Understanding Pore Scale Emulsification During Surfactant Injection: A Visualization of Emulsion Formation Using Microchips and Core Flooding Visualizing Cell

Abstract

Abstract Utilizing a surfactant solution to create an emulsion in a rock's pore space has been proven to enhance heavy oil production. By obstructing some of the pores in the rock, fingering is reduced, and micro-displacement efficiency is improved, ultimately increasing oil recovery. This technique is also valuable in reducing the interfacial tension between oil and water by inducing phase dispersion and altering the physical characteristics of the oil in the reservoir. While previous research has concentrated on increasing oil recovery through in-situ emulsion, there has not been much exploration into the pore-scale level of emulsion formation and its impact on recovery performance. Our study aims to explore the effectiveness of polyvinyl alcohol (PVA) surfactant as an emulsifying agent for medium to heavy crude oil, leading to the formation of water-oil emulsions. Our methodology involves injecting formation water into the microchip using a pump to achieve initial water saturation and adding oil to attain irreducible water saturation. Lastly, we will introduce the PVA surfactant to the chip and use image processing software "ImageJ" to analyze images throughout the process to gather valuable insights about its performance compared to alkaline injection. During the microfluidics experiment, it was observed that introducing PVA surfactant to the system resulted in the recovery of 27.8% of the Initial Oil in Place (IOIP). In contrast, alkaline injection yielded a lower recovery factor of 20.5%. This is attributed to the superior emulsion formation capabilities of PVA injection, leading to increased droplets, which caused blockage and prevented micro water channel formation, ultimately increasing the recovery factor. Notably, when the experiment was conducted under reservoir conditions, the recovery factor of the PVA surfactant decreased to 17.5%. However, it still demonstrated the ability to form emulsions. PVA surfactant was found to be a favorable option as it did not cause any damage or alteration to the rock sample, as confirmed by Scanning Electron Microscopy (SEM). The SEM analysis showed no change to the rock sample before and after conditioning with the surfactant for one week. Therefore, based on these findings, PVA surfactant is deemed a viable and practical option along with other surfactant types, such as Anionic surfactants, for enhanced oil recovery. The results suggest that PVA surfactant injection presents superior emulsion formation capabilities compared to alkaline injection. It is recommended that further research be conducted to explore further potential applications of PVA surfactants in EOR.