Note: Descriptions are shown in the official language in which they were submitted.
35~
-1-
"BOREHOLE TELEVIEWER 5YSTEM USING
MULTIPLE TRANSDUCER SUBSYSTEMS"
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention lies in the field of acous~ic
15 logging systems for boreholes. More particularly, it is
concerned with the lo~ging of deep boreholes in the earth.
Still more particularly, it concerns the use of an acous-
tical transducer which transmits a beam of high frequency
acoustic energy into the borehole directed in a radial
20 plane, and receives the returned reflected acoustical
energy signal from a reflecting surface, such as the wall
of the borehole, and transmits a processed electrical scan
signal derived from such received signal, to the surface
of the earth, through the cable which supports the instru-
25 ment, or sonde, for further processing.
Still more particularly, it concerns improve-
ments in such acoustic logging devices and in particular
the use of two or more transducer systems on a single
rotating assembly so that multiple probing signals are
30 sent outwardly from the axis of the borehole and multiple
reflected sonic signals are received, converted to elec-
trical scan signals, which are then utilized in various
ways.
Still more particularly, this invention concerns
35 improvements in methods and apparatus for processing mul-
tiple simultaneous analog electrical scan signals (ESS) in
the sonde for transmission to the surface in real time,
over conventional logging cables which may have only a
--2--
single, or possibly only two conventional intermediate
frequency signal transmission channels.
2. Description of the Prior Art
This field of science and engineering is not
5 new. It has been in useful operation in the logging of
boreholes in the earth, such as oil and gas wells, for a
number of years. There are various patents issued on
selected features of these systems, and including the
basic system, which form no part of this invention.
Examples of the prior art are illustrated by
U.S. Patent No. 3,369,626 entitled: "METHOD OF AND
APPARATUS FOR PRODUCING A VISUAL RECORD OF PHYSICAL CONDI-
TIONS OF MATERIALS TRAVERSED BY A BOREHOLE", issued
February 20, 1968 in the name of J. Zemanek, Jr. There is
15 also U.S. Patent No. 3,663,619 entitled: "THREE-DIMEN-
SIONAL PRESENTATION OF BOREHOLE LOGGING DATA", patented
June 6, 1972 in the name of Charles L. Dennis; U.S. Patent
No. 3,550,075 entitled: "SYSTEM FOR DISPLAYING TIME
INFORMATION IN ACOUSTIC WELL LOGGING SYSTEM", issued
20 December 22, 1970 in the name of D. W. Hilchie et al; and
U.S. Patent No. 3,835,953 entitled: "ACOUSTIC CALIPER
LOGGING", issued September 17, 1974 in the name of
Jerald C. Summers. There is also additional art recorded
in the form of other patents, and in technical papers pre-
25 sented at technical society meetings, so that furtherdescription or statement of the art is not necessary at
this time.
s~
--3--
SUMMARY OF THE INVENTION
It is a primary object of this invention to pro-
vide a number of improvements in the design and construc-
tion of borehole logging instruments employing acoustical
S probing beams, and reflected sonic signals, and in the use
of data from these instruments.
It is a further object of this invention to pro-
vide at least two or more transmitting receiver transducer
systems (T/RTS) operating independently to provide mul-
10 tiple electrical scan signals~ which are used coopera-
tively, in combination, to provide more informat:ion than
would be possible by their separate use.
It is another objective of this invention to
provide apparatus and methods for processing multiple ESS
15 in a sonde for improved transmission over single or double
transmission channels in conventional electrical logging
cables.
In the prior art, the rotating system, which is
part of the logging instrument, or sonde, is lowered into
20 the borehole in the earth by means of a long cable,
unwound from a drum, and passing over a measuring wheel
mounted at the mouth of the well, at the surface. Such
cables comprise a multiple set of conductors, which can be
used in various ways to transmit data from the sonde to
2~ the surface, and also to transmit power and/or control
signals from the surface to the sonde. The main limita-
tion of these instruments has been the use of only a
single transmit/receive transducer system (T/RTS). Thus,
in logging a hole it is necessary in advance to make a
30 judgment as to which type of transducer, measuring a
selected parameter, will be the most useful in a given
subsurface situation.
In this irlvention the improvement lies in the
use of two or more T/RTS. These are mounted on the same
35 rotating assembly as the normal single T/RTS~ in a known
geometrical relationship to the first one. There may be
two, three, four or more additional T/RTS and these may
have the same electrical characteristics as the first one,
s~
or they may each be differen~ from the other. By the use
of different T/RTS, it is possible to probe into the earth
to a deeper or shallower depth, depending upon the charac-
teristic and the frequency of the T/RTS. For example, one
5 of the problems of the conventional system is that it has
a high frequency T/RTS, and high frequency sonic waves in
the fluid in the well, such as drilling mud, suffer a high
attenuation. Thus, the penetration of the sonic beam is
limited by this attenuation, due to the fact that the
lO sonic waves must travel a selected distance through the
mud, or other fluid in the wellbore. By making the T/RTS
of a lower frequency, the attenuation becomes less, and
thus the sonic beam probes to a greater depth, or radial
distance from the transducer into the rock wall.
With a plurality of similar transducers,
arranged in a common plane transverse to the axis of the
rotating assembly of the sonde, equally spaced circumfer-
entially, a plurality of scans are made simultaneously, as
the sonde is moved vertically at a selected constant rate.
20 Thus, a shorter vertical spacing along the wall of the
borehole is provided for each scan. This permits a much
finer detail of scanning or probing. Conversely, it per-
mits a higher rate of logging to get the same spacing of
scan or probe traces
The arrangement of multiple T/RTS can be in a
horizontal plane circumferentially spaced, or in a ver-
tical plane longitudinally spaced. This use of arrays of
T/RTS will provide a stronger, better-focused scanning
beam, of higher energy. Thus, the penetration of the beam
30 can be greatly increased.
Another problem addressed by the invention is
how these multiple ESS can be transmitted to the surface
by the use of logging cables which were originally
designed for transmitting relatively low frequency elec-
35 trical logging signals, and so on, that is, signals ofless than about 50 KHZ. The apparatus and methods of processing the mul
tiple ESS form an aspect of this invention. The partic-
--5--
ular apparatus design depends on a number of factors, such
as:
a) the nwmber of separate T/RTS and resulting
ESS;
b) whether the frequencies of the T/RTS are
the same or different;
c) whether the complete received signals are
required~ or simply measurements of ampli-
tude of reflection, and time of travel, or
depth of penetration, or caliper;
d) whether selective portions of each of two
ESS can be gated to combine the two por-
tions as a single signal;
e) whether a single transmission channel is
provided in the cable, or more parallel
channels,
f) the nat-ure of the transmission channels,
that is, their frequency pass bands; and so
on.
These and other aspects of this invention will
be described in detail in relation ~o the drawings.
3~i~
BRIEF DESCRIPTION OF THE DRAWINGS
.. . .
These and other objects and advantages of this
invention and a better understanding of the principles and
details of the invention will be eviden~ from the fol-
S lowing description ~aken in conjunction with the append~ddrawings, in which:
FIGURE 1 il]ustrates the prior art simply in the
arrangement of the logging sonde held concentric with the
wellbore by means of radial centering springs supported by
10 a cable which runs over a measuring wheel, the rotations
of which are functions of depth.
FIGURE 2 illustrates one embodiment of this
invention employing two T/RTS arranged 180 apart in a
horizontal plane on the rotating assembly.
FIGURE 3 illustrates one method of utilizing the
two T/RTS of FIGURE 2.
FIGURE 3A illustrates the surface apparatus that
might be used in combination with the downhole apparatus
of FIGURE 3.
FIGURE 4A illustra~es the relative operation of
higher frequency versus lower frequency T/RTS, while
FIGURE 4B illustrates the gating operation of the two
T/RTS shown in FIGURE 4A.
FIGURE 5 illustrates the received signal from
25 the two transducers of FIGURE 4A.
FIGURE 6 illustrates the use of time delay
between the two T/RTS of FIGU~E 3 combined with the gating
system of FIGURE 4B.
FIGURES 7 and 7A illustrate two variations of a
30 system employing two separate T/RTS.
FIGURE 8 illustrates the main mechanical con-
struction of a single T/RTS mounted on the rotating
assembly in the sonde.
FIGURE 9A, 9B, 9C, and 9D illustrate the pos-
35 sible arrangement of two, three, four, and six, T/RTS in ahorizontal plane, equally spaced, circumferentially.
FIGURE 10 illustrates a system in which multiple
T/RTS are provided on the rotating system~ but these are
~ 3
--7--
separated in a longitudinal direction in a common radial
plane through the axis of rotation.
FIGURE 11 illustrates the possibility of using
multiple T/RTS in a linear array horizontally so that beam
5 formin~ techniqiles may be used to provide a better focused
and more penetrating beam than would be provided by a
single I'/RTS.
FIGURES 12A, 12B, and 12C represent various
methods of transmission and utilization of the scan signal
10 from multiple T/RTS.
FIGURE 13 illustrates a variation of FIGURE 10.
FIGURE 14 is an extension of portions of FIG-
URES 2 and 3, illustrating how four separate T/RTS can be
mounted on the rotating assembly and can be connected as
15 desired to the pulser and to the cable.
FIGURE 15 is an extension of FIGURE 3, illus-
trating the use of multiple pulsers, one for each of the
separate T/RTS so that parallel output scan signals are
provided simultaneously.
FIGURE 16 is a modification of part of FIGURE 15
showing alternate transmission of two or more electrical
scan signals which may be from T/RTS of the same or dif-
ferent frequencies.
FIGURE 17 illustrates the time scheduling of the
25 alternate transmissions of the two or more electrical scan
signals of FIGURE 15.
