1. TransAT – OLGA Coupling
June 2014
S. Reboux, N. Pagan
ASCOMP

2. 1D-TransAT Coupling
Motivations

3. Coupling paradigm: the oil & gas context
Separator
Oil
Gas
Water
Horizontal-flow 1D
models
3D CFD/CMFD
3D CFD/CMFD
Vertical-flow 1D
models
Near Horizontal-flow 1D models
3D CFD/CMFD
3D CFD/CMFD
3D CFD/CMFD
Wellbore Models
Downhole Models
 Darcy’s type of models
3D CFD/CMFD

4. Coupling paradigm : why and what’d be done
Observation: flows in reservoir, wellbore and surface installations are tightly interrelated
Solution: Coupling the various modeling approaches at different scales
Result: Improved accuracy, Reduced uncertainty, Enhanced decision process

5. Potential examples of 1D/TransAT coupling
Manifold splits, tee splits, elbows or bends: Transient redistribution of oil, gas or water phases before flow into downstream pipes.
Subsea tree or jumper: cool-down after well shut-in
Slug catchers: transient overall efficiency in response to ram-pup, pigging surge, etc…
Oil spills: design optimization of subsea containment designs that are connected to a riser.
Piping inserts / inline equipment: investigate discontinuities between up and downstream multiphase slip flow patterns
Separators: captures efficiency and re-entrainment in response to ramp-ups, surges, etc…

6. 1D-TransAT Coupling
Model basics

7. Coupling strategy and validation criteria
Conserved quantities:
mass fluxes
heat fluxes
TransAT
OLGA
Validation criteria based on:
continuity of mass fractions
continuity of internal energy
continuity of pressure
Boundary coupling
Unsteady simulations

8. Semi-implicit coupling method
At each time step:
TransAT receives pressure data from OLGA, together with the sensitivity of the pressure to different mass fluxes. They define a local linear constraint.
TransAT determines pressure and mass fluxes by iteratively solving the implicit equation:

9. 1D-TransAT Coupling
Validtion

10. Validation case # : single-phase flow in a pipe
Purpose:
Validate the pressure-flux coupling scheme for single-phase flows at steady state.
Coupling
boundary P0
Water Inflow
TransAT
OLGA
Coupling boundary
The pressure profile do not match exactly because the pressure drops are slightly different in TransAT and in OLGA.
This is because the inflow profile set in TransAT does not match (in this case) the one specified in OLGA

11. Validation case # 2: slugs across a coupling boundary
interface
Oil
Water
Oil Inflow
OLGA:
- 1D, 20m long pipe
Pressure outlet condition at the top, closed node at the bottom.
Three different sources at the first section from bottom, for coupling
TransAT:
- 2D-axisymmetric 4m long pipe
- Inlet boundary condition (oil inflow) at the bottom, coupling boundary condition at the top

12. Validation case # 2: slugs across a coupling boundary
Comparison of the profiles obtained with
OLGA (uncoupled simulation, 1D)
TransAT (uncoupled simulation, 2D axisym.)
OLGA-TransAT (coupled, 1D/2D axisym.) P0 P0 P0
OLGA
TransAT
OLGA
TransAT
Oil Inflow
Oil Inflow
Oil Inflow

13. Validation case # 2: slugs across a coupling boundary

14. Validation case # 2: slugs across a coupling boundary

15. Validation case # 2: slugs across a coupling boundary

16. Validation case # 2: slugs across a coupling boundary

17. Validation case # 3: Rayleigh-Taylor instability
Coupling
interface
Oil (300K)
Water (280K)
Wall
TransAT
OLGA
coupling
OLGA:
- 1D, 20m long pipe
Closed node at top and bottom.
Three different sources at the first section from bottom, for coupling
TransAT:
- 2D-axisymmetric 4m long pipe
- Wall at the bottom, coupling boundary condition at the top

18. Validation case # 3: Rayleigh-Taylor instability
Comparison of the profiles obtained with
OLGA (uncoupled simulation, 1D)
TransAT (uncoupled simulation, 2D axisym.)
OLGA-TransAT (coupled, 1D/2D axisym.)
OLGA
OLGA
TransAT
TransAT

19. Validation case # 3: Rayleigh-Taylor instability
Water flowing DOWN
Oil flowing UP
Water flowing DOWN
Oil flowing UP

20. Validation case # 3: Rayleigh-Taylor instability
U > 0
U < 0
t=5s
U > 0
U < 0
U > 0
U < 0
t=7s
t=8s
U > 0
U < 0
U > 0
U < 0
t=9s
t=10s

21. Validation case # 3: Rayleigh-Taylor instability

22. Validation case # 3: Rayleigh-Taylor instability

23. Validation case # 3: Rayleigh-Taylor instability

24. Validation case # 3: Rayleigh-Taylor instability

25. Validation case # 3: Rayleigh-Taylor instability
The results obtained using OLGA or TransAT (alone) are not consistent for this test case.
The oil velocity is under-predicted by OLGA (perhaps because it is using friction models based on flow regimes from fully developed flows)
The evolution in time of heat fluxes, mass fractions and pressure variations given by OLGA cannot be trusted quantitatively under these conditions.
The coupled simulations suffer from this lack of consistency between the models of the two codes, but they are nonetheless stable, give plausible results and satisfy the conservation laws.

26. Rayleigh-Taylor instability: results
Pressure at the coupling interface
Mass fluxes at the coupling interface
Mass fraction at the coupling interface
Heat flux at the coupling interface
Temperature at the coupling interface

27. 1D-TransAT Coupling
Applications

28. 1D – 3D CFD (production line – Separator)
1D pipe model
(GAP)
3D CFD
(TransAT)

29. 3D CFD – 1D (capping of oil spills – ship)
1D riser model
(OLGA)
Purpose:
Proof of concept for complex multiphase flow with 3D/1D coupling.
Demonstrate the robustness and physical consistency of the coupling method for subsea applications
Coupling
2D or 3D CFD
(TransAT)

30. Zoom on coupling boundary
3D CFD – 1D (capping of oil spills – ship)
Riser
(Olga)
t=0
t=9s
Zoom on coupling boundary
(TransAT)
t=7s

31. 3D CFD – 1D (water-oil mixing using jets)
Mixing of water and oil in pipeline using jets of recirculated fluid

32. 3D CFD – 1D (water-oil mixing using jets)
(modelled with TransAT)
Mass flow rate to CATHARE
Pressure from CATHARE
Tracer
Injection

33. 3D CFD – 1D (water-oil mixing using jets)
(Flow field in TransAT/CATHARE)

34. 3D CFD – 1D (Cross heating of oil wells)

35. 3D CFD – 1D (Cross heating of oil wells)