Flow Assurance and Multiphase flow - part 1 By Prof ... - Aker Solutions


Flow Assurance and Multiphase flow - part 1 By Prof ... - Aker Solutions

Flow Assurance and Multiphase flowMultiphase flow• Offshore• Subsea• Deepwater• Long transportation• (Near) ArcticScandpower Petroleum TechnologyProf. Rune W. TimeDepartment of Petroleum EngineeringgUniversity of StavangerSeminar at Aker Solutions, Stavanger – May 31st, 2011

Outline and time schedule8.30 – 9.15 Flow regimes and impact on phase slippage,fluid concentrations and pressure drop inpipelines9.25 – 10.15 Hydrates, wax and asphaltenes10.25 -11.00 Multiphase flow – influence from interfaces,compression effects and wavesSeminar at Aker Solutions, Stavanger - May31st, 20112

Flow regimes and impact on phase slippage, fluidconcentrations and pressure drop in pipelinesTransparent pipeQ GGasQ LLiquid• Stratified liquid and gas – is there a flow? How to decide?• Some concepts are needed:• Flow speeds• Fluid fractions• Flow patterns (”regimes”)Seminar at Aker Solutions, Stavanger - May31st, 20113

QUIZ:A simple(st) case of two-phase flowEqual inflowQ L = Q GGasLiquidHorizontal pipeline312Stabilizedinterface ?• How to decide?• Any guideline principles?4

Basic quantities and definitions:- Superficial velocities and fluid fractionsq GU GSu GAu Lq LU LSSuperficial velocities :UULSqLAqAA LA GMixture velocity :U U U mix LS GSGGSApparent liquidfraction (”noslip”):qLULSL q q U UL G LS GSSeminar at Aker Solutions, Stavanger - May31st, 20115

Basic quantities and definitions:- True velocities and Slipq Gu GAu LA Lq LA GTrue (phase) velocities :uuLGqAqALLGGSlip velocity :uSuGuLNOSLIP condition:andu L = u G = U mixSlip ratio :S S=1u Gu LSeminar at Aker Solutions, Stavanger - May31st, 20116

Basic quantities and definitions:- True liquid fraction versus noslip fractionq GU GSu GAu LA Lq LU LSA GTrue (real) volume fractionApparent(”noslip”): LALALAGULSq LU LSL q q U UULS1 USL G LS GSGSSeminar at Aker Solutions, Stavanger - May31st, 2011S = Slip ratio7

True fraction versus mixture velocityTrue fraction noslip fraction (S = 1)as mixture velocity increasesULSL11 U ULSFlow regimeGSS dependence !Liquid fra actionSegregated g flows( Keeping constantratio U LS /U GS )Mixed flowsLUULS ULSGS0U mixSeminar at Aker Solutions, Stavanger - May31st, 20118

Flow regimes in horizontal pipesFlow directionspeedIncreas sing flowLowvelocityInterm mediate velocit tyStratified smoothflow (SS)Stratified wavyflow (SW)Elongated bubbleflow (EB)Slug flow (I)igh velocityHiSeminar at Aker Solutions, Stavanger - May31st, 2011Dispersed bubbleflow (DB)Annular (wavy)flow (A-AW)9

IFlow regime map – horizontal pipesU LS (m/s)10Elongated1 bubble bbl flow(EB/I)0.1Dispersed bubble (DB)Slug flow (I)StratifiedwavyStratified smooth flowflow (SS) (SW)Annular -annular wavy -annular mist flowLow veloc cityIntermediate velocityTaitel and Dukler2.5 cm i.d. Pipeair-water flowat atmosphericconditionsMandhaneFlow directionStratified smoothflow (SS)Stratified wavyflow (SW)Elongated bubbleflow (EB)Slug flow (I)0.01High velocityDispersed bubbleflow (DB)Annular (wavy)flow (A-AW)0.1 1 10 100U GS (m/s)Seminar at Aker Solutions, Stavanger - May31st, 201110

Flow regimes and map – vertical pipesFlow regime mapFlow regimes - typesDispersed bubbles(small)AnnularflowSlug –flowchurnSeminar at Aker Solutions, Stavanger - May31st, 201111

