Use of alkaline agents in enhanced oil recovery is recommended in association with other chemicals such as surfactants and polymers, in- order to take benefit of synergistic effects which improve the cost efficiency ratio of chemical processes. One critical factor in these processes is to predict the transport of the alkali from the injection well to the production well. That is the aim of the flow model described in the paper.

The main physicochemical phenomena responsible for alkali consumption are taken into account in the model, i.e.

the reaction between alkali and acid components of crude oil,

the reactions of injected alkali with reservoir brine and minerals,including dissolution and ion exchange phenomena.

As far as dissolution processes are concerned, a previous work has shown that they are kinetically dependent, even at field scale, and that the thermodynamic equilibrium assumption is not valid. Kinetic equations are used that take into account the inhibiting effects of compounds formed during dissolution.

A methodology is developed to obtain the parameters needed for numerical simulation. This methodology is applied to natural consolidated sandstone rocks containing clay minerals. A satisfactory agreement is observed between simulation results and experimental data provided by batch tests and flow experiments. The model can be used to calculate the transport of the alkali slug at field scale and to help the selection of operating parameters such as type and concentration of alkali, and size of the alkaline slug.

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