Recovery of carboxylic acid tracers in two phase flow experiments with Danish chalk

There is mounting evidences that modified salinity flooding can positively impact oil recovery in some types of reservoirs. Hypotheses have been proposed linking the modified salinity effect with the changing “wettability” and adsorption of petroleum components on rock surfaces. The distribution of oxygenated compounds, primarily carboxylic acids, in the different phases can significantly impact the wettability of the rock surface, which results in changing recovery factors. Active polar compounds govern the interfacial behavior of the crude oil and can act as “anchors” binding crude oil on the chalk surface, which can be mobilized by different injection fluids. To reveal the mechanism, it is necessary to understand the distribution of those “sticky molecules” in different phases. This study examines the distribution of different carboxylic acid molecules in a two-phases flow experiment in carbonate rock using Danish North Sea reservoir chalk. The approach is to spike tracers into crude oil and monitor their recovery during a core flooding experiments. The oil phase in the effluent is analyzed by liquid-liquid extraction followed by mass spectrometry analysis. The partitioning of those acid tracers on chalk and in aqueous phase was also examined in two-phase equilibrium to assist with the interpretation of the experimental observations.