The behavior of drilling fluids at high temperatures, particularly those which are water based drilling fluids, is unpredictable and, , has not been totally understood. In this way, optimizing the composition of the fluids becomes one of the main factors for the control of their properties. This is so because the rheological properties of the drilling fluids can present great differences at ambient temperature and in the interior of the well. This work aimed to evaluate the behavior of clay drilling fluids with polymer and lubricant additives at high temperature. Therefore studies were performed on the rheological properties, filtration and pH. The results evidenced that the fluids studied presented low values for the rheological properties and high values for the filtration properties. In addition to that, thermal aging caused a degradation process of the additives used, mainly the xanthan gum, resulting in pH reduction and in the caramelization of the fluids.
Drilling fluids; Temperature; Degradation; Additives
