Reservoir management has lately received significant attention in the oil industry because of the sizable potential increment in profit associated with optimized strategies, together with the increased reliability of new reservoir flow simulation techniques. Long-term (more than five years) management is especially challenging partially because of the difficulties brought by the uncertainty associated with forecasting oil production and price. In this work, we first propose a risk measure of a given production strategy with respect to uncertainty in the oil price. This measure is interpreted as the value of information associated with an uncertain oil price. Decision makers can leverage value of information of oil price, for example, to qualify potential risks associated with the lack of knowledge of the market, to compare an exploitation strategy with the optimal strategy in the utopian situation where future oil price is known, and to evaluate possible capital investments for a better forecast of oil price. Then, we present a numerical approach using reservoir flow simulation to estimate efficiently this risk measure. The computational cost of this numerical method does not increase with the number of possible oil price scenarios considered, and this is a desirable feature when simulation is time-demanding. To the best of our knowledge, value of information of oil price has not been addressed using complex reservoir flow simulation. The approach is validated on a synthetic case and two real field waterflooding scenarios: a relatively small field with eight wells, and a larger field with 174 wells. In both cases, we analyze 10,000 oil price scenarios, quantify the risk of waterflooding production strategies obtained through optimization, and estimate the monetary value associated of oil price forecasts with different degrees of market information and knowledge.