The traditional approach to probabilistic resources assessment is based on separate assessment of each potential reservoir with subsequent aggregation of these separate estimates. This approach does not allow to incorporate the mutual dependence between confirmation of different reservoirs which is determined by the fact that genetically related exploration objects share some of the geologic factors. Depending on which aggregation method is used, either over- or underestimation of total resources takes place, the magnitude of this error can be significant. This shortcoming can become critical when carrying out geological and economic assessment of a set of small exploration objects separate development of which is uneconomic.
In this paper a method of joint probabilistic assessment of the entire set of exploration objects is presented, which allows to avoid aggregation and the related bias of the result. The practical application of this method as applied to the exploration assets of Bashneft is reviewed. The paper also addresses the existence of correlation between any amounts of the resources on the one hand and some certain set of reservoirs which is the most probable one for this particular amount, on the other. A recommendation is given to use this correlation when forming variants of production and surface facilities. This allows dismissing the intuitive approaches to formation of sets of ‘confirmed’ reservoirs for scenario calculations, automatize the process and improve the quality of the economic assessment of exploration blocks (or separate prospects with multiple potentially productive reservoirs). This method has also been widely applied in the Bashneft PJSOC.
References
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