SPWLA TWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11,198O

THE HIGH TEMPERATURE WELL LOGGING SYSTEM

FOR GEOTHERMAL WELL

Toshinobu Itoh*
Makoto Miyairi*
Kiyoshi Kimura**

ABSTRACT

High temperature well logging tools for Geothermal well have been de-
veloped by the co-operation with the Japanese Petroleum and Electrical
Companies under the sponsorship of Japanese Government. The tools developed
on this project are as follows:

- Multi-spacing Electrical - SP Log

. Micro-spherical - Caliper Log
* P-S Acoustic - Caliper Log
(Including of Micro-seismograph Log)
- Optical Borehole TV
- Production Logging Tools
(Temperature, Pressure, Continuous Flowmeter and Borehole Sampler)

The environmental conditions of these tools are: temperature as high as

275C and pressure as high as 500 kg/cm2. After the high temperature test of
these tools, these tools were field tested during 1978 and 1979 at the bore-
hole conditions of Depth: lZOOm, BHT: 202"C, BHP: 150kg/cm2. All the tools,
except the optical borehole TV, were successfully operated during long period
tests.

According to the field test, the optical borehole TV, which consists of
a camera tube, could be used only 4 hours at the borehole temperature of
15O"C, and a high temperature TV, which consists of a semiconductor image
sensor, is now under the development. The final temperature tarqet of this
TV camera is 4 hours at boreholk temperatures as high as 250C. -

INTRODUCTION

Table 1 is a list of fundamental logging tools for the formation eva lua-
tion of geothermal wells, and Table 2 is a list of environmental research
targets and period ical schedule of the tools to be developed.

* Japan Petroleum Exploration Co., Ltd.

** Teikoku Oil Co., Ltd.

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SPWLA TWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-l 1,198O

Table 1. Well Logging for Geothermal Reservoir Evaluation.

PARAMETERS LOGGING ITEMS

a) Formation Depth and * Multi-spacing Electrical Log

Thickness * SP Log
Induction Log
Dual Later0 Log
Gamma-Ray Log

b) Fracture * Sonic Log (P and S Waves)

(Location, Dip and Strike) * Micro-seismogram Log
Multi-Arm Micro Caliper
Sonic Borehole Televiewer
Dipmeter
* Optical Borehole TV

c) Permeability and Porosity * Micro-resistivity Log

* SP Log
* Caliper Log
* Sonic Log
Neutron Log
* Density Log

d) Production Profile * Temperature Log

* Pressure Log
* Caliper Log
* Borehole Sampler (Multi-stage)
* Optical Borehole TV
* Continuous Flowmeter

e) Miscellaneous * Cement Bond Log

* Casing Collar Locator
* Optical Borehole TV

The maximum temperature of 275C at phase I was so selected that teflon

materials can be used as an electrical insulator of the logging cable and cable
head up to such temperature and the maximum temperature of 350C at phase II
was so selected because the temperatures of hydro-thermal wells in Japan are
mostly less than 320C. The case of temperature higher than 350C will be the
next stage of this project.

The tools marked * in Table 1 were started to develop at phase I from

1976, and put into a field test during 1978 and 1979. All the tools, except
the optical borehole TV, were successfully operated in the field test under
the borehole conditions of Depth: 1200m, BHT: 202C and BHP: 130kg/cm2.

The field test showed that the optical borehole TV, which consists of a
camera tube, can only be used 4 hours under the environmental temperature of
150C; the high temperature TV, which consists of a semiconductor image sensor,

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 Table 2. Geothermal Well Logging Tools.

MINIMUM
FIRST PHASE (1976-1979) SECOND PHASE (1980 - )
SONDE HOLE
TOOLS DIAMETER DIAMETER MAXIMUM MAXIMUM OPERATING MAXIMUM MAX IMUM 3PERATING REMARKS
(inches) (inches) TEMP. PRESS. TIME TEMP. PRESS. TIME
(c) (kg/cm2) (hours) (c) (kg/cm2) (hours)

