Title : Investigating causal factors and mitigation strategies for severe internal corrosion in sweet gas compression facilities: A case study of Majnoon oilfield GTF trains.
Abstract:
Objective: This study aims to identify the causal factors for severe internal corrosion and scaling observed within the compressor loops of Gas Treatment Facilities (GTF Trains 1 & 2). The primary goal is to provide technically viable and cost-effective recommendations for remediating piping network degradation considering evolving process parameters.
Methodology: The compressor loop was sectionalized for detailed analysis, involving inspection of vessels, filters, and piping networks. The methodology included:
- Sludge and Solid Analysis: Analyzing the composition of deposits in critical vessels (MBD-500, MBD-700, and MAK-300) to distinguish between corrosion products and inorganic components like sand and clay.
- Material Inspection: Evaluating the condition of Carbon Steel (CS) infrastructure through Ultrasonic Testing (UT) and physical inspections during maintenance.
- Water Chemistry: Assessing the impact of formation water and condensate dropout on corrosion kinetics.
- Chemical Evaluation: Reviewing the suitability and dosing rates of the incumbent gas corrosion inhibitor (GCI)
Key Findings:
Corrosion Mechanisms: While wet gas pipelines from DS2 and CPF1 remain in good condition, severe localized corrosion was confirmed in GTF sections following discharge coolers.
- Causal Factors: Changes in process conditions led to increased pressure and temperature, causing significant moisture dropout and condensation. Dissolved CO2 in this water forms corrosive carbonic acid, further aggravated by Cl− ions from formation water.
- Operational Impact: Inefficient removal of condensate due to choked drain lines led to water and solids carryover, resulting in heavy fouling of compressor strainers with rust particulates and silica. This caused high vibrations on compressor impellers, necessitating frequent bundle replacements.
- Material Vulnerability: Scrubber vessels (MBD-500/700) lacked internal coating, facilitating corrosion initiation on Carbon Steel surfaces.
Recommendations:
Material Upgrades: Replace Carbon Steel (CS) with Stainless Steel (SS) for piping downstream of coolers and for cooler headers.
