True
Stratigraphic
Thickness
and
True
Vertical
Thickness
R.
M.
Bateman
Date
9/5/78
Amoco
International
Oil
Company
Chicago
sww
Illinois
]gyp
Code
60601
Program
Title
Nemo
Address
Coy
PmgramDescdpeogEgueflone,Vonegles,eM.
The
program
solves
the
problem
of
finding
the
True
StraLlgraphic
Thickness
and
the
True
Vertical
Thickness
of
a
formation
from
a
knowledge
of
the
well
deviation
and
azimuth,
the
bed
dip
and
azimuth
and
the
measured
bed
thickness.
If
well
is
deviated
a
°
from
vertical
in
direction
HAZ
and
bed
dips
0
°
from
horizontal
In
direction
DAZ
then
if
well
enters
bed
at
A
and
exits
at
a
the
following
relations
hold
Measured
Thickness
(MT)

AB
True
Vertical
Depth
Difference
between
A
and
B

MT
Cosa
True
Stratigraphic
Thickness
MT(Cos
a
•
Cos
$

Sin
a
•
Sint)
•
Cos
ULU

au>)
True
Vertical
Thickness
.
TST/Cos
0
Operating
Limns
and
Mulling*
Assumptions
made
are
that
the
bed
is
of
uniform
thickness
with
upper
and
lower
boundaries
parallel.
If
(04
)
is
greater
than
90
°
the
well
enters
the
bed
from
the
underside.
In
that
case
answers
for
TST
and
TVT
are
given
as
negative
numbers.
Program
111eseriplitm
_
DO
NOT
USE
THIS
SPACE
The
computed
results
will
display:
a.
The
measured
thickness
b.
The
True
Vertical
Depth
Difference
between
the
top
and
the
bottom
of
the
bed
c.
The
True
Stratigraphic
Thickness
d.
The
True
Vertical
Thickness
A
typical
case
is
illustrated
for
the
user
to
check
his
transposition
of
the
algorithms
to
his
particular
model
of
PPC.
User
Insiruelions
I
Wneliatiin
]Bed
Well
Bed
Azimuth Azimuth
+
STEP
aystaucnous
INPUT
DATA,UNITS
KEYS
OUTPUT
OATITUNITS
I
2
3
A
.
5
6
7
Measured
depth
of
formation
top
Measured
depth
of
formation
bottom
Well
deviation
from
vertical.
Well
azimuth
in
degrees
from
North
Feet
Feet
°
A
I
B
I
entail
enteil
D
E
A
B
entee
C
E
C
I
entee.
D
I I
Bed
dip,
from
horizontal
°
Top
Bed
in
deszoee
from
Worth
_azimuth
°
Hit
E
for_printer
diepley,
(NN97)
or
sequential
d415).ey
(HV67)
Bottom
MT
TVD
Diff
TST
TVT
Worked
Example
1
2
3
4
5
6
7
Well
Deviation
30
.
to
128
0
Azimuth
Bed
Dip
25
Co
45
Azimuth
Top
of
bed
5642'
Bottom
of
bed
5878'
5642
5878
30
128
2
_
25
45
Hit
E
5642.00
5878.00
236.00
204.58
179.16
197.68
OPERATING
LIMITS
It
is
assumed
that
the
true
stratigraphic
thickness
is
the
same
at
the
point
the
well
enters
the
bed
as
it
is
when
the
well
leaves
the
bed.
It
is
also
assumed
that
the
well
deviation
and
azimuth
do
not
change
as
the
well
crosses
the
bed.
If
the
bed
is
highly
dipping,
it
is
possible
that
the
well
will
in
fact
enter
the
bed
from
the
"bottom"
side
and
exit
from
the
"top"
side.
If
this
occurs,
the
answers
for
TST
and
TVT
will
appear
as
negative
numbers.
/Top
I
Bottom
Bottom
MT
Diff
TOT
TVT
CONCLUSION
WORKED
EXAMPLE
Well
is
deviated
30°
to
128°
azimuth.
Bed
is
dipping
25°
to
45°
azimuth.
Top
of
the
bed
is
measured
on
the
log
at
5,642
feet.
Bottom
is
found
at
5,878.
The
PPC
once
again
provides
a
simple
and
practical
solution
to
a
complex
problem
which
to
date
has
only
been
soluble
via
some
rather
questionable
nomograms.
While
the
program
discussed
is
illustrated
by
use
of
an
HP
calculator,
the
authors
find
no
reason
why
other
similar
makes
and
models
of
PPC
should
not
be
used
provided
the
trigonometric
functions
behave
in
the
same
way
that
the
HP
functions
do
for
limiting
cases
such
as
negative
angles.
The
computed
results
show:
REFERENCES
Measured
thickness
=
236.00'
1.
Bateman,
R.
M.,
and
Konen,
C.
E.:
"The
Log
Analyst
and
the
TVD
difference
=
204.38'
Programmable
Pocket
Calculator
—
Part
III
—
Dipmeter
TST
=
179.16'
Computation",
The
Log
Analyst,
Volume
XIX,
No.
1,
January
TVT
=
197.68'
February,
1978.
6
MARCHAPRIL,
1979