Ionic Liquid-Based Formulation for Inhibiting Calcium Sulfate Scale in High-Pressure High-Temperature Wells

Abstract The persistent problem of sulfate scale formation in oil and gas operations, primarily involving anhydrite (CaSO4) and barite (BaSO4) scales, poses significant operational challenges. These scales, resulting from mixing incompatible waters rich in sulfate ions with calcium or barium ions, obstruct fluid flow and cause substantial damage to production equipment. The conventional commercial solutions to this issue, such as the use of acids, chelating agents like Hydroxamic Acid and EDTA, and mechanical methods like pigging and downhole tools, are often hampered by limitations including high costs, high-temperature, environmental concerns, and limited effectiveness against certain types of scale. To overcome the existing challenges, an innovative approach using an ionic liquid as a scale inhibitor was introduced in this study. The chosen ionic liquid, 1-Butyl-2,3-dimethylimidazolium hexafluorophosphate (1B3DM6FP), is specifically introduced to target sulfate scales. This environmentally friendly solution offers a more efficient approach for managing scale formation, particularly at high-temperature conditions encountered in deep wells. To evaluate its effectiveness, we conducted a series of static bottle experiments, providing an in-depth analysis of the inhibitor's ability to prevent scale formation and its interactions with scale-forming ions. The first time, the performance of 1B3DM6FP was thoroughly examined at temperatures of 150°F and 320°F over an extended period. The results from these tests indicate that 1B3DM6FP exhibits substantial potential in inhibiting sulfate scale formation, outperforming traditional methods in several key aspects. The performance of IL at high temperatures is substantially high due to its higher thermal stability. The IL proved to be a stable scale inhibitor for several days. The scale inhibition potential was in direct relation with the concentration of the IL means higher inhibition was achieved with higher concentrations. 1wt% IL resulted in blank solutions without any scale after almost a week of ageing. IL application could mark a significant advancement in scale management strategies within the oil and gas industry, highlighting a shift towards more sustainable and effective solutions at high-temperature conditions. This study not only underscores the challenges of sulfate scale management but also emphasizes the importance of innovative approaches like the utilization of ionic liquid (1B3DM6FP) as an efficient and green scale inhibitor.