Análises da molhabilidade e da adsorção de tensoativos em rocha calcária

Abstract

The current scenario of the oil industry involves exploring and producing reserves with big technical challenges, in this way, it becomes increasingly necessary to know the mechanisms that impact the oil production. An example of this is the new discoveries in the Brazilian sea, with the pre-salt, composed of large accumulations of high commercial value light oil. However, a determining factor to be considered is the type of reservoir rock predominant in the formation of its reserves. These rocks are composed almost of carbonates of calcium that form the carbonate rocks, mainly limestone, which in the majority of them are oil-wet, a factor that Decreases the recovery of oil. Thus, studies have been developed in this type of rock in order to reverse its wettability and improve productivity. One way of change the wettability of the reservoir is through the chemical methods involving surfactants, which by their amphiphilic nature have the ability to adsorb at interfaces and surfaces according to their affinity, reducing the free interfacial energy, which can reverse the wettability of the rock, facilitating the flow of oil and thus, improving its recovery. The objective of this work was to study how different types of surfactants adsorb in limestone, and if they were able to alter their wettability. For this, the finite bath method was used for three surfactants: OCS (anionic), C16TAB (cationic) and ULTRANEX 110 (nonionic), varying parameters such as temperature, adsorption mass (limestone), contact time and concentration of surfactant. Contact angle analysis was also performed to analyze wettability and zeta potential. OCS was the only surfactant that presented significant adsorption in the rock, possibly due to the presence of electrically charged ions. The increase in temperature from 30 ° C to 50 ° C caused a decrease in the adsorption capacity. The limestone in natura presented mixed wettability, with strong affinity to the oil, after treatment the wettability decreased to oil, however it also decreased in relation to water. The measurements of zeta potential showed that the eletrostatic attractions played an important role in the adsorption, obtaining greater value in the module for the OCS.