ABSTRACT: Reserve estimation entails the interpretation of geologic and quantitative calculation of the petro-physical data, PVT (Pressure, Volume, Temperature) and production histories of the reservoir to estimate the reserve. Reserve estimation using Decline Curve Analysis attempts to answer the question of reserve evaluation based on performance trend. Various techniques have been developed for computing reserve estimates. This study therefore focused on  Decline Curve Analysis using two fields as a case study. These are MN1 Sand Ofron field, and the Eleke (E1) field. Particular emphasis was laid on the determination of decline rate from the graph of production rate versus cumulative production which was also used to obtain the maximum produced oil and consequently the stock tank oil initially in place (STOIIP) when the decline curve analysis was used.