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Another example is to show the inter-boundary separation only on the y axis. In this example you can see that the blue well uncertainty combined with the planned well uncertainty uses up all the separation.
Figure 104: Ladder plot using inter-boundary separation only.
nhs xmplsyoucns h h mosdng oushz dsh blu wll
h pl nn dw ll’s n
lbw n
2350 ft. to 2450 ft.
CONTENTS
Points to Ponder
You now have an understanding of how collision avoidance is calculated and presented. There are a few key points to remember when dealing with collision risk. 1. Every well we drill has the potential to turn into catastrophe. Just because the probability of collision is low does not mean we can be casual about this. Some collisions just cost money but some cost lives. 2. Make sure that anyone signing off on a dispensation to drill with low separation factor has a full understanding of the implications. I have seen dispensations simply be passed up the management levels to the point at which a person signing off on it is unaware of the risks. 3. Overlapping ellipses does not mean a collision but the probability of collision rises rapidly with proximity. 4. It is possible to reduce the calculated probability of collision by making the ellipses bigger (using cheaper survey tools). This is not the intention, of course, but for this reason beware of using probability calculations on their own. They should be used when evaluating risk having chosen best survey practice.
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