THE USE OF PRODUCED WATER IN WATER-BASED DRILLING FLUIDS: INFLUENCE OF CALCIUM AND MAGNESIUM CONCENTRATIONS

Abstract

The Urucu oilfield (Amazon Basin, Brazil) has a large volume of produced water with a high concentration of salts. The treatment and disposal of its produced water are very difficult, justifying its reuse. In this work, synthetic produced waters, with different concentrations of calcium and magnesium salts, are used in the formulation of water-based drilling fluids. A full 32 factorial design is applied to evaluate the influence of these salts on fluid rheology and filtrate. Magnesium concentration did not influence the properties of the fluid, but higher concentrations of calcium (43.63g/L) caused undesirable outcomes, including the presence of precipitate, high volume of filtrate, thick cake formation, and rheological properties with low power of carrying gravels. The high content of sodium in the produced water eliminated the need of adding NaCl to drilling fluid, making the developed fluid less expensive. The best composition was obtained using produced water with maximum magnesium concentration (9.411g/L) and minimum calcium concentration (0.733g/L).