Assessing Structured Uncertainty in a Mature Fractured Reservoir, Using Combination of Response Surface Method and Reservoir Simulation

Abstract

Abstract In recent years the oil industry has given great importance to reservoir uncertainty analysis, because, it would control the financial uncertainties; however, the development of a method that could model it based on pure reservoir simulation would be complex while the influence of the parameters on reservoir performance is non linear. Therefore, different approaches such as experimental design, response surface methodology and Monte Carlo simulation have been combined with reservoir modeling to simplify addressing the uncertainties. In this work, dynamic model of a fractured mature reservoir has been constructed from a static primary structure. But, this process is totally crucial and challenging, because of limited knowledge of fracture network parameters and characteristic, that could be source of uncertainty in reservoir performance. Therefore, response surface method is used to realize the most influential parameters on pressure drop and recovery factor changes, regarding their practical levels of uncertainties during the development of fractured reservoir model. The present approach is performed to magnify the significant parameters and developing compatible and more realistic proxy equation for forecasting oil recovery from a typical low permeable fractured reservoir. The proxy model allows Monte-Carlo analysis to determine sensitivities and the quantification of the impact of uncertainty on production forecasts. Furthermore, it helps making reliable decision during the reservoir development. Results indicate that the oil recovery is more sensitive to aquifer strength, fracture permeability and block height. However the interaction between other parameters such as matrix size, fracture permeability and aquifer volume, showed a degree of importance during this analysis. Monte-Carlo analysis forecasts wide range of oil recovery for this field development. The result indicates that the range of fracture permeability and aquifer characteristic should be attained carefully to reduce degree of uncertainties in field development strategies.