1) Multi-spacing
16, 32, 64 inches
Electrical Log 2-7/8 3-1/2 275 750 20 350 1000 20
Normal
- SP
2) P-S Sonic Log 4 7-5/8 275 500 4 350 600 6 P-S micro-seismogram
log
3) Micro-spherical 4 7-5/8 275 500 20 350 600 20 Ceramic pad
Log - Caliper
4) Optical Borehole 3-7/8 5 150 300 4 - Camera tube
TV 3-7/8 5 - 250 500 4 Semiconductor image
I
sensor
w 5) Temperature Log 1-11/16 2 275 500 20 350 700 20 Platinum-resistance
1

6) Pressure Log 1-11/16 2 275 500 20 350 700 20 Diaphragm-strain

gauge
7) Continuous Flor- 1-11/16 2 275 500 20 - Potentiometer
meter
1-11/16 2 - 350 750 20 Synchro-resolver

8) Borehole Sampler 4 5 275 500 20 - Single stage

2-7/8 3-1/2 - - - 350 700 20 Multi-stage

9) Neutron-Density 4 7-5/8 - 275 500 4

Log - Caliper -
Gamma Ray
O) Cable 13mmf3 - 275 500 20 - Teflon sheath
1Ommfl - - 350 1000 20 Dioxide metal powder,
Ceramic enamel
coating
SPWLA TWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11, 1980

is now under the construction. The final temperature goal of this TV camera
is shown in Table 2.

The Neutron-Density Logging tool will be developed in Phase II using the

technologies for high temperature instrumentation developed at Phase I.

DEVELOPMENT OF HIGH TEMPERATURE LOGGING SYSTEM

1, Fundamental Elements of Logging System.

a) Logging Cable.

The specification of armoured cable is as follows:

Conductor s 7 conductors
Teflon sheath of PFA
3 of 7 conductors are electrically shielded for the
transmission of TV video signal and acoustic wave
signals.
Armour wire Iron alloyed steel wire (not stainless steel)
Outside diameter 13mmfl,800kg/1000m
Stretch strength o 10 12tons

Several kinds of armour wire were subjected to electrical and chemical

erosion test, especially by the use of low pH solutions, and tests show some
kinds of iron alloyed steel wire are much stronger than the stainless steel
wire to chemical and electrical erosion. The details of the metal erosion
will be discussed in the later.

The feasibility studies of high temperature cable used at Phase II (350C,

1000 kg/cm2 and 20 hours operation) were also achieved during the period of
Phase I. The high temperature cable at the environmental conditions written
above will consist of the ceramic enamel coated wire or dioxide metal powder
sheathed wire.

b) Cable Head.

The most difficult point at which to seal cable head from the borehole
fluid is an inlet of cable conductors to the cable head housing. Therefore,
the several kinds of JOY connector which consist of a rubber cap were put
into the high temperature and high pressure test. However, no satisfactory
results were obtained because of the poor sticky contact between the teflon
sheath and rubber cap.

Therefore, the new teflon diecast sealing system was developed as shown
in Figure 1. The wire inlet of cable head housing is covered by the teflon
diecast seal and the teflon sheath of cable conductors are hurried into this
teflon seal as a one piece by means of a melting process.

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 SPWLATWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY S-11,1980

Fig. 1. Teflon Diecast Cable Head.

c) Mechanical Seal for Pressure Protection.

G
An "0" ring is used as a mechanical seal at the connection between the
cable head and pressure chamber of down hole instruments. Therefore, several
kinds of "0" ring which consist of EP Rubber, Viton, Silicon Rubber, Teflon
and Metal were put into the high temperature and high pressure test.

Table 3. High Temperature and High Pressure Characteristics of Elastomors.

Characteristics
Materials Remarks
(29O"C, 500 kg/cm2)

Viton Elasticity decrease with To be replaced after the

temperature increasing. several times used.

EP Rubber Good elasticity. Not available to the oil bath.

Poor resistance to the oil.

Teflon Poor elasticity. To be used with the combina-

Poor sealing ability at low tion of another elastomor
pressure. "0" ring.

Metal Excellent resistance to Can be used up to 700C.

high temp. and high To be replaced at every con-
pressure. netting operation.
Very poor elasticity.

Silicon Extreme decrease of elas- Not available at high

ticity with temperature temperature.
increasing.

DuPont Kalrez Intermediate elasticity. Not available at temperature

Elasticity decrease with as high as 275C.
temperature increasing.

