The Biggest Elephant in the Room in Unconventional Scale Programs: Iron

Abstract The development of unconventional basins across North America for the past decade initially caused some in the industry to wonder if challenges found in unconventional basins would require new chemistries and technologies. As the basins have been produced and water chemistries evaluated and treated, it has become clear that established scale inhibitor chemistries and methodologies are suitable to treat unconventional scaling scenarios. However, the number of applicable chemistries can be limited as some of the most common scale inhibitor chemistries have been found lacking in iron tolerance. The biggest lesson learned over the course of the past decade has been to not underestimate the role that iron can play as spoiler not only in performance of scale inhibitor chemistries, but also in test methodologies and monitoring techniques. While the need to account for iron in conventional programs has not been taken for granted, the amount of iron produced in unconventional production basins has led to a re-evaluation of just how severely iron in solution can impact scale programs from product testing and selection all the way through to program monitoring. This paper highlights the brine chemistries in major North American unconventional basins, especially regarding iron. Test methods and results from dynamic scale loop and anaerobic static bottle testing will be highlighted as well as the limitations of using field brines in product evaluations. Field observations will be discussed to support the importance of proper product selection as well as monitoring techniques. This subject has implications for the industry as unconventional basins across North America continue to search for program improvements to drive reductions in total operational costs. Additionally, as unconventional basins are developed outside of North America, the lessons learned can be applied to efficiently develop best in class scale inhibitor programs. As appreciation for the impact of high levels of iron on scale inhibitor performance continues to evolve, there is a possibility that a smaller amount of iron tolerant scale inhibitors will limit the treatment options available in unconventional production basins.