Erosion Management Strategy for High Risk Assets

1. Erosion Management Strategy for High Risk Assets Based on DNV RP O501 Methodology Xiaoda Xu Website:www.corrosionguru.com E-Mail: Corrsionguru.com@gmail.com

2. Outline Upstream erosion management practice Sensitivities of production variables on erosion Free flowing well erosion management Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

3. Erosion in Sand Free System - API RP14E The API (American Petroleum Institute) Recommended Practice 14E defines a critical velocity above which “erosion may occur”, and recommends that the maximum velocity in the system be limited to this critical velocity, effectively sizing “flowlines, production manifolds, process headers and other lines transporting gas and liquid in two-phase flow…”. The critical velocity is defined by the empirical equation: Vm* = C / m Where C = an empirical constant (=100 ft/s(lbs/ft3)0.5 for continuous flow) m = the gas/liquid mixture density at operating temperature and pressure, lb/ft3 Vm* = the maximum allowable mixture erosional velocity, ft/s The value of C has no theoretical justification. The API committee compromised on this value after reviewing the values proposed by different companies which ranged from 60 to 160 ft/s(lbs/ft3)0.5 based on steam plant experience. API RP 14E states a suggested value of C=125 ft/s(lbs/ft3)0.5 be used for intermittent two-phase flow. The equation was widely used throughout the industry back 90s , however it should be noted that: It only applies to two-phase gas/liquid flow It does not apply to flow containing solids (e.g. sand). Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com

4. API RP 14E : Summary Advantages: Easy to use ?? Disadvantages: Only includes one factor for erosion – density of medium Factors not included are: flow geometry, type of metal, sand size, Reynolds number Does not specify the tolerable amount of erosion in terms of loss of wall thickness No sand provision Flaw: Formula suggests that the limiting velocity could be increased when fluid density is decreased. – but field and laboratorial evidence shows that sand in gas (low density) causes higher erosion than sand in liquids (high density) “Though this equation is often applied it is widely accepted to be misleading or incorrect” – UK HSE RR115, 2003 Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com

5. Upstream Practice Example: Type footer details here | 10 March 2016

6. Industrial Practice Example: cont… ‘First Pass’ Velocity Limits for Avoiding Erosion which lays down ‘rule-of-thumb’ velocity limits for the avoidance of erosion damage in non-solids containing environments. For solids-containing environments a ‘maximum velocity’ is quoted which relates to a ‘safe limit’ below which further assessment of the likely erosion wastage rate is considered unnecessary. Calculation of Erosion Rates which makes recommendations for evaluating the erosion and erosion-corrosion rates where the velocity limits for solids-containing duty in the ‘First Pass Velocity Limits for Avoiding Erosion’ flow chart are exceeded, or where greater precision is required than afforded by a simple velocity limit for nominally solids-free conditions. The flow chart uses a range of erosion rate models which can be classed as ‘Simple’ Erosion Rate Models and ‘Full’ Erosion Rate Models. • Harwell - ‘Sandman’ Model should be used for multiphase flow (annular mist or stratified flow) • Tulsa Model should be used for single phase flow and/or multiphase slug flow. Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

7. Comparison of multiple models-cont… Scenario 2, Liquid flow with solids • Liquid Density = 769 kg/m3 • Liquid Viscosity = 1.08 x 10-3Pas • Sand particle size = 150 microns • Sand density = 2650 kg/m3 • Elbow diameter = 55 mm • Elbow r/D = 1.5 • Elbow material steel grade (Brinnell Hardness = 210) • Sand concentration = 0.1 ppmw -- – UK HSE RR115, 2003 Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

8. Comparison of multiple models Scenario 1, Gas flow with solids • Gas Density = 4.82 kg/m3 • Gas Viscosity = 1.1 x 10-5Pas • Sand particle size = 150 microns • Sand density = 2650 kg/m3 • Elbow diameter = 55 mm • Elbow r/D = 1.5 • Elbow material steel grade (Brinnell Hardness = 210) • Sand concentration = 21.6 ppmw -- – UK HSE RR115, 2003 Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline|

9. DNV RP O501 “DNV RP O501 is one of the most comprehensive available on erosion management. It gives design guidelines on straight pipes, welded joints, reducers, elbows and blind tees.” – UK HSE RR115, 2003 Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

10. DNV RP O501 Variables: Gas rate Higher gas rate, higher erosion rate Water rate Higher water rate, higher erosion rate *the impact of water rate is much lower Gas pressure Lower gas pressure, higher erosion rate Pipe sizing Smaller piper, higher erosion rate Dragging effect Consider through fluid viscosity Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

11. DNV RP O501 Variables: cont… Piping geometry Specific geometry: smooth pipe, pipe bend, pipe with weldment, reducer / contraction, blind Tee and Intrusive probe Solids Higher density, higher erosion rate Higher mass flow, higher erosion rate Larger size, higher erosion rate up to 100um No difference in shape Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com

12. DNV RP O501 Disadvantages: Limit capability of parameter study Solids shape and other physical properties are not accounted except density and PSD Labour intensive and time consuming for the parameters sensitivity study. Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

13. Process Variables impact: elbow Superficial velocity 32 m/s, 36m/s, 40m/s Reduced pressure and constant flow

14. Process Variables impact, elbow cont… Superficial velocity 32 m/s, 28m/s, 25m/s Reduced flow and pressure simultaneously

15. Process Variables impact, elbow cont … Superficial velocity 32 m/s, 28m/s Reduced flow and pressure, with increased water rate Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

16. Process Variables impact , valve restriction Increased choking and constant flow and pressure Erosion guideline |

17. Process Variables impact: valve restriction.. Increased choke, reduced flow and pressure simultaneously Type footer details here | 10 March 2016

18. Process Factors for Erosion Management Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

19. Type A Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

20. What is in Type A • Even slight restriction may cause severe erosion concern near control valve even with low level of solids • Elbow is prone to erosion with current flow conditions • Erosion aggravates with higher solids contents • High production impact Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

21. Type B Type footer details here | 10 March 2016

22. What is in Type B • Erosion around control valve is sensitive to valve position and solids contents • Erosion around elbow is sensitive to solids content • Erosion probably aggravates in the future production conditions Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

23. Type C Type footer details here | 10 March 2016

24. What is in Type C • Erosion around control valve is sensitive to valve position and solids contents • Erosion around elbow is NOT sensitive to solids content under current production conditions • Erosion around elbow is acceptable under current production Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

25. Type D Type footer details here | 10 March 2016

26. What is in Type D • Erosion around control valve is NOT sensitive to valve position and solids contents • Erosion around control valve is acceptable under current production conditions • Erosion around elbow is NOT sensitive to solids content undercurrent production conditions • Erosion around elbow is acceptable under current production conditions Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

27. Well characterisation for erosion purpose Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |

28. Conclusion Time to leave API 14E One-size-fit-for-all erosive velocity limit is not applicable for upstream gas well production Erosive metal loss is a combination factors of pressure, gas rate, solids, piping geometry, choking position etc, etc, etc… Grouping the wells according to their behaviour gives much better idea to focus limit resource on great impact wells Updated the management strategies for each type of wells will lead to better flow assurance • Review • Monitoring • Avoid unnecessary choking • Production /pressure prediction • inspection result feedback • validation Author: Xiaoda Xu, www.corrosionguru.comcorrosionguru.com@gmail.com Erosion guideline |