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Shawn Kenny, Ph.D., P.Eng.Assistant Professor
Faculty of Engineering and Applied ScienceMemorial University of Newfoundland
Lecture 04 – Flow Assurance
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Lecture Goals
Students will be able to: identify key factors influencing flow assurance,
hydraulic and thermal analysis of product flow in pipeline systems, and
use simple tools for assessing single phase flow pipeline hydraulics and thermal analysis
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Reading List
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# Document
4.1 Cochran,S. (2003). Recommended Practice for Hydrate Control and Remediation. World Oil, September, pp.56-65. [2003_Cochran_RP_Hydrate_Control_Remediation.pdf]
4.2 Wasden, F.K. (2003). Flow Assurance in Deepwater Flowlines/Pipelines. Deepwater Technology, October, pp.35-38. [2003_Wasden_FA_Deepwater_Flowlines.pdf]
4.3 Watson, M., Pickering, P. and Hawkes, N. (2003). The Flow Assurance Dilemma: Risk versus Cost? E&P, May, 4p. [2003_Watson_Flow_Assurance.pdf]
4.4 Geertsen, C. and Offredi, M. (2000). Highly Thermally Insulated and Traced Pipelines for Deepwater. 12th Deep Offshore Technology Conference, New Orleans, USA, 13p.[2000_Geertsen_Insulated_Traced_Deepwater_PL.pdf]
4.5 Maksoud, J. (2004). Petro-Canada Investigates Flow Assurance Challenges. Offshore, pp.112-113. [2004_Maksoud_ FA_Challenges_Petro_Canada.pdf]
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Overview Flow Assurance System Deliverability
Line sizing Production rate Pressure profile and boosting
Thermal Behaviour Temperature profile Passive or active mitigation
Product Chemistry Single, multiple phase Waxing, asphaltenes Hydrates Scaling, erosion, corrosion
Operability Characteristics Steady-state, transient Shut-down, start-up
System Performance Mechanical integrity System reliability
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Ref: McKechnie et al. (2003)
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Flow Assurance Hazards Mechanical
Corrosion Erosion
Flow Slugging Emulsion
Deposition Scaling Sand Wax & asphaltenes Hydrates
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Ref: Hydro (2005)
Ref: BakerHughes (2005)
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Flow Assurance Strategies Mechanical
Hydraulics Line sizing Pumping, compressor Chillers, heaters
Processing Dehydration Chemical removal
Intervention Inline pigging Plug removal
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Ref: Hydro (2005)Ref: Rosen (2005)
Ref: Paragon (2005)
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Flow Assurance Strategies Thermal
Burial Insulation Heating
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Ref: Hydro (2005)
Panarctic Drake F-76 Flowline Bundle
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Flow Assurance Strategies Flow Performance
Drag reduction Drag reducing
agents (DRA) Liners
Inhibitors Methanol Mono-ethylene
glycol (MEG)
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Ref: Hydro (2005)
Ref: BakerHughes (2005); Ridao (2004)
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Pipeline Hydraulics – Goals Line Sizing
Primary function for product transport Transport rate (e.g. MMBBL/day, m3/day) Pressure
Steady-State Conditions Operating pressure & temperature profile
Facilities Design Slug catcher, tank farm Compression, chillers
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Pipeline Hydraulics – Drivers Operating Cost
⇓D ∝ frictional losses & ∆pressure
Construction Cost ⇑ D
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Pipeline Hydraulics – Key Parameters Product Characteristics
Phase & composition Chemical constituents