FIGURE 18 illustrates one embodiment of appar-
atus for transmitting two or more simultaneous analog
electrical scan signals by converting them to double fre-
30 quency analog electrical scan signals for transmission
over a single transmission channel.
FIGURE 19 illustrates the time scheduling of the
two simultaneous electrical scan signals and the sequen-
tial transmission of the double frequency scan signals.
FIGU~ES 20A, 20B, 20C, 21A, and 21B illustrate
different embodiments for transmission of two or more ESS
to the sur~ace, over a single and/or a double transmission
channel cable.
3 5
-8-
FIGURE 22 illustrates one embodiment of surface
apparatus for receiving and recording analog and digital
ESS.
FIGURE 23 illustrates an apparatus for providing
5 separate digital signals comprising the amplitude of a
reflection, and the time of travel, or distance of pene-
tration, and multiplexing the two digital signals.
FIGURE 24 illustrates an extension of FIGURE 23,
in which plural digital signals of amplitude and caliper
10 from plural ESS are multiplexed and transmitted over a
single transmission channel.
~5 3
BRIE~ DESCRIPTION OF THE PREFERRED EMBO~IMENTS
Definitions:
There are a number of words designating elements
or parts of the invention that will be us~d frequently
5 during the following description. I propose to define
these in advance so that words may be saved in the
description. 1. Sonde. This is the sealed logging
instrument that contains the transducers, the controls,
and power means for driving the transducers. 2. Rotating
10 assembly or drum. This is the assembly on which the
transducers are mounted, and which rotates about the axis
of the sonde~ 3. The transducers. These are the means
to generate a sonic beam responsive to the application of
a high frequency voltage or pulses to the transducer. In
15 some instances the sonic generator can also be used as a
sonic wave detector. In other ins~ances one of a pair of
transducers is used as a detector. These units will be
called Transmit/Receive Transducer System or T/RTS.
4. While principal use of this sonde is in logging ver-
20 tical boreholes in the earth, it can equally well be usedin horizontal boreholes, etc. The proper word to use for
indicating the position of two parts spaced along the axis
is longitudinal, but the word vertical will be used when
convenient. Also, a plane transverse to the axis of the
25 sonde will be called transverse plane, or horizontal
plane, and so on.
Description
Referring now to the drawings and in particular
to FIGURE 1, which is indicated as prior art, there is
30 indicated generally by the numeral 10, a logging sonde 12
which is supported in a vertical borehole 22, by means of
a cable 20 shown passing around a measuring wheel 25 at
the surface. The rotations of the wheel ~5 measure the
length of cable that has passed over the wheel. The rota-
35 tions of the wheel 25 are transmitted by means 26 throughan appropriate drive system, -to control the movement in
the direction representing verticality, in any display
system that might be used.
~iiS3~
-10-
The sonde 12 is supported by radial centering
springs 18 so that the axis of the sonde is coaxial with
the borehole 22. A section of the sonde indicated by num-
eral 14 rotates by motor means in the sonde, at a selected
5 constant rate. A probing beam of sonic energy 16 passes
out radially from the rotating portion 14 to probe the
wall and provide information regarding the character and
the parameters of the wall 22, and the material o~ which
the wall is composed. This wall might be a steel casing
10 surrounded by cement in a drilled borehole in a rock for-
mation, or it might be an open borehole.
Referrin~ now to ~IGURE 2, there is shown, to a
larger scale, a view of parts of a sonde, improved
according to the teaching of this invention. Very little
15 information will be provided regarding the normal elec-
tronic circuits in the space 31. These are fully
described in many configurations in the patent literature
referred to earlier. Wherever the circuitry would be dif-
ferent in this invention it is, of course, fully described
20 as will be clearly seen in the figures.
The sonde 30 comprises an outer shell 12 o~ con-
ventional construction. In the lower portion a cylin-
drical bulkhead 50 is fastened rigidly and sealed to the
outer shell and a downwardly extending axial post 42.
25 Bearings (not shown) are provided on the post 42, so that
a cylindrical tube or sleeve 34 can be rotated about the
post 42 by means shown as the dashed line 38, controlled
by motor 36. Such a rotating sleeve, as indicated, is
common to the prior art design.
On the sleeve 34 is mounted a first T/RTS 46
with its outer face tangential to the surface of revolu-
tion, as the sleeve 34 rotates. This T/RTS 46 is periodi-
cally excited by electrical circuits which will be
described, and transmits radially outwardly a sonic beam
35 indicated by the numeral 16, which passes to the wall 22
o~ the borehole~ which may be cased or uncased. Part of
the sonic energy is reflected backwardly to the T/RTS.
The conducting outer surface of the T/RTS is connected to
~5~3S~
a slip ring 44. A brush or electrical contact, stationary
in the sonde, contacts the slip ring as the sleeve rotates
and transmits on the lead 46' ~he electrical scan signal
reflected fro~ the wall of the borehole.
In the normal design of a borehole acoustic
logger, or bor~hole televiewer (BHTV), only one such T/RTS
46 is provided, and the signal is collected from the slip
ring 44 by the brush and passes by conductor 46' to cir-
cuits in the electronic package 31, which are conven-
10 tional. The processed signal then passes up through a
transmission channel in the cable 20, which is normally a
pair of conductors, or a coaxial cable, to the surface,
where it is utilized.
In this invention, at least a second T/RTS is
15 mounted on the rotating assembly comprising the sleeve 34,
etc. It is energized in a manner similar to that of the
T/RTS 46 and produces a scan signal which goes by means of
the lead 48' to the electronic package in space 31 and to
the surface in a manner similar to that of 46'. As will
20 be discussed in greater detail in connection with FIG-
~RES 8, 9A, 9B, 9C, 9D, 10 and 11, various combinations of
multiple ~/~TS arranged in a common horizontal plane,
equally spaced circumferentially, can be provided which
will provide certain benefits. Also the multiple T/RTS
25 can be provided in a longitudinal array, whereby other
benefits can be realized, or in some combination of cir-
cumferential and longitudinal arrays.
One possible electronic circuit that might be
used with the apparatus of FIGURE 2 is illustrated in
30 FIG~RE 3. Here the two T/RTS 46 and 48, labeled A and B
respectively, are rotated by the means 38, as previously
described, by the motor 36. The rotating slip rings are
shown as 44, four of them are shown, two of them are con-
nected internally to the T/RTS ~8 and 46 respectively, and
35 two slip rings are connected to a compass unit 60, which
is well known and provides a member which remains in a
fixed azimuth as the sonde moves vertically in the hole.
On each rotation of the rotating assembly 34, an
~s~
-12-
electrical pulse signal is provided as a selected point on
the rotating assembly passes -the constant azimuth angle of
the compass. This can be a magnetic compass, which might
be useful in logging an open hole, or a gyro compass, or
5 its equivalent, as would be well known in the art. By
means of the signal received from 60 that passes inter-
nally to the slip ring, and by the collector to line 60',
the orientation of the sonde with respect to an absolute
azimuth such as north, can be determined. Thus, it can be
10 represented on north/south or east/west displays, etc.
Use of a compass is well known in the prior art
The manner in which the T/RTS are used to probe
the wall of the borehole is illustrated in F~GURE 3 for
completeness as to the electrical circuits in the upper
lS righthand portion of the FIG~RE 3. A power supply at 84
supplies power by resistor 176 to capacitor 86, and passes
through the primary 88 of a transformer, to junction 90
and ground 78, which is connected ~o the negative poten-
tial of the power supply. A triggered rectifier, or gate
20 control rectifier, 80 is connected between the potential
at the junction o~ resistor 176 and capacitor 86 to the
ground 78.
There is a timing means 74 which is conven-
tional, operated by a clock of constant frequency, and
25 including a counter means, such that at a selected time a
signal pulse can be placed on line 75 to the trigger con-
nection 82 of the controlled rectifier 80. ~hen the
trigger pulse arrives, the capacitor having been previ-
ously charged to the full potenti~l of 84, now discharges
30 throu~h the rectifier 80 to the ground and this large cur-
rent passing through the primary 88 of the transformer
generates a corresponding voltage in the secondary 89 of
the transformer, which goes by line 92 to the line 68,
which can be connected to one or the other of the two
35 T/RTS 46 or 48, as selected by the switch 62.
The switch 62 can be as simple as a relay, which
is controlled by a potential on line 64; that is, con-
trolled by means of a signal ~rom the surface through one
-13-
of the multiple conductors of the cable 20, as is we]l
known in the art. Cons;der that the pulse of high voltage
is delivered by line 92 to the line 48', which means it is
delivered to the T/RTS 48 and the transmitter puts out a
5 pulse of sonic energy of selected amplitude and frequency.
This propagates outward radially through the mud in the
annulus of the borehole (or liquid o~ selected composi-
tion), to an obstruction such as the surface of the
casing. Here part of the sonic energy is reflected and
10 passes backward over the same path to the T/RTS 48, where
it generates a corresponding received signal, or elec-
trical scan signal, which comes back from the T/RTS 48
through line 48' 3 through the switch 62, to the box 66
which is marked S. Box 66 is a switch of a particular
15 nature which is used for cutting off the receiving ampli-
~ier 70 from the line 68 during the period that the high
voltage is on the line 92 to generate the transmitted
sonic pulse. The frequency of the transmitted sonic
signal may be as high as l Meg. HZ, or higher, and too
20 high to transmit over the transmission channel of the con-
ventional logging cable. It may be necessary to pass this
through a signal detector, which converts the high fre-
quency ESS to a relatively low frequency unidirectional
analog signal, which can be transmitted over the cable.
25 Thus at a selected short time delay after that pulse is
sent from line 92 to 48 and transmitted into the liquid,
the connection from line 68 through the switch 66 and line
68' to the amplifier 70 is now connected, and the ampli-
fied reflected signa] is passed by line 72 which is a high
30 frequency transmission channel, for transmitting the scan
signals through the cable to the surface. The timer 74
applied, through 76, the necessary gating potential to the
switch 66. This can be as simple as an AN~ gate which is
open during the time that the potential is applied to 92,
35 and is closed shortly after that potential disappears.
