RockWorks | Borehole Operations | I-Data | Length Composite Weighting (LCW)
Use this program to compute length-weighted averages for a single column of I-Data values, based on data sampled at regular or irregularly-spaced intervals. "Length Composite Weighting" (LCW) refers to a process in which the interval values (e.g. geochemistry) are multiplied by their corresponding thickness. These values are then summed and divided by the sum of their thicknesses. In other words, a number of intervals are averaged in such as way that the thicker intervals are weighted more heavily.
Length Weighted Value = ∑ ( ( v1 * t1 ) ... ( vn * tn ) ) / ∑ ( t1 .. tn )
where v = I-Data value and t = I-Data Interval Thickness
The results of the LCW computations will be stored in a selected I-Data column in the project database.
There are four different methods for computing the LCW:
- For a single stratigraphy unit
- For bench increments defined by elevations
- For depth increments
- For the entire borehole
Feature Level: RockWorks Standard and higher
Menu Options
Step-by-Step Summary
- Input/Output
- Input (I-Data): Click to select the name of the existing I-Data column that contains the measurements to be analyzed.
- Output (I-Data): Click to select the name of the I-Data column in which the computations are to be stored. Any existing data will be overwritten.
! If you need to add a new column to the I-Data table, just click the button to the right.
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- Compositing Method
- Stratigraphic: Choose this option for a single I-Data record to be computed for a designated stratigraphic unit. If a portion of an interval lies partially inside the confining stratigraphy, it is truncated accordingly.
- Stratigraphic Unit: Click to select the name of the formation for which a single I-Data value is to be recorded.
- Elevation (Bench) Increments: I-Data values are computed for each elevation range (bench). If a portion of an interval lies partially inside the bench, it is truncated accordingly. Note: Be sure to specify a starting elevation as opposed to a depth of zero for the "Reference Elevation".
- Reference Elevation: Click here to enter the starting elevation for the computations.
- Elevation Increments: Click here to enter the elevation increments for which the length-weighted values are to be computed.
- Borehole Increments: I-Data values are computed for each depth increment. If a portion of an interval lies partially inside the increment, it is truncated accordingly.
- Depth Increments: Click here to enter the depth increments for which the length-weighted values are to be computed.
- Entire Borehole: A single I-Data value is computed for the entire borehole.
- Apply to...
Use these options to tell the program whether the analysis is to be performed for the current borehole, all enabled holes, or all boreholes in the database.
- Access the RockWorks Borehole Manager program tab.
- Be sure you have a column available in the I-Data table for the length weighted computations which will be recorded there. See Defining I-Data Columns for more information.
- Select the Borehole Operations | I-Data | Length Composite Weighting menu option.
- Establish the desired program settings, as discussed above.
- Click the Continue button to proceed with the computations.
The program will read the contents of the input I-Data track, determine the existing intervals for the selected input column, and compute the length-weighted values using the selected method. The resulting values will be recorded in the selected output I-Data track.
The following diagram illustrates three of these LCW computations. The red bargraph shows the original data sampled at irregular intervals. The blue bargraph shows LCW computations for the baby-blue stratigraphic unit using the "Stratigraphic" method described above. The pink bargraph shows the LCW computations based on the "Elevation" method and a 10-unit sampling interval. Finally, the green bargraph shows the LCW computations based on the "Borehole Increments" (depths) and a 12-unit sampling interval.
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