Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
Micro-Scale Mechanisms of Pore-Blocking by Emulsion Droplets
Submission Author:
Clarice de Amorim , RJ
Co-Authors:
Clarice de Amorim, Rafael Valladares de Almeida, Ranena V. Ponce F., Marcio CARVALHO
Presenter: Clarice de Amorim
doi://10.26678/ABCM.ENCIT2022.CIT22-0234
Abstract
Pore-blocking efficiency is a key factor when dilute and stable emulsions are used as flow diversion agents to increase oil recovery and reduce water mobility in preferential flow paths. Emulsion plugging occurs when droplets of the dispersed phase are trapped in the pore throats as they flow through porous media. The capturing phenomenon is highly dependent on the drop-to-pore size ratio, the dispersed phase concentration, and capillary number. Thus, understanding the transport of droplets and the physical mechanisms of pore-blocking at the micro-scale is fundamental for a proper design of emulsion flooding as an enhanced oil recovery (EOR) method. The performance of oil-in-water (O/W) emulsions as pore-blocking agents was investigated by studying the transport of oil droplets through transparent porous media. To this end, a 2D PDMS/glass micromodel with varying constriction sizes was fabricated in-house. Mineral O/W emulsion systems with two distinct drop size distributions were formulated to conduct the tests at different capillary number. The tests were performed by recording the injection pressure response during the sequential flow of an aqueous phase, followed by emulsion (oil drops dispersed in the aqueous phase) and then followed by a second slug of aqueous phase. The association of microfluidic devices and imaging techniques provided a simple way to visualize the droplets’ capture phenomena, combining it with the pressure behavior during emulsion flooding. Detailed visualization of the flow was achieved by high-speed live image acquisition at different stages of the test to analyze the features of emulsion flooding and the droplets’ capture mechanisms. The results from the flow tests visualization and the pressure drop behavior allowed identifying the capture mechanisms responsible for the droplets’ entrapment. Droplets larger than the pore throats were captured by the straining mechanism, while the smaller ones were adsorbed on the pore walls, blocking the pores by droplet accumulation (bridging). At low capillary number (Ca < 1E-4), a larger number of droplets were captured in the pore throats because of the stronger capillary forces. As the capillary number was increased above a threshold value, the viscous force was large enough to overcome the capillary resistance and the droplets were able to deform and re-enter the flow stream. This behavior was quantitatively demonstrated by comparing the mobility of the emulsion to that of the aqueous phase.
Keywords
EOR, Emulsion Flooding, Injectivity tests, Mobility Control, Microfluidics, oil-in-water emulsions
