Post-ILI Corrosion Assessment & Wax Control Strategy

Description

After an in-line inspection of a pipeline in West Africa, a client discovered significant wall loss in the first three miles of the line. The tool also returned significant wax deposits, casting doubt on the current wax management efforts in place.

The wells producing to the pipeline historically produced H2S; however, the worst offenders were shut-in quickly after it was discovered that they were producing extremely high concentrations of the sour gas.

GATE was asked to support plan development to address the current status of the line based on measured wall loss, determine path forward on corrosion control, and make recommendations on improvements to wax management plan.

Results

The corrosion study carried out determined the estimated remaining life for the pipeline based on the most severe defects and highlighted recommended areas for repair. In addition to this, a root-cause analysis identified the most likely source of corrosion to be the presence of H2S in the system. Recommendations were provided to improve estimated remaining life by controlling H2S concentration and improving corrosion inhibition effectiveness in the pipeline.

An assessment of historical wax deposition and composition data yielded recommendations on the mitigation measures that most significantly impacted wax deposition in the pipeline. This information was used to generate a recommendation on highest priority activities to improve wax management for the pipeline.

Technical Achievements & Benefits

  • Individual assessment of all significant defects identified by the inspection tool to determined associated reduction in maximum allowable operating pressure (MAOP).
  • Statistical estimation of remaining life based on observed pitting rates.
  • Evaluation and identification of likely corrosion mechanisms based on operating history and defect morphology.
  • Identification of highest impact wax control activities based on historical wax returns volumes and composition analyses.