Flow assurance with ANSYS CFD

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2 Agenda Introduction Flow assurance with ANSYS Risk avoidance Hydrates Sand transport Horizontal gas-liquid flows Gas liquid flow in vertical pipes 2010 ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary

3 Risk avoidance Need to ensure Operating conditions within envelope of safe operation Modeling for risk avoidance Fluid flow and heat transfer Non-Newtonian rheology Temperature dependant properties Can perform these simulations with a high degree of confidence 2010 ANSYS, Inc. All rights reserved. 3 ANSYS, Inc. Proprietary

AIR-FILLED FOUR-PIPE TUBE BUNDLE L. Liu, G. F. Hewitt, S. M.

4 Risk avoidance Heat transfer in bundled pipelines EXPERIMENTAL AND CFD STUDIES OF HEAT TRANSFER IN AN AIR-FILLED FOUR-PIPE TUBE BUNDLE L. Liu, G. F. Hewitt, S. M. Richardson 2010 ANSYS, Inc. All rights reserved. 4 ANSYS, Inc. Proprietary

Simulations used for Stability of wax layers Transient start-up

5 Wax and hydrate formation Wax formation clogging Flow can alter structure Most promising strategy Thixotropic visco-plastic fluid Simulations used for Stability of wax layers Transient start-up Coupling with 1D codes 2010 ANSYS, Inc. All rights reserved. 5 ANSYS, Inc. Proprietary

Goodarz Ahmadi, Chem Engng Sci 62 (2007) 6155 6177

6 Hydrates Computational modeling of methane hydrate dissociation in a sandstone core Kambiz Nazridoust, Goodarz Ahmadi, Chem Engng Sci 62 (2007) ANSYS, Inc. All rights reserved. 6 ANSYS, Inc. Proprietary

8 Ideal vs Real IDEAL GAS REAL GAS SUBSONIC REGION SHOCK Mach Number SHOCK HEATING Mach Number NO J-T HEATING J-T HEATING Static Temperature Static Temperature 2010 ANSYS, Inc. All rights reserved. 8 ANSYS, Inc. Proprietary

9 Sand/Particulate Transport Sand is often produced out of the reservoir in both onshore and offshore production systems, particularly in reservoirs that have a low formation strength Sand production may be continuous, or sudden - as when a gravel pack fails The sediment consists of finely divided solids that may be drilling mud or sand or scale picked up during the transport of the oil Sand deposition could lead to corrosion of the pipeline Mean Slurry Pressure Gradient, Pa/m 4500 Skudarnov et al, Newitt et al, 1955 FLUENT CFD - Schiller Drag 3500 FLUENT CFD - Wen & Yu Drag Mean Slurry Velocity, m/s 1 Problem of sand deposition and reentrainment Inclined pipelines, pigging sand plug pipeline Particulate modeling in ANSYS Fluent 13. Y / D Fluent CFD: dp = 120 um Matousek, 2002 (dp = 120 um) Fluent CFD: dp = 370 um Matousek, 2002 (dp = 370 um) Solids Volume Fraction 2010 ANSYS, Inc. All rights reserved. 9 ANSYS, Inc. Proprietary

$Operating envelope: Gravel packs Design criteria for gravel packs Minimum pump rate to avoid rat holing screen out Maximum pump rate to avoid formation fracture Need to determine safe envelope of$

10 Operating envelope: Gravel packs Design criteria for gravel packs Minimum pump rate to avoid rat holing screen out Maximum pump rate to avoid formation fracture Need to determine safe envelope of operation Critical velocity/shear stress for settling The relevant parameters calculations were only possible via a robust 3D Computational Fluid Dynamics Simulation (CFD). The application of the critical shear stress methodology for open hole gravel packs design in multizone completion projects indicates less conservative results which can make possible operations in critical operational windows scenarios. Horizontal open hole gravel pack placement requirements in selective completion projects, Anais do ENAHPE ANSYS, Inc. All rights reserved. 10 ANSYS, Inc. Proprietary

Terrain slugging Pressure Drop 60000 50000 40000 30000 20000 10000 0 4 5 6 7 8 9 5 4,5 4 3,5 3 2,5 2

Hydrodynamic slugging Hydrodynamic Slugging Waves grow on the liquid surface to bridge the pipe Kelvin-Helmholtz instability the cause for wave formation and slugging Modeling of interfacial

