Page 201 - Drilling Technology in Nontechnical Language

192 Drilling Technology in Nontechnical Language Second Edition

and this will give an inclination error in the reading; sag can, however,
be calculated.

Multiple wells from a single location

Frequently, several wells are drilled from a single surface installation.
This might be a platform offshore, or a small area on land. Having wells
close together at the surface provides better project economics, as all the
production equipment can be located together.

Once the first well is drilled, the next well may have a risk of colliding

with the first well. As subsequent wells are drilled, collision risk increases.

One way to visualize this is with a spider plot (fig. 8–10). The grey circles
show the eight surface locations of these wells, and each empty circle
shows a survey position. This is a view looking from above, as if the wells
could be seen below the surface.

Fig. 8–10. Spider plot showing many wells from one location

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