As will be shown in FIGURE 7, as many parallel
transmitted signals as desired can be used, by multiplying
the network of the grid controlled rectifier 80 and trans-
~3~3~L
former 90. FIGU*E 7 illustrates a case of two separate
T/RTS being powered simultaneously, and of course, any
number greater than two can likewise be powered by adding
on circuits similar to the two shown.
S The particular usefulness of the system of
FIGURE 3 will be evident if the two T/RTS 46 and 48 are of
different frequencies. If the transducers are of dif-
ferent frequencies, the beams of higher frequency have a
shorter depth of penetration through media 9 such as the
10 mud in the borehole. Lower frequency sonic beams are less
attenuated and have a greater distance of penetration.
Therefore, if it is desired to probe simply the inner wall
of the casing or the wall of the borehole, then a high
frequency T/RTS would be used.
There is a factor called "aperture" which is a
function of the ratio of diameter of the transducer to the
wavelength of the sonic signal. The higher the frequency,
the shorter the wavelength, and the larger the aperture
for a given diameter transducer. The larger the aperture,
20 the sharper the beam width and the bet-ter the "focusing"
of the sonic energy.
A high frequency transducer has better beam
forming, but unfortunately, has a shorter penetration.
Therefore, for short distances of probing, a high fre-
25 quency transducer would be used. On the other hand, whereit is desired to probe well beyond the wall of the bore-
hole, a pulse of sonic energy of a lower frequency that
would be less attenuated in its passage through the mud
and the material surrounding the borehole would be used.
30 On the other hand, a lower frequency transducer of the
same diameter would have a smaller aperture and will not
be focused as sharply. Also, the beam focus or image
detail will not be as good as it would be for a higher
frequency transducer.
In FIGURE 3A a portion of the circuit of
FIGURE 3 showing the switch 62, the transmit/receive
switch 66, amplifier 70, and cable 20, are connected at
the surface to an amplifier 71 and to an analog-to-digital
~ 5 35
-15-
converter 73, and to a recorder 77. More will be said
about the surface portion of the system later. However,
FIGURE 3A provides an indication of how the scan signals
provided by the ~wo T/RTS 46, 48, can be successively
5 transmitted by switching the relay 62 by means of the
transducer select switch 69.
Referring now to FIGURE 4A and considering the
system of FIGURE 3 with two T/RTS 46 and ~8, consider the
T/RTS 46 as high frequency, providing a beam 16 as indi-
10 cated in FIGURE 1 and the T/RTS ~8 being of lower fre-
quency, and having a beam 32 as in FIGURE 2.
The sonic energy delivered to the surrounding
liquid by a T/RTS has an optimum zone ZA-100 for the high
frequency T/RTS, and a different zone ZB-102 for the lower
15 frequency T/RTS 48. In general, the range, or radius from
the T/RTS to the optimum position in the æone A of useful
scanning 100, will be shorter for the higher frequency
T/RTS, than the zone B-102 for the lower frequency T/RTS.
If 46 is a high frequency T/RTS, and 48 is a corresponding
20 low frequency T/RTS, and if the zones A-100 and B-102 are
not mutually overlapping, it is then possible to use the
high frequency T/RTS during the time that the pulse of
energy traverses the near zone A-100, and use the lower
frequency T/RTS 48 during the time that the pulse beam
25 traverses the distant zone B 102. The way to do this is
illustrated in FIGURES 4B and 5.
Referring now to FIGURE 5, in line 128 there is
a trace called SA, or scan signal of transducer A. Con-
sider that the high voltage pulse along line 92 (of
30 FIG~RE 3) occurs at the time T0 and a sonic pulse is sent
out from the transducer A. For a short time interval 108,
to time Tl, no received signal is passed to the receiving
amplifier 70. Then a reflected transmission 106 passes
through the fluid in the borehole to the transducer, and
35 at a selected time T2 later, a reflection comes back from
the borehole wall, identified as SA'. After a time TS the
energy of the sonic beam is insufficient to provide a
satisfactory received signal.
-16-
If the low frequency transducer is pwlsed at T0
plus one-half revolution and occupies the same position as
the high frequency transducer had, the trace will be like
SB in line 130, and trace 110 will be the scan signal pro-
5 ~ided by the low frequency transducer. Of course, at atime about T2 there will be some reflection SB', probably
of lower amplitude and broader time duration than the
reflection SA' of the high frequency transducer. There-
afte~, there will still be sufficient energy to traverse
10 part of the rock behind the wall of the borehole where
there may be a reflecting surface, such as the bottom of a
hole or vug, and a signal SB " is provided. There may
even be other reflected signals such as the one indicated
by SB "'.
It will be clear from examining the traces 106
and 110 that in the region of the reflection SA' that the
high frequency transducer whose record is 106 provides a
much improved record in the near field than the lower fre-
quency transducer 110 does. Consequently, it is desirable
20 to prevent the recording and display of the portion of 110
up to the time TS, and during that period, the gating
pulse 116 of FIGURE 4B causes the high frequency signal
from transducer A to be present, such as trace 112. At
the time TS, the gating pulse 102 passes the signal from
25 the second transducer B to provide the remainder of trace
112 at times T3 and T4.
By this means, it will be clear that by making
use of two T/RTS of different frequencies and by proper
delay of one electrical scan signal with respect to the
30 other electrical scan signal, and gating the two scan sig-
nals appropriately, as has been described, a combination
of the two scan signals provides a much improved record in
the near fie]d, and having a greater depth of penetration
in the far field, than would be provided by either one
35 alone.
In FIG~RE 6 is illustrated the case where the
plurality of T/RTS are all of the same frequency, and the
cable can transmit only a single electrical scan signal at
-17-
any one time. One way of handling the plural signals is
to delay one with respect to the other and sum the two, to
provide a signal of improved signal-to-noise ratio.
FIGURE 6 shows the original scan signal of T/RTSA on line
5 138A which would be identical to the trace 106 of
FIGURE 5. Trace 142 shows the same trace 106' provided by
the second transducer B, which, of course, is delayed by
180~ of rotation of the rotating system. If trace 106 on
line 138 is delayed by the time period 126, or one-half
10 revolution, it appears as 106" on line 140, which would
be identical to, and in-phase with, the trace 106' pro-
duced by the T/RTS beam B. By summing those two signals
106'' and 106', the results are shown on line 144 as a
trace of A ~ B, of improved amplitude and signal-to-noise
15 ratio. Thus, the event on trace 106 which occurs at time
T2 will now be much more pronounced on line 144, at the
time T2'.
Instead of delaying one trace with respect to
the other when the two T/RTS are of the same frequency and
20 summing and transmitting the sum signal to the surfaceg it
would be much more desirable to be able to transmit the
two signals separately, and cotemporaneously, to the sur-
face. This could be done, for example, if there were two
transmission channels instead of the cable 20, or if there
25 was a mu]tiplex system by means of which a plurality of N
signals could be sampled at a high rate of sampling, and
the successive samples from each of the separate signals
would be transmitted in sequence to the surface. There
they would be demultiplexed by means which are well known
30 in the art.
Refer now to FIGURE 7 which has been previously
mentioned in conjunction with FIGURES 3 and 4. There is
shown the situation in which there are two T/RTS as in
FIGURE 3, numbers 46 and 48 respectively. Each of the two
35 T/RTS have a transmit signal applied through leads 172 and
174 respectively, to leads 46' and 48' to the T/RTS A
and ~. The timing for these transmit signals is provided
by a counter 166 which has a clock signal over lead 18~
3 5
-18-
from a constant frequency clock or oscillator 164. By
prearrangement, the counter counts up to selected numbers,
which indicate selected timing; and the two trigger recti-
fiers 80 of the transmission source assemblies, which have
5 previously been described in detail in relation to
FIGURE 3, are then controlled by the leads 169 and 170
from the counter or timer 166, to the control gate 82 and
82' respectively.
The counter 166 also provides gating pulses or
10 timing pulses on leads 167 and 168 to the transmit/receive
switch 150. This disables the detecting apparatus fol-
lowing the switch 150 while there is the high potential
signal applied to the T/RTS from the transmission elec-
tronics over leads 172 and 174. However, a~ter the short
15 in-terval 108 of FIGURE 5 after the transmission pulse is
sent, the T/RS 150 will then enable the electronics fol-
lowing through leads 46" and 48" to amplifiers 152 and
154, and through gating means 156 as described in relation
to FIGURE 4B.
The timing for this gating is derived from the
clock 164 over lead 184. The time delay unit 160 wh.ich
follows the gating controls 156, 158 is controlled by the
counter over lead lB4, 185. The gating units 156, 158 and
the delay unit 160 carry out the operations described in
25 connection with FIGURE 5. Following these three units the
two signals are added together by means of a pair of
resistors 162 being applied together to the input to an
amplifier 180, the output of which goes to the transmis-
sion channel 178 in the cable 20. Thus, by means of this
30 apparatus so far described in FIGURE 7, the action would
be to create the sum trace shown on line 132 of FIGURE 5
and transmit that trace to the surface, for recording and
display.
As mentioned previously and shown in FIGURE 7A,
35 the case where there are two transmission channels in the
cable 20, such as 186 and 188 of FIGURE 7A, it is then
possible to come from a T/RS switch 150 directly to ampli-
~iers 152 and 154 and apply the ampli~ied signals, one to
each of the two transmission channels.
