Reservoir and Economic-Uncertainties Assessment for Recovery-Strategy Selection Using Stochastic Decision Trees
- Philippe Vincent (Neptune Energy) | Thomas Schaaf (Storengy)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- November 2019
- Document Type
- Journal Paper
- 1,575 - 1,592
- 2019.Society of Petroleum Engineers
- decision making process, uncertainty management, joint technical and economic evaluation, recovery strategy, risk analysis
- 12 in the last 30 days
- 151 since 2007
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The field-development phase before investment approval is characterized by relatively large uncertainties at the time important decisions have to be made. For instance, it is crucial to select an appropriate recovery strategy (depletion or injection) to obtain optimal hydrocarbon cumulative production while ensuring good profitability of the project. Evaluation of the reservoir along with economic uncertainties and quantification of their impact are needed before the field-development concept selection.
In this paper we describe how to stochastically assess reservoir and economic uncertainties and the screening process used to select the best recovery strategy. Our chosen methodology is a combination of uncertainty studies, including continuous, discrete, and controllable parameters. The different screened scenarios are combined in a stochastic decision tree, built up through decision and chance nodes, to establish a distribution of recoverable volumes and rank the recovery strategies given a chosen criterion. A second uncertainty study is performed by adding economic uncertainties to the initial set of reservoir uncertain parameters. Eventually, a new decision tree is established, and scenarios are ranked using economic criteria.
We present an application of this methodology to an oil field from the Norwegian continental shelf and how recovery strategies are ranked in this paper. The described methodology has exhibited the risks and uncertainties carried by the project, as it was possible to rank the different solutions on the basis of the dispersion of the recoverable volumes distribution and/or on the net present value (NPV). In the context of a marginal- or large-capital-expenditure (CAPEX) project, a robust P90 case is required, and this might, therefore, influence the choice of the recovery strategy. For instance, a scenario yielding the largest hydrocarbon volume might not be selected because it requires too many wells and/or too large an investment if one of these criteria is defined as the most important. In addition, the combination of uncertainty studies enabled a full economic evaluation covering the entire recoverable-volumes distribution whereas in many projects, economic evaluation is focused on the P90, mean, and P10 scenarios.
The two-step integrated approach allows a decision to be made while taking into account both reservoir and economic aspects. A combined stochastic approach to the reservoir and economic uncertainties avoids a biased decision. All cases are stochastically covered and screened using a systematic and unified methodology that gives the same weight to each scenario.
|File Size||1 MB||Number of Pages||18|
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