Table 3 is a summary of the test results and Figure 2 is the "0" ring
samples after the high temperature and high pressure test.

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I SPWLA TWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11, 1980

The metal "0" ring has a

good sealing ability if the
surrounding temperature is as
high as 290C. However, be-
cause of their poor elasticity,
the metal "0" ring must be re-
placed at every connecting
operation.

According to the results

of high temperature and high
pressure test of "0" rings,
the double "0" ring system,
which is a combination of the
EP rubber and viton "0" ring,
was adopted in this project.

d) Heat Insulating System

for Down-hole
Electronics.

Because the maximum tem-

perature of commercially
available electronics parts is
normally, 175"C, and ones such
as SCR's and chemical capaci- 0
tors are less than 150C.
Therefore, a heat insulating (I.$.l

system must be developed for

the protection of the down-
hole electronics.
Fig. 2. Samples of "0" Rings.
Figure 3 is a time-temper-
ature build-up curves inside
the heat insulating chamber correspond to outside temperature of the chamber.
The down side of this figure is a schematic diagram of heat insulating cham-
ber which consists of Dewar's flask and heat sink. A super-insulator is
inserted between the outside cylinder and inside cylinder of flask in order
to prevent heat radiation between them.

As shown in Figure 3, the inside of this heat insulating chamber can be

held at a temperature as low as 150C for 4 hours under the normal logging
conditions as logging speed: 500m/hr, BHT: 275C and Depth: 2000m.

During Phase II, a special cooling system, which consists of the Dewar's
flask and cryostat or refrigerator, may be necessary.

Figure 4 is a schematic diagram of the cable head with bridle cable for
Electrical Logging and Figures 5 and 6 are the outside views of cable winch
and the logging control panel respectively.

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 SPWLATWENTY-FIRST ANNUAL LOGGING SYMPOSiM, JULY 8-11.1980

LDGGING SPEED 50091

MUD TEMP too-c
250 %
DOWN SPEED
2000m

TIME (mln)

.
m

Fig. 3. Temperature Response Curve and

Schematic Diagram of Heat Insu-
lating Chamber.

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SPWLATWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, .IUL.Y 8-11, 1980

Fig. 5. Cable Winch. Fig. 6. Logging Control Panel.

2. Production Logging Tools.

a) Temperature Survey.

Because the outside diameter of Production Logging tool is limited to

l-11/16 inches due to the dimension of production logging well head, the heat
insulating chamber for the protection of heat damage of down-hole electronics
cannot be adopted for use on such small diameter of tool. Therefore, although
the temperature resolution of platinum resistance sensor is much lower than
that of quartz crystal sensor, a platinum resistance sensor having a ternper-
ature resolution IS 0.5OC in the tempera-ture range rrorni) to 300C was adopted
in this project, because down-hole electronics were not required and good
stability was obtained at the high temperature environment.

b) Fressure Measuring Tool.

A high resolution quartz cryst.aI pressure transducer was considered as a

sense:' of the down-hole pressure logging tool. However, the weii stabilized
crystal sensor at high temperature was not commercially available at the start
of this project. Therefore, the pressure transducer of diaphragln-straingauge
type was adopted on this project.

c) Continuous Flowmeter.

The diameter of continuous flowmeter is l-11/16 inches and the flow rate
passing through the impeller can be controlled by the several diameters of
flow rate control basket which is attached to the Losging Probe.

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 SPWLA TWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11, 1980

Two types of sensor for detecting the impeller rotating speed were pre-
pared, the one is a rotary potentiometer for low flow rate and the other is
a synchronous resolver for high flow rate.

d) Borehole Fluid Sampler.

The prototype equipment is 4-inch diameter, 5-feet length and the sampler
volume is 1.8 litres. The remote controlled valve is driven by 3-phase motor
of 3-inch diameter.

Figures 7 and 8 are the outer views of production logging tools developed
on this project.

Fig. 7. Temperature Tool. Fig. 8. Continuous Flowmeter.

3. P-S Acoustic Logging Tool.

Figure 9 is a block diagram of P-S acoustic logging, and Figure 10 is the

skid base of the acoustic sensors. Two pairs of P wave and S wave transducers
are mounted in the skid base which is pressed against the borehole wall by
means of a back-up plate tightly.

