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Subject: Help - Downhole communication

Date: 06/15/00 at 3:03 AM
Posted by: Colin Hetterley
E-mail: colin.hetterley@baesystems.com
Message Posted:

I am undertaking a Systems Engineering course, and have been given a
problem to solve:

I have to send a half duplex signal along a vertical drill string (upto a maximum of 10 km
in length). Cabling is not allowed, and the 'inhernet properties' of the tube must be used.
The tube is formed by 20m length sections of mild steel which have an internal dia of 12 cm
and an external dia of 16 cm.
Sections are screwed together. The tube will be filled with "mud" (liquid of varying viscosity
used to lubricate the drill bit heads).
The tube is down a hole of approximately 25 cm dia, which will be filled with "mud" also.
The signal to be transmitted is a digital word of about 100 bits.

I having been looking in to this problem, and am now thinking that ULF, VLF radio
transmission is going to be a solution to investigate. However, I can not seem to find much
helpful information. I will need to justify my proposed soultion, so will need to know power
required to transmit a signal, attenuation effects etc.

Any help would be greatly appreciated.

TIA
Colin Hetterley


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