1. Erosion Management Strategy for High Risk Assets
Based on DNV RP O501 Methodology
Xiaoda Xu
Website:

2. Upstream erosion management practice
Outline
Upstream erosion management practice
Sensitivities of production variables on erosion
Free flowing well erosion management
Erosion guideline |
Author: Xiaoda Xu,

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,

4. API RP 14E : Summary Disadvantages: Easy to use ??
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,

5. Upstream Practice Example:
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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.
Erosion guideline |
Author: Xiaoda Xu,

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
Erosion guideline |
Author: Xiaoda Xu,

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
Erosion guideline|
Author: Xiaoda Xu,

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
Erosion guideline |
Author: Xiaoda Xu,

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
Erosion guideline |
Author: Xiaoda Xu,

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,

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.
Erosion guideline |
Author: Xiaoda Xu,

13. Process Variables impact: elbow
Gas rate production
Water rate production
Casing pressure production
Tubing pressure production
Gas flow path
MSCFD
BBPD
PSI
4300
306 91 82
Tubing
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
Erosion guideline |
Author: Xiaoda Xu,

16. Process Variables impact , valve restriction
Gas rate production
Water rate production
Casing pressure production
Tubing pressure production
Gas flow path
MSCFD
BBPD
PSI
4300
306 91 82
Tubing
Increased choking and constant flow and pressure
Erosion guideline |

17. Process Variables impact: valve restriction..
Gas rate production
Water rate production
Casing pressure production
Tubing pressure production
Gas flow path
MSCFD
BBPD
PSI
4300
306 91 82
Tubing
Increased choke, reduced flow and pressure simultaneously
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18. Process Factors for Erosion Management
Controllable?
Known with great impact
Gas rate
Y/N
Gas pressure
Valve position (remote) Y
Water rate
Unknown with great impact
Solids N
Valve position (manual)
Erosion guideline |
Author: Xiaoda Xu,

19. Type A Well Name Type A 4177 726 179 76 Tubing Well
Gas rate production
Water rate production
Casing pressure production
Tubing pressure production
Gas flow path
Well Name
MSCFD
BBPD
PSI
Type A
4177
726
179 76
Tubing
Erosion guideline |
Author: Xiaoda Xu,

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
Erosion guideline |
Author: Xiaoda Xu,

21. Type B Well Name Type B 1299 511 113 40 Tubing Well
Gas rate production
Water rate production
Casing pressure production
Tubing pressure production
Gas flow path
Well Name
MSCFD
BBPD
PSI
Type B
1299
511
113 40
Tubing
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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
Erosion guideline |
Author: Xiaoda Xu,

23. Type C Well Name Type C 863 207 85 43 Tubing Well Gas rate production
Water rate production
Casing pressure production
Tubing pressure production
Gas flow path
Well Name
MSCFD
BBPD
PSI
Type C
863
207 85 43
Tubing
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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
Erosion guideline |
Author: Xiaoda Xu,

25. Type D Well Name Type D 444 337 100 61 Tubing Well Gas rate production
Water rate production
Casing pressure production
Tubing pressure production
Gas flow path
Well Name
MSCFD
BBPD
PSI
Type D
444
337
100 61
Tubing
Type footer details here | 12 November 2018

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
Erosion guideline |
Author: Xiaoda Xu,

27. Well characterisation for erosion purpose
Control measures
Type A
Severe erosion rate even at low solid rate under current production condition, avoid any choking, inspection and reviewing
Type B
Sensitive to solids for both choking and elbow, avoid choking, monitoring, inspection and reviewing
Type C
Sensitive to solids at choking, avoid choking monitoring, inspection and reviewing
Type D
Minimum erosion rate even at high solid rate under current production , reviewing only
Erosion guideline |
Author: Xiaoda Xu,

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
Erosion guideline |
Author: Xiaoda Xu,