Approbation of approaches to modelling oil displacement by gas in a slim-tube

Background. The basic method for determining the minimum mixing pressure (MMP) of oil and gas is to conduct an experiment on the displacement of oil by gas in a slim-tube. The result of the experiment is a set of dependencies of the displacement coefficient on the pumped pore volume of gas at different pressures. In order to correctly predict the mixing mode in reservoir conditions, it is necessary to adapt the numerical model to the experimental results.

Aim. The aim of the work is to determine the optimal approaches to modeling an experiment on oil displacement by gas in a slim-tube and a set of data necessary to achieve high accuracy of adaptation.

Materials and methods. Materials: results of experiments on oil displacement by gas in a slim-tube. Methods: numerical simulation using hydrodynamic simulators Eclipse 300 and Eclipse 100.

Results. The Todd–Longstaff model of miscible displacement shows the best convergence with experimental data under the modes of immiscible displacement and full miscibility. The use of this model to perform predictive calculations is advisable under the condition of complete miscibility of oil and gas in the reservoir. A more correct approach to adaptation is based on the modification of the functions of Kro, Krg, Scr from interfacial tension when using a composite model. In addition to the data of standard studies, in this case, it is necessary to use the results of the VIT test.

Conclusion. The paper considers options for adapting the results of laboratory experiments on the displacement of oil by gas in a slim-tube, based on the use of the black oil model and the composite model. It is shown that the adaptation option based on the modification of the Kro, Krg, Scr functions from interfacial tension makes it possible to achieve the most accurate coincidence of the calculated data with the actual ones. At the same time, in order to configure the PVT model of reservoir fluids, the data of typical studies of reservoir fluids must be supplemented with the results of VIT tests. The limits of applicability of the Todd–Longstaff model are established.

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