Production forecasting always play an important role in decision-making for the corporate management and architecting company's strategy. In an oil or gas upstream company, the yearly projection of future hydrocarbon production is a routine practice for preparing annual business plan. As sub surface uncertainties pose a huge threat for upstream company, achieving the forecasted crude oil and gas production is challenging in most cases. For national oil companies, having multiple Assets and thousands of wells where reservoirs underpinning different projects at different stages of field development, there arises a need of unified production forecast process that ensures forecast quality. In view of this, Kuwait Oil Company (KOC) initiated a process for improving forecast process adopting best reservoir management practices. In order to make reliable predictions, the engineer must be knoweledgable in variety of techniques to cover the wide range of conditions that are encountered in forecasting process. At the same time, engineer should have enough experience of reservoir behavior to alert the ways in which a given procedure might be changed to yield the most reasonable outcome. In case of using multiple methodology during preparation of forecast, the results obtained by each method and its underlying factor of judgment must be accounted.