Synthesis of a Novel Ester-Based Drilling Fluid Applicable to High Temperature Conditions

Ester-based drilling fluids based on aliphatic esters were introduced in 1990. Esters can be synthesized from fatty acids and alcohols. Previous studies indicated that ester hydrolysis in drilling fluids happens only under certain conditions. In order for ester hydrolysis to occur, two primary conditions must be present: high temperature and excessive hydroxyl. When the temperature exceeds $300°F$⁠, ester hydrolysis can occur under the presence of excessive hydroxyl. Hydrolysis breaks down the ester component into its parent carboxylic acid and alcohol. The current study shows that the stability of ester-based drilling fluids at high temperature conditions depends on the composition so that the selection of proper components and additives such as emulsifiers, stabilizers, copolymers, viscosifiers, and rheological modifiers can increase the temperature stability of the fluid. Hereby, the application of an ester-based drilling fluid is improved up to $350°F$⁠. The composition of the provided fluid is unique in the view point of its higher thermal stability against the previous formulations provided in literature. Furthermore, the experimental results of this study show the favorable effect of hot-rolling pressure on barite sag and electrical stability of the mud, i.e., increasing the pressure at three particular temperatures of $300°F$⁠, $325°F$⁠, and $350°F$ reduced the barite sag and at some instances increased the electrical stability.