Performing APE in Legacy Models
Subtopics:
Related Topic:
Automatic Parameter Estimation
To perform automatic parameter estimation (APE) in legacy models:
1. Select the model input parameters you want to vary by clicking the Auto checkbox beside each parameter in the Parameters dialog box.
2. Click the start Auto button on the model toolbar to start the auto match. WellTest adjusts the parameters to improve the history match between the simulated and measured pressures.
The APE Status dialog box opens. You can wait for APE to stop after it has met its convergence criteria, or click the Stop button on the APE Status dialog box.
If an acceptable match is not obtained, you should manually adjust the parameters and repeat the APE process, or consider a different reservoir model.
Advanced APE Options
Weighting Points
You may want to weight some data points more heavily than others when performing APE. For example, when analyzing buildup data to get an estimate of average reservoir pressure, it is more important to match the data at the end of the buildup, than the start of the buildup. Similarly, if a wellbore effect is observed, you may want to ignore those points when history matching.
APE tries to minimize the error between the synthetic (model) pressures and the measured pressures. The error terms for weighted points are amplified in the convergence algorithm. In other words, APE tries really hard to converge on weighted points, less hard converging on points without weighting, and ignores deselected points.
The model toolbar contains a number of buttons above the Auto button that are used for weighting points.
- The blue icon (
) is for selecting points - The yellow icon (
) is for weighting points - The white icon (
) is for excluding points
To weight points:
1. Click the yellow icon ().
2. Move the mouse over any plot with measured data, such as the History plot, the Derivative plot, or the Typecurve plot.
The cursor changes to a spray can.
3. Spray the data points you would like to add weighting to by clicking over the measured pressures. Right-clicking changes the weighting of data points back to a normal weight.
Excluding Points
A similar procedure is used to exclude points:
- This icon (
) selects all points. - This icon (
) excludes all points outside the selected flow period, and selects all points within the selected flow period. - This icon (
) icon selects 10 equally spaced points within the selected flow period, and excludes all other points. - This icon (
) weights or unweights the point immediately preceding the selected flow point (e.g., the final flow pressure).
Selecting the APE Method
The APE algorithm may be selected by right-clicking any model plot and selecting APE method from the right-click menu. For details on APE methods, see automatic parameter estimation (APE).
