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.

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.

Phase equilibrium calculations with quasi-Newton methods

2015 ◽  
Vol 406 ◽  
pp. 194-208 ◽  
Author(s):  
Dan Vladimir Nichita ◽  
Martin Petitfrere
Keyword(s):  
Phase Equilibrium ◽  
Newton Methods ◽  
Quasi Newton ◽  
Equilibrium Calculations

Application of Multiple-Mixing-Cell Method To Improve Speed and Robustness of Compositional Simulation

SPE Journal ◽  
2015 ◽  
Vol 20 (03) ◽  
pp. 565-578 ◽  
Author(s):  
Mohsen Rezaveisi ◽  
Russell T. Johns ◽  
Kamy Sepehrnoori
Keyword(s):  
Phase Equilibrium ◽  
Gas Injection ◽  
Computational Time ◽  
Simulation Methods ◽  
K Value ◽  
Acceptable Accuracy ◽  
Multiple Mixing ◽  
Tie Lines ◽  
Tie Line ◽  
Equilibrium Calculations

Summary Standard equation-of-state-based phase equilibrium modeling in reservoir simulators involves computationally intensive and time-consuming iterative calculations for stability analysis and flash calculations. Therefore, speeding up stability analysis and flash calculations and improving robustness of the calculations are of utmost importance in compositional reservoir simulation. Prior knowledge of the tie-lines traversed by the solution of a gas-injection problem translates into valuable information with significant implications for speed and robustness of reservoir simulators. The solution of actual-gas-injection processes follows a very complex route because of dispersion, pressure variations, and multidimensional flow. The multiple-mixing-cell (MMC) method, originally developed to calculate minimum miscibility pressure of a gas-injection process, accounts for various levels of mixing of the injected gas and initial oil. This observation suggests that the MMC tie-lines developed upon repeated contacts may represent a significant fraction of the actual simulation tie-lines encountered. We investigate this idea and use three tie-line-based K-value-simulation methods for application of MMC tie-lines in reservoir simulation. In two of the tie-line-based K-value-simulation methods, we examine tabulation and interpolation of MMC tie-lines in a framework similar to the compositional-space adaptive-tabulation (CSAT) method. In the third method, we perform K-value simulations based on inverse-distance interpolation of K-values from MMC tie-lines. We demonstrate that for the displacements examined, the MMC tie-lines are sufficiently close to the actual simulation tie-lines and provide excellent coverage of the simulation compositional route. The MMC-based methods are then compared with the computational time by use of other methods of phase-equilibrium calculations, including a modified application of CSAT (an adaptive tie-line-based K-value simulation), a method using only heuristic techniques, and the standard method in an implicit-pressure/explicit-concentration-type reservoir simulator. The results show that tabulation and interpolation of MMC tie-lines significantly improve phase equilibrium and computational time compared with the standard approach, with acceptable accuracy. The results also show that computational performance of the MMC-based methods with only prior tie-line tables is very close to that of CSAT, which requires flash calculations during simulation. The K-value simulations by use of MMC-based tie-line-interpolation methods improve the total computational time up to 51% in the cases studied, with acceptable accuracy. The results suggest that MMC tie-lines represent a significant fraction of the actual tie-lines during simulation and can be used to significantly improve speed and robustness of phase-equilibrium calculations in reservoir simulators.

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