Pipeline Configuration Route length Nominal diameter Bathymetric & topographic
profile Thermal Profile
Pipeline, soil conductivity Air, water temperature
Initial Boundary Conditions Inlet pressure, temperature Outlet pressure, temperature
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Ref: Terra Nova DPA
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Fluid Mechanics – Single Phase Flow Parameters
Oil, gas or water Newtonian fluid
Some heavy oils are non-Newtonian
Constant Flow Rate Pressure Gravity
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Pressure Term
Nominal Pipeline Radius
Velocity Profile Shear Stress
Elevation
ElementalLength
Ref: White (1986)
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Fluid Mechanics – Single Phase Flow
Uniform Velocity
Shear Stress f – Fanning factor u – mean velocity ρ – fluid density
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Fluid Mechanics – Integral Formulation
If Constant Over dL Diameter Velocity Friction (viscosity) Density (gas flow)
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Integral Form Not Practical Variation in Properties
Velocity, density, friction coefficient Oil and Gas Flow
Heat loss f ∝ Re ≡ µ(T)
Gas Flow Density
Δρ ∝ ΔP ≡ ΔQ & Δz Constant mass flow rate
ΔU ∝ Δρ Compressibility Joule-Thompson (⇓T ∝ ⇓P)
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Frictional Losses
Assumptions Smooth, uniform internal diameter Incompressible fluid Function of Reynolds number
µ ≡ viscosity (Pa·s)
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Frictional Losses (cont.) Friction Coefficient
Fanning [f] Hydraulic
radius Manning [m]
Diameter m = 4f
Parameters Reynolds
number, Re Surface
roughness, k k ≈ 0.05mm Corrosion,
erosion, wax, etc.
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Loss ∝ U
Loss ∝ D
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Energy Balance Per Unit Length ≡ mass flow rate (kg/s) Δh ≡ change in enthalpy (J/kg) ΔEPE ≡ change in potential energy (J/kg) ΔEKE ≡ change in kinetic energy (J/kg) ΔQT ≡ heat loss (W) ΔW ≡ external mechanical work (W)
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Line Sizing – Gas Flow Panhandle A Formula
Empirical Large diameter pipelines Relatively low pressure (7MPa)
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• Q ≡ Flow rate (m3/day)• E ≡ efficiency factor (typically 0.92)• po ≡ Reference pressure (MPa)• To ≡ Reference temperature (K)• p1 ≡ Upstream pressure (MPa)• p2 ≡ Upstream pressure (MPa)
• L ≡ Pipeline length (km)• T ≡ mean temperature (K)• G ≡ gas gravity (air = 1)• D ≡ pipeline diameter (mm)
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Line Sizing – Oil Flow Rule of Thumb
Trade-off CAPEX ⇔ OPEX
D ≡ in; Q ≡ BBL/day 1 BBL = 42 US gal =
35 Imp gal 1 BBL = 158.97 L
D ≡ mm; Q ≡ m3/s
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Example 4-01
Consider the following pipeline system transporting 100kBBL/day single phase oil Oil density, ρ = 850 kg/m3 Viscosity, µ = 0.01 Pa·s = 10 centipoise Inlet pressure 5MPa Arrival pressure 1MPa
Calculate the line size for a 25km pipeline
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Example 4-01 (cont.) Line Sizing Rule of
Thumb
Using API 5L (2007) Select D = 12″ (12.75″) Select D = 323.9mm Guess WT = 12.7mm
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U =QA=
0.184m3 / sπ4
0.3239 - 2 × 0.0127( )2m2
= 2.63m / s
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Example 4-01 (cont.)
Check Erosion Velocity Reduces wall thickness Generates noise Empirical expression
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Example 4-01 (cont.) Reynolds Number
Fanning Friction Factor Assume k = 0.001
f = 0.0059
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Example 4-01 (cont.)
