A method for calculating the probability distribution for oil in place and recoverable reserve is presented. A stochastic reservoir model describing spatial variability is specified and conditioned on available observations. A large set of possible reservoirs are generated from the specified model by stochastic simulation. This set of simulated reservoirs displays the uncertainty and variability in the stochastic model and they can be further processed to

  • obtain probability distributions for oil in place and recoverable reserve,

  • compare contributions to the uncertainty,

  • constructing maps showing the uncertainty,

  • evaluate reduction in uncertainty when drilling new wells,

  • study the uncertainty in the lateral extension of the reservoir.

The first part of the paper outlines the stochastic models for the geometry and the petrophysics. The last part shows several examples of results from case-studies. Emphasis is made on graphical presentations of maps and probability distributions.

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