The FTA 1000 oscillating pendant drop apparatus was modified and used to measure the dilational elasticity modulus and interfacial tension of Gibbs crude oil in different dilutions of NaCl and CaCl2 brines. The brine samples were diluted by 100, 500 and 1000 parts from an initial ionic strength of 0.6724M. The crude oil samples were not diluted, but used at full strength. Measurements were conducted at both 25 and 50°C to understand the effects of crude oil viscosity on dilational elasticity modulus values. Results showed that although dynamic moduli values for Gibbs crude oil depended on temperature, aging time, brine composition and brine ionic strength, interfacial tension and rate of changes of interfacial tension values displayed little variations. The interfaces formed from the monovalent brines appeared to be slightly more rigid, although all interfaces tested were highly elastic. The elastic nature of oil-water interfaces immersed in both monovalent and divalent brines were similar at the initial ionic strength of 0.6724M, but diverged with brine dilution. Diluted divalent brines affected the Gibbs oil interface formation and dynamic moduli properties more strongly that diluted monovalent brines, and lead to increased interface growth. It appears that there may exist a kinetic rate of film formation that is affected by temperature during aging. Finally, as the dynamic moduli created a wide array of results while interfacial tension changed little, dynamic modulus values are an important consideration for any oil recovery system, as fluids move in a dynamic fashion. The outcomes of this research may explain related stability results, namely that lower ionic strength brines form more stable emulsions for Gibbs field oil as well as for other crude oils previously examined. These results might impact the interpretation of several enhanced oil recovery processes.
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