An overview of CFD applications in flow assurance From well head to the platform Simo Simon Lo
Contents – From well head to the platform Heat transfer in Christmas tree • Multiphase flow in long pipe • Severe slugging in riser • Sand transport in pipes • Temperature effects in transportation of viscous oil • Hydrate formation • Slug flow around pipe elbow • Riser V&V • 3 phase separator • Wave impact on platform • Launching of lifeboat •
Flow in and around a Christmas tree
Flow inside a Christmas tree
Temperature distribution inside a Christmas tree
Oil and gas flow in 100m pipeline
Severe slugging in riser, Uni of Cranfield, UK Experiment Star-CD-1 1 Star-CD-2 0.8 Riser DP, bar 0.6 0.4 Riser top 0.2 0 50 100 150 200 250 300 350 Flow time t, s 4 inch riser Riser DP = P base - P top 10.5 m 55 m pipeline Riser base
DEM – particle transport in pipe
DEM - Pneumatic conveying of particles in pipe
Slurry flow in horizontal pipe Horizo rizontal l slu slurry rry pip ipelin line flo low Unif iform rm so solid lid vo volu lume me fra ract ctio ion (vf vf) ) Me Measu sure reme ment pla lane g g 1m m and slu slurry rry ve velo locit city y (V) (V) V V D D L=1 =10m m Liq iquid id ve velo locit city y Inle let Mid Middle le Outle let Pa Part rticle icle vo volu lume me fra ract ctio ion
Slurry flow in pipe Unif iform rm so solid lid vo volu lume me fra ract ctio ion (vf vf) ) Me Measu sure reme ment pla lane g g 1m m and slu slurry rry ve velo locit city y (V) (V) V V D D L=1 =10m m d=2 =270 µ m , , vf =0 =0.2, d=4 =480 µ m , , vf =0 =0.203, d=9 =90 µ m , , vf =0 =0.19, D=5 =51.5mm mm V=5 V=5.4 m/ m/s s D=5 =51.5mm mm V=3 V=3.41 m/ m/s s D=1 =103mm, mm, V=3 V=3 m/ m/s s d=1 =165 µ m , , vf =0 =0.189, d=1 =165 µ m , , vf =0 =0.0918 d=1 =165 µ m , , vf =0 =0.273, D=5 =51.5mm, mm, V=4 V=4.17 m/ m/s s D=5 =51.5mm mm V=3 V=3.78 m/ m/s s D=4 =495mm mm V=3 V=3.46 m/ m/s s
Effects of cooling in transportation of viscous oil Temperature, density and viscosity after 200m. • Densit sity y Temp mpera rature re Visco Viscosit sity y 20 20 cP cP 120 120 cP cP
Wall shear stress and pressure drop along pipe Increase in wall shear stress and pressure drop as viscosity • increases. 0.35 0.30 Wit ith co coolin ling 0.25 Shear Stress [N] 0.20 0.15 Iso sotherma rmal 0.10 0.05 0.00 Sec. Sec. Sec. Sec. Sec. Sec. Sec. Sec. Sec. Sec. 01 02 03 04 05 06 07 08 09 10 A-1 0.084 0.075 0.075 0.075 0.075 0.075 0.075 0.075 0.075 0.075 6 6 6 6 6 6 6 6 6 6 A-2 0.145 0.174 0.203 0.226 0.247 0.264 0.280 0.293 0.305 0.315 5 0 0 9 3 9 2 6 2 4
A CFD hydrate formation model Oil-dominated 3 phase flow • Hyd ydra rate + + water r Hyd ydra rate Oil il Water r Gas s Eulerian multiphase flow model: • Phase 1: Oil – continuous fluid • Phase 2: Gas – dispersed bubbles • Phase 3: Water/hydrate – dispersed droplets ( f H =0) turn into • hydrate particles ( f H =1)
Hydrate formation process Methane (CH 4 ) from gas bubbles is dissolved into the oil. 1. Water droplets come into contact with dissolved CH 4 , turn into 2. hydrate particles when the temperature drops below the hydrate nucleation temperature. The dissolved gas is consumed in the hydrate formation 3. process. Hyd ydra rate + + water r Hyd ydra rate Oil il Water r Gas s
Temperature, hydrate and dissolved gas Hyd ydra rate fra ract ctio ion in in water r (Hydrate starts to form when temperature drops below 15.6°C.) Temp mpera rature re of oil il (Note areas cooler than hydrate nucleation temperature of 15.6°C.) Ma Mass ss fra ract ctio ion of disso issolve lved gas s in in oil il (Dissolved gas is consumed in hydrate formation and recovered when hydrate formation is completed.)
