Effects of ultrasound on the removal of emulsion plugging in oil reservoirs

Abstract

The generation of water-in-crude oil emulsions in a reservoir can cause formation damage due to droplet trapping at pore spaces. The removal of the damage is anticipated to be inexpensive and eco-friendly when done with ultrasound as opposed to chemical demulsifiers. The influence of ultrasonic power and frequencies on the removal process, however, is not well understood. Additionally, the process's underlying mechanism is largely speculated. In this study, the effect of ultrasound on the removal of emulsion plugging in oil reservoirs was investigated using a glass micromodel. Emulsion blockage during oil production was replicated in the micromodel and subjected to different ultrasonic frequencies (20 and 40 kHz) and powers (100–1000 watt). The experiments demonstrate that when ultrasonic power and frequency increase from 100 to 1000 watt and 20–40 kHz, respectively, demulsification effectiveness decreases. Ultrasound at low frequency (20 kHz) and power (100 watt) proved to be the most efficient condition to dislodge trapped emulsions in the micromodel pores, facilitate droplet coalescence and increase fluid recovery. The percentage of recovered emulsions increased to 58 % when the micromodel was exposed to ultrasound (20 kHz, 100 watt), as opposed to 53.3 % in the case without ultrasound. This study provides insights into the microscopic behavior of emulsions under the influence of ultrasonic waves, allowing petroleum engineers to optimize ultrasound demulsification process.