Abstract: This invention relates to the use of chlorite-based antimicrobials in a manner where the time of biocidal activity is extended for the microbial control in the water used for drilling, completion and remediation of wells. The invention involves mixing of a compatible extender in the form of sodium chlorate with sodium chlorite to form an antimicrobial formulation. This combination is used with an acid on the site to generate chlorine dioxide which is injected into the water used for hydraulic fracturing or remedial workover. The formulation is a much more effective bactericide for the subterranean oil and gas rich formations. The potency and longevity of biocidal activity is controlled by varying the ratios of chlorate and acid which provide different profiles of the antimicrobial activities.