Assisted Procedures for Definition of Production Strategy and Economic Evaluation Using Proxy Models

Abstract

Abstract New techniques for reservoir development are essential for dealing with the complexities of geological models. In this sense, numerical simulation is the tool used to define the quality of a production strategy. However, the process to define variables such as well numbers, completion layer, open timeline and operational conditions demand several simulations due to the high time consumption and computational effort. Sub-optimal results can be obtained from manual processes. Automatic processes can mitigate this problem but the computational effort is increased as a result of the number of simulations generated in the process. In order to minimize this problem, this paper proposes an assisted procedure for its automatic part using proxy models to accelerate the process. Furthermore, due to the reduced time to evaluate options, it allows a better evaluation of the solution space using better optimization techniques. Proxies have been used in important applications such as risk analysis and history matching but the use for definition of production strategy is not common. The proposed methodology involves the following components: statistical methods, experimental planning to generate the response surface methodology for the generation of proxies and consistency checking. The results show that it is possible to apply proxy models for this type of problem and they can identify the best production strategies, reducing the computational effort during the process. The suggested procedure is to use proxies in the automatic part of the assisted procedure used in the optimization process. The main contribution of this work was the demonstration that proxy models can be used for the definition of production strategies, bringing an additional option to the decision analysis process linked with petroleum field development. Introduction The main activity in reservoir engineering is the planning of strategies and economic evaluation for the development and management of petroleum fields. The numerical simulation is useful in a definition of a production strategy during the appraisal and development phases, especially in offshore heavy oil fields due to the low economic return, limited flexibility and importance of reservoir modeling. The flexibility is limited because of the requirements to design the production facilities based on the low amount of information. The use of reservoir simulation has several constraints, such as: high number of blocks, variables and attributes which are time-consuming for the simulation and processes analysis, mainly in complex fields. Besides the high number of possibilities in a production strategy definition and the computational time linked with the numerical simulation, the process can be slow, forcing simplifications in the optimization process and consequently, decreasing the probability of finding better solution for the problem. Proxy models can be used as an auxiliary tool to deal with some of these constraints. This technique can simplify models with lower confidence levels in some outputs and an alternative for the numerical simulator in several procedures that do not require a higher precision in the results and a reduced number of simulations. Proxy models have been used in reservoir engineering applications, including uncertainty modeling, sensitivity analysis, history matching (Peng and Gupta, 2003 and Risso, 2007), risk assessment (Risso et al. 2007), performance prediction, upscaling (Schiozer et al., 2008) and development optimization (Venkataraman, 2000). In this study, proxy models have been used in an assisted procedure for production optimization, involving an integration of automatic and manual parts, for a definition of production strategies, bringing an additional option to the decision analysis process linked with petroleum field development. Figure 1 presents the general idea of proxy model application used in this study.