A specially designed S wave transducer has only response to the torsion-

al wave but has not response to the compressional wave. The pulsed P and S
waves are transmitted from the respective acoustic transmitter into the forma-
tion alternately with a repetition rate of about 10 pulses/see.

The P and S wave trains detected by the respective receiver are sent to
the surface through Preamplifier and logging cable, and then, recorded on 35-
mm film by means of a continuous wave train recorder. Those waves are also
sent to the time and amplitude analyzer simultaneously, and then AT and

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I SPWLA TWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11, 1980

Power Ponel

Centralizer
Connector Panel

Cable Head . Monitor

AT-Amp. Panel
3
00
00

z=
Heat Insulat(

Comero

Vlicroseismograr
Panel

Arm Drive
Arm Drive
Mechnism
Control Ponel

Skid Base

Down Hole Equipment Surface Panel

4

Fig. 9. Block Diagram of P-S Sonic Log. Fig. 10. Skid Base of P-S Sonic Tool .

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 SPWLA TWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11, 1980

amplitude of first arrival wave are recorded at the standard logging film.
The caliper, which is detected as the distance between the skid base and
back-up plate, is also recorded in the logging film.

Laboratory experiments showed that the S wave transducers must be press-

ed against the borehole wall with a pressure of about 2 kg/cm2 to get a suf-
ficient S wave signal. However, the P wave transducers must be apart from
the hole wall to avoid the contact noise, which is caused by the slip between
the hole wall and the surface of acoustic holder.

The pressure holders which contain the acoustic elements are so attached
to the skid base body that the acoustic path formed by the transmitter-skid
base body-receiver must be disconnected mechanically by means of a hydraulic
system, and moreover, the skid base body is also slitted with a specially de-
signed shape in order to suppress the acoustic signal passing through the
skid base body. Therefore, the acoustic signals which arrive at receivers
are only the waves which passed through the formation.

Figure 11 is examples of wiggle trace of P and S waves which are record-

ed on 35-mm film.

The arm driving system of the back-up plate will be explained with the
Micro-spherical Logging.

P s P s

(a) (b)

Fig. 11. Example of Wiggle Trace of P-S Sonic Log.

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SPWLA TWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11, 1980

4. Electrical Logging Tool.

Figure 12 is an outside
view of Multi-spacing Elec-
trical Log of which electrode
spacings are 16, 32 and 64
inches, respectively.

The diameter of sonde is

65mm0 and the body was made
of ceramic diecast block.
Therefore, the sonde itself
can be used up to 6OO"C, how-
ever, the maximum operating
temperature is limited to
275"C, because of using the
teflon bridle cable. Fig. 12. Multi-spacing ES Tool.

5. Micro-spherical Logging Tool.

Figure 13 is an outside view of

the sonde pad of Micro-spherical Log-
ging tool. The resistivity measuring
pad is made of machinable soft ceram-
ics, because the usual rubber pad can
not be used in the high temperature
geothermal well.

The tool measures l-inch and 2-

inch spacing resistivities and also
the caliper as the distance between
the resistivity measuring pad and
back-up plate.

Figure 14 is a schematic diagram

of arm driving system of the micro-
pad and back-up plate. Those plates
are closed while the sonde is going
into the hole, and then, opened and
pressed against the hole wall by
means of the spring expansion force.

Fig. 13. Micro-spherical Tool.

The movement of arm open and
close is controlled by means of a 3-
phase induction motor. The motor is put inside the oil chamber, the pressure
of which is always balanced with the hydrostatic pressure in the hole by the
use of metal bellows. Therefore, the power of the motor is only required to
counter balance the force of spring expansion.

As explained under the Mechanical Seal, the ability of water sealing of

the "0" ring is extremely weak at the high temperature and high pressure en-
vironment. The water leak passing through the "0" ring set in the arm driv-
ing shaft was seen often even if the pressure is balanced between the mud

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SPWLATWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11, 1980

pressure and the inner pressure of

oil chamber. This trouble at the
logging operation was improved by
the use of metal bellows covering
the arm driving shaft.

Figure 15 is an outside view

of such metal bellows used as a
water seal at the moving parts.

