The production of high salinity brines (Total Dissolved Solids (TDS) > 250,000 ppm) during oil and gas production is known to cause severe scaling issues. When high TDS conditions are coupled with high concentrations of dissolved iron in a produced water, the challenges for controlling scale deposition increase significantly. The formation of the more common mineral scales (barium/strontium sulfate, calcium carbonate, and calcium) is expected in these produced waters and often other challenges associated with high TDS brines include the propensity for halite (sodium chloride) deposition to also occur in these environments as well. The elevated iron content present in these brines not only introduces the potential for deposition of iron-related scales but is also known to have a negative impact on scale inhibitor performance against calcium carbonate and barium sulfate scales. However, the impact on the inhibitor is different for both types of scale. The objective of this work is to evaluate the performance efficiency of polymeric and phosphonate-based scale inhibitor blends under both static and dynamic testing conditions using a synthetic brine with high TDS and varying concentrations of dissolved iron (up to 250 ppm).

The synergistic effects of combining these chemistries will be evaluated for this work. Dynamic Scale Loop (DSL) and static bottle testing will be used to determine the performance the efficiencies of the developed products.

When tested individually under a mixed scaling scenario with a high TDS and high iron containing brine, the scale inhibitors selected for this study had performance efficiencies (MED) values of 200 ppm or greater. However, when polymer/phosphonate scale inhibitor blends were evaluated a significant improvement in performance efficiency was observed.

This paper will give a detailed account of testing conducted to identify inhibitors capable of preventing the deposition of calcium carbonate and iron-related scales in challenging environments by utilizing the synergistic effects of the scale inhibitor chemistries.

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