The program includes the following appraisal models, which differ in the amount of input and sophistication.
Calibrated. (Full Material Balance or "FMB")
This is the most complex model and involves the total of the petroleum system logic. The end result reflects the uncertainty due to the input variables and the model variance.
Deterministic.Does use the same model as the calibrated one, but reproduces only the variance that is due to the input variables.
This option assumes that hydrocarbon charge is present, but asks to what extent a trap is filled.
Here the hydrocarbon charge is also assumed to be present, but the amount in the trap is estimated by estimating the depths of the HC/Water contact, which might be an Oil/Water Contact or a Gas/Water Contact. In addition the program asks for the percentage of gas in the vertical HC column. If > 0 the a gascap is modeled.
This model allows the user to derive estimates of HC charge derived by other programs to be used in Gaeapas, instead of the Calibrated option.
The calibrated model includes all the phases of the program flow, while the others use a selection of the total flow. The most complete is shown below:
The first sheet of input asks the user to decide on the various options, described more in detail elsewhere. This part is evaluated for inconsistencies. If there are any errors, a list will be shown. If not, the next input sheets become accessable.
The program validates the input beyond the options. If any errors in relation to the options chosen, a list of errors appears. If correct, the program calculates the results. The program uses various statistical procedures to estimate and adjust probabilities by using Bayes rule and Monte Carlo modelling with standard 10,000 cycles. Apart from HC charge calibration, the program uses worldwide data as prior distributions and regressions, making the program similar to the so-called "Expert Systems".These worldwide "prior" data involve API gravity, Porosity, Top Seal, Temperature Gradient, PVT correlations, Recovery Efficiency, etc.
After a successful run, a form with output results is shown. It has four tabs, of which the first contains the estimates of the recoverable hydrocarbons.
The user decides if he whishes to export the results to a spreadsheet, or use the printing facility of Gaea50. The data in a table can be collected and put on the Clipboard.