The oil/water partitioning components such as alkylphenols and aliphatic acids naturally exist in crude oil compositions at different initial concentrations of hundreds or even thousands of ppm depending on the location of the reservoir compared to the site of original rocks. During contact with sweeping injection brine, those compounds diffuse from oil phase to water phase due to oil/water partitioning behaviours. As a result, their concentration in oil contacting with water will be attenuating during water injection. Their concentration profile in water injection history contains the information related to diffusion in oil and water phase, interstitial velocity of water and oil saturation. This paper presents the research results of theoretical model and numerical model of the washed-out process of alkylphenols in the late stage of water injection. The research results have proposed approximate analytical expression for concentration of alkylphenols at the late stage of water flooding. In this regard, at the sufficient large injection volume the alkylphenol concentration attenuates exponentially and the attenuation rate depends on parameters such as partitioning coefficient, oil saturation and interstitial velocity of water and oil and diffusion coefficients. The simulation concentration results obtained from UTCHEM simulator for the 5-spot model showed a good match with analytical calculation results. The research results can be used as the basis for developing methods to assess water flooding systems as well as oil saturation. The results can also be used for study of transport of non-aqueous phase liquid (NAPL) in environmental contamination. Keywords: Residual oil saturation, waterflooding, tracer, partitioning organic compounds, enhanced oil recovery.
Development of new oil/water partitioning tracers for the determination of residual oil saturation in the inter-well region of water-flooded reservoirs