Three-Phase Equilibrium Calculations for Compositional Simulation

2007 ◽  
Author(s):  
Abbas Firoozabadi ◽  
Kjetil Braathen Haugen ◽  
Lixin Sun
Keyword(s):  
Phase Equilibrium ◽  
Compositional Simulation ◽  
Three Phase ◽  
Equilibrium Calculations

Three-Phase Flash in Compositional Simulation Using a Reduced Method

SPE Journal ◽  
2010 ◽  
Vol 15 (03) ◽  
pp. 689-703 ◽  
Author(s):  
R.. Okuno ◽  
R.T.. T. Johns ◽  
K.. Sepehrnoori
Keyword(s):  
Phase Equilibrium ◽  
Case Studies ◽  
Computational Time ◽  
Co2 Flooding ◽  
Compositional Simulation ◽  
Two Phase ◽  
Three Phase ◽  
Compositional Simulator ◽  
Complete Failure ◽  
Flash Calculation

Summary CO2 flooding at low temperatures often results in three or more hydrocarbon phases. Multiphase compositional simulation must simulate such gasfloods accurately. Drawbacks of modeling three hydrocarbon phases are the increased computational time and convergence problems associated with flash calculations. Use of a reduced method is a potential solution to these problems. We first demonstrate the importance of using three-phase flash calculations in compositional simulation by investigating difficulties with two-phase equilibrium approximations proposed in the literature. We then extend an algorithm for reduced two-phase flash calculations to three-phase calculations and show the efficiency and robustness of our algorithm. The reduced three-phase flash algorithm is implemented in a multiphase compositional simulator to demonstrate the speed-up and increased robustness of simulations in various case studies. Results show that use of a two-phase equilibrium approximation in reservoir simulation can result in a complete failure or erroneous simulation results. Simulation case studies show that our reduced method can decrease computational time significantly without loss of accuracy. Computational time is reduced using our reduced method because of the smaller number of equations to be solved and increased timestep sizes. We show that a failure of a flash calculation leads directly to reduced timestep sizes using the UTCOMP simulator.

An algorithm for three-phase equilibrium calculations

1986 ◽  
Vol 10 (3) ◽  
pp. 269-276 ◽  
Author(s):  
J.-S. Wu ◽  
P.R. Bishnoi
Keyword(s):  
Phase Equilibrium ◽  
Three Phase ◽  
Equilibrium Calculations

Application of a Reduced Method in Compositional Simulation

SPE Journal ◽  
2009 ◽  
Vol 15 (01) ◽  
pp. 39-49 ◽  
Author(s):  
R.. Okuno ◽  
R.T.. T. Johns ◽  
K.. Sepehrnoori
Keyword(s):  
Phase Equilibrium ◽  
Convergence Property ◽  
Compositional Simulation ◽  
Compositional Model ◽  
Fluid Properties ◽  
Compositional Simulator ◽  
Implementation Problems ◽  
Critical Regions ◽  
Equilibrium Calculations ◽  
Conventional Algorithm

Summary Simulating gas-injection processes requires a compositional model to predict the fluid properties resulting from mass transfer between reservoir fluid and injection gas. A drawback of compositional simulation is the efficiency and robustness of phase equilibrium calculations. Reduced methods for phase equilibrium calculations have been studied as a potential solution to improve the efficiency of compositional simulation. However, most of those studies have been performed only in standalone calculations, and the robustness and efficiency of a reduced method has not been confirmed in compositional simulation. In this research, we develop a robust and efficient algorithm for a reduced method and validate it in compositional simulation. We examine the efficiency and convergence property of the conventional algorithm for a reduced method and solve several implementation problems in a compositional simulator. The reduced method is implemented in UTCOMP, a compositional implicit-pressure/explicit concentration (IMPEC) simulator, to demonstrate the performance for various numbers of components and degrees of miscibility. The results show that the reduced method enables significant savings in execution time of compositional simulation without loss of accuracy compared to standard methods. Also, we observe that the reduced method exhibits improved robustness, especially for miscible processes where composition paths go near critical regions.

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