Pressure Drop
Friction loss only
Allowed ΔP = 5MPa – 1MPa = 4MPa ∴ Reselect D
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Example 4-01 (cont.) Using API 5L (2007)
Select D = 14″ = 355.6mm Assume WT = 12.7mm
Acceptable ΔP26
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Example 4-01 (cont.) Field Life Scenario
Reduced production rate 10 years 20kBBL/day
Produced water CO2, H2S
Potential Water drop out Extensive corrosion at clock position 6 and low spots
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Multiple Phase Flow Phase
Gas Liquid (oil, water) Solid (sand)
Flow Regime Multiple modes Irregular flow Vibration
Emulsion Oil / water
mixture ⇑ Viscosity ∝ ⇑ ΔP
Slugging Hydrodynamic,
elevation induced Process upset,
shut down Surge
⇑ Volumetric, mass flow rates
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Ref: Hydro (2005)
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Heat Transfer Mechanisms Conduction
Direct contact Relatively inefficient
Convection Flow or circulation
Natural or forced (advection)
Radiation Electromagnetic
energy Emissivity
Ability to absorb and radiate energy
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Thermal Effects Flow Assurance
Viscosity effects on pressure drop Process facilities Wax, asphaltene, hydrate formation
Material behaviour Reduced strength Corrosion rates Creep
Mechanical design Thermal expansion Upheaval, lateral buckling
Shut-in & start-up operations Flow assurance Axial walking, ratcheting
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.31
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Heat Transfer – Conduction Fourier Law
Q ≡ heat loss per unit length (W/m)
t ≡ time (s) k ≡ material thermal
conductivity (W/m/K) S ≡ surface area (m2) T ≡ temperature (K) U ≡ heat transfer
coefficient (W/m2-K)
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Heat Transfer – Steady State
Integrate per Unit Length Annular layer Temperature gradient
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QT
r dr, ΔT
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Heat Transfer – Multiple Layers
Heat Transfer Coefficient
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Heat Transfer – Soil Effects
Buried Pipeline ri ≡ inside pipe radius ro ≡ outside pipe
radius in contact with the soil
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Thermal Conductivity Parameters
Common Materials (W/m/K) Steel 45 Concrete 1.2 Soil 1.0–2.0 Neoprene 0.26 PP syntactic 0.15–0.20 PU syntactic 0.10–0.15 PU light foam 0.02–0.03
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Heat Transfer Coefficient
Non-insulated Single Wall 25 W/m2K Burial decrease U by
~1/3 Pipeline Bundle
≈ 1.5–2.5 Insulated Pipe-in-Pipe
≈ 3.0.–6.0 Insulated Pipe-in-Pipe
≈ 0.5–1.0
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Steady State Thermal Profile
Parameters m – mass flow rate (kg/s) U – heat transfer coefficient (W/m2-K) Cp – specific heat capacity (J/kg-K)
Oil ≡ 1800 and Gas ≡ 2500 T0 – ambient temperature (°C) T1 – pipeline temperature at section 1 (°C) T2 – pipeline temperature at section 2 (°C)
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.39
Ref: Maksoud (2004)
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.40
Ref: Maksoud (2004)
ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Example 4-02
Calculate the heat loss coefficient (U) for an in-air, single wall, steel linepipe with no external or internal coatings. Do = 508mm t = 12.7mm k = 45 W/m/K
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
Example 4-03 Calculate the heat loss
coefficient (U) for the following pipe-in-pipe system Inner Pipe
Do = 406.4mm t = 17.5mm k = 45 W/m/K
Polypropylene Foam t = 45mm k = 0.22 W/m/K
Casing t =12.7mm k = 45 W/m/K
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ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2009 S. Kenny, Ph.D., P.Eng.
References API 5L (2007). Specification for Line Pipe, Forty-fourth Edition. 44th
Edition. BakerHughes (2005). http://www.bakerhughes.com/bakerpetrolite Hydro (2005). http://www.hydro.com/ormenlange/en Paragon (2005). http://www.paraengr.com Rosen (2005). http://www.roseninspection.net Maksoud, J. (2004). Petro-Canada Investigates Flow Assurance
Challenges. Offshore, pp.112-113. Ridao, M.A. (2004). “Optimal use of DRA in oil pipelines”. IEEE
International Conference on Systems, Man and Cybernetics, pp.6256-6261.
Watson, M., Pickering, P. and Hawkes, N. (2003). The Flow Assurance Dilemma: Risk versus Cost? E&P, May, 4p.
White, F.M. (1986). Fluid Mechanics. 2nd Edition, McGraw-Hill, ISBN 0-07-069673-X, 732p.
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