What is the best way to crossplot the points in a series of channel structures?
The primary method of selecting points for crossplotting is by using polygons. This approach is favoured because of its speed and efficiency.
- To best utilise this approach with channel structures, draw an arbline down the center (or most significant section) of your channel (see Creating an Arbline).
- In Arbline View, select the new line and draw a polygon highlighting the channel structure (see Picking Polygon in Arbline View).
- Create additional arblines and polygons for each of your channel structures.
Note: The crossplots will permit overlapping polygons, allowing you to have polygons such as "Channel 1", "Channel 1 High Porosity", etc.
- In the crossplot window, select and deselect the polygons to highlight the points inside each channel.
Crossplot points in specific channel
To crossplot all the points in a specific channel, you will need to use a different approach. By using a Volume Sculpting process on the input volumes, you can constrain the points available for the crossplot (see Volume Sculpting).
- Draw a polygon that closely follows the edge of the channel structure in Map View.
- Create a Volume Sculpting process: "P-Impedance - Channel 1"
- Volume: P-Impedance
- Top horizon: Channel top event
- Base horizon: Channel base event (Or channel top + estimated channel thickness)
- Constrain to Area: Channel edge polygon
- Use the result of this process as one of the inputs to the crossplot.
For the more complex, multiple channel case, repeat the procedure for each channel, resulting in one impedance volume for each channel, e.g. "P-Imp Channel 1", "P-Imp Channel 2". Then try the following:
- Configure the crossplot to use the original (unsculpted) P-Impedance and Vp/Vs.
- Select a probe that includes all the channels.
- Select the crossplot Plot Type as Point by Point.
- For the Colour Data Set, select the output from a volume maths process defined as:
- Process: Volume Maths, "Channel Identifier"
- Symbol: "C1" Volume: "P-Imp Channel 1"
- Symbol: "C2" Volume: "P-Imp Channel 2"
- Formula: if(!isNaN(C1),1,if(!isNaN(C2),2,0))
This example can be extended to any number of channels. The performance will be slower than the polygon/section approaches described earlier.