- 1 9 -
The situation illustrated in FIGURE 7A is
exemplified a little more completely in FIGURE 12B to
which reference is now made. Here, the lines 46' and 48'
carrying the reflected scan signals from the T/R'rS 46 and
5 48, go to the T/RS switch 150, then to amplifiers 152
and 154. The amplified signals then go to the two sepa-
rate channels of transmission through the cable; namely,
186 and 188. The surface end of the cable 20 is similarly
shown and the conductors now 186' and 188' go to analog-
10 to-digital converters 268 and 270. The digitized signals
then go to a digital recorder 266 in a conventional
manner. While two separate analog-to-digital converters
are shown, they could, of course, be combined into a
single instrument, as is well known in the art.
In FIGURE 12A is shown an alternative circuit,
in which the signals from the T/RS switch 150 are ampli-
fied in amplifiers 152, 154 and then go to a multiplexing
means 260, the output of which on a single line goes to
amplifier 180 and to a single transmission channel 178 in
20 the cable 20 to the surface. At the upper end of the
transmission channel 178' connects to a demultiple~ing
unit 261, which converts the combination signal on line
178' back to the two component signals, which were ampli-
fied by the amplifiers 152 and 154. These two component
25 signals 46"' and 48" ' on the output of 261 go to ampli-
fiers 262 and 264 and then to a conventional digital
recorder 266 for later playback and display.
FIGURE 12C illustrates how a playback of the
recorder 266 can provide the two original signals 46" '
30 and 48" ', so that as in the case of FIGURE 7 these two
signals can be combined after one of them is delayed in
the timed delay unit 272 and combined in the combination
of resistors 274 and 276 to the single -trace which goes to
the display device.
Therefore, the combination of FIGURES 7, 7A, and
12A, 12B, and 12C provide sy~bolically three separate
methods of transmission of the signals from multiple T/RTS
from the subsurface sonde to the surface, to be recorded
~53~
-20
and/or displayed. While it is possible to have any one of
many different displays, which do not form a part of this
invention, the most common display means can only repre-
sent a single scan signal at a given time. It is conven-
5 ient, therefore, either to combine two or more signals ashas been described in FIGURE 7. Of course, more than two
separate T/RTS scan signals can be summed to provide a
single sum signal to transmit to the surface.
Another way of transmitting multiple scan sig-
10 nals to the surface is to have a separate transmissionchannel for two or more separate scan signals so that they
can be transmitted separately and simultaneously to the
surface over independent transmission channels as in FIG-
~RES 7A and 12B.
The third method has just been described as the
one in which a plurality of simultaneously recorded sig-
nals can be transmitted over a single transmission circuit
to the surface by the process of multiplexing. Devices
for doing multiplexing are commercially available and need
20 not be further described.
In general, it is very desirable to separate out
at the surface each of ~he separate electrical scan sig-
nals so that they could be recorded as a function of time,
or as a function of depth of the sonde below the surface
25 in separate recording channels. The best way of doing
this is to record them on separate channels of a multiple
channel analog recorder, such as are available in the art,
or to digitize each of the separate signals and to record
them separately on separate recording channels of a
30 digital magnetic recorder. Another way would be to store
the digitized separate signals into one or more separate
digital memories, partic-ularly random access memories,
such as are now available on the market.
So far in this description of the broad aspects
35 of my invention, I have described the use of multiple
T/RTS arranged Oll the ro-tating assembly in a horizontal
plane. And, as has been described, there are a number of
particular advantages to the use of the multiple T/RTS
arranged at various azimuths on the rotating assembly.
5 35
-21-
There is one important advantage of multiple
similar T/RTS scanning the circular path at slightly
delayed time intervals, one after the other. If these
multiple signals can be brought to the surface separately,
5 then it is possible to record ~hem and then to play out
each of the separate traces sequentially. In view of the
continuous vertical motion of the sonde, each of these
T/RTS scans a horizontal scan trace on the wall of the
borehole which is theoretically independent of each of the
10 others. For example, if there were two similar T/RTS, one
spaced 180 behind the other, it would be possible either
to show a finer detail of scanning display along the bore-
hole, or to permit the sonde to be moved vertically twice
as rapidly, and still have the same condition of trace
15 spacing in vertical dimension, as would be obtained at
half of the vertical velocity of the sonde with a single
T/RTS system, as at present.
One reason for the high cost of logging is
because of the time it takes to make a log. The longer it
20 takes, the longer is the commercial use of the well
delayed, the longer the logging equipment is utilized, and
the greater the cost of the logs. Thus, speeding up the
vertical rate of travel of the sonde could materially
reduce the cost of logs, without providing any reduced
25 utility or value of the resulting records. It is qui-te
possible that as many as four or more T/RTS could be used
to obtain a logging speed four times, or more, the present
speed of logging with a single T/RTS.
It is also important to use multiple T/RTS in a
30 vertical array that is arranged in a plurality of dif-
ferent horizontal planes on the rotating assembly. Such
multiple T/RTS would be preferably aligned in a vertical
plane throwgh the axis of rotation although this is not
required.
For a description of the manner in which the
multiple T/RTS can be built in-to the instrument, reference
is made to FIGURE 8 which shows the present method of
mounting a single T/RTS 200 on the rotating assembly 206.
-22-
The rotating assembly has an internal surface 210 which is
adapted to fit snugly the outside of the rotating sleeve
34 illustrated in FIGURE 2. Thus a plurality of T/RTS
could be mounted vertically on a suitable cylinder such as
5 206 of sufficient longitudinal dimension as shown in
FIGURE 2. Some means such as a set screw or other
suitable means 208 would be provided to hold and anchor
these rings or cylinders 206 to the rotating sleeve 304 to
maintain a rigid rotating assembly. A thin metal
10 sheet 212, preferably made of non-magnetic material, has a
central opening which is slightly larger than the diameter
of the T/RTS 200. The T/RTS is a thin slab of a cylinder
of suitable ~aterial which is piezoelectric or electro-
strictive. The slab 200 is anchored to the thin sheet 212
15 by positioning it in the center of the opening and locking
the two together by suitable resilient adhesive means,
which will anchor the slab but maintain a resilient adhe-
sive means, which will anchor the slab but maintain a
resilient type of mounting. Thus, no interference is
20 offered to the proper vibration of the transducer, as
electrical signals are applied to the electrodes on the
top and bottom surfaces.
A volume of backing material indicated as 214 is
formed in a suitable shape. The front surface attaches to
25 the sheet 212. This backing material is made of a mixture
of a very fine powder of a very dense metal, such as tung-
sten mixed and sealed into a resilient plastic material.
The backing serves to absorb the vibrations transmitted by
the back side of the T/RTS; that is, the surface of the
30 slab which faces the flat surface of the backing material.
Both surfaces of the piezoelectric slab vibrate
in opposition to each other; and unless one of these is
greatly attenuated, the two will partially cancel each
other. Thus, there will be only a very small part of the
35 energy transmitted perpendicular to the top surface of the
slab, or T/RTS 200. The type of backing material which
has just been described is conventionally used in the art
and forms no part of this invention and need not be
described further at this time.
-23-
The lead 202 connected to the top surface of the
T/RTS 200 goes through a drilled opening 204 as is indi-
cated schematically in FIGURE 3. Other openings will also
be present for the passage of additional signal leads,
5 like 202 from other T/RTS mounted on the sleeve 34. With
this description of the conventional method of mounting
and building the rotating assembly, etc., no further
description will be made, except to indicate how addi-
tional separate transducer slabs, such as 200, can be uti-
10 lized.
FIGURES 9A, 9B, 9C, and 9D indicate possiblecombinations of two or more I'/RTS. ~or instance, in
FIGURE 9A two slabs 200A and 200B are shown mounted upon a
single ring 260 at 180 azimuth from each other. In
15 FIGURE 9B three T/RTS 200A, 200B, and 200C are positioned
at 120 azimuth from each other. Similarly, in FIGURE 9C
the spacing is 90 and in FIGURE 9D the spacing is 60.
Other spacing arrangements or construction details can be
provided, of course, and those shown in FIGURES 8, 9, 10,
20 11, and 12 are just by way of illustration, and not by way
of limitation
In FIGURE 10 is shown an embodiment which uti-
lizes a plurality of T/~TS units 226A, 226B, and 226C
arranged on a selected rotating assembly 220, each unit
25 having its own backing material 214 and arrayed along a
longitudinal plane through the axis of rota~ion. One of
the important things that can be done with an array of
this sort is to provide, at least in the vertical dimen-
sion, a greater dimension of transducer. A larger diam-
30 eter transducer, of course, provides a much better colli-
mated beam, which is of real value in providing grea-ter
detail o-f the reflecting surface which it is designed to
probe.
There has been a great deal of theoretical and
35 engineering work done on the transmission of signals from
various types of linear arrays of transmitters. The same
logic that has been developed can apply to high frequency
radar antennas, or to sonar antennas, or seismic antennas,
s~
-2~-
both transmitting and receiving. These arrays, while
important in transmitting a more suitable beam of energy,
also provide a greater receiving sensitivity than a single
small transducer, as is normally used.
In FIGURE 10 an axis 232 is shown, in a diame-
tral plane, of the rotating assembly 220. The oval con-
tour 230 indica~es the shape of the beam in rela-tion to
its diameter, as a function of the distance, or radius,
away from the transmitter along the axis 232. This shape
10 230 can be improved by simultaneously energizing the sepa-
rate transducers in accordance with the theory. This
theory has been developed over the years and is well known
and is fully described in the literature. See, for
example, Albers, Underwater Acoustics Handbook II,
15 pp. 180-205. The type of beam form shown in FICURE 10 is
indicated as the possible improved type of transmitted
beam and receiving sensitivity when the proper theory is
used and the individual beam elements 226A, 226B, and 226C
are supplied with transmitting signals in proper phase and
20 amplitude rela-tion. Since the electronics of beam forming
is ~ell known, no further description of a beam forming
circuit is necessary.
