Estudos dos efeitos intrínsecos e extrínsecos na estabilidade de emulsões do tipo A/O de petróleo pesado

Abstract

The present thesis proposes to evaluate the intrinsic and extrinsic factors that affect the stability of heavy oil W/O emulsions. For this, W/O emulsions were first prepared by adding 0.1 to 30% w/v of aqueous phase containing deionized, formation water and saturated saline solutions. The factors evaluated were: characteristics of the aqueous phase (such as pH, conductivity and ionic strength), gravitational separation, temperature, droplet size distribution (DSD), acidity and interfacial tension. In a second step, W/O emulsions with 10% w/v of aqueous phase were prepared for pressure tests at 1.0∙106 Pa for 24 hours with carbon dioxide (CO2) and nitrogen (N2) gases. The results showed that emulsions prepared with some salts of acid pH and high ionic strength showed kinetic instability with aqueous phase separation after a certain time, while the others remained stable for 30 days and even when subjected to maximum heating of 80 °C. Regarding the average DSD, emulsions with acid pH salts showed higher values and the lowest values occurred in emulsions with deionized water. The acidity was altered in relation to the dehydrated oil, mainly in the presence of acid and basic pH salts. The interfacial tension of the dehydrated oil increased in the presence of salts, especially those with acidic pH and high ionic strength. In saline medium and basic pH, there was a considerable reduction in the value of the interfacial tension. In general, pressurization with the different gases had little effect on emulsion properties such as gravitational stability, average DSD and interfacial tension when compared to the previous results (no pressure). However, deformation was observed in the interfacial film of some drops in emulsions with salts of basic pH. After pressurization with CO2, the acidity of the emulsions with calcium chloride, carbonate and sodium bicarbonate increased, indicating that the gas may have chemically interacted with the aqueous phase of these samples. The interfacial tension of oil after pressurization and different types of aqueous phase was not significantly altered, except at the interface between oil pressurized with CO2 and deionized water. Water phase properties such as pH, ionic strength, ionic radius of the cation and valence are important in the study of saline petroleum emulsions. Pressurization did not change the stability of the emulsions, however chemical interactions with the gases occurred