Avaliação físico-química de soluções micelares aplicadas na remoção de reboco

Abstract

When drilling an oil well, drilling fluids are used for the purpose of, among others, forming a thin layer in the reservoir rock formation that will prevent migratory flows from the well to the formation or vice versa. The removal of this thin layer, called grout, is of paramount importance for a desirable cementation. In order to remove the grout, washing mattresses are usually used, which need to remove the grout completely and leave the rock water-wettable. In addition, these mattresses need to be compatible with the cement paste and the drilling fluid. From this context, this work aims to develop and apply alcoholic micellar solutions and solutions containing mixtures of surfactants. In order to choose the best formulation, statistical studies of the Scheffé and central composite simplex network planning type were performed. The formulations were used in the plaster cleaning tests in a temperature range from 30 to 65 degrees Celsius, in order to evaluate the cleaning efficiency of the formulation in the face of the change in physical appearance through the turbidity point limit. For the formulations that completely removed the plaster and that presented a lower percentage of active matter (surfactant and/or alcohol) in their composition, surface tension, rheology and wettability measurements were performed as a way to evaluate and guarantee their applications. In addition, the study of compatibility between the washing mattresses and the cement paste was carried out, as well as the evaluation of the compressive strength of the cement after its contamination. The alcoholic micellar solution achieved 100% efficiency in the removal of plaster at all temperatures, only in the tests with a higher content of active matter (surfactant and alcohol), preferably with n-butanol. On the other hand, for the surfactant mixture solutions, 100% plaster removal efficiency was obtained for all temperatures in the tests with the highest percentage of 7EO lauryl alcohol. After these findings, formulations 10 (2.0% surfactant + 2.0% n-butanol + 96% brine) for the first system and 5 (2.0% LA 5EO + 2.0% LA 6EO + 4.0% LA 7EO) for the second system were chosen. These two formulations kept the rock water-wettable and were compatible with cement paste, which after hardening, showed compressive strength of 10.37 Mpa and 11.27 Mpa, respectively. Thus, it can be concluded that the formulations are suitable for use of olefin base fluid grout cleaning, being an alternative for use in oil field