In the course of a recent investigation on the formation damage associated with HEC gels, we found no published comprehensive work on the interactions between HEC gels, the geochemistry of the formation, and the gel breakers. Recognizing this lack of information and in view of the popularity of HEC gels as viscosifying agents, we have embarked on sharing our findings with the oil and gas industry in several parts, the first of which is presented below.

In this paper, we will review fundamentals on cellulose chemistry and cellulose quality as related to the manufacturing of HEC polymer, the formation of "fish-eyes" and "micro-gels" and the degradation mechanisms of HEC gels by temperature, acids, bleach, and enzymes. Finally, we will present practical measures to alleviate formation damage. These measures includes adequate polymer and gel quality control (MS/DS ratio) as well as the implementation of proper field practices (control of the pH, filtration of the gels, etc.).

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