Colleagues,
I intend to run some test DHEM and DHMMR surveys over a deposit which
contain several different types of sulphide mineralisation. To assist the
interpretation, we want the intrinsic conductivities of the ores and host
rocks for the EM surveys and the intrinsic resistivities for the MMR (these
not always being the inverse of each other in a complex earth). Thus we
intend to do some conductivity and resistivity logging. Ground conditions
are poor and the holes will need to be cased. For the resistivity logs, the
casing will need to be slotted.
I have the following questions/concerns:
1. Can we obtain 'reasonable' resistivities through slotted casing? (I
appreciate that the slots should overlap, but fear that the casing may add
a 'DC shift' to the data.)
2. What is the optimal slotting pattern? (For downhole IP, I have used
slots 15cm-20cm [6"-8"] long with ~5cm [2"] overlap which spiral along the
casing with a 120 degree separation between slots. This has produced useful
results, but they may not be optimal.)
3. Any suggestions on effective ways to cut the slots?
thanks,
jb
John Bishop
Mitre Geophysics Pty Ltd
P.O. Box 974, Sandy Bay, 7006, Australia
ph: +613 6225 4556 fax: +613 6225 4553
email [EMAIL PROTECTED]
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