An overview of CFD applications in flow assurance From well head to the platform 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 1 Experiment Star-CD-1 Star-CD-2 Riser top Riser DP, bar 0.8 0.6 0.4 0.2 4 inch riser 0 50 100 150 200 250 300 350 Flow time t, s 10.5 m Riser base 55 m pipeline Riser DP = Pbase - Ptop
DEM particle transport in pipe
DEM - Pneumatic conveying of particles in pipe
Slurry flow in horizontal pipe Horizontal slurry pipeline flow Uniform solid volume fraction (vf) and slurry velocity (V) g Measurement plane 1m V D Liquid velocity L=10m Inlet Middle Outlet Particle volume fraction
Slurry flow in pipe Uniform solid volume fraction (vf) and slurry velocity (V) g Measurement plane 1m V D L=10m d=90 µm, vf=0.19, D=103mm, V=3 m/s d=270 µm, vf=0.2, D=51.5mm V=5.4 m/s d=480 µm, vf=0.203, D=51.5mm V=3.41 m/s d=165 µm, vf=0.189, D=51.5mm, V=4.17 m/s d=165 µm, vf=0.0918 D=51.5mm V=3.78 m/s d=165 µm, vf=0.273, D=495mm V=3.46 m/s
Effects of cooling in transportation of viscous oil Temperature, density and viscosity after 200m. Temperature Density Viscosity 20 cp 120 cp
Wall shear stress and pressure drop along pipe Increase in wall shear stress and pressure drop as viscosity increases. 0.35 Shear Stress [N] 0.30 0.25 0.20 0.15 0.10 With cooling Isothermal 0.05 0.00 Sec. 01 A-1 0.084 6 A-2 0.145 5 Sec. 02 Sec. 03 Sec. 04 Sec. 05 Sec. 06 Sec. 07 Sec. 08 Sec. 09 Sec. 10 0.075 0.075 0.075 0.075 0.075 0.075 0.075 0.075 0.075 0.174 6 0.203 6 0.226 6 0.247 6 0.264 6 0.280 6 0.293 6 0.305 6 0.315 6 0 0 9 3 9 2 6 2 4
A CFD hydrate formation model Oil-dominated 3 phase flow Oil Water Gas Hydrate + water Hydrate 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 1. Methane (CH 4 ) from gas bubbles is dissolved into the oil. 2. Water droplets come into contact with dissolved CH 4, turn into hydrate particles when the temperature drops below the hydrate nucleation temperature. 3. The dissolved gas is consumed in the hydrate formation process. Oil Water Gas Hydrate + water Hydrate
Temperature, hydrate and dissolved gas Temperature of oil (Note areas cooler than hydrate nucleation temperature of 15.6 C.) Hydrate fraction in water (Hydrate starts to form when temperature drops below 15.6 C.) Mass fraction of dissolved gas in oil (Dissolved gas is consumed in hydrate formation and recovered when hydrate formation is completed.)
Pigging Overset mesh for moving pig Stratified gas-liquid flow Dispersed solid-liquid flow
Dynamic forces on pipe elbow in slug flow Model the long pipe using OLGA with slug tracking Pressure and temperature Mass flux, velocity and density of each phase Flow direction Model pipe elbow using STAR-CCM+
Pressure variation due to slug flow pass elbow Note the passing of liquid slug in blue. Note the increase in pressure as liquid slug passes. Gas volume fraction Pressure on the outer part
Comparison Coupling model Experiment Slug frequency (Hz) 0.5 0.5 Slug velocity (m/s) slug front: 2.8 to 3.6 slug tail: 3.0 to 3.5 3.6 Peak force on bend (N) 44 to 54 40 to 60 Maximum force on bend (N) 54 60 In industrial design with safety factor 2 : maximum force 141 N
Flow-Merging T-junctions Application Proving Group Planar 60º 90º 21
Jumpers Application Proving Group JumperRec JumperBend 22
Pig Launcher / Cross over Application Proving Group 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-span cross-stream displacement Mid-span stream-wise displacement 25
Separator Modeling strategy: Local model of diffuser and vane pack Global model of separator Upstream pipework Gas outlet Vane packs Downcomer Inlet Inlet Diffuser Vortex breaker Baffle plate Oil outlet
Nottingham Multiphase flow in bend pipes Large bubbles Medium bubbles Small bubbles Liquid 4-phase model 27
3-phase separator Gas Oil Water Courtesy of Rhine Ruhr / LSIM Australia 28
Wave loading on platform High fidelity with multi-physics: Wind and wave loadings Stress
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.