Abstract Deepwater reservoirs pose significant challenges worldwide to companies exploring and producing such reservoirs because of the high exploration, development, and production costs. Great uncertainty and risk attend the evaluation of deepwater reservoirs because of the environment, sparse well control, and lack of direct measurement of reservoir properties. Proper modeling of deepwater reservoirs provides companies with tools to evaluate these reservoirs and quantify risks associated with their development. There are five critical areas in the process of modeling deepwater reservoirs. These are geological and geophysical modeling, reservoir characterization, reservoir flow modeling, facilities/flow assurance, and uncertainty/risk analyses. This paper presents methodologies found useful by experience in the modeling of deepwater reservoirs. Actual field cases describe our experience in using systematic steps based on the five critical areas to model the Zia reservoir, a Manatee reservoir in the Troika Basin, and the Magnolia reservoirs using the Markov Chain Monte Carlo technique.