6. Optical Borehole TV.

The usefulness of optical

borehole TV for getting the
visual informations of the hole
wall is well known. The optical Fig. 15. Metal Bellows.
image of the hole wall is led
into the image sensor passing
through the refraction mirror which rotates 360 degrees about the center axis
of the image'sensor.

Since the maximum operating temperature of image sensors commercially

available is 55C on a camera tube and 90C on a semiconductor image sensor,
these sensors must be put deep inside the heat insulating chamber for the
protection of heat damage of sensors. Under these conditions, it is very
difficult to rotate the image sensor synchronized with the rotating speed of
mirror, because there is too little room to put a synchronizing system in-
side the heat insulating chamber. Therefore, the image at the surface moni-
tor will rotate in accordance with the rotation of the down hole mirror.

The optical image upright positioner, which is set between the image
sensor and rotating mirror, was developed for holding the image at the up-
right position.

Figure 16 is a diagram of the optical image upright positioner, which

consists of the combination of specially designed prism and complex lens
assembly. The prism rotates at half speed to the mirror rotating speed, but
in a direction counter to that of the mirror, and the focusings of the image
can also be adjusted by moving the center lens at the image upright positioner.

The image of magnetic north at the compass is always led into the image
sensor passing through the center axis of this optical system. Therefore, the
image displayed at the surface monitor is a complex of the hole wall photo-
graph and the magnetic north at the center scope.

According to the field test of this optical TV which consists of the

camera tube sensor, the maximum operating time was 4 hours at hole tempera-
tures as high as 15O"C, the higher temperature TV camera, which consists of
the semiconductor image sensor, is now under the construction. The final goal
of operating time on such TV cameras is 4 hours at borehole temperatures as
high as 250C.

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 SPWLA TWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11,
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SPWLATWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11, 1980

7. Chemical and Electrical Erosion of Tools.

The special problem with geothermal well logging tools is a chemical and
electrical erosion of the tool, because the large amount of chemical materi-
als desolvedin the drilling mud and producing fluids.

Figures 17 and 18 are samples of eroded cable armour wire, and bellows
used at the oil chamber of the motor.

Several kinds of steel samples were put into the chemical and electrical
erosion test, which showed that some kinds of iron alloyed metal and aluminum
had a relatively long life even if those were put into the low PH solutions.

Fig. 17. Samples of Eroded Cable Fig. 18. Samples of Eroded Bellows.
Armor.

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 SPWLA TWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11,

RESULTS OF FIELD TEST

Figure 19 shows log examples, which were measured at the test well of
Nigorikawa T303 (Depth: 1200m, BHT: 202C and BHP: 130kg/cm2) and Figure 20
is part of the P-S acoustic log and also the wiggle trace of the acoustic
wave.

The P wave acoustic log and wiggle trace record, which are measured with
the casing inserted, can also be used as a cement bond log.

Over 15 wells. which have nearly same hole conditions as N- gorikawa T303,
were iogged during-the field test of-the tools in 1978 and 1979,-and the log
interpretation for the respective wells was made by the use of standard
petroleum log interpretation techniques.

CONCLUSION AND DISCUSSION

Although suitable test wells, which satisfy the hole conditions written
in the specification of tools, are not available in Japanese geothermal
fields at this moment, over 15 wells which have nearly the same hole condi-
tions as Nigorikawa.T303 were used in the field test of the tools during 1978
and 1979, and all the tools, except the optical borehole TV, were successful-
ly operated in those field tests,

The maximum operating time of optical borehole TV, which consists of a

camera tube, was only 4 hours at a hole temperature of 150C, and a new TV
camera, which consists of a semiconductor image sensor, is now under construc-
tions and will be put into the field for tests this year.

During Phase II, starting in 1980, the main purpose of this project is
to develop a 350C high temperature cable. However, the field test in which
hole temperature is as high as 275C must be continued for the evaluation of
tool reliability; also, the fundamental studies of rock properties in geo-
thermal fields continue to aid in the development of new geothermal well log
interpretation methods.

Moreover, the Neutron-Density Log for 275C and the digital recording of
logging data will also be developed during 1980 to 1981.

