Loading...
Investigation into the effect of temperature on nitrogen foam behavior
Al-Riyami, Hamed
Al-Riyami, Hamed
Citations
Altmetric:
Advisor
Zerpa, Luis E.
Editor
Date
Date Issued
2022
Date Submitted
Keywords
Collections
Research Projects
Organizational Units
Journal Issue
Embargo Expires
Abstract
Thermal enhanced oil recovery is touted as the most effective recovery method for heavy oil with steam being the most common injectant, but unfortunately, conformance issues such as gravity override and channeling are rife in steam injection processes. Foam has been used to mitigate conformance issues in gas injection processes, however, at high temperatures these issues return due to the rapid decay of foams and degradation of surfactants.
Literature reports many investigations of the formulation of surfactants and additives to improve the stability of foams. However, the study of foam behavior at higher temperatures is lacking as most studies aim to understand foam decay at ambient temperatures for dry foams. This work aims to shine some light on the issues of studying foam behavior at lower temperature for high temperature applications and to generate better insight into the decay behavior of foams at higher temperatures in closed environments.
Established foam decay analysis methods such as test tubes and dynamic foam column tests were employed to highlight the dependance of foamability and stability of surfactant foams on temperature and the inadequacy of low temperature analysis to predict high temperature foam performance. It was found that some surfactants perform comparatively better than others when stabilizing foams at high temperatures, even when their low-temperature performance was worse. It was also shown that foamability was differently sensitive to temperature for the different surfactants.
This work introduces a methodology to visually analyze foams in a sealed high-pressure high-temperature cell. Using three different surfactants, foam was visually analyzed at different temperatures, and it was found that the decay behavior of foams tends to split around the 40 °C mark. Below that temperature, a dry polyhedral foam is observed for most of the decay that is primarily driven by drainage and evaporation, while at temperatures above 40 ºC, a wet spherical foam is observed for most of the decay and the mechanisms governing the decay depend on the surfactant being used.
For anionic surfactants, it was found that wet foams decay through the Marangoni flow induced by temperature fluctuations across the bubbles’ surfaces, which are exacerbated at higher temperatures. When a lamella ruptures, if the adjacent bubbles are sufficiently different in size, the gas influx from the smaller bubble to the larger one combined with the liquid in the lamella and the bubbles themselves causes new bubbles to be formed due to the shearing of the liquid.
The results also showed that at temperatures above 120 °C the decay of the foams was primarily occurring at a middle layer within the foam structure rather than the top layer that is exposed to the gas phase. The decay occurred in the form of splitting, where large bubbles burst and form smaller ones, that shifts the foam downwards making it appear as if the top layer is exhibiting the bulk of the decay.
For nonionic surfactants, the decay is more complex and depends on the phase behavior of the surfactant molecule with temperature. As the temperature increases, the aggregation of the monomers into larger structures such as micellar, lamellar, and isotropic structures, changes the way foam decays. It was found that at 90 °C, the decay of the foam occurred primarily at the liquid-foam interface which is attributed to the preferential aggregation of the monomers into larger structures in the liquid phase, as opposed to adsorption to the gas-liquid interface.
Overall, this work showed that foam behavior can either be independent of the surfactant behavior with temperatures, as is the case with anionic surfactants, or coupled to the thermodynamic behavior of the surfactant molecule, as in the nonionic surfactant, and is significantly different between low and high temperatures.
Associated Publications
Rights
Copyright of the original work is retained by the author.