Slanted verticals

The SONRIS data indicates a well surface location and a bottom hole coordinate. The interactive map shows a straight line between the two, sort of indicating that the well bore is vertical, then goes horizontal from there.

It's recently dawned on me that this isn't necessarily true. A number of the wells have a perforation point that's offset from the surface location. i.e. the line drawn on the SONRIS map is not necessarily the correct location and orientation of the lateral.

A lot of the bores on SONRIS have strange looking angles on the lines drawn on the map, but the actual lateral could still run directly N-S.

I did a little geometry thinking and realize that, since the vertical depth of these wells is 10,000 feet, you can do a considerable offset between the surface location and penetration point and not increase the length of the vertical bore that much.

For instance, on a 10,000' vertical, offsetting the surface location 5000' from the perforation point only adds 11% to the length of the vertical bore.

I know some wells around lakes have slanted verticals. Are they using slanted verticals for lesser obstructions? It would seem that you have considerable freedom in choosing the surface location even if you want a particular location for the perforation point.

How difficult is it to drill a slanted vertical? Is it difficult to increase the slant past a certain angle?

I've seen quite a few applications that have slightly slanted verticals. Have any of you seen many wells that have more significant slants?

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Permalink Reply by John Avatar on October 6, 2009 at 7:49
Small anomalies, such as the Yegua sands in Jefferson County, are often overshadowed by overhanging faults and directional drilling allows the operator to come into the reservoir from an angle and complete the well structurally higher than would be possible with a well drilled vertical.
Permalink Reply by king john on October 7, 2009 at 4:29
thanks john. i knew there had to be a reason. that makes sense to me. what is a small anomalie ? the Yegua sands ?
kj
Permalink Reply by Missy on October 9, 2009 at 15:53
Electro, What can you tell me about a well pad that may possibly have two rigs on it? Does that mean one rig AFTER the other, or two rigs side by side? Should the surface use/release state this? Why would this be done? I am looking at a surface use/release and it seems the O&G is most interested in my giving them a well bore easement? Or is that standard on these things?The landman mentioned the double rig thing earlier,but then says he really doesnt know what the plans are.

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