Management of Barium Sulfate Precipitation in Rich Iron and High pH Environment during Stimulation Operation

Abstract The quality of base fluid used in the preparation of different stimulation and wellbore cleaner recipes is very critical toward high efficient job. However, due to the limited access to adequate quality water sources, efforts to minimize the operational impacts of such less quality source is grown rapidly. High sulfate mixing water is well known example of such low quality water and which results in sulfates deposits during stimulation operation. In this paper, an effective management of barium sulfate precipitation in high pH and iron rich environment is presented. A simulated low quality water with high sulfate content of more than 500 ppm and produced water of high barium and iron contents were proposed and prepared for this study. Static jar compatibility tests at high pressure and temperature were conducted at different ratios to study the potential precipitation of sulfates and iron deposits. Precipitated solids were identified by Scanning Electron Microscope (SEM) and aqueous phases were analyzed by ICP-OES and IC for barium, iron and sulfate content. Then, three different scale inhibitors (SI) were assessed at different loadings for their efficiency to prevent scaling. Chelating agent was also used to enhance the efficiency of scale prevention and work to chelate iron ions presented in the produced water. The effect of high pH in the precipitation quantity was also studied. Results showed high potential of barium sulfate precipitation at different maxing ratios. At higher ratios of produced water, the presence of more iron deposit was observed. Analysis confirmed the barium sulfate deposition during the static jar tests. Scale inhibitors performance were found to be functions of loading and the presence of iron. Chelating agent improve the performance of SI and led to minimum precipitation potential. An optimized fracturing recipe was designed utilizing the high sulfate source water and proved to minimize the impact of sulfates scaling. The use of the chelating agent was found to be critical to enhance the scale inhibitor tolerance toward iron presence.