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Application of Sector Modeling Approach in a Probabilistic Study of a Giant Reservoir
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, ECMOR XVII, Sep 2020, Volume 2020, p.1 - 13
Abstract
Computational requirements may be one of the most relevant parameters in model-based decision analysis process of giant and complex reservoirs. This may make probabilistic studies very time consuming. One proposal to work around this problem is to divide the reservoir model into sectors and use them as isolated models (Sector Modeling approach) during the decision analysis processes, assuming that isolated sectors representativeness is acceptable. The study case is a benchmark of giant offshore carbonate reservoir, analogous to pre-salt reservoirs in Brazil, which was divided into four sectors, representing four production regions with separate production systems (platforms), each one starting in different periods.
A probabilistic study is performed to evaluate if the behavior of the combination of the Isolated Sectors models (ΣSisolated) is representative of Full Field models (FF). It is also compared the behavior of Sector 1 using its Isolated Sector models (S1) and FF models. This study considers the use of 100 geological scenarios of the UNISIM-III model, combined with scalar uncertainties (relative permeability curves, faults transmissibility, PVT, well productivity/injectivity).
In this paper, it is proposed a methodology to evaluate differences between the two sets of models. Results show good correlation between the behavior of Sector 1 in S1 and FF models. ΣSisolated models are representative of the overall behavior of the FF models, presenting great correlations between both model sets. However, it is a bias indication conservative scenarios since cumulative oil production and Net Present Value (NPV) are lower, compared to the FF models. The average NPV relative difference is 13%, and thirteen models present considerable relative differences between the two sets of models (higher than 20%). A deeper study is performed using the models where highest and lowest NPV relative differences are observer to identify the main reasons of those differences. Also, it is evaluated if the behavior of the ΣSisolated models are representative of the FF models performing risk analysis quantification and selection of representative models.
To apply the Sector Modeling approach in the study case, it is necessary to consider that there is a considerable computational gain when using the Isolated Sector models, but there are models with considerable relative differences. Thus, if one chooses to adopt this methodology in the decision-making process, isolated sector models can be used during optimization processes that require a high number of simulations. Moreover, the decision making should be based on the results observed for the FF models.