Evaluation of Barium Sulfate (Barite) Solubility Using Different Chelating Agents at a High Temperature

Abstract

Barium sulfate (barite) is one of the widely used weighting materials in the preparation of drilling fluid for deep oil and gas wells. Barite is not soluble in the regular solvents; such as, hydrochloric acid (HCl) and other acids. Therefore, in this study, we focused on evaluating the dissolution of the industrial barite particles in different chelating agents. Chelating agents; such as, diethylene triamine penta acetic (DTPA), ethylene diamine tetra acetic (EDTA), and hydroxyethyl ethylene diamine tri acetic (HEDTA) acids with high and low pH values were used in this study. The effect of the base of chelating agents, namely alkali and alkali earth hydroxides, on the dissolution of barite was also investigated. For the first time, the optimum pH, concentration, and base (sodium or potassium) of chelating agents which yielded the maximum dissolution were investigated in this study at a high temperature. Previous studies did not consider the wellbore constraints during their experiments and they used chelating agent volume to barite weight ratio, which could not be implemented in the real wells. In this study and for the first time, we considered the wellbore volume (chelating agent volume that can be used) and the barite weight (filter cake) during the dissolution experiments. Based on the results obtained from this study, potassium base DTPA-K5 and EDTA-K4 of a concentration of 20 wt.% were found to be the most effective chelating agents to dissolve barite. The solubility of barite was found to be 26.8 g/L in a solution containing 20 wt.% of DTPA-K5 and 25.6 g/L in a solution containing 20 wt.% of EDTA-K4 during a soaking time of 24 hrs and a pH value above 11 at 200°F.