This paper was prepared for the 3rd Numerical Simulation of Reservoir Performance Symposium of the Society of Petroleum Engineers of AIME, to be held in Houston, Tex., Jan. 10–12, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.

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Miscible and partially-miscible displacement processes can be modeled as two- and three-component systems. This approach allows rapid, relatively low-cost compositional simulation of these oil recovery processes. If results are marginal or favorable, a more complex simulation study may be justified.


Miscible displacement has been extensively studied and modeled with the goal of helping develop an economical oil recovery process. Most work has been oriented toward understanding the physical processes and modeling laboratory-scale miscible displacement. Although many field-scale tests have been completed, there is general acceptance that miscible displacement is usually not economically viable because of high costs and poor recovery efficiency. The efficiency is usually lowered by viscous fingering, unfavorable mobility ratios, and gravity overriding of the solvent. As economic conditions change, there are increasing economical, conservation, and regulatory incentives to reinject gas and gas liquids into oil reservoirs. There is some hope that recovery efficiencies can be improved in these projects by controlling mobilities with alternating or simultaneous water-solvent injection.

This paper describes how two classes of miscible problems can be modeled as two- or three-component systems with a general compositional simulator. The results could be expected to be similar to those that would be obtained from other simulators. The modeling illustrated here is generally for the purpose of determining the feasibility of specific miscible displacement projects.


The mechanics of miscible displacement can be complicated and difficult to model with complete accuracy. For completely miscible situations, the primary modeling problem lies in applying the exact dispersion coefficients for each individual component of the oil-solvent system. We have avoided this difficulty by assuming that a completely miscible system can be modeled with sufficient accuracy by using a binary oil-solvent system.

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