Pigging – Overset mesh for moving pig St Stra ratif ifie ied gas-liq s-liquid id flo low Disp isperse rsed so solid lid-liq -liquid id flo low
Dynamic forces on pipe elbow in slug flow Mo Model l the lo long pip ipe usin sing OLGA A wit ith slu slug tra rackin cking Pressure and temperature Mass flux, velocity and density of each phase Flow direction Mo Model l pip ipe elb lbow usin sing ST STAR AR-C -CCM+ M+
Pressure variation due to slug flow pass elbow Note the passin ssing of liq liquid id Note the in incre crease se in in pre ressu ssure re as s slu slug in in “b “blu lue”. ”. liq liquid id slu slug passe sses. s. Pressu Pre ssure re on the outer r part rt Gas s vo volu lume me fra ract ctio ion
Comparison Coupling model Experiment Slug frequency (Hz) 0.5 0.5 slug front: 2.8 to 3.6 Slug velocity (m/s) 3.6 slug tail: 3.0 to 3.5 Peak force on bend (N) 44 to 54 40 to 60 Maximum force on bend (N) 54 60 In in indust stria rial l desig sign wit ith sa safety y fact ctor r ‘2’: ma maximu ximum m force rce 141 141 N N
Flow-Merging T-junctions A pplication P roving G roup Planar 60º 90º 21
Jumpers A pplication P roving G roup JumperRec JumperBend 22
Pig Launcher / Cross over A pplication P roving G roup 23
Oil Platform Riser Vortex Induced Vibration Riser pipe via FV Stress • URANS (Unsteady-Reynolds Average NS) • k- ω turbulence model y+<10 • 2 nd order time fluid and solid • – Time step 1/100 of Vortex Shedding Period Implicit Coupled – Morphed 1 per time step • Good Agreement • – Drag (C d ) Shedding (S t ), Natural frequency 24
Oil Platform Riser Vortex Induce Vibration Mid Mid-sp -span cro cross-st ss-stre ream m disp ispla lace ceme ment Mid Mid-sp -span st stre ream-w m-wise ise disp ispla lace ceme ment 25
Separator Modeling strategy: • – Local model of diffuser and vane pack – Global model of separator Upstream pipework Gas outlet Vane packs Downcomer Inlet Vortex breaker Inlet Diffuser Oil outlet Baffle plate
Nottingham – Multiphase flow in bend pipes Larg rge bubble les Me Mediu ium m bubble les Sma Small ll bubble les Liq iquid id 4-p -phase se mo model 27
3-phase separator Oil il Gas s Water r Court rtesy sy of Rhin ine Ruhr r / LSI SIM M Au Aust stra ralia lia 28
Wave loading on platform • Hig igh fid idelit lity y wit ith mu mult lti-p i-physics: ysics: • Win ind and wave ve lo loadin ings s • St Stre ress ss
High fidelity, large domain, time dependent
Launching of life boat LIFEBOAT LAUNCHING • combined 6 DOF, overlapping mesh, VOF (compressible)
Conclusions CFD is becoming more widely used in flow assurance to study: • – Flow details in 3D: pipelines, equipment, junctions, valves, … – Thermal management, conjugate heat transfer, cold down, temperature dependent density and viscosity, hydrate, wax, ... – Fluid-structure interactions: VIV in risers, sloshing in tanks. CFD technology is being developed to support the modelling of • the complex flows: – Advanced grid generation methods. – Advanced multiphase flow models. – Fast parallel solver to handle large complex models. – Powerful visualisation technique to explain the complex flow.
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