Non Damaging Drilling Fluid (NDDF) is a polymer mud system mostly used in the reservoir sections to avoid formation damage. Non degradable compositional fine solid e.g. Bentonite (clay) is not used in NDDF to decrease the reservoir damage and environmental pollution. It incorporates long-chain, high molecular weight polymers; some of which are viscosifiers and some are fluid loss control agents while others are multifunctional. All these polymers are very much vulnerable to bacterial attack or biodegradation by which the complex molecules are broken down by micro-organisms to produce simpler compounds. Due to this, the Bactericides are commonly used to kills the bacteria in the NDDF containing natural polymers. In this work, an attempt has been made to study the effect of varying composition of Bactericide/Biocide on the different properties of laboratory formulated NDDF and to choose its optimum composition for the oilfields of Upper Assam Basin based on the mud parameters generated in the laboratory and the required mud parameters in these oilfields. Thus, this paper reports the effect and optimum composition of Bactericide to control the biodegradation of the NDDF.