Another capability of a linear antenna, such as
shown in the upper part of FIGUR~ 10, is that by proper
25 phase and amplitude control of the electrical signal
applied to the transducers, the main axis of the beam
which is shown as 232, for example, can be tilted, so that
the axis could be along the lines 240A, or 240B, or 240C,
etc., for example.
It is possible to use a second similar assembly
224 having a plurality of say three T/RTS, numbers 228A,
228B, and 228C, etc. The beam 231 could likewise be
tilted at angles 242A, 242B, or 242C, for e~ample, similar
to the angles of 240A, 240B, 240C. It is clear, there-
35 fore, if one of these assemblies is used as a transmitter
and transmits along the direction 240C and ~he other unit
22~ acts as a receiver and directs its receiving beam
along the line or axis 242C, then at a surface such as
~5 ~5
-25-
271, there will be a reflection of the transmltted energy.
The beam on axis 242C will be reflected back along axis
242C to the array of the unit 224. Also, by changing the
angles or tilt of the beams 230 and 231, the optimum point
5 of reflectivity can be changed from 271 to 271' or 271 ",
for example, and so on. The manner in which the tilt of
the beam can be changed is something that can be con-
trolled by means of the amplitude or frequency of a vol-
tage or current supplied to the circuit that does the beam
10 forming, and of course, this control can be provided from
the surface ~hrough a control conductor in the cables -to
the sonde. Thus, if the received signal as indicated by
the beam 231 can be transmitted -to the surface, and viewed
on a display, the beam tilting circuits can be varied to
15 change the radius over a wide range for careful explora-
tion of the material behind the wall of the borehole.
Of course, as has been described earlier, to get
deeper penetration of the beam, it is preferred to use as
low a frequency of oscillation of the transducer as pos-
20 sible without endangering the precision and detail of the
; measurement.
Also, where the liquid medium in the wellborecan be changed during the period of time the logging is
done, it may be wise to provide a suitable liquid medium
25 that offers the lowest attenuation to the sonic signals
utilized in the scanning process
Referring now to FIGURE 13, there is shown a
T/RTS system which is a further extension of FIGURE 10 and
includes a plurality of T/RTS in both a horizontal plane
30 and a vertical plane. Thus, assemblies 280, 28~ compare
to 220 and 22~ of FIGURE 10, but differ in that there are
two sets of vertically spaced T/RTS. Assembly 280
includes also an array 290A, 290B, 290C, and a vertically
spaced array 292A, 292B, and 292C. As in FIGURE 10, array
35 286 cooperates with array 288 to provide one transducer
286 for transmission and one transducer for reception, for
example. These are preferably multi-element so that beam
forming and tilting can be provided.
-26-
Similarly, arrays 290 and 292 cooperate with
each other in the same way. However, one of the advan-
tages of FIGURE 13 is that arrays 286, 288 can be lower
frequency, and arrays 290 and 292 can be higher frequency.
5 This is shown in FIGURE 13 by the indicated axes of the
two ~/RTS systems. Thus the effective radius of detection
of 286, 288 is 294 at radius 294', whereas the radius of
detection of 290, 292 is 298, at radius 298', which is
considerably shorter than 294'. Of course, both sets of
10 beams would be remotely controllable to different axes and
different effective radii.
FIGURE 11 illustrates the use of multiple trans-
ducers in a horizontal plane, which can provide beam
forming, in a way similar to the arrays of FI~URES lO
15 and 13.
I will now discuss how multiple ESS are trans-
mitted to the surface by the use of logging cables which
were originally designed for transmitting relatively low
frequency electrical logging signals, i. e., signals of
20 less than 50 KHZ.
Referring now to FIGURE 14, here is shown sche-
matically a rotating assembly 34, having four separate
T/RTS 46A, 46B, 46C and 46D, instead of two as shown in
FIGURES 2 and 3. These are arranged in the same tran-
25 sverse plane, perpendicular to the axis of rotation. Eachone is connected by conductors 46A', 46B', 46C', 46D', to
a multi-point switch 62' which is patterned after the
switch 62 of FIGURE 3, controlled by signal over dashed
line 64. A pulser, identical in all respects to the
30 pulser of FIGURE 3 shown in the dashed box 81, has three
terminals, one being provided with power 84, another pro-
viding the power output on lead 92, to transmit a sonic
signal, and a third lead 75, which provides a timing
signal to the pulser. Although not shown, the lead 75
35 would go to a timing device, such as 74 of FI~URE 3, which
would also be connected to time the transfer switch 66
marked T/RTS in FIGURE 14. The output of the T/RTS would
then go through an amplifier 70~ through a detector 67 to
~ 3
-27-
the transmission channel 72 of the cable 20 as shown in
FIGURE 3.
Earlier it was pointed out that any number of
T/RTS, as desired, can be provided on the rotating
5 assembly although only two were shown in FIGURE 3 and only
a single pulser was shown. In FIGURE 15 a similar circuit
is provided in which separate pulsers 81A and 81B are pro-
vided so that each of the T/RTS can be operated separately
from the others.
In FIGURE 15 each of the pulsers 81A and 81B are
supplied by power from the supply 84 through separate
leads 84A, 84B, and through separate resistors 16~A and
162B. The timing signal comes from the counter 166, which
is supplied with a clock signal from a clock 164 through
15 the line 182. The counter, or control 166 also provides
another signal output on leads 167 and 168 to the
transmit/receive switch 150. The switch 150 disconnects
the ou-tput leads 48" and ~6" whenever the pulser signal
is on the leads 46' and 48', which are connected through
20 slip rings to the two transducers T/RTS 46 and 48 respec-
tively.
Thus, with the apparatus of FIGURE 15, two sim-
ultaneous sonic signal transmissions are being carried on,
and the received signals are being transmi~ted through
25 lines 48 " and 46 ". The signals on these output lines
can go directly to the cable if there are two separate
transmission means. However, they can be combined, as
will be described in connection with FIGURES 16 and 18, if
there is only a single transmission system in the cable.
30 As also shown in FIGURE 3, a compass, preferably a direct
reading compass, such as a flux gate compass, for example,
or other available compasses provides a signal pulse on
output line 60' whenever the scanning T/RTS crosses a line
directed to the north. The pulsers are timed so that the
35 transmission pulses to the multiple T/RTS are synchron-
ized.
Since transmission of mu].tiple scan signals
involves the logging cable, it might be desirable to look
-28-
at the subject of the cable, which is the only means of
communication between the sonde and the surface. The log-
ging cables that are utilized for operating the borehole
televiewer are generally the same cables that are used for
5 many other types of sensing apparatus, which are used for
the logging boreholes and for the detection of various
properties of the subsurface formations. In the logging
of electrical resistivity, self-potential, and other types
of electrical phenomena, the signals are of much lower
10 frequency than they are in the borehole televiewer. A
cable with an ordinary conductor pair for transmitting the
signals is fully adequate. It is generally believed that
the commercial logging cables in use at ~he present time,
which may be from 20,000 to 30,000 feet in length, will
1~ adequately handle signals in the range of 50 to 100 kilo-
hertz (KHZ) or kilobits per second.
The desired resolution of the scan signals that
are transmitted to the surface may be set down as the fol-
lowing: In the measurement of caliper or the distance of
20 penetration of the sonic signals through mud and the rock
wall of the borehole, the minimum resolution desired would
be to .05", and 256 units of this would cover a radial
distance of penetration of about 13 or 14'l.
In the measurement of azimuth the conventional
25 timing is for 360 transmission pulses in a rotation of
360 giving a minimum angular resolution of 1. In the
measurement of signal amplitude, a six-bit digital value
for amplitude would indicate a minimal resolution of about
1 1/2%.
To transmit the scan signals with these minimum
resolutions would take 256 x 360 x 6 x 3 ~revolutions per
second) or 1.6 million bits per second. With such a high
data rate, it would obviously be impossib]e to transmit a
complete sonic scan signal by digital transmission,
35 although digital transmission would provide more precise
amplitude transmission. While there are available in
industry high frequency transmission channels, such as
coaxial cables and fiber optic channels, these are not
5~3
-29-
generally available today in logging service. In the
future it is very likely that they will be available, in
which case the data rates could be much higher, such as
would adequately handle complete scan signal digital
5 transmission.
There is distinct advantage in having multiple
T/RTS, such as two T/RTS, of different frequencies. If
one T/RTS is in the high frequency range, and the other in
a lower frequency range, the precision of amplitude mea-
10 surements at short distances from the transmitters wouldbe available with the high frequency unit, and a greater
depth of penetration into the rock would be available with
the low frequency transducers.
One method of handling this type of signal would
15 be to first delay one with respect to the other, until the
two scan signals are in phase, and then gate the high fre-
quency scan signal for a certain selected time interval,
and then gate the lower frequency scan signal. By this
means, a single analog signal can be transmitted over the
20 present cables very satisfactorily and still utilize the
benefit of two T/RTS.
Another way of utilizing the present cables
effectively with more than one T/RTS is to process the
analog scan signals in the sonde to determine khe ampli-
25 tudes of the reflected signals, and the correspondingradius of caliper, at the time of the return signal.
These two quantities can be expressed digitally in a rela-
tively few bits, so that as many as four such pairs of
signals could be transmitted sequentially, as by multi-
30 plexing, over the existing single analog transmission cir-
cuit in the conventional cables.
One type of present logging cable utilizes seven
conductors, of which two would be utilized for the trans-
mission channel and the other four would be used for con-
35 trol, power supply, etc. However, it could be possible touse four of the conductors to provide two separate con-
ductor pairs for analog transmission of the scan signals.
If there are two analog kransmission channels, two ESS
-30-
from two T/RTS coul.d be transmitted to the surface
independently and simultaneously, as analog signals, in
the conventional manner. Or the two transmission channels
could provide for transmission of eight separa-te scan sig-
5 nals when processed to transmit only the amplitude of thereflected signal and the time of the reflected signal.
