[Proj] Deepwater Horizon. Where is the bottom of the well?

[Karney, Charles]

Here are some questions related to the Deepwater Horizon accident and
the drilling of relief wells for the readers of this list in the oil
industry.

(1) What is the method of determining the position of an instrument 3km
down a well?  Is it seismic, dead reckoning, or what?

(2) What is the typical absolute accuracy of the measured position,
horizontally and vertically (and, if possible, specifically with
reference to the leaking well)?  What is the *relative* accuracy?
(I.e., I can imagine that the absolute accuracy is poor because of the
unknown properties of the intervening rock.  However, it might be
possible to "find" the same position when drilling the relief well if
the same method is used.)

(3) Is the drill bit instrumented to return the position?  How?  Or does
a separate logging package need to be inserted into the well?  At what
frequency would this be done?

I can piece together some of the answers from wikipedia.  However, maybe
I can get more autoritative and more specific answers from this list.

	  --Charles

-- 
Charles Karney <ckarney at sarnoff.com>
Sarnoff Corporation, Princeton, NJ 08543-5300

Tel: +1 609 734 2312
Fax: +1 609 734 2662