Threat · Flow Assurance
Corrosion
Metal loss on the inside of tubing and flowlines driven by produced water carrying dissolved CO2 (sweet), H2S (sour) or oxygen.
What it does
CO2 forms carbonic acid that thins and pits the wall. H2S also drives hydrogen into the steel and can cause sulfide stress cracking. It is controlled with inhibitors, corrosion resistant materials, coatings and cathodic protection, and confirmed by monitoring.
Basics
| Sweet | CO2, general metal loss and pitting |
| Sour | H2S, iron sulfide films, cracking risk |
| Materials for H2S service | NACE MR0175/ISO 15156 |
| Mitigation | Filming inhibitors, corrosion resistant alloys, coatings, cathodic protection |
Common failures
- Pinhole leak or wall thinning in the flowline
- Cracking of steel not qualified for sour service
Troubleshooting
- Symptom
- Coupon or probe rates climbing
- Likely cause
- Inhibitor underdosed or not reaching the water phase
- What to check
- Check pump delivery and dose, then retest the rate