An external breaker system, consisting of a combination of enzymes, has been used to remove polymer damage at low to moderate temperatures. This enzyme mixture produces a stepwise breakdown of cellulose polymers at temperatures ranging from 60 °F to 140°F. The polymer is initially reduced to D-glucose and cellobiose. The complete hydrolysis of the cellobiose is subsequently afforded by the enzyme combination. The entire hydrolysis of the polymer occurs rapidly; therefore, the enzyme complex can be applied as an external breaker after the workover operations have been completed. Post workover injection of the enzyme complex allows blocking gels to retain maximum strength during operations. The enzyme combination is compatible with the brines used to prevent damage from swelling clays. The result is a blocking gel that is reduced to a clean non-viscous fluid that is easily recoverable.

Keywords:
breaker treatment, polymer, concentration, cellulose, gel, drilling fluid property, filter cake, enzyme combination, enzymatic breaker system, permeability
Subjects:
Drilling Fluids and Materials, Hydraulic Fracturing, Drilling fluid selection and formulation (chemistry, properties), Drilling fluid management & disposal, Fracturing materials (fluids, proppant)
Copyright 1993, Society of Petroleum Engineers
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