PVTSIM Nova - PVTsim Nova - Next Generation · 2016. 6. 27. · PVTsim extended with tuning options, common EoS, and flow assurance capabilities (aqueous mixtures, hydrate, wax and

Next Generation Equation of State

PC-SAFTAdvantages of PC-SAFT

Copenhagen DenmarkCalsep A/SParallelvej 12DK-2800 Kgs. Lyngby

Good prediction of pure component vapor pressures and liquid densities

Better derivatives of density than cubic EoS (also better compressibility and speed of sound)

The model has its foundation in statistical mechanics, and it specifically accounts for size and shape of the molecules

PC-SAFT shows good results for modeling asphaltene precipitation

An association term accounting for hydrogen bonding can be included

The association term improves predicted properties of aqueous mixtures compared to the cubic EoS

Dubai UAECalsep FZ LLC, Dubai Internet CityBuilding 14, Office 210P.O. Box 500534

Houston USACalsep, Inc., 10370 Richmond Avenue, Suite 1375Houston, Tx 77042

Kuala Lumpur MalaysiaCalsep Asia Pacific Sdn Bhd,Suite 19-05, G-Tower,199 Jalan Tun Razak, 50400

[email protected]

PhoneFax

+45 45 87 66 46+45 45 87 62 72

+971 4 391 3667+971 4 390 8208

+1 281 759 0844+1 281 759 0845

+60 3 2162 6551+60 3 2162 1553

www.calsep.com

Advanced Modeling

GOM Reservoir Fluid

Experimental

Cubic EoS

PC-SAFT

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Pressure

brochure_v5.indd 1 18-09-2013 20:27:54

Next Generation Equation of StatePC-SAFT For more information visit www.calsep.com

For decades cubic equations of state (EoS) have been an industrial standard for phase equilibrium calculations in the oil industry. The industry has learned to take the most out of those equations and get away with their known weaknesses.

So why look for alternatives?

PVT simulations are finding their way into complex production systems including online systems for surveying and planning production and for evaluating the impact of production changes. In an attempt to match all phase properties it is often seen that a patchwork of different thermodynamic models are used. This is thermodynamically inconsistent and it would be preferable if all phases and phase properties could be handled by a single model. The PC-SAFT EoS has those basic qualities.

PC-SAFT stands for Perturbed Chain Statistical Association Fluid Theory and was developed from molecular theory.

Compressibility and Gas Z-Factors

Z-factor predictions with PC-SAFT are superior to cubic EoS simulations over a wide range of temperatures and pressures. The same is seen when simulating liquid compressibilities over large pressure ranges.

C7+

Characterization

Calsep has developed its own PC-SAFT C7+

characterization procedure and implemented it in PVTsim. The starting point for using the PC-SAFT model in PVTsim is a compositional analysis of the reservoir fluid. Compared to using a cubic EoS no additional input is necessary. The characterization procedure implemented in PVTsim will give good predictions for the phase behavior of a wide range of reservoir fluids, including both oils and condensates.

While cubic equations can model phase equilibria of hydrocarbon mixtures quite well, they are inaccurate for liquid densities unless a volume correction is used. Pressure derivatives and gas phase Z-factors are almost unaffected by the volume correction and continue being inaccurate.

Although the PC-SAFT model is based on advanced molecular theory, only 3 component specific parameters (m, σ and ε) are required to model both phase equilibria and bulk properties of hydrocarbon mixtures. The results for compressibility, speed of sound and gas Z-factors are superior to what is seen with a cubic equation. This makes the PC-SAFT equation well suited to model phase equilibria for systems with more than one liquid phase as for example oil-asphaltene mixtures.

Association Term

For polar mixtures with strong molecular interactions (for example water-alcohol mixtures) it is possible to use the PC-SAFT model with an association term which will specifically account for association between polar components. The association term requires only two extra parameters (associating energy and volume). This accurate description of the polar-polar molecular interactions makes it possible to obtain a very good description of aqueous mixture properties. Results show that aqueous mixture densities and speed of sound are simulated much better with PC-SAFT with association than with a cubic EoS.

PC-SAFT and Asphaltenes

Capturing the correct volumetric changes with pressure is important when simulating if asphaltenes precipitate. PC-SAFT has shown good results when simulating asphaltenes onset points and modeling the effect of gas injection on the precipitation of asphaltenes.

Calsep wants to set the standard for the next generation EoS. The ambition is to make the PC-SAFT model available in all calculation options in PVTsim.

PC-SAFT will provide users of Calsep’s software with a thermodynamic modeling tool, which until now has been reserved for a limited number of scientists.

The compressibility factor

with association contribution

and association strength

Segments

Chains

Interactions

PVT simulations have been a Calsep trademark since the company was founded in 1982. Several publications on PVT algorithms and models carry Calsep’s name . Calsep is the company that developed the PVT simulator, PVTsim.

PVTsim is used by more than 250 oil and engineering companies throughout the world. A close contact with the oil industry is secured by the many consulting projects within EoS modeling and flow assurance carried out by Calsep’s specialist team of consultants.

Historical Background

Advantages over Cubic EoS

A Part of

1982

Calsep was founded in 1982

to offer simulation services to the oil and gas industry.

Calsep released the 1st version of the PVT

simulator, PVTsim.

PC-SAFT

an alternative to cubic EoS.

PVTsim extended with tuning options, common EoS, and flow assurance capabilities (aqueous mixtures, hydrate, wax and

asphaltenes). Interface options to reservoir, process and flow simulators.