Most of the crude oil is already recovered and discovering new oilfields tend to be challenging and difficult. Implementing an EOR method is essential to enhance the production life of mature oil fields and to make them economically more attractive. Especially, for heavy oil reservoirs chemical flooding is besides thermal methods promising. Only a limited number of alkali flood projects alone are reported worldwide. Phase screening represents the first step of experiments and gives information about the ability of various alkali solutions to generate in-situ surfactants at different concentration ranges.

In this study, carbonate-based alkalis were screened on their effect on in-situ soap generation. Two oil reservoirs both located in the Matzen oil field (Austria) were observed, where an alkali flood project will be realized in the near future. In lab scale, were phase experiments with various concentrations of carbonate-based alkalis (sodium and potassium carbonate) screened at the water-oil-ratio 5:5. Formulations with synthetic and real softened brine were compared, using dead oil and viscosity-matched oil with cyclohexane. Samples were observed over time (100 days) to figure out their equilibrium at reservoir temperature. Afterwards large-scale samples were prepared and viscosity measurements performed.

Potassium carbonate (K2CO3) is not well investigated in the literature as an alkali agent yet. It showed very promising results in all performed trials and generated remarkably more amounts of in-situ surfactants compared to Na2CO3, which is the most frequently used alkali performer. Additionally, in most concentrations the micro emulsion viscosities were lower. Thus, potassium carbonate might be an interesting candidate in future alkali applications.

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