03 - Pipeline Hydraulics

Shawn Kenny, Ph.D., P.Eng.Assistant ProfessorFaculty of Engineering and Applied ScienceMemorial University of [email protected]

ENGI 8673 Subsea Pipeline Engineering

Lecture 03: Pipeline Hydraulics

2 ENGI 8673 Subsea Pipeline Engineering – Lecture 03© 2008 S. Kenny, Ph.D., P.Eng.

Lecture 03 Objective

To provide an overview of flow assurance To provide simple tools for assessing single phase flow pipeline hydraulics


Overview Flow AssuranceSystem Deliverability

Line sizing Production ratePressure profile and boosting

Thermal BehaviourTemperature profilePassive or active mitigation

Product ChemistryWaxing, asphaltenesHydratesScaling, erosion, corrosion

Operability CharacteristicsSteady-state, transientShut-down, start-up

System PerformanceMechanical integritySystem reliability

Ref: McKechnie et al. (2003)Ref: Watson et al. (2003)


Flow Assurance HazardsMechanical

CorrosionErosion

FlowSluggingEmulsion

DepositionScalingSandWax & asphaltenesHydrates

Ref: Hydro (2005)

Ref: BakerHughes (2005)


Flow Assurance StrategiesMechanical

Hydraulics•

Line sizing

•

Pumping, compressor•

Chillers, heaters

Processing•

Dehydration

•

Chemical removalIntervention•

Inline pigging

•

Plug removal

Ref: Hydro (2005)

Ref: Rosen (2005); Paragon (2005)


Flow Assurance StrategiesThermal

BurialInsulationHeating

Ref: Hydro (2005)

Panarctic Drake F-76 Flowline Bundle


Overview Flow Assurance

Lecture FocusOverview of steady-state, single phase flow

Associated Technical IssuesMultiphase, dense flowTransient flowStart-up, shut-down conditionsRisk and mitigation strategies


Key Engineering Factors

Pipeline HydraulicsLine Sizing•

Primary function for product transport

Steady-State Conditions•

Operating pressure & temperature profile

Facilities Design•

Slug catcher, tank farm


Drivers

Production RateFlow rate, throughputVelocity, pressure

Operating Cost ⇓ D ∝ losses & Δpressure

Construction Cost⇑ D


Hydraulics – Key Input ParametersProduct Characteristics

Phase & compositionChemical constituents

Pipeline ConfigurationRoute lengthNominal diameterBathymetric & topographic profile

Thermal ProfilePipeline, soil conductivityAir, water temperature

Initial Boundary ConditionsInlet pressure, temperatureOutlet pressure, temperature

Ref: Terra Nova DPA


Fluid Mechanics

Single Phase FlowOil, gas or waterNewtonian fluid•

Some heavy oils are non-Newtonian

Constant Flow RatePressureGravity

Pressure Term

Nominal Pipeline Radius

Velocity Profile Shear Stress

Elevation

Elemental Length

Ref: White (1986)


Single Phase Flow Mechanics

Uniform Velocity

Shear Stress

Pressure Term

Pipeline Radius


Elevation

Elemental Length

( )2 22 0dZr dP r dL g r dLdL

π τ π ρ π+ + =

2 0dP dZgdL r dL

τ ρ= − − =

2

2f uρτ =

2

0dP f u dZgdL r dL

ρ ρ∴ = − − =

• f

≡

Fanning friction factor• u ≡

mean velocity• ρ ≡ fluid density

Ref: White (1986)


Integral Formulation

If Constant Over dLDiameterVelocityFriction (viscosity)Density (gas flow)

Pressure Term

Pipeline Radius


Elevation

Elemental Length

2

0dP f u dZgdL r dL

ρ ρ= − − =

( ) ( )2

2 1 2 1 2 1 0f uP P L L g Z Zr

ρ ρ− = − − − − =

Ref: White (1986)


Integral Form Not PracticalVariation in Properties

Velocity, density, friction coefficientOil and Gas Flow

Heat loss •

f ∝

Re ≡ μ(T)Gas Flow

Density•

Δρ

∝

ΔP ≡ ΔQ & ΔzConstant mass flow rate•

ΔU ∝ Δρ

CompressibilityJoule-Thompson (⇓T ∝ ⇓P)


Frictional Losses

AssumptionsSmooth, uniform internal diameterIncompressible fluidFunction of Reynolds number•

μ ≡ viscosity (Pa s)

Re U Dρμ

=


Frictional Losses (cont.)Friction Coefficient

Fanning [f]•

Hydraulic radius

Manning [m]•

Diameter

•

m = 4fParameters

•

Reynolds

number, Re

•

Surface roughness, k

k ≈ 0.05mmCorrosion, erosion, wax, etc.

