Brownfields are often characterized by a varying degree of maturity, both within the field and within individual reservoir units. This variation makes infill drilling more prospective in areas with fewer well penetrations and completions and less production. However, these areas are inherently more uncertain, with geological, petrophysical, and structural parameters particularly affected. A novel workflow solves the complex problem of uncertainty assessment and risk management in a brownfield redevelopment. Traditionally, a single deterministic reservoir model is built, matched, and used for predictions and infill planning. The availability of sophisticated simulation workflow tools enable the team now to explore the practical aspects of performing sophisticated reservoir description, static model construction, history matching, and forecast uncertainty analysis. Incorporated into multiple equiprobable reservoir descriptions, uncertainties are carried from the static model construction throughout the entire dynamic modeling process. History matching is conducted for all realizations, and the match quality is assessed by means of statistical analysis. The workflow facilitates generating hydrocarbon thickness maps by using the average column thickness of many simulation models instead of a dedicated single one. Target selection also accounts for possible sweep and sand risks by means of maps showing the standard deviation of the column thickness. The new framework is applied to a conceptual redevelopment of a brownfield. It increases the understanding of fluid flow processes in the reservoirs and is a vital component of the decision and risk analysis for the concept selection stage.