With a pair of T/RTS of different frequencies, the ampli-
tude of the high frequency reflection and caliper of the
low frequency reflection could be combined for transmis-
10 sion.
Of course, where the multiple T/RTS are in thesame horizontal plane and spaced circumferentially on the
rotating assembly, they can individually be delayed in
time until they are all in phase, and they can then be
15 stacked to provide a signal of improved signal-to-noise
ratio.
Another combination which would be very useful
would be to provide two analog transmission circuits and
~o use two identical T/RTS on the rotating assembly, so
20 that at the surface there would be two scan signals per
revolution of the rotating assembly, and thus a shorter
vertical spacing between scans on the display could be
provided. Conversely, the sonde could be moved vertically
at twice the normal ].ogging rate, and still provide the
25 precisely same log that would have been provided with the
slower vertical logging rate, and a single T/RTS. Thus,
by using two or more identical T/RTS, it would be possible
to increase the rate of logging with the borehole telev-
iewer by a factor of two, or three, or more, depending
30 upon the number of T/RTS. This would provide a consequent
cut in the time for providing a log. Since one of the
major components of the cost of logging is for the idle
rig time, this could be cut in half if two T/RTS were
used, and so on.
Earlier it was mentioned that by means of an
apparatus to increase the fre~uency of the scan signals,
say b~ a factor of two, ~wo such signals could be trans-
mitted over a single transmission channel cable, sequen-
3S~L
-31-
tially, in the same time that it previously took to
transmit one of them. Of course, this would raise the
maximum frequencies in the analog scan signals and might
not be fully satisfactory. In such a case, it might be
5 desirable to alter the minimum data requirements on one of
the several measurements made. For example, it might be
possible to transmit one sonic pulse on each of two T/RTS
every two degrees of rotation of the rotating assembly,
but alternating the signal from one T/RTS to the other.
10 In this way, the separate ESS would be as normally trans-
mitted, and two such scans made by two separate T/RTS
could then be alternately transmitted over a single cable,
each in more or less a conventional manner. Of course,
another way of doing this would utilize the apparatus of
15 FIGURE 3, except that the switch 62, instead of being a
slow mechanical switch, would be a very fast electronic
switch capable of alternating connections at millisecond
intervals.
This would be a type of multiplexing in which
20 the transmission time is shared between the two trans-
ducers sequentially. Of course, the two ESS must be
placed in phase by adding time delay to one or the other
of the ESS, as shown in FIGURE 6, by the delay means 160.
On this same basis, three or four or more T/RTS can be
25 used sequentially with some lessening of the resolution.
Referring now to FIGURE 16, which is a modifica-
tion of FI~URE 15 showing alternating rapid switching of
the leads 75A and 75B by switch 21. It is shown as a
separate switch for clarity but is most conveniently done
30 in the counter 166. Switch 21 is shown as controlled by
means 21' from the counter 166. Thus, instead of trans-
mitting signals from both T/RTS, each (say at 1 of rota-
tion), the first T/RTS is transmitted say at l; line 402
of FIGURE 17; then one degree later line 404, the other,
35 but not the first; one degree later line 406 the first is
again pulsed, and the sequence continues. Only one is
pulsed at a time, each degree, to produce sequentially
signals 412, 414, 416, 418, and so on.
~s~s~
Of course, the two transducers are not
coincident, so the ESS from one of them, say on lead 48"
is delayed by time delay means 160, for one-half period of
rotation. This is done by the TD means 160 which can con-
5 veniently be one of the charge coupled devices which arecommercially available on the market and need no further
description. The two signals are then added by the resi-
stor network 385, 385', and applied to amplifier 386 and
transmission line 342.
As shown by FIGURE 17, at any one instant there
is only one ESS being transmitted so no gating means is
re~uired. The two ESS can be identical, that is, from
identica] T/RTS. However, they can be from dif~erent
T/RTS, such as indicated in FIGURE 17 showing a high fre-
15 quency T/RTS on lines l, 3, 5 and a lower frequency signal
(having later return of energy) on lines 404 and 408.
With reference to FIGURE 18, there is shown a
memory unit 380, which has four separate memory components
MlA, MlB, M2A, M2B, etc., numbered respectively 381A,
20 381B, 382A, and 382~. Two switches 374A and 374B are pro-
vided, one at the inlets to the memories, and the other at
the outlets from the memories. The two leads 370 and 372
-from the A/D converters 268 and 270 go to the two inlet
switches 374A, which can alternately connect these two
25 lines to the first pair of memories MlA and MlB respec-
tively, and on command, can switch the two lines to the
second pair of memories M2A and ~2B, and so on.
The second switch 374B operates in a similar way
but is 180 out of phase with the first switch 374A. In
30 other words, when the leads 370 and 372 are connected to
the first two memories, and switch 374B is connected to
the second two memories, and vice versa. The outputs from
the switch 374B ~o to D/A converters 375 and 375', then to
gating means 384 and 384', through two equal resistors 385
35 and 385', where they are joined together and to a line
drive amplifier 386, the output of which is connected to
the transmission charmel 342 of the cable. The bit rate
fro~ the analog-to--digital converters 268 and 270 is iden-
35~
-33-
tical to the rate of bit loading into Lhe memories through
switch 374A and is controlled by a clock oE frequency CF1
on line 387A, which comes from a clock C2 164B. The
readout from memory through switch 374B is controlled by a
5 higher frequency bit rate CF2, supplied on lead 387B from
the clock C2. The bit rate CF2 is normally twice that of
CF1. However, if three or more separa-te T/RTS are to be
multiplexed on the cable, CF2 would be 3 or more times
CFl.
There is a mechanism M, 378 driven by the base
clock 164, which controls the switches 374A and 374B
through means indicated by the dashed lines 376. These
two switches are switched synchronously, but as mentioned,
are out-of-phase. One is loading one pair of memories
15 while the other is reading out of the second pair of memo-
ries, and so on. Also, the gating means 384 is controlled
by a third frequency from clock Cl, 164A. Each of the
clocks Cl, C2 and M are controlled by the base clock C,
164, and frequencies are divi.ded down in a manner well
20 known in the art. However, while the frequencies for each
of the controls may be different, they are all synchro-
nously related through C.
Refer to FIGURE 19, and consider for purpose of
illustration that the two T/RTS are coincident on the
25 rotating. They are not physically coincident, of course,
since they are spaced 180 degrees from each other, ~ut
this can be taken care of by time delay means 160 as has
previously been explained. Thus the delayed signal 436
from A on line 430, which is shown by (A + Delay), is in
30 phase with the signal 438 from B on line 432. Both start
at T0 and last till T2. The rectangle between lines 428
and 432, and T0 and T2 is shaded to indicate a first pair
of memories MlA, MlB, into which these two ESS are loaded.
The next two ESS 436' and 438' are loaded in the second
35 memories M2A, M2B.
While the second ESS are being loaded, the pre-
viously loaded 436 and 438 are being unloaded, in sequence
at double rate, as 436A and 438A. This sequence is
5 3
-34
repeated. When the second memories M2A and M2B are
loaded, the next two will switch back to MlA and MlB and
so on. Thus, while two separate scan signals are being
recorded, simultaneously each one degree of rotation, the
5 two scan signals are being transmitted a~ double frequency
in sequence.
Of course, the two T/RTS can be similar, in
which case it would be possible to log at double speed,
without loss of detail, or they can be different ~one high
10 frequency and one low frequency) in which two separate
logs can be recorded. Each of the ESS transmitted can be
composite ESS, obtained by first gating a high frequency
ESS to provide a short range scan, and then gating a lower
frequency ESS for the longer range scan. Thus the two
15 transmitted ESS could be provided from four separate
T/RTS, two high frequency and two low frequency, and
so on.
Returning to FIGURE 18, the purpose of the
gating means 384 is that the two scan sign~ls which are
20 read out at a double bit rate will be transmitted sequen-
tially in the time that a pair of transmit-receive signals
is loaded into the opposite pair of memories in parallel.
Of course, only one of these 436A and 438A is read out at
a time. For example, the switch 374B is connected as
2S shown to the lower pair of memories. I~ may be desired,
for example, that M2A should be transmitted first, and so
that is read ou-t at double bit rate and passed by the
gating means 384 and through resistor 385 and amplifier
386 ~o the line 3~2 to the cable. When that is completed,
30 the second scan signal in M2B controlled by gate 384' is
read out at the higher bit rate, and is transmitted in a
similar manner to the line 342 in the cable. By the time
these two have been read out completely, the next pair of
reflection signals have been loaded into the top pair of
35 memories. The switches 374A and 374B are then operated,
connecting the inlet switches to the second pair of memo-
ries and the outlet switches to the first pair of memo-
ries, and so on.
~ 3
-35-
While I have shown in FIGURES 16 and 18 only two
ESS, it will be clearly understood that this is shown by
way of example, and not by way of limitation. Therefore,
the apparatus can be extended to transmit 3, 4, or more
5 simultaneous ESS by loading into memory at a first fre-
quency, and reading out of memory at a frequency higher by
a factor of 2, 3, 4, or more, and transmitting the
read-out signals sequentially.
FIGURES 15 through 19 illus~rate the use of mul-
10 tiple T/RTS so that in each revolution of the rotaryassembly, 2, 3, 4, or more -times as much information can
be recorded on each revolution, without change in the
basic mechanical system of the sonde. This provides the
opportunity to log at higher speeds without loss of essen-
15 tial information, and also provides the opportunity torecord multiple logs at the same or higher speed, pro-
viding additional information.
Referring now to FIGURES 20A, 20B, and 20C,
there are shown three circuits by means of which two elec-
20 trical reflection signals from two T/RTS on line 48' and46' are switched by T/RS 150, and on the output lines 48"
and 46" they go through separate amplifiers 152 and 15~.
