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Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Chemical and Biochemical Engineering

Supervisor

Anand Prakash

Abstract

Emulsions created at different stages of crude oil production and processing present a number of problems and challenges. There is need to monitor emulsion layer in separation vessel to avoid its ingress into separated oil or water phases. It is also important to study role of different impurities and conditions on emulsion stability which determines the ease or difficulty on its breakup to separate the individual phases. There is also need to have a good understanding of emulsion rheology and effect of different variables on its flow behavior. There is currently a lack of suitable technique to monitor emulsion layer in separation vessels due to problems such as fouling, opacity and variable nature of crude oil composition and presence of impurities.

The primary stage of this work, intended to develop an ultrasonic technique for on-line process monitoring to track and characterize emulsion phase generated during production and cleaning of crude oil. Ultrasonic based techniques have been explored to monitor interface position between water and emulsion layers and oil and emulsion layers in separation vessels. This study tested the potential of ultrasonic techniques for monitoring separation of water, oil and emulsion phases. The oil phase consisted of either mineral oil or crude oil and water content of their emulsion was between 20 to 40%. The tests were conducted in a 4-inch diameter and 20-inch tall column. Measurements of acoustic velocity, pulse attenuation were made with a 3.5 MHz frequency probe operating in through transmission mode. The presence of a phase a phase type at a probe location was easily and quickly identified by changes in either acoustic velocity, attenuation or their combination. In the emulsion layer, acoustic properties are observed to depend on droplet size and their concentration. A significant change in signal either from oil to emulsion or from water to emulsion was observed and demonstrated the potential of the technique for such operations.

The second phase of this project, investigates potential of ultrasonic techniques to characterize water-in-oil emulsions using and compares with other methods. The emulsions were prepared with mineral oil and crude oil samples and the effects of different variables including mixing intensities, temperature, surfactant and fine solid particles concentrations have been observed. The emulsion mixtures prepared with samples of light and heavy crude oil investigated effects of asphaltenes concentration on emulsion stability. The emulsions were characterized for their stability, droplet size distribution and rheology. Emulsion droplet structure is observed with optical microscopy and stability is examined by separation of water phase with time and its composition changes were tracked by ultrasonic techniques. The ultrasonic parameters recorded are changes in acoustic velocity, signal attenuation and its frequency spectrum. The ultrasonic probe captured the variation of droplet concentration of dispersed water phase in the e mulsion with time.

The final stage of this investigation, studies the rheological behavior of various emulsions in terms of providing a better understanding. This rheological study consists of several factors including mixing speed, shear rate, shear stress, temperature, pH, salt content; solid particle, addition of surfactants concentration, and droplet average diameter have been studied. It has been designed in order to provide an understanding of water-in-oil emulsion flow behavior and contribute to technological developments to oil production problems specific to this crude.

Summary for Lay Audience

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