Abstract This paper describes the successful case study of a new approach to a Fall Off Test (FOT) for reservoir characterization and pressure surveillance in a mature oil field with waterflooding. The main objectives are to evaluate fundamental reservoir properties, to study uncertainties attributed to well-to-well communications, and to validate the presence of potential fractures. The first step was the evaluation of current waterflooding performance at the sand layer level using injectivity behavior and petrophysical information, prioritizing high remaining oil reserves. Also, well candidates were screened against wellbore integrity and operational execution. Once the technology was ready for deployment, a customized log acquisition, and reservoir surveillance program was designed for slickline operation to acquire fall-off test data in every mandrel properly. Finally, the interpretation was made in specialized software, which served as input to update analytical models and improve reservoir understanding. The proposed technology offers an innovative way to improve reservoir management through a cost-effective and credible application for pressure surveillance, taking advantage of selective-string capabilities for zonal evaluation. In addition, the methodology can be applied in oilfields where permanent downhole sensors are installed in intelligent completions for water injection purposes.