One of them (FIGURE 20A) goes to a time delay means 160 as
previously discussed, to bring the two signals into phase.
25 They are then stacked by means of the resistor assembly
162A and 162B, and then passed through the amplifier 180
to the single transmission channel 178 of the cable 20.
As previously mentioned, it would be desirable
that the two T/RTS be mounted on the same rotating
30 assembly in the same transverse plane so that they would
be synchronous and they would be scanning along two sepa-
rate closely spaced parallel lines. By adding the two
signals the resulting signal, which would be the sum of
the two, would be of higher signal-to-noise ratio, and
35 therefore preferable to either one alone.
In FIGURE 20B there is shown a similar system
handling two separate T/RTS scan signals which go by means
of lines 48" and 46" to amplifiers 152 and 15~. One of
-36-
these signals goes through a time delay means 160 so that
the two signals would be in phase. However, they then go
through gating means 156 and 158, which are timed over
line 184 from a clock C, 164. If the tw~ ~/RTS are of
5 different frequencies, one, for example, is a high fre-
quency conventional type of transducer whose signal, say
for example, is on 48" , and a low frequency transducer
has its electrical scan signal on 46". Then a portion of
the higher frequency scan signal lasting at least as long
10 as the first reflected signal from the wall of the bore-
hole is first gated by 156 through the resistor assembly
162A and 162B, through amplifier 180 to line 178 in
cable 20. Then the second gate 158 is opened to transmit
later arrival of possible reflections from greater dis-
15 tances beyond the wall of the borehole. The lower fre-
quency scan signal is then transmitted through resistor
162B, a~plifier 180 and through line 178 to the surface.
In this way, two separate T/~TS can each provide valid
information best suited to their operating frequency, and
20 the total received signal transmitted up the single trans-
mission circuit 178 will be of greater value than either
one of the signals from either one of the T/RTS.
FIGURE 20C illustrates another method o han-
dling two independent T/RTS scan signals which, passing
25 through the T/RS 150 are then amplified by means 152 and
154 and go to a multiplexer of conventional form 260. As
is well known, the multiplexer then combines these two
independent signals by, in effect, chopping the analog
signals up into short pieces which are then alternately
30 transmitted through the line driver amplifier 180 and
through the transmission channel 178'. At the surface the
multiplexed signal is then demultiplexed in the box 261,
and the original two signals are delivered over lines
46"' and 48"' to amplifiers 262 and 264 to a
35 recorder 266.
A clock 164 in the sonde provides a ~iming
signal over line 184 to the multiplexer 260, and also
through a control conductor 184' in the cable 20, to line
~ 5
-37-
lg4" and the de~ultiplexer 261. These clock signals syn-
chronize the operation of the multiplex and demultiplex
operations.
The multiplexer can be used with analog or
5 digital signals. Normally the analog signals are sent to
a sample and hold circuit and are then sampled at the rate
of the clock 164. Their amplitudes are measured ancl con-
verted to digital signals of a selec-ted number of bits,
say for example, six bits. These sequential digital words
10 of six bits each, one :Erom one T/RTS and the next from the
second T/RTS are then transmitted as a string of digi-tal
bits over the single transmission channel 178'. At the
demultiplexer a reverse action takes place, where the
output o~ the demultiplexer on lines 46"' and ~8"' can
15 be, if desired, converted back to analog signals or may
very usefully be recorded as digital signals in the
recorder 266. The rapid bit stream can be recorded satis-
~actorily on digital recorders, such as magnetic tapes or
discs and so on. On the other hand, high frequency analog
20 signals can be recorded in analog form on magnetic tape,
such as the well-known video tape cassettes. This will be
discussed more ~ully in connection with FIGU~E 22.
Referring now -to EIGURES 21A and 21B, there are
shown means by which a pair of T/RTS can provide indepen-
25 dent electrical scan signals, which passing through theT/RS 150 are amplified through amplifiers 152 and 154 and
then are transmit-ted -through the cable 20 on two separate
analog transmission circuits 186' and 188'. At the sur-
face, the signals transmitted on the two separate lines
30 are converted to digital signals by the ~/D converters 268
and 270, which provide digital signals which can then be
recorded on recorder 266 for later playback.
FI~URE 21B illustrates one manner in which the
recorded data on recorder 266 can be utilized. The two
35 digital signals are read out from the recorder 266 through
the lines 46"' to a time delay device 272, such as was
shown in FI~URES 20A and 20B, and through line 48"'. The
two signals are then added by means of the resistor
,, ~
~38-
combination 274 and 276 to the display, not shown but well
known in the art. Ln -this case, what has been ~one is to
provide to the recorder signals from two T/RTS of the same
frequency, and they are shown being stacked and the
5 stacked signals going -to a display.
Referring now to FIGURE 22, there is shown a
typical set of recorders and devices that can be used at
the surface to utilize the signal that has been generated
in the sonde. While signals from multiple T/RTS can be
l0 recorded, FIGURE 22 illustrates the case of a pair of
digital signals, such as amplitude and calipers, which are
multiplexed on the cable. The cable 20 is shown being
metered up and down by means of a wheel 25, driven by the
movement of the cable. The wheel as it turns rotates an
15 encoder 350 which transmi-ts pulse signals which are indi-
cative of the angle of rotation o~ the wheel 25. The
encoder 350 is a conventional device and outputs a signal
over line 350' which goes to a digital tape recorder A,
266.
In FIGURE 22 there are shown several types of
recorders. One is called a tape recorder 266. The other
is 352 and is labelled a CRO recorder, or a cathode ray
oscilloscope type recorder. This u-tilizes analog signals,
such as the conventional electrical scan signals. The
25 tape recorder is generally a video tape cassette or disc
drive~ which records digital signals of high frequencies.
FIGURE 22 is based on the assumption of a digital trans-
mission with two signals being multiplexed.
The sonic signals on the cable transmission
30 channel 342 go directly through lead 3~2 to a tape
recorder 266. The depth encoder 350 going by lead 350' to
the ~ape recorde.r indicates information corresponding -to
depth of the sonde. The sync signal, or the north pulse
coming from -the compass, is separated out in -the sync sep-
35 arator, marked SS 351, and the north indicating pwlsetravels by line 60 " to the tape recorder. Thus, all
essential information arriving over the ~ransmission
channel is stored in the tape recorder 266 and can be
-39-
played back later to recover the original signal for
display in any one of a number of different ways.
So far as the two scan signals are concerned,
they travel over lead 342' to S~ 351. There the sonic
5 signal is separated out and goes over line 316 to the
D-MUX 354. The synchronizing signal taken off the line
342' is used over line 318 to control the rate at which
the demultiplexer operates so as to be in synchronism with
the multiplexer in the sonde. The demultiplexer 354 is
10 indicated as a synchronous switch that transmits the
incoming signals on 316 to two separate lines 316' and
318'. Thus digital signals from each of the two T/RTS are
then applied to individual digital-to-analog converters
356 and 358 respectively. The individual outpu-ts are then
15 taken by lines 316" and 318" to the cathode ray recorder
352, which is a very fast recorder, responsive to the
normal frequencies of the electrical scan signals.
One possible example of the two separated sig-
nals calls for one to be a reflection signal and the other
20 to be a caliper signal. These can come from a single
T/RTS or can be taken from two separate T/RTS, one of high
frequency and one of low frequency, which has previously
been discussed. Conventional photographic means are pro-
vided to form the logs la~elled 360A and 360C, respec-
25 tively amplitude and caliper logs.
The signals on line 316' and 318' from the dem-
ultiplexer 354, which are individual digital signals, may
also be recorded directly on recorder B 266'. The differ-
ence between this recorder 266' and recorder 266 is that
30 the signal recorded on the tape recorder 266 is a multi-
plexed signal which can, if desired, be played back later
through D-MUX 354, through D/A converters 356, 358 and
displayed as individual logs and so on. On the other
hand, tape recorder 366' has two channels, each one
35 recording a complete digital signal transmitted from the
sonde.
It is possible, o~ course, also to send the
analog signals that would come from line 316" and 318"
3 5
-40-
to an analog tape recorder such as 266" for storage and
later playback.
While in FIGURE 22 the two signals are indicated
as amplitude and caliper signals, it will be clear that
5 they can be complete digital electrical scan signals or
they may be analog electrical scan signals which are
transmitted by two separate transmission lines, as in
FIGURE 21A.
Referring now to FIGURE 23, there are shown two
10 channels for processing of the ESS. The inputs are taken
from the output portion of FIGURE 15 and shows two output
signals 48" and 46" from the T/RS 150. One of these
goes to the dashed box 302, and the other goes to the
box 302', which is identical in all respects to the
15 box 302. However, none of the internal detail of 302' is
shown, since it would be identical to that shown in the
dashed box 302.
Following the signal on lead 48" from the
T/RS 150, the signal is amplified at amplifier 304 and
20 detected at the box DE, 306. Since the received signal is
generally a very high frequency electrical signal, it is
necessary to process this signal to provide the envelope,
which is a lower fre~uency unidirectional analog signal.
The detected signal is the one which is conventionally
25 transmitted to the surface. The deteetor 306 is a conven-
tional part of the present-day televiewer and forms no
part of this invention.
The detected signal on line 324 goes back to the
"amplitude" channel, to amplifier 308, and peak detector
30 310. This peak detector determines the highest amplitude
of the received signal, and the sample-and-hold 312 makes
a temporary record of the amplitude of the signal. This
peak amplitude that is sampled now goes to an analog-to-
digital converter 314, which measures the amplitude to six
35 binary bits, and this digital number is transmitted
through lines 316 to the multiplexer 320.
At the same time, the signal on line 324 also
goes to the detector 306 and to the "caliper" channel, by
~3
-4:L-
line 326. This starts with a variable gain amplifier 328.
