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Pipeline Failures - Composite Pipelines
- 1. PART 2 Integrity Hazard Classification for Spooled Composite Pipelines Severe Slug Flow at Well Start-up Events Causes >80% of Composite Pipeline Failures David Richardson, P.Eng. (403) 880-2835 david@trustedpipelineadvisor.com (Production Gathering)
- 2. Definition – Spooled Composite Pipelines License Material Codes FCLP / FPHT / FPLP / FS30 / FSLP / WSLP High-density polyethylene (HDPE), helically wound fiberglass / steel strands with a thermoplastic protective outer jacket
- 3. Managing Pipeline Integrity – Composite Pipelines • TRIAGE - Risk Assessment / Composite Pipelines • positions operators to pin-point bad-actor well- pipeline combinations • field ops can easily moderate well start-up ferocity to eliminate severe slugging that contributes to >80% of historical composite pipeline failures (gathering) • future composite pipeline failures can be avoided
- 4. 1 2 3 4 5 SUM PERCENT 5 378 101 37 6 64 586 6% RISK CLASS 4 381 77 80 12 174 724 7% 1258 35% SERIOUS 3 2455 428 222 43 385 3533 34% 1647 34% MODERATE 2 2492 490 132 29 204 3347 32% 7571 30% LOW 1 1675 353 82 24 152 2286 22% 10476 100% TOTAL 7381 1449 553 114 979 70% 14% 5% 1% 9% SUM PERCENT OF TOTAL SEGMENT COUNT Summary / Composites Increasing Likelihood of Composite Failure SEGMENT COUNT Consequence Business Loss ($) TRIAGE – Integrity Hazard Service (Alberta) considers exposure to severe cyclic slug flow (gathering) • identifies bad-actor well-pipeline combinations Risk Assessment - CompositesAlberta October, 2020 10,476 Licensed Pipelines Status = OperatingManaging Pipeline Integrity – Composite Pipelines
- 5. Types of Slug Flow
- 6. Types of Slug Flow • Hydrodynamic Slugs • steady-state flow condition • intermittent sequence of liquid plugs followed by longer gas bubbles • contributes to moderate pressure cycles within the flowing pipeline • in-situ water inventory remains constant 10,476 Licensed Pipelines Status = Operating
- 7. Types of Slug Flow • Hydrodynamic Slugs • cyclic steady-state flow condition Horizontal Inclined + 5 degree 10,476 Licensed Pipelines Status = Operating
- 8. Types of Slug Flow • Terrain-Induced Slugs • high-pressure / high-shear transient flow condition • results in cyclic liquid unloading of in-situ stagnant liquid from pipeline 10,476 Licensed Pipelines Status = Operating 0.0 6.0 12.0 18.0 24.0
- 9. Types of Slug Flow • Pigging Slugs • one-time transient flow condition • slug volume = total liquid in pipe minus volume dumped into the separator during pig transit 10,476 Licensed Pipelines Status = Operating
- 10. Types of Slug Flow • Severe Slugging / Rate-Change Slugging • short duration cyclic transient flow condition • 5X – 25X production rate surges with corresponding substantial pressure cycles • short-duration / high-velocity slugging 10,476 Licensed Pipelines Status = Operating 0.0 180.060.0 120.030.0 90.0 150.0 seconds Pressure-kPa 1250.0 0.0 250.0 500.0 750.0 1000.0 #1 Cause of Composite Pipeline Failures
- 11. Implication of Severe Slugging to the Integrity of Composite Pipelines
- 12. • Severe slugging impacts the riser causing unbalanced thrust forces • forces act to “open-up” / straighten the riser • resultant axial stresses contribute to critical upheaval forces that rupture composite pipelines at the riser 10,476 Licensed Pipelines Status = Operating Severe Slugging Impact Forces act to Straighten the Riser Implication of Severe Slugging to the Integrity of Composite Pipelines Critical upheaval forces are applied to composite pipeline
- 13. 10,476 Licensed Pipelines Status = Operating • the “cap pressure” forces acting on the fixed steel riser produce the force “S” that tends to push the composite pipe in the upheaval direction v, q, p S Implication of Severe Slugging to the Integrity of Composite Pipelines Severe slugging induced by production surge Composite pipeline Steel pipeline / risers S = applied longitudinal tensile stress (constrained for buried pipeline) • unconstrained (surface) pipeline will elongate and bend (Bourdon Effect)
- 14. 10,476 Licensed Pipelines Status = Operating • Overburden forces prevent elongation of the composite pipeline accentuating applied stress at riser connections Implication of Severe Slugging to the Integrity of Composite Pipelines v, q, p S v, q, p Overburden load causes pipeline to resist tendency to elongate Buried Composite Pipeline Axial Force
- 15. 10,476 Licensed Pipelines Status = Operating • Severe slugging translates into cyclic upheaval buckling forces at riser connections • cyclic applied forces cause fatigue failure of fibers and eventual rupture of HDPE liner v, q, p S Implication of Severe Slugging to the Integrity of Composite Pipelines Cyclic upheaval buckling forces cause rupture of composite pipelines at riser connections
- 16. Conclusion #1 10,476 Licensed Pipelines Status = Operating • Most composite pipeline failures (gathering) occur because of exposure to excessive upheaval buckling forces at the connection to steel risers attributed to short-duration severe slugging at the time of detrimental well start-up events
- 17. Conclusion #2 10,476 Licensed Pipelines Status = Operating • Moderating severe slugging during well start-up events will eliminate nearly all future composite pipeline failures in production gathering service • steady-state hydrodynamic slug flow is not capable of creating critical unbalanced forces at riser connections
- 18. 84% of reported failures can be re-classified as being caused by excessive axial impact forces attributed to; severe cyclic slug flow or water hammer 10,476 Licensed Pipelines 544 Failure Events Historical Failures Re-Classified
- 19. PART 3 Integrity Hazard Classification for Spooled Composite Pipelines Water Hammer Causes >80% of Composite Pipeline Failures in Water Injection Service David Richardson, P.Eng. (403) 880-2835 david@trustedpipelineadvisor.com