12 Hydrodynamic slugging Hydrodynamic Slugging Waves grow on the liquid surface to bridge the pipe Kelvin-Helmholtz instability the cause for wave formation and slugging Modeling of interfacial instabilities will be crucial Problems due to slugging Fatigue High frictional pressure drop End of production when low flow rates Production slop due to high static pressure changes due to long slugs ANSYS, Inc. All rights reserved. 12 ANSYS, Inc. Proprietary

13 Problem Description Gas Inlet Liquid Inlet Splitter plate Diameter: 0.078m Length: 37m The entrance to the pipeline is arranged to give a stratified flow, in which the gas flows above the liquid in parallel streams, and slugs originate from waves at the gas liquid interface that grow to fill the pipe cross-section. International Journal of Multiphase Flow 32 (2006) ANSYS, Inc. All rights reserved. 13 ANSYS, Inc. Proprietary

Results: Slug Origin and Growth Slugs are developed from long waves that grow to bridge the pipe Kelvin Helmholtz Instability Slugs and Large Waves Slug: Liquid layer ahead of it is relatively deep,

14 Results: Slug Origin and Growth Slugs are developed from long waves that grow to bridge the pipe Kelvin Helmholtz Instability Slugs and Large Waves Slug: Liquid layer ahead of it is relatively deep, while the liquid height drops sharply behind its tail. Large waves: More gradual decrease of liquid height in their tail profile Some slugs grow as they travel the pipeline and others are dampened and disappear before reaching the outlet of the pipeline ANSYS, Inc. All rights reserved. 14 ANSYS, Inc. Proprietary

Hannibal slug catcher simulation Courtesy Genesis Oil and Gas consultants Gas pipeline from off-shore field to land-based Hannibal terminal Slug catcher separates residual liquid from gas at end of

18 Hannibal slug catcher simulation Courtesy Genesis Oil and Gas consultants Gas pipeline from off-shore field to land-based Hannibal terminal Slug catcher separates residual liquid from gas at end of pipeline Plan to increase pipeline capacity to supply new power station Does capacity of slug catcher also have to be increased? Inlet from pipeline Gas outlet Liquid outlets Inlet conditions for liquid-gas from Olga 1D pipeline model Estimated cost of modifying slug catcher $25M 2010 ANSYS, Inc. All rights reserved. 18 ANSYS, Inc. Proprietary

Slug Catcher High Flow Operation Can slug

19 Slug Catcher High Flow Operation Can slug catcher cope with increase in capacity of pipeline? Yes! Peak Level Liquid carry-over only in form of fine aerosol Flow rates Liquid carry-over 2010 ANSYS, Inc. All rights reserved. 19 ANSYS, Inc. Proprietary

Flow regime map in vertical flows 2010 ANSYS,

3D churn flow simulations 2010 ANSYS, Inc.

25 Modeling vertical flows Design challenges A priori identification of flow regime/transition Flow maps available for simple riser configurations Frequency and severity of slugging Pressure surges, fatigue, erosion etc ANSYS, Inc. All rights reserved. 25 ANSYS, Inc. Proprietary

26 Possible modeling options in CFD 1. Resolved bubbles simulation with VOF model Computationally expensive 2. Combination of models Eulerian model for dispersed flow regime (implicit) VOF model for slug flow regime (explicit) Switch models appropriately Multi-fluid VOF 3. Eulerian model with appropriate sub-models Account for bubble coalescence and breakup Use appropriate drag laws for various bubbles 2010 ANSYS, Inc. All rights reserved. 26 ANSYS, Inc. Proprietary

28 = 0.25 m/s s U l s U g Experimental conditions Experimental conditions to demonstrate fidelity/robustness of models Bubbly regime A few flow conditions where an initially bubbly flow transitions to a slug flow regime Two different fluid combinations Air-Water Air-Oil 6 m 67 mm 5 m Well mixed inlet Bubble diameter = 5 mm Cross-sectional data collected. Chemical Engineering Science 65 (2010) ANSYS, Inc. All rights reserved. 28 ANSYS, Inc. Proprietary

33 VOF model Air-water system in churn turbulent regime Pipe length truncated to 3m to interest of computational time 7 inlets for air Initial air bubble of size around 10 mm Bubbles coalesce to form big bubbles 2010 ANSYS, Inc. All rights reserved. 33 ANSYS, Inc. Proprietary

36 Conclusion Increasing use of detailed simulations for understanding issues in flow assurance Improvements in ANSYS CFD 13 suited for modeling flow assurance. High confidence in modeling gas-liquid flows in vertical and horizontal flows. Interesting time ahead! 2010 ANSYS, Inc. All rights reserved. 36 ANSYS, Inc. Proprietary