Page 210 - Open-Hole Log Analysis and Formation Evaluation

80
the
the
the
may
time
In
With
3600
1800
To
1200
900
short
when
order
count
might
made.
lower
speed
during
speeds
speeds
two
be
-
inactive
related.
to
Logging
counted
the
constant,
obtained
obtained
be
adequate
However,
the
ft/min
very
speed
in
constants,
formation
the
rate
and
electronics
tool
at
produces
and
at
for
in
that
if
The
a
runs.
period
a
at
the
less
a
constant
Gamma
Speed.
Cin feet/bour)
was
and
the
illustrate
slow
the
the
differences
the
average
selected
of
short
count
figure
the
time
logging
whose
30
long
known
more
will
rays
2
1
formations
the
than
4
in
3
the
CONSTANTS
poor
averaging
same
type.and
time
out
rays
efficiency
(in
time
equivalent
time
be
following
count
by
rate,
10.6:
can
improve
logging
100
Time
of
time,
the
with
expense
expense
per
to
time
size
is
both
ft/min
period,
of the
activity
be
or
a
expense
the
according
On
one
rules
(e.g.,
‘increase
interval
accurate
estimate
is
of
to
hour
or
the
and
1
of
speeds
seconds)
gamma
the
environment,
obsolete
of good
more
an
constants,
Constant
the
resulting
the
is
statistical
known
used
constant
two
the
longer
(100
statistics
counted
the
ray
measured
in
being
1
(900
intrinsically
of absolute
variations.
to
bed
first.
the
than
interdependence
a
thumb
the
for
for
detector
second)
except
time
gamma
and
real
a
low
counter
orders
of
1
shown
are
ft/hr
60
run,
in
number
100.
somewhat
it
more
measurement
=
will
time
rays
second.
very
bed
average
with
detectors
inordinately
accuracy.
radioactivity
count
of
the
the
measured.
1.5
gamma
resolution.
At
Thus,
can
On
constant
the
logged
logging
second,
better
have
seconds
background
and
a
long
short
generally
2
level
ray
variations, various
accurate
at
be
ft/s)
encloses.
X
cases
the
constant
the
With
bed
Thus,
or
some
logging
of magnitude,
units,
their
absolute
time
of
count
speed
60
and
resolution
count rates
two
time
moved
count
choice
the
interval
high
the
they
actual
estimate
seconds.
future
and
rate.
counted
knowledge
second
long
speed
measured.
use
past
required
recognized:
rates.
can
must
period.
activity
resolution
for
between
run,
minutes),
is
different
was
ofa
time,
time
depending
Note
associated
is
a
of the
very, very
The
constants
the
be
for
be
are-inter-
time
logging
that,
of time;
In
count
logging

1 rate, of resulting Ideal Response X gamma 360,000 will emit a period of hours, the source tays each second over emits an average of 100 gamma ifa source of gamma rays example, For are subject to. statistical variations. All radioactive processes TIME and __on the of API is increase This over a 196 ll. O
2 Effect of detector size
3. "Zero length detector", slow logging speed
4 “Zero length detector", fast logging speed
197
Deep Induction
Short Normal
Gamma Ray
formation

Run | 80 Feet/ Minute
Time Constant | sec

Gamma Ray
|
30 Feet/ Minute
3
nN
<€
oe
Time Constant 2 sec

“FIGURE 10.6 Effects of Logging Speed and Time Constant on Gamma Ray Log.