Re16

=f

( )101 4 log Re 0.4ff

= −

0.3240.0014 0.125Ref −= +

Loss ∝

U

Loss ∝

D


Analysis of Turbulent Flow

Theoretical TreatmentEmpirical coefficientsSensitive to surface roughness

0.75 0.25 1.75

4.75

0.241L QPD

ρ μΔ =

Ref: White (1986)


Pipeline Hydraulics Calculations

Energy Balance per Unit Lengthmass 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)

( )Δ +Δ +Δ +Δ + Δ = 0PE KE Tm h E E Q W

m


Line Sizing – Gas Flow

Panhandle A FormulaEmpiricalLarge diameter pipelinesRelatively low pressure (7MPa)

1.07881 0.53943 0.4606 2.61821 2438 10 o

o

T p pQ E G Dp LT

− −⎛ ⎞ ⎛ ⎞−= × ⎜ ⎟ ⎜ ⎟

⎝ ⎠⎝ ⎠• 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)


Line Sizing – Oil Flow

Rule of ThumbTrade-off CAPEX ⇔ OPEX

D ≡ in; Q ≡ BBL/day1 BBL = 42 US gal = 35 Imp gal1 BBL = 158.97 L

D ≡ mm; Q ≡ m3/s500QD =

840D Q=


Example 3-01

Calculate the line size (nominal diameter) for a horizontal, single phase oil pipeline

Flow rate, Q = 0.342 m3/sFluid density, ρ = 950 kg/m3

Viscosity, ν = 2 ×10-5 m2/s = 20 centistokesSurface roughness, k = 0.006mmPipeline segment length, L = 100mHead loss, hf = 8m


Example 3-01 (cont.)

Modified Moody Chart

Ref: White (1986)



Using Modified Moody Chart

Corresponds to smooth wall

Line size

ν −= × 93.51 10kQ

βπ υ

−= = ×3

113 5

128 2.012 10ghQL

β= =0.416Re 1.43 72,100

ν π ν= =

4Re UD QD

⇒ = 0.302D m


Example 3-02

Consider the following pipeline system transporting 100kBBL/day single phase oil

Oil density, ρ = 850 kg/m3

Viscosity, μ = 0.01 Pa·s = 10 centipoiseInlet pressure 5MPaArrival pressure 1MPa

Calculate the line size for a 25km pipeline



Line Sizing Rule of Thumb

Using API 5L (2007)Select D = 12″ (12.75″) = 323.9mm•

Guess WT = 12.7mm

100000 14.1" 358500 500QD mm= = = ⇒

( )-

3

2 2

0.184 / 2.63 /0.3239 2 0.0127

4

Q m sU m sA mπ

= = =×



Reynolds Number

Fanning Friction FactorAssume k = 0.001•

f = 0.0059

( )( )( )34

850 2.63 0.3239 2 0.0127Re 6.67 10

0.01kg m m s m mU D

Pa sρ

μ

− ×= = = ×

⋅



Check Erosion VelocityReduces wall thicknessGenerates noiseEmpirical expression

max

3

122 122 4.2850

mUskg

mρ

= = =

max2.63 4.2m mU U oks s

= < = ∴



Pressure Drop

Friction loss only

Allowed ΔP = 5MPa – 1MPa = 4MPa•

∴

Reselect D

( )( ) ( )232 0.0059 850 2.63 250005.81

0.14925kg m m s mf U LP MPa

r mρ

Δ = = =

2

0dP f u dZgdL r dL

ρ ρ= − − =



Using API 5L (2007)Select D = 14″ = 355.6mm•

Assume WT = 12.7mm

Acceptable ΔP

20.29852.63 2.150.3302

Q m m mUA s m s

⎛ ⎞= = =⎜ ⎟⎝ ⎠

( )( )( )34

850 2.15 0.3302Re 6.03 10

0.01kg m m s mU D

Pa sρ

μ= = = ×

⋅

( )( ) ( )232 0.006 850 2.15 250003.57

0.1651kg m m s mf U LP MPa

r mρ

Δ = = =



Field Life ScenarioReduced production rate•

10 years

•

20kBBL/day

Produced water•

CO2

, H2

S

Potential •

Water drop out

•

Extensive corrosion at clock position 6 and low spots

202.15 0.43100

Q m kBBL day mUA s kBBL day s

⎛ ⎞= = =⎜ ⎟

⎝ ⎠


Multiple Phase FlowPhase

GasLiquid (oil, water)Solid (sand)

Flow RegimeMultiple modesIrregular flowVibration

EmulsionOil and water mixture ⇑ Viscosity ∝ ⇑ ΔP

SluggingHydrodynamic, elevation inducedProcess upset, shut down

Surge⇑ Volumetric, mass flow rates

Ref: Hydro (2005)


Reading List1.

Cochran,S. (2003). Recommended Practice for Hydrate Control and Remediation. World Oil, September, pp.56-65.

[2003_Cochran_RP_Hydrate_Control_Remediation.pdf]

2.

McKechnie, J.G.and

Hayes, D.T. (2003). Pipeline Insulation Performance for Long Distance Subsea Tie-Backs. 14p. [2003_McKechnie_Insulation_Performance_Long_Distance_Tie_

Backs.pdf]

3.

Wasden, F.K. (2003). Flow Assurance in Deepwater Flowlines/Pipelines. Deepwater Technology, October, pp.35-38.

[2003_Wasden_FA_Deepwater_Flowlines.pdf]

4.

Watson, M., Pickering, P. and Hawkes, N. (2003). The Flow Assurance Dilemma: Risk versus Cost? E&P, May, 4p. [2003_Watson_Flow_Assurance.pdf]


ReferencesAPI 5L (2007). Specification for Line Pipe, Forty-fourth Edition. 44th

Edition.BakerHughes (2005). http://www.bakerhughes.com/bakerpetroliteHydro (2005). http://www.hydro.com/ormenlange/enParagon (2005). http://www.paraengr.comRosen (2005). http://www.roseninspection.netRidao, 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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03 - Pipeline Hydraulics