Predicting well production rate with time plays a very vital role to having an effective reservoir management, guiding investors and making crucial and important decision in any oil and gas industry. Forecasting production rate could be done by either deterministic or probabilistic approach with the latter being more reliable in the face of uncertainty. The Arp’s Decline curve model which is mostly used in predicting reservoir production rate with time has three models: Hyperbolic, Harmonic and Exponential models. This study focuses on the use of exponential model with the aid of a simulator to history match and predicts a filtered well production data. The result from this study shows that with an assumption of a triangular probability distribution, the Arp’s exponential decline model is associated with 45% risk factor as a predicting tool. Finally, in order to reduce this inherent uncertainty level, the initial production rate (IP) should be double checked before use.