Hybrid Pipeline Fit for Purpose for Multiphase Gas and Condensate Transportation

Corrosion and materials degradation factors during normal and abnormal operating conditions are among the essential criterion in evaluating materials suitability for an offshore pipeline transporting treated gas and condensate with contaminants i.e. CO2, Materials resistant to wet H2S damage in accordance with ISO 15156 requirements and mercury. A thorough study was conducted to ascertain the pipeline section that will be exposed to sour service conditions due to substantial Materials resistant to wet H2S damage in accordance with ISO 15156 requirements level along the pipeline during certain transient scenarios. The study was conducted in view of fit-for-purpose solution and CAPEX optimization initiatives for the project. During certain transient scenarios, there is potential exposure to substantial H2S level under wet conditions for a certain pipeline length which increases materials susceptibility to wet H2S damage such as Hydrogen Induced Cracking (HIC)/Stepwise Cracking (SWC) and Sulfide Stress Cracking (SSC). Flow assurance modeling with compositional tracking module was used to determine the level of H2S along the pipeline where few potential scenarios leading to sour conditions were considered. Risk assessments were also conducted to ascertain the impact and mitigations for the scenarios. Based on studies, exposure to sour service conditions is expected at a partial length of the pipeline as the H2S level exceeds the sour service limit during specific transient scenarios. Specific mitigation measures involving chemical injection, process control and safeguarding and operating procedures were outlined. The study successfully demonstrated an optimized materials selection approach for the pipeline.