Changing the BO Filter Criteria
The BO Filter Criteria form lists all the filter criteria that can be used to calculate breakouts. A feature is only classified as a breakout if it meets all the requirements set as filter parameters.
If you have selected 4 arms caliper type on the Input Definition form, the 4 arms tab on the BO Filter Criteria form is active and the 6 arms tab is disabled. If you selected 6 arms caliper type on the Input Definition form, the 6 arms tab on the BO Filter Criteria is active and the 4 arms tab is disabled.
Not all the parameters are applied by default, see the table below for an overview.
| Default values for the Breakout filter parameters | |
|---|---|
| 4 Arm Caliper Data | 6 Arm Caliper Data |
| Elongation = 1 in | Shape Coefficient = 5% ** |
| Tool Rotation = 5m / 45 deg | Elongation = 1 in * |
| Washouts = 0.5 in | Asymmetry = 50% *** |
| Key Seats = 0.25 in | Washouts = 0.5 in |
| High/Low Side = 5 deg / 10 deg * | Hihg/Low Side = 5 deg / 10 deg * |
| * filter parameter not applied by default | |
| ** The assumption is that the breakout depth is greater than 5% of the minimum well diameter. Avoiding the absolute value discards the breakouts detected by two calipers. | |
| *** This means that at least one half of the total elongation is symmetrical to the borehole axis. | |
It is possible to change the parameters that are used for the calculations. You can select or deselect parameters by using the relevant checkboxes. To change the value of a parameter, it must be selected as a filter criteria. Whenever you make changes in the selection of parameters, or a change in the values of any of the selected parameters, you must recalculate the Caliper Analysis.
Although not selected by default for six-arm caliper analysis, the Elongation and High/Low side of the hole filter options can be useful in particular cases.
The filter settings for automatic identification of borehole breakouts are not applicable to every case, each filter should be modified to fit individual borehole conditions. For example, when a well is severely damaged, the coefficient of shape can be more restrictive (e.g., | SC | > 10%). When a breakout coexists with a keyseat at the same depth, the coefficient of asymmetry may need to be less restrictive (e.g., Acn < 70%). If the direction of maximum elongation in a washed-out well corresponds to the direction of breakouts in the same well, it is possible that an apparent washout is really a very wide breakout that embraces the entire well circumference. In this case, the washout filter may need to be less restrictive (Cmin – Bit Size < 1 inch, for example). In each case, the result of automatic breakout processing should be compared with the projection of the pads in cross section from the corresponding depth interval.
The filter parameters on the form are split into inclusion criteria and exclusion criteria. For an overview of the nomenclature on the form, see Caliper Nomenclature.
4 arms caliper filter parameters
Inclusion criteria
When one of the following two parameters is selected, a feature is identified as a breakout only if it meets the criteria as specified. If both parameters are selected, both criteria must be met for a feature to be identified as a breakout.
Elongation If selected, the difference between the maximum and minimum calipers must be more than the specified value (length) to be identified as elongated borehole.
Tool Rotation If selected, an elongation is considered a breakout if the caliper tool rotates less than the specified amount over the specified depth range.
Exclusion criteria
When one of the following three parameters is selected, a feature is identified as a breakout only if it does not meet the criteria as specified.
Washouts If selected, a feature is not considered a breakout when the difference between the minimum caliper and the bit size is greater than the specified value. The feature is considered a washout.
Key Seats If selected, a feature is not considered a breakout when the difference between the bit size and the minimum calipers is greater than the specified value. The feature is considered a key seat.
High/Low Side of the Hole If selected, a feature is not considered a breakout if the well deviates more than the specified angle (0° to 90°), and the hole azimuth is less than the specified value away from the elongation direction (or the elongation direction + 180°). The feature is considered a key seat.
6 arms caliper filter parameters
Inclusion criteria
When one of the following two parameters is selected, a feature is identified as a breakout only if it meets the criteria as specified. If both parameters are selected, both criteria must be met for a feature to be identified as a breakout.
Shape Coefficient If selected, the shape coefficient or its absolute value must be greater than the specified value to be identified as elongated borehole.
Elongations If selected, the difference between the maximum and minimum calipers must be more than the specified value (length) to be identified as elongated borehole..
Exclusion criteria
When one of the following three parameters is selected, a feature is identified as a breakout only if it does not meet the criteria as specified.
Asymmetry If selected, a feature is not considered a breakout if the normalized coefficient of asymmetry is greater than the specified value. The feature is considered a likely keyseat.
Washouts If selected, a feature is not considered a breakout when the difference between the minimum caliper and the bit size is greater than the specified value. The feature is considered a washout.
High/Low Side of the Hole If selected, a feature is not considered a breakout if the well deviates more than the specified angle (0° to 90°), and the hole azimuth is less than the specified value away from the elongation direction (or the elongation direction + 180°). The feature is considered a key seat.
Once you are done updating the settings on the form, click OK to close the form and if you have not done so yet, recalculate the Caliper Analysis.