Abstract

Decision analysis applied to petroleum field development is always strongly related to risk due to uncertainties in the process. An important part of risk evaluation can be accomplished through the evaluation of the impact of uncertainties in the performance of the petroleum fields, yielding higher possibility of success, quantification of possible loses, minimization of sub-optimal development and identification of opportunities.

The objective of the present work is to use the quantification of the impact of uncertainties related to chemical flooding (injection of Alkali-surfactant-polymer) using the concept of Representative Models (RM) integrated with economic uncertainties to improve the production forecast in a Brazilian onshore field with 19 years of production history. The main advantage of this process is to provide a few adjusted models (RM) which are selected based on the integration of objective functions previously defined in the context to represent those uncertainties. These RM are selected to represent all combined models which compose the distribution curve (risk curve) the process. The distribution curve is obtained through the concept of derivative tree technique, combining the possible scenarios using the numerical simulation to predict the reservoir behavior. The numerical simulation is used to give more reliability to the process and to give a detailed analysis for each model in order to provide integration with economic analysis which is used in the risk mitigation. The importance of this process is to provide a detailed analysis of the impact of the chemical injection in the decision making process. An automated tool and the utilization of a defined methodology to quantify the impact of uncertainties are used to speedup the process and to improve the viability of the procedure with a significant reduction of time and effort, yielding greater reliability of the production forecast with the improvement of the decision making process.

Introduction

In the last few years, the petroleum industry has experimented a significant increase in the oil prices. As a consequence, many projects that were not viable in the past have been reviewed and improved oil recovery projects have received more attention.

Risk always associated to a petroleum field, with minor or major intensity, depending on its life phase. An important part of risk evaluation can be accomplished through the evaluation of the impact of uncertainties in the performance of the petroleum fields, yielding high possibility of success, quantification of possible losses, minimization of sub-optimal development and identification of opportunities. There are many uncertainties that can influence the success of an E&P project. One of the challenges in this area is to integrate the effect of these uncertainties and to select the uncertainties that have a significant impact on the decision making process.

To achieve a more reliable decision analysis, different types of uncertainties must be integrated with each other. Depending on the complexity of the problem size of the reservoir and importance of the project, it is not possible to include all uncertain parameters and in order speed up the process, some auxiliary tools and simplifications are necessary. The methodology to quantify the impact of uncertainties used in this paper was development by Costa and Schiozer (2003). Some aspects of this process such as gradual combination to define the critical attributes, reduction of levels of discretization for each attribute were used in this paper to improve the chemical flooding by the concept and selection of representative models (RM).

The objective of this work is to use the quantification of the impact of chemical uncertainties related to chemical flooding (injection of Alkali-surfactant-polymer) to improve the sweep and displacement efficiency in a Brazilian onshore field located at Potiguar Basin with 19 years of production history.

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