Gas – concentration profilesSnapshot of dispersed bubble flowPipeGas fraction GUpLeads to vertical differences:• Gas- liquid wetting (evt. water)• Asymmetric corrosion (”6’oclock”)• Shear stress & Erosion rates• Heat transfer ratesSeminar at Aker Solutions, Stavanger - May31st, 201112

Particle slurries in multiphase flowLarge gas bubbleD:\BACKUP 2009 - DET ASTRONOMISKE ÅRET 2009\Åpent Hus 17mars09\Utvalgte high-speed videoer\ Water speed 1Seminar at Aker Solutions, Stavanger - May31st, 201113

Particle slurry regimes - dunesSuspended particles in liqudFlowDunesRabenjafimantsoa and Time ( UIS) - project with Statoil 2000-2005Seminar at Aker Solutions, Stavanger - May31st, 201114

Oil-water-gas flow regime mapREF:http://www.iceweb.com.au/Flow/multiphase_1.htmSeminar at Aker Solutions, Stavanger - May31st, 201115

Importance of flow regimesMuch more than just ”flow appearance”:Field plan and development• Multiphase simulation, pressure and fluid fraction determination• Slip ratio and fluid transport rates in long pipelines• Multiphase pumping• Decisive for quality of multiphase meteringFlow assurance, safety• Process stability and control• Pipeline and equipment vibration and fatigue• Erosion• CorrosionSeminar at Aker Solutions, Stavanger - May31st, 201116

The challenge of calculatingpressure drop in long traversesThe pressure gradient varies along the pipedue to variation in pipe diameter, inclinationand mixture density (pressure dependent)PoutP indlPressure at exit:P P PoutinSum of pressure drop in all pipe segmentChallenge in multiphase flow:• The pressure profile depends on the pressure!• Requires iterative numerical solver17Seminar at Aker Solutions, Stavanger - May31st, 2011

Robust – ”homogeneous” pressure drop modelfor two-phase flowxU GSPressure gradient versus UGS for contant ULS12000U LSFriction :dp dx fFriction factor4 1 f (Re) mUD 22mix*Pressure gra adient (Pa/m)100008000600040002000Constant Uls= 3m/sTotalHydrostatic: dp mg sin dxh00 5 10 15 20 25 30Ugs (m/s)Acceleration:dp dU m UmixdxdxamixSeminar at Aker Solutions, Stavanger - May31st, 2011EXCELversion18

Two-phase pressure drop model – Excel versionU GSU LSQuantity Symbol Value UnitGas density rog 10 kg/m^3Liquid density rol 1000 kg/m^3Kinematisk gas viscosity nyg 1,50E-06 m^2/sDynamic gas viscosity myg 1,50E-05 Pa*sLiquid viscosity myl 3,00E-03 Pa*sPipe diameter D 1,50E-01 mPipe inclination 20,0 deg 3,49E-01 radAcceleration of gravity g 9,81E+00 m/s^2Slip ratio S 1,2Superficial liquid velocity ULS 35m/s 3,5 Superficial gas velocity UGS 1,3 m/sMixture velocity Umix 4,8 m/sGas fraction epsg 0,236363636Liquid fraction epsl 0,763636364 dp 4 n12Mixture density rom 766 kg/m^3 C Re m mUmixdx D2Mixture viscosity mym 2,29E-03 Pa*s f dp mg sin dxhdp dU m UmixdxdxamixReynolds number Re 2,40E+05Friction factor f 3,86E-03Friction pressure drop dPdx_f 9,08E+02 Pa/mHydrostatic pressure drop dPdx_h 2,57E+03 Pa/mAccelerational pressure drop dPdx_a Pa/mTotal pressure drop dPdx 3,48E+03 Pa/m19

The World is Dynamic! – need for Measurementand Control- Even constant inflow of multiphase flow mixtures into pipelinedoes not mean that the individual flowrates (G,L) are constant !- Need for multiphase metering for survey and control !Separation approachWeatherfordMixing approachMPM20

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