Grapher 3 Used to Create Geophysical Well Logs

Grapher 3 can be used in combination with Didger 2 to obtain information from hard copy geophysical well logs. Geophysical well logs refer to borehole geophysical data obtained during drilling. Many older geophysical well logs are only available on paper, making the use of these logs in applications difficult. A combination of Grapher and Didger allows full control over all of the properties of the log and allows you to create cross sections with multiple logs.

To start, open Didger 2 and either digitize the paper well log using a digitizing tablet or scan the paper log using a scanner and digitize on-screen. Export the data to a Golden Software Data (*.DAT) file. Due to different scales on different axes, it may be necessary to recalibrate the project between curves. After digitizing and exporting all of the traces on the log, open Grapher 3.

In Grapher, choose the Graph | New Graph | Line/Symbol command and specify the data file created in Didger. Accept the default colors and line styles by clicking OK in Line/Symbol Plot 1 dialog. Under the View menu, choose Style | Window w/ Graph Manager. This will allow you to see the various parts of your plot and their properties at the same time. In the Graph Manager, click once on the words "Graph 1" to select the entire graph. To add a second curve, press the Add Plot button. Select the second curve’s data file. Use the same Y axis and a new X axis. This allows the scale for the X variables to be different. In the example plot below, there are four different curves and four different X axes.

A popular request of geophysical well log users is to have data "wrap" around after reaching a maximum value. The data should then restart on the left side of the graph at a higher scale. This is achieved in Grapher 3 by clipping the curve at the X axis maximum. Then, create a new curve from the data set using a second X axis. In the example below, notice that there are two gamma curves and two gamma axes. The second axis starts at 0 and has a much higher maximum than the first axis. This creates a smaller scale copy of the first curve.

Another popular feature is the ability to fill above or below a curve. In the graph below, the far right most curve is filled.

After creating several logs like the one below, create a cross section in Grapher by adding lines between logs that connect the same zones on each of the logs.

This geophysical log of an exploration drill hole shows curve "wrapping" and curve filling to an X Axis value.

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