Estudo do fenômeno de prisão diferencial e da estabilidade térmica de fluidos argilosos.

Abstract

Due to technological advances, the oil wells drilling at great depths are increasingly constant and, consequently, higher drilling problems are encountered. The differential sticking, phenomenon that occurs when the drill string is stuck, without rotation, preventing the movement, but with the drilling fluid circulating normally, it is one of the problems observed. Another problem encountered in drilling deep wells is the temperature range. As the depth of the well increases, the temperature at the underside of the well increases, this causes a negative effect on the progress of drilling well, because the fluid properties are affected by the temperature and its behavior is unpredictable and, in fact , not yet fully understood. Thus, to develop a formulation that adequately support ambient of higher temperatures and lower risks of prison tubes is challenging, mainly because little attention is given to the proper design of fluids. Thus, this study aimed to evaluate the thermal stability and the performance of clay fluids under high temperatures and differential sticking conditions. Therefore, studies were made of Theological properties, filtration, pH, density, lubricity and differential sticking. The results showed that: for fluids prepared only with clay, the clay concentration and temperature are key factors to change of theological properties and filtration of fluids, because they alter the degree of flocculation and dispersion of clays and, due to the absence of lubricating characteristic of the fluids, the primordial factor in reducing the risk of differential sticking are the filtration of properties (VF, ER, and K). For clay fluids additivated with polymers, lubricant, the DSC tests do not indicate, in a real way, the degradation temperature of the fluids, which are thermally stable at 93°C and, fluids with lubricant characteristics ensure a lower risk of the differential sticking, because the lubricity, in this case, is the most influential factor.