51316-7771-Iron Effects on Scale Inhibitor Performances for Laboratory and Field Operations

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Product Number: 51316-7771-SG

ISBN: 7771 2016 CP

Author: Haiping Lu

Publication Date: 2016

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The presence of various levels of iron can be found in field brines accompanying oil and gas production. The primary sources of iron in oilfield operations are the formation mineralogy or the sequences of corrosion. It has been noticed that the presence of iron has adverse effects on the performance of scale inhibitors. There are two possible predominant factors: 1) iron poisoning of the scale inhibitor molecule and 2) the formation of Fe(OH)3 from the oxidation of Fe2+ where the scale inhibitors are absorbed on Fe(OH)3 to increase the treatment dosage rate. Nevertheless additional factors such as the formation of FeCO3 various brine pH values and residual oxygen during tests all impact the testing results and induce variability on iron effects to scale inhibitor performance.This paper will discuss the iron effects on scale inhibitor performance with specific anaerobic tests designs to determine the Fe2+ effect(s) on the performance of carbonate and sulfate scale inhibitors in the presence of up to 1000 parts per million (ppm) Fe2+. It was found that even with 1000 ppm of Fe2+ the minimum effect concentration (MEC) of tested phosphonate and polymer inhibitors can be between 25 and 50 ppm under testing conditions favorable for FeCO3 precipitation. Studies into several factors on the performance of carbonate scale inhibitors in the presence of Fe2+ are also presented such as various pH values and FeCO3 scaling tendency. Furthermore the Fe2+ effects on the performance of sulfate scale inhibitors will also be discussed in the absence of bicarbonate; which eliminates the impact of FeCO3 formation on the scale inhibitor performance.The investigations of iron effects on the performance of scale inhibitors can help to understand the mechanism of iron interference during laboratory scale testing and field operation gain an insight on the impact of corrosion products on scale treatment programs and provide the reference information for optimizing the treatment rate for both corrosion and scale inhibition.