Identifying and quantifying sources of uncertainty

Field appraisal Is most commonly targeted at reducing the range of uncertainty in the volumes of hydrocarbons in place, where the hydrocarbons are, and the prediction of the performance of the reservoir during production. 

The parameters which are included in the estimation of STOMP, GIIP and ultimate recovery, and the controlling factors are shown in the following table. 

It should be noted that the recovery factor for a reservoir is highly dependenf upon the development plan, and that initial conditions alone cannot be used to determine this parameter. 

In determining an estimate of reserves for an accumulation, all of the above parameters will be used. When constructing an expectation curve for STOIIP, GIIP, or ultimate recovery, a range of values for each input parameter should be used, as discussed in Section 6.2. In determining an appraisal plan, it is necessary to determine which of the parameters contributes most to the uncertainty in STOIIP, GIIP, or UR. 

Take an example of estimating gross rock volume, based on seismic data and the results of two wells in a structure (Fig. 7.2). The following cross-section has been generated, and a base case GRV has been calculated. 

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