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20.15 Using Ladder Plots
The ladder plot is simply a graph of the separation to target wells against the measured depth of the planned well. They are very useful for determining which well to watch for at which depth.
The y-axis can either be the true centre to centre distance or more usefully, the inter-boundary distance of the zones of uncertainty to the object wells.
Be sure to understand the value on the y axis. The most common will be a simple centre to centre separation but ladder plots are more useful if they include uncertainty.
Figure 102: Basic ladder plot.
In this example the uncertainty is shown as a shaded area around the wellbores.
Figure 103: Ladder plot with uncertainty added.
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