processes associated with metal dissolution/film formation and associated hydrogen evolution. The results obtained were modeled based on a crack tip strain rate based approach, where the rate limiting step was the metal dissolution/FeS formation and the corresponding hydrogen generation reaction. CORROSIONJOURNAL.ORG100 150 200 250 300 350 400 450 500 K J 0.2 mm -Air K J maxload -Air K J 0.2 mm -Env K J maxload -Env K J (MPa√m) dK/dt (MPa√m/s) X65 parent pipe pH = 5 p H2S = 0.46 psia FIGURE 2. Effect of K-rate on the measured J 0.2 mm for API 5L X65 in sour environments on coated samples. 15 140 J 0.2 mm 5 wt% NaCl Uncoated pH 5, 1 psia H 2 S J maxload J 1 mm 120 100 80 60 40 20 0 0.01 0.1 K-Rate (N . mm -3/2 /s) J (N/mm) FIGURE 3. Effect of K-rate on the measured J 0.2 mm on API 5L X6 in sour environments on uncoated samples. 16

Application of the Electrochemical Permeation Method for Hydrogen Diffusion Coefficient Determination in Pipeline Steel 10G2

“…One of the most important scientific and technical problems of recent years is the problem of extending the life of the safe operation of gas pipelines due to the increased risk of technogenic accidents caused by insufficient operational reliability of the metal [1][2][3]. The most common type of damage to structural materials (such as steel, copper, aluminum, etc.)…”