Hydraulic fracturing and Enhanced Oil Recovery (EOR) polymer floods present new and technically challenging demands for biocides with the need to couple high performance with system compatibility to provide flexible and effective treatment programmes.Formulated tetrakis hydroxymethyl phosphonium sulfate (THPS) technologies have been developed that have improved compatibility at high dose concentrations with friction reducers and biopolymers used in EOR programmes and fracturing applications. The updated formulations have shown enhanced biocidal efficacy against acid producing bacterial (APB) species. Typical fracturing fluid systems have been investigated and the ability to introduce biocide and oxidising breakers effectively demonstrated.Supplementary mitigation of iron sulfide and organically coated inorganic scale typically rich in iron sulfides referred to as schmoo has also been investigated using optimised levels of THPS and polymeric additive. Key Words: THPS Tetrakis hydroxymethyl phosphonium sulfate hydraulic fracturing EOR polymer floods friction reducer polyacrylamide guar slickwater gel frac “on-the-fly” souring schmoo iron sulfide.