logging-while-drilling resistivity-at-the-bit...
TRANSCRIPT
Description
Applications
Schematic illustration of the Resistivity-at-the-Bit tool (LWD-RAB).
Specifications
ODP Logging Services, Lamont-Doherty Earth Observatory, Rt. 9W, Palisades, NY 10964
Logging-While-DrillingResistivity-at-the-Bit Tool
♦ Detection of resistivity heterogeneity viaazimuthal resistivity images
♦ Lithology estimation♦ Instantaneous detection of casing and coring
points♦ Accurate resistivity when mud is salty or
formation resistivity is high♦ Detection of early invasion of borehole fluids
into the formation
The Resistivity-at-the-Bit tool (LWD-RAB) makesazimuthal resistivity and gamma ray measurements whiledrilling. Using an azimuthal positioning system,measurements are acquired around the borehole to create ahigh resolution, 360-degree resistivity image of the drilledhole. The RAB tool may be connected directly behind thebit or further back in the bottom hole assembly. It may berun with other LWD tools such as the ADN, ISONIC orNMR. Typically, the RAB data are stored in memory withinthe tool and retrieved at the end of the bit run. As an option,the data may be transmitted to a surface acquisition systemif a Measurement-While-Drilling (MWD) power pulse toolis run in conjunction with the RAB.
Assembly of the RAB tool aboardthe JOIDES Resolution.
Optional uphole connector
Batteries
Upper sensor
Middle sensor, containing focused ring electrode
Azimuthal gamma ray
Field-replaceable stabilizer
Lower sensor
Float valve boreRbit electrode
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6/2002
A c
ompa
riso
n be
twee
n Lo
ggin
g-W
hile
-Dri
lling
Res
isti
vity
-at-
the-
Bit
(R
AB
) an
d w
irel
ine
log
data
. The
mea
sure
men
ts p
rovi
deel
ectr
ical
imag
es o
f th
e bo
reho
le w
all (
left
sid
e) a
nd lo
g cu
rves
of
elec
tric
al r
esis
tivi
ty a
nd n
atur
al r
adio
acti
vity
(ri
ght
side
). T
heLW
D d
ata
(im
ages
, dee
p-, m
ediu
m-,
and
shal
low
-but
ton
resi
stiv
ity c
urve
s, an
d ga
mm
a ra
y pr
ofile
) sho
w fr
actu
re p
atte
rns,
alte
ratio
ntr
ends
(den
oted
by
arro
ws)
, and
hig
h ga
mm
a ra
y v a
lues
that
may
be
indi
cati
ve o
f hyd
roth
erm
al fl
uid
flow
alo
ng fr
actu
res.
(Fig
ure
cour
tesy
of t
he O
DP
Leg
193
ship
boar
d pa
rty.
)
pipe
dep
th w
irel
ine
HN
GS
Pota
ssiu
m (
wt%
)
HN
GS
Tho
rium
(pp
m)
025
HN
GS
Ura
nium
(pp
m)
NG
T G
amm
a R
ay (
SGR
)
HN
GS
Gam
ma
Ray
(H
SGR
)
030
0(g
API
)
RA
B G
amm
a R
ay (
GR
)
Res
istiv
ity D
eep
(ID
PH)
Res
istiv
ity M
ediu
m (
IMPH
)
0.1
100
(Ωm
)
RA
B R
BD
RA
B R
BM
RA
B R
BS
0
20
40 60 80
10
0
120
140
160
Depth (mbsf)
FM
S C
alip
er (
C1)
FM
S C
alip
er (
C2)
616
(inc
hes)
FM
SS
tati
c N
orm
aliz
atio
nD
ynam
ic N
orm
aliz
atio
n
RA
BS
tati
c N
orm
aliz
atio
nD
ynam
ic N
orm
aliz
atio
n