Simulation of Miscible Flow Including Bypassed Oil and Dispersion Control
- Keith H. Coats (Coats Engineering) | L. Kent Thomas (ConocoPhillips Co.) | Ray Gene Pierson (ConocoPhillips Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- October 2007
- Document Type
- Journal Paper
- 500 - 507
- 2007. Society of Petroleum Engineers
- 5.2.2 Fluid Modeling, Equations of State, 5.5 Reservoir Simulation, 4.1.2 Separation and Treating, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 1.6 Drilling Operations, 5.4 Enhanced Recovery, 5.8.6 Naturally Fractured Reservoir, 5.4.2 Gas Injection Methods, 5.5.8 History Matching, 5.2.1 Phase Behavior and PVT Measurements, 6.5.2 Water use, produced water discharge and disposal, 5.1.5 Geologic Modeling, 5.3.4 Reduction of Residual Oil Saturation, 5.4.9 Miscible Methods, 5.1 Reservoir Characterisation, 5.8.8 Gas-condensate reservoirs
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This paper describes methods for the simulation of first-contact miscible (FCM), multicontact miscible, and vaporizing gas drive, which include logic to account for bypassed oil. Dispersion control is included for FCM cases.
First-contact miscibility may be simulated in fully compositional mode with any number of components, N SUBSCRIPTc , or in two-pseudocomponent equation-of-state (EOS) mode. Pseudoization is performed internally in the model so that hydrocarbon-fluid density and viscosity, as functions of pressure and composition, are the same as calculated in N SUBSCRIPTc -component mode. Bypassed oil and dispersion control are based on an extension of Koval's (1963) method. This procedure allows the user to adjust the fractional flow of oil during upscaling or history matching to match fine-grid or historical results. This feature can be used to simulate both water-alternating-gas (WAG) and tertiary-recovery projects where solvent injection is preceded by a water-injection period.
Example cases are included to illustrate the techniques presented in this paper. Results are also given on the efficiencies of the algorithms.
Simulation of miscible and vaporizing gas-drive processes in heterogeneous reservoirs with a compositional model requires the proper treatment of bypassed oil, "viscous fingering," and "channeling" that may occur on a model-sublayer basis. Data from a sidetrack well near an injector in the Prudhoe Bay miscible-gas project indicate that miscible-flood residual-oil saturations, S SUBSCRIPTorm , in the field are on the order of 5% pore volume in the well-swept zones and are higher in less-swept zones (McGuire et al. 1995, 2001, 2002). This residual, or "bypassed," oil saturation will be vaporized in conventional compositional simulators with continued gas injection even when S SUBSCRIPTorm is included in the water/hydrocarbon relative permeability algorithm.
Methods for predicting the performance of unstable miscible displacement in heterogeneous reservoirs have been presented previously by other authors (Koval 1963; Todd and Longstaff 1972; Thomas et al. 1991; Ballin et al. 2001). Koval developed an analytical method analogous to the Buckley-Leverett theory for calculating oil recovery as a function of both solvent-/oil-viscosity ratio (i.e., fingering) and the local level of heterogeneity (i.e., channeling) in porous media. Todd and Longstaff presented the development of a two-component hydrocarbon numerical simulator for prediction of miscible-flood performance in a modified black-oil simulator. They also described a three-component model, which required inclusion of a fourth conservation equation in an existing three-phase simulator. Thomas et al. presented channeling logic in a modified black-oil model similar to that introduced by Koval to simulate the feasibility of nitrogen injection in the fractured Ekofisk reservoir. Ballin et al. describe a compositional upscaling method for the simulation of produced-gas injection in the Cupiagua gas/condensate reservoir that modifies the velocities of individual pseudocomponents.
This paper presents generalized methods for the simulation of FCM, multicontact miscible, and vaporizing gas-drive processes. The techniques allow bypassed oil to be calculated implicitly as a function of pressure and composition during the simulation. Dispersion control for simulation of FCM processes is based on an extension of Koval's method. A single parameter is used to adjust the amount of dispersion during upscaling or history matching to match fine-grid or historical results. This feature can be used to simulate solvent-injection and WAG-injection processes and tertiary-recovery projects where solvent is preceded by water injection. Example cases are presented that illustrate both the bypassed-oil and dispersion-control techniques introduced in the paper.
|File Size||1 MB||Number of Pages||8|
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