SPE-176253-MS How Powerful Material Balance Analysis Method for Predicting Gas Flooding Performance H. R. Sutoyo, T. Ariadji, P. A. Aziz, and M. L. Mahendra, Bandung Inst. of Tech Copyright 2015, Society of Petroleum Engineers This paper was prepared for presentation at the SPE/IATMI Asia Pacific Oil & Gas Conference and Exhibition held in Nusa Dua, Bali, Indonesia, 20 –22 October 2015. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright. Abstract Gas Flooding is one of the reservoir production management methods which commonly used in the petroleum industry in order to improve oil recoveries and maintaining reservoir pressure. This study discusses two methods in analyzing gas flooding, i.e., material balance analysis and reservoir simulation methods. The objective is to examine the ability and advantages of material balance method with respect to reservoir simulation. The studied field has three productive zones which consist of two light oil zones and one dry gas zone. Gas flooding scenario was conducted in one light oil reservoir and was modeled using both material balance and reservoir simulation methods to predict reservoir performance for about 14 years and the results were compared to investigate the effect of gas injection. The material balance method employs production, PVT, pressure data, and averaged properties of geological model for a single tank model. On the other hand, the reservoir simulation method uses a compositional model to investigate in detail the effect of injected gas to reservoir fluid behavior and the oil recovery The examinations indicate that the material balance analysis method shows the advantages of a requiring much less data, but could give reasonably accurate results. Furthermore, the application of material balance analysis in gas flooding could be used for gas injection rate optimization for a very short time manner and could assist for further development of reservoir simulation. For future development, material balance analysis could be used to analyze gas flooding scenario to save time and cost rather than reservoir simulation which takes longer time. Introduction Nowadays, the petroleum world is commonly reaching the mature field era where the peak of oil production is already passed. It is very important to have a good reservoir production management to improve oil recovery. Through lean gas injection as an alternative for gas flooding mechanism. Lean gas sources can come from produced gas from reservoir and will be injected into reservoir. This methods is called gas cycling. A good reservoir management is needed to optimize the oil recovered while cycling the produced gas. As we need to optimize the performance of this cycling, there will be several methods to predict its performance. Prediction methods that will be analyzed in this study is material balance analysis and reservoir simulation method. Reservoir simulation as we know will spend a lot of cost and time while predicting gas cycling