Since developments in the biotechnological field contribute to the implementation of new enzyme breakers for removing polymer damage, significant improvements in well productivity have been proved mostly in horizontal and multilateral wells. Indeed, a delayed clean-up treatment is often required for removing the filtercake after drilling when the drawdown of the well is not enough. Conventional acid treatments promote a rapid, localized reaction resulting in a partial, non-uniform removal of the mud cake. Additionally more and more restrictive regulations push to find less corrosive and more environmentally safe clean-up options including low toxic oxidizing agents and enzyme breakers. Historically, the enzyme's applications have been limited to low temperature treatments due to their pH, salts and temperature concerns. Recently, new temperature-stable, polymer specific enzymes have been isolated and investigated for degrading the polysaccharides (starches and viscosifying agents) commonly used in the Drill-in Fluids.

This paper describes the laboratory evaluations performed on three new enzymes with the aim to develop a non-corrosive clean-up treatment specifically designed for degrading starches, xanthan gum and scleroglucan at temperatures reaching 100°C. Static break tests showed that these polymer-specific enzymes aggressively attack the polysaccharide backbone resulting in a complete break of the polymer. Nevertheless the treatment fluid do not have an immediate reactivity, which might ensure a uniform distribution of the fluid across long pay sections with minimal leak off during placement. Degradation is very effective and the generated fragments are small, soluble molecules. Besides the temperature and pH dependence, the influence of different heavy brines (CaCl2, CaBr2, etc.) on the enzyme activity and salting-out effect were also investigated. The optimal application concentration range for each brine was identified. By coreflooding tests the effectiveness of these breakers in removing the filtercake has been confirmed and the non-damaging properties of the degraded fragments assessed.

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