Study and Application of Removing Oilwell Barium Sulphate through Complexing Method

The chelating agent used was mainly composed of diethylene triamine pentacetic acid (DTPA). It was neutralized with KOH until the pH was 13, and then treated with a certain amount of inorganic salts. This solution was used to dissolve out barite powders. The experimental results showed that, at a certain mass ratio of DTPA, the efficiency of potassium salts as solubilizing agent was 2 times of that of sodium salts due to the effect of the solution viscosity. Increasing the mass ratio of the inorganic salt, the efficiencies of potassium carbonate, potassium fluoride and potassium chloride as solubilizing agents in dissolving barite were correspondingly enhanced. At 10% of potassium carbonate, 47.79% of barite was dissolved. After 4 h of reaction, the conglomeration of barite led to an increase in reaction area, increasing the solubilizing efficiency of potassium carbonate to a value that was 10.56% higher than that of potassium fluoride. After reacting for 12 h, the reaction tended to complete, the solubilizing efficiency of potassium fluoride was instead higher than that of the potassium carbonateby 12.39% because of the salt effect on the reaction endpoint. The steady configuration of the DTPABa^3-ions was obtained through computerized simulation, and the cause of low complexation constant of barium ions was analyzed. A chelating agent was chosen based on the study and was used on a well blocked with barite. The flowback fluid was analyzed for inorganic salts and precipitated sulphate using XRD. Barium was found in the precipitates, indicating that the well was successfully unblocked.