Session: 04-01-03 Flexible Pipes & Umbilicals III

Paper Number: 125047

125047 - A Modeling Method of Predicting Service Life at Crack Threshold Stage for Tensile Armor of Flexible Pipes Under Scc-Co2 Environment 

Cracks triggered by Carbon Dioxide of Stress Corrosion Cracking (SCC-CO₂) have been identified as a new failure mode in flexible pipes, yet a method of predicting its occurrence, especially the stage of crack initiation (T₁) is lacked in the industry. The root cause of SCC cracks is complex, the experiment observation shows the cracking may initiates from different locations and grows along different paths. As a startpoint, this paper introduces a methodology of T₁ prediction on the basis of equivalent initial flaw size (EIFS) theory and back extension of Paris linear section. It implies the condition that SCC-CO₂ cracks initiate from corrosion pit and propagates through grain boundaries. The influential factor from environment mainly includes the stress utilization factor (UF), CO₂ fugacity and operational temperature. After the preliminary calibration with data retrieved from dissected pipes retrieved from different oil fields, the model is able to predict typical trends agreeing with the most field observations. Investigation continues to understand the mechanisms leading to some deviations and to explore potential solutions and improvements. The presented approach is anticipated to provide a reliable and consistent prediction of nucleation duration in determining SCC-CO2 service life. Furthermore, the model in this methodology would be further calibrated and validated against tests and field experiences.  

Presenting Author: Wenye Ye Baker Hughes

Presenting Author Biography: High performance research engineer with 7+ years of experience leading dynamic finite element analysis initiatives, product life cycles, multi-scale simulations, fracture mechanics, and electronic component analysis across technical enterprise and academic environments. Currently the Leading Mechanical Engineer at Baker Hughes, working on various research programs related to offshore flexible pipes, including service life of tensile armor under the SCC CO2 environment, corrosion crack analysis, bent collapse design, etc.

Authors:

Wenye Ye Baker Hughes
Qi Yang Baker Hughes
Marcelo Ribeiro Baker Hughes
Carlos Ribeiro Baker Hughes
Linfa Zhu Baker Hughes
Alberto Alvino Baker Hughes
Andrew Roberts Baker Hughes
Zhimin Tan Baker Hughes