The quantitative assessment of the risk associated with the economic exploitation of a hydrocarbon field is mandatory to support, in an efficient and comprehensive way, the decision process guiding the development management system of an oil company.
The Full Range Risk Analysis (FRRA) approach developed in Eni E&P Division allows the identification of uncertainties arising from each step of an integrated reservoir study, and the evaluation of their impact on recoverable reserves and on the economic value of a project. This methodology has already been successfully applied in the concept selection and concept definition phases of field development projects. Recently it has been further improved to be employed both in the evaluation stage, of a new discovery, and in the revamping of mature fields with production history.
The Full Range Risk Analysis is aimed at investigating the whole range of possible reservoir development combinations. Its main objectives are:
the support of the sanction of an economic discovery, considering an acceptable and accepted risk;
the estimation of the value of information (VOI) of new data acquirement and the comparison between different appraisal strategies;
the choice of the best development plan taking into account the main impacting reservoir uncertainties (mainly during concept selection phase);
the quantification of downside/upside potential of the reservoir and of residual risk associated to field with production history.
The presented workflow is a valuable tool in assessing the risk associated to a particular development scenario taking into account the entire surface and sub-surface uncertainties and therefore a methodology to support decisions in development projects.
The FRRA methodology is fully based on Montecarlo approach and massive simulations of 3D reservoir models.
The current paper describes in detail the standard FRRA workflow along with the latest developments of the methodology, starting from the uncertainty definition phase up to the frequency distribution of the target variable, i.e. ultimate recovery, plateau length, NPV.