Waterflooding is an important method for improving oil recovery, it consists of injecting water into selected injector wells to displace the oil to the surrounding producer wells while maintaining reservoir pressure. When water breaks through to the producer however, this secondary recovery technique can cause some production problems. A particular issue is mineral scale formation resulting from the mixing of incompatible brines. An example is barite precipitation following the mixing of barium rich formation water with an injection water high in sulphate. Accurately predicting the fraction of injection water being produced is therefore of paramount importance to accurately predict mineral scale formation and prevent its damaging effect on productivity. This paper will describe a newly developed in-house computer program to track and analyze injection water fractions in produced wells and discusses its impact on mineral scale prediction and management. The computer tool is used to study produced water profiles from two oil fields located in the North Sea and in the Gulf of Mexico. The benefits and drawback of ions commonly employed (i.e., chloride) to track injection water breakthrough are reviewed and compared against a “reactive ion” methodology developed FAST project at Heriot-Watt University. The results of the current study show that the reactive ion methodology was particularly effective at tracking low injection water fractions even when the raw data has a high noise-to-signal ratio. Further analysis reveals how plots that highlight the ion concentration deviate from their expected value, which can be used to monitor geochemical reactions taking place in the reservoir, as well as evaluate the efficiency of scale inhibitor squeeze treatment and help production chemists plan their scale management program more effectively.