F.A.S.T. VirtuWell™ is a combination of useful tools which Fekete's Production Optimization Group has developed for modeling wellbores. It allows you to do the required calculations quickly and easily, and to perform sensitivities to various operating conditions.
More often than not, it is due to missing information. If a cell is left blank, it does not necessarily indicate to the program that the cell is equal to zero. Try to enter in zero for relevant required data, and the graph should plot. For example, in the pipe page, if you enter in the following into the table:
This data will not output a graph because oil rate is one of its necessary inputs. Entering a zero in the Oil Rate column results in a calculation of a value for outlet pressure and the output of the relevant graph, as demonstrated in the table below.
With 0 for a flow rate of oil, gas and/or water, the static gradient will be calculated.
However, if two of the fluids have been selected, no pressure will be calculated.
The reason is that in order to calculate any pressures for a multiphase system, the proportions of all the phases must be known. With no flow occurring, there is no way to know what fluids are in the wellbore, leading to a non-unique set of solutions.
Another reason that calculations may not be performed is that there is invalid or missing data. The cell where there is a problem will be highlighted in red.
The difference between the two depths deals with if you are doing a measurement of the pathway taken by the wellbore (MD) or the direct straight line distance to a certain point (TVD). The following picture shows a wellbore with corresponding MD and TVD values.
In the "Gas AOF/TPC" page, select "AOF Type: Reservoir".
Then proceed to enter in reservoir information into the provided table. Finally click on the "Transfer Reservoir AOF" button. This transfers the AOF data to the "Multiple AOF" table.
Repeat the previous steps changing the required parameters for each reservoir. Each time the transfer the transfer button is pressed, the new data is inserted at the top of the table, moving the existing data down. The effect of changing reservoir parameters can then be observed from the "Multiple AOF" plot.
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