Towards modelling physical and chemical effects during wettability alteration in carbonates at pore and continuum scales
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Understanding what controls the enhanced oil recovery during waterflooding of carbonate rocks is essential as the majority of the world’s remaining hydrocarbon reserves are contained in carbonate rocks. To further this understanding, in this thesis we develop a pore-scale simulator that allows us to look at the fundamental physics of fluid flow and reactive solute transport within the porous media. The simulator is based on the combined finite element – finite volume method, it incorporates efficient discretization schemes and can hence be applied to porous domains with hundreds of pores. Our simulator includes the rule-based method of accounting for the presence of the second immiscibly trapped fluid phase. Provided that we know what chemical conditions initiate enhanced oil recovery, our simulator allows us to analyse whether these conditions occur, where they occur and how they are influenced by the flow of the aqueous phase at the pore scale. To establish the nature of chemical interactions between the injected brines and the carbonate rocks, we analyze the available experimental data on the single-phase coreflooding of carbonate rocks. We then build a continuum scale simulation that incorporates various chemical reactions, such as ions adsorption and mineral dissolution and precipitation. We match the output of the continuum scale model with the experimental data to identify what chemical interactions the ions dissolved in seawater are involved in.