ACKNOWLEDGEMENT

The authors wish to express their appreciations to Japan Petroleum Ex-

ploration Co., Ltd. and Teikoku Oil Co., Ltd. who allowed us to present this
paper at the SPWLA Meeting, and also express their appreciations to Mr. Y.
Kaneko, Geothermal Energy Research and Development Corp., Mr. T. Takeyama,
Kaihatsu Kogyo Corp. and Mr. M. Nishino, Osaka Denpa Corp., who gave us kind
instructions and valuable advice.
SPWLATWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11.1980

Fig. 19. Example of Logs in the Test Well of Nigorikawa T-303.

 SPWLATWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11.1980

P-S Sonic Log

0 M icro -
Caliper
CD
-0 Sonic Log Seismograph
; Log

0 IO
0 ImVl IO ImVl
LI_L_L~_L_L~-I-LA-L-Ll-l_LJ-l-LJ-J
iIT

270 170 70 CDsec/ft 1 S wave P wave

6 (jisec/ft) 150 100 50
t-u-uad II II 11 11 11 11 11 11 11 11 I I

Fig. 20. Example of P-S Sonic Log

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SPWLA TWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11, 1980

REFERENCES

Los Alamos Scientific Laboratory, 1977, Hot Dry Rock Geothermal Energy De-
velopment Project Annual Report Fiscal Year 1977, LA-7109-PR, Progress Report,
Los Alamos Scientific Lab., University of California.

Moran, J. H. and Attali, G., 1968, Wireline Logging Operation to 50,000 Feet:
8th World Petroleum Congress, June 10-16, Moscow, Russia, p. 149-158.

Vagelatos, N., Steinman, D. K. and John, J., 1979, True Formation Temperature
Sonde (TFTS): Transactions, SPWLA, 20th Annual Logging Symposium, Tulsa, OK,
June 3-6.

Veneruso, A. F., Polito, J. and Heckman, R. C., 1978, Geothermal Logging

Instrumentation Development Program Plan [U]: SANDIA Lab., August.

Veneruso; A. F. and Stoller, H. M., 1978, High Temperature Instrumentation

for Geothermal Applications: Transactions, Geothermal Resource Council, Vol.
2, July.

Veneruso, A. F. and Coquat, J. A., 1979, Technology Development for High Tem-
perature Logging Tools: Paper KK Transactions, SPWLA, 20th Annual Logging
Symposium, Tulsa, OK, June 3-6.

ABOUT THE AUTHORS

TOSHINOBU ITOH

He received M.S. degree from the Department of Electronic

Engineering of Nihon University in 1958. From 1958 until
1960, he worked as a field engineer of Schlumberger Well
Surveying Corp. In October 1960, he joined Japan Petro-
leum Exploration Co., Ltd. as a log analyst. In April
1965, he was transferred to the Central Technical Labora-
tory of JAPEX as a geophysical engineer. In March 1973,
he received Ph.D from the Department of Atomic Energy
Engineering of the University of Tokyo. In 1975, he
worked as a guest researcher for the Institute of.Geo-
physics, Technical University of Clausthal, F.R.G. He is
presently the vice-president of the Central Laboratory of
JAPEX and also working in the Exploration Department of
JAPEX as a technical supervisor.

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 SPWLA TWENTY-FIRST ANNUAL LOGGING SYMPOSIUM, JULY 8-11, 1980

ABOUT THE AUTHORS (Continued)

MAKOTO MIYAIRI

He graduated from the Department of Resources Development

Engineering of Tohoku University in 1972. In April 1972,
he joined Japan Petroleum Exploration Co., Ltd. as a
field engineer. In February 1973, he was transferred to
the Central Technical Laboratory of JAPEX, where he is
presently working as a research engineer of Applied
Geophysics.

KIYOSHI KIMURA

He graduated from the Electrical Engineering Section of

Mining Engineering Department of AKITA University in 1959.
In April 1959, he joined Teikoku Oil Co., Ltd. (TOC) as
a field engineer. In May 1965, he was transferred to the
Technical Laboratory of TOC, where he is presently the
Chief of Well Logging Section.

Central Technical Lab., Japan Petroleum Exploration Co., Ltd.

3-5-5, Midorigaoka, Hamura-machi, Tokyo, Japan

Technical Lab., Teikoku Oil Co., Ltd.

g-23-30, Kita-Karasuyama, Setagaya-ku, Tokyo, Japan

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