Applications of Solid, Slow-Release Scale Inhibitors in Fractured Reservoirs

Abstract Regardless of whether a well is being developed onshore or offshore, inorganic scale is a persistent challenge in oilfield operations, and this challenge is worsened by the use of seawater or reuse of high salinity produced brines. Thus, scale control programs are a standard part of most wells. Liquid scale inhibitors are most common, but alternatives are available in the form of solid, slow-release inhibitors. While liquid products lose their efficacy as soon as they are produced from the well, slow-release solids can provide much longer periods of protection. If properly selected and applied, it is possible to see multiple months of protection against scale formation. This paper will discuss multiple case studies describing how these products can be successfully used. Focus will be given to a family of products that combine high activity, extended release, and favorable cost-to-treat. In this paper, we will discuss initial laboratory results used to screen and compare the performance of various commercially available products. In some cases, the release behavior of a given composition is achieved by controlling the chemical composition of an active molecule; in other cases, the release behavior is achieved by controlling the physical properties of a composition (for example, through the use of encapsulation or barrier materials). Differences in release behavior are apparent, and although direct field comparisons are difficult to make, we anticipate these differences will translate to differences in performance in downhole environments. Field results will be discussed, demonstrating that the utility of these products extends beyond laboratory testing. In a representative 6-well trial in the Bakken reservoir, North Dakota, scale protection was achieved for approximately 10 months as indicated by monitoring returns in the produced fluids. A separate 6-well case study in the Uinta Basin, Utah is forecast to yield similar results. Downhole equipment prone to scale buildup and eventual failure was kept online and scale-free for multiple months, indicating effective protection by the solid slow-release treatment. Slow-release scale inhibitors have been available on the market for many years, but it can be challenging to achieve consistently positive results that provide confidence that a well is protected. A correct understanding of the scope and limitations of these products is an important first step, and this paper will help provide that foundation. Our goal is to demonstrate that effective slow-release scale inhibitor treatments are possible, but the treatment strategy needs to properly integrate downhole conditions, a product's properties and behavior and a target protection profile (e.g., length of protection, type of scale, etc.).