The need for this arises from the fact that the received
signal becomes weaker and weaker, depending on how far it
has traveled into and ou~ of the rock wall. Consequently,
5 the signal is amplified in an amplifier that provides
increasing gain or amplification, with increasing time of
travel of the pulse and its reflection. Thus, even at the
remote end of its path, the amplitude of the reflection
from a flaw or obstacle, will be large enough to be mea-
10 sured.
In the method of determining the precise time ofarrival, the amplified signal from 328 goes to a differen-
tiator 330, and to a comparator 332.
The counter 344 is controlled by the sync signal
15 on line 184. The counter provides two different frequen-
cies F1 and F2. The high frequency F1 controls the digi-
tizer 314 and the counter 322. The lower frequency F2
controls the multiplexer 320, which controls the two six
bit signals on input lines 316 and 318. The lines 316
20 carry the six bit signal from the A/~ converter 314. The
six bit lines 318 bring the signal from the counter 322,
which has counted the time to the reflection in terms of
digital bits.
Thus there is on one channel, line 324, a mea-
25 sure of the "amplitude" of the signal and on the otherchannel, line 326, a measure of the time of travel, or
caliper. These two six bit binary numbers then are passed
sequentially to a parallel to-serial converter. Here the
parallel words of six bits are converted to serial words
30 of six bit, and transmitted to line drive amplifier 340
and to cable channel 342.
The multiplexing is done by alternately sampling
one or the other of the boxes 314 and 322, corresponding
to each of the separate initiations of the sonic signal.
35 So for each transmission resulting from the pulsers of
FIGURE 15, there is obtained two six bit binary numbers
which are alternately transmitted through the parallel-
serial- (P/S) converter ~o the cable 342. The switching
~ 3
-42-
is accomplished by means of the gate control apparatus 315
over leads 348A and 348B. Also, if a sec~nd scan signal
is being provided over line 46" to the signal processor
302'9 the same switch or gate means 315 is also supplied
5 by means of leads 348A' and 348B'.
The compass signal comes in on line 60' from the
compass 60 as shown in FIGURE 15, and goes into the ampli-
fier 340, and also through lead 60'' to the amplifier
340', which amplifies the output of the second signal pro-
10 cessor, and goes by lead 342' to the cable. As shown,there are two transmission channels 342 and 342', each
handling the output of a different T/RTS.
Consider again the signal processor in the
dashed box 302. If there is a single scan signal on input
15 line 48" , this signal breaks two ways -one through the
amplitude branch, and one through the caliper branch. In
one mode of operation both measurements of amplitude and
caliper are made on the same transducer ESS. As will be
discussed in connection with FIGURES 4A and 4B, with the
20 use of two T/RTS, one of high frequency and one of low
frequency, the two ESS can be combined into a composite
scan signal, which, in the early part is recorded by the
high frequency T/RTS, and in the later part is recorded by
the low frequency T/RTS.
It will be clear, therefore, that in a second
mode of operation, using a composite ESS, that the ampli-
tude channel can provide amplitude information from the
early part, and caliper information from the later part.
In a third mode of operation a first pair of
30 measurements of amplitude and caliper are made from the
early part. The measuring parts of FIGURE 23 are then
reset, and the operation is repeated again in the later
part of the composite ESS.
Thus it is contemplated in the use of two trans-
35 ducers, one of high frequency to provide amplitude at thefirst reflector, the wall of the borehole, and a lower
frequency one ~o provide -the time of travel of the cal-
iper. By use of switches 324' in line 326, and 324 " in
-~3-
line 46'', with connector 341, it is possible to utilize a
high frequency transdllcer on line 46" so that the caliper
measurement in the processor 302 would correspond to the
caliper of the lower frequency transducer while the ampli-
5 tude would be corresponding to the higher frequency trans-
ducer.
I previously pointed out that by use of gating
means, a high frequency and a low frequency transducer
could be gated sequentially onto a single transmission
lO channel and thus, such a composite signal on 48 " would
provide, without the switches 3241 and 324 " the amplitude
and caliper measurements respectively from both trans-
ducers.
In FIGURE 23 I have shown a pair of switches
15 324' and 324". With the switches as shown, a single ESS
on lead 48" could be connected to both the amplitude and
caliper channels 324, 326 of processor 302. In another
mode of operation, switch 324' is moved to lead 341, as is
also switch 324'', so that the ESS on 46" goes to the
20 caliper channel while 48 " goes to the amplitude channel
of the processor 302.
While I illustrate in FIGURE 15 a processor that
would transmit and receive two sonic signals from two
transducers 46 and 48 respectively, it will be obvious
25 that the same apparatus can be used with a
transmit/receive switch 150' (FIGURE 24) to handle 3, 4,
or more separate signals as it does the two signals on
leads 46' and ~i8'. Also, each of these single transducers
can be combined as previously mentioned, so that two
30 transducers together provide one pair of signals of ampli-
tude and caliper. Thus, to transmit four such signals in
digital for~ on a single transmission line it could uti-
lize eight separate transducers, four of high frequency
and four of low frequency, and so on.
Also, I have shown in FIGURE 23 that two sepa-
rate transducers providing signals on lines 48 " and 46"
could each be composed of the gated scan signals from a
pair of high and low frequency transducers.
~5 ~ 5
-~4-
Referring now to FIGURE 2~, there is shown a
modification of FIGURE 23. Briefly, six T/RTS are shown
and indicated by letters A, B, C, D, E, and F. These all
lead into a transmi-t/receive switch 150A that controls all
5 of the reflected signals on the leads which are identified
by the indication HFl, LFl, HF2~ LF2, HF3, and ~F3, etc.
In other words, there are six or more transducers, three
of them high frequency, which produce measurements of
amplitude, as shown in the amplitude line of 302. The
10 other three transducers are low frequency, and they will
pass ~hrough circuits corresponding to the caliper line of
box 302 of FIGURE 23.
Since the amplitude signals are taken from the
short range transmission, that is, from the wall of the
15 borehole, they will all be multiplexed together by MUXl,
320A. All of the low ~re~uency signals of caliper will be
multiplexed in 320B. All of the signals coming into the
multiplexer 320A and 320B are now digital. They are con-
trolled by the clock signal on 184, which goes by lead
20 184A to the two multiplexers. This timing signal also
goes to the parallel-to-serial converter 32~'.
The P/S converter does two things, it stores
each of the six signals coming from the two multiplexers
and reads out the bits in serial order. Also by means of
25 a switch 391 it reads all of the signals from multiplexer
1 and then switches over and reads them from multiplexer
2, then 1, and so on. Of course, the three pairs of sig-
nals can be read out and transmitted in other combina-
tions. The output of the P/S converter then goes to the
30 amplifier and line driver 3~0 and to a single transmission
channel 342 in the cable 20.
While FIGURE 24 shows that two separate T/RTS,
such as HFl and LFl together provide one pair of data, the
six T/RTS shown would not even fully load a single trans-
35 mission channel.
Another way o~ handling the individual T/RTSwould be as indicated in FIGURE 23 where the jumper lead
341 is not connected, and both the amplitude and caliper
-~15-
channels process the signal from a single T/RTS. That is,
the signal from 48 " goes to both lines 324 and 326 and
another signal from T/RTS 46 goes by line 46" to the
second processor 302'. In this format, only four T/RTS
5 can be handled on one transmission channel.
Refer back now to FIGURES 4A and 4B. There are
shown two T/RTS 46 and 48. One 46 is a high frequency
transducer (possibly in the range of .75 to 1.25 MH2),
while 48 would be a lower frequency transducer (possibly
10 in the range of 250 KHZ to 850 K~Z). They transmit beams
of sonic information 16, and 32 respectively. It is well
known that the higher frequency beam has a shorter dis-
tance of penetration in a liquid or solid medium. Corre-
spondingly, lower frequency beams have a greater distance
15 of penetration.
The best range of usefulness of the high fre-
quency T/RTS is ZA, 100, while for the lower frequency
T/RTS the best range is ZB. Thus, by using both, a much
greater range of usefulness is provided, ZA -~ ZB.
20 FIGU~E 4B shows -the gating time schedule in which the
first gate 116 on line 134 passes the high frequency ESS
from T0 to TS, and then the second gate 122 on line 136
passes the low frequency ESS from time TS onward.
While not shown, the multiple pairs of digital
25 numbers transmitted from FIGURE 24, go by conductor 342 -to
the surface, along with the clock signal to the multi~
plexers 32A, 32B on lead 184B'. At the surface the
digital signals are demultiplexed, converted to analog
signals and s-tored or displayed.
What has been described is basically a system of
multiple T/RTS in a sonic borehole scanner or borehole
televiewer, which has a plurality of transducer assemblies
by means of which the combination of scan signals from the
plurality of T/RTS can provide information of greater
35 value, more effectively, and more efficiently, than can be
done with a single T/RTS.
The multiple T/RTS can, of course, be arranged
with respect to each other in azimuthal array in a hori~
-46-
zontal plane, or in a vertical array in a vertical plane,
or in combinations of multiple horizontal planes and/or
multiple vertical planes as has been fully described.
When the words "high frequency" and 1'1Ow fre-
5 quency" are used to characterize the properties of thetransducers, they ~ean transducers that have natural
oscillation frequencies in the ranges of about 0.5 to
about 1.5 M~IZ, and from about 75 to about 750 KHZ, respec-
tively.
Also described is a group of embodiments of
apparatus for processing multiple analog electrical scan
signals detected in the sonde, by means of multiple T/~TS
on the rotating assembly. These can be processed in a
number of ways which have been illustrated and described,
15 and transmitted to the surface. This can be by way of a
normal single channel logging cable or a multiple channel
logging cable or an improved logging cable, which might
have very high frequency transmission capability, such as
by the use of coaxial cable channels, or optical fiber
20 channels, and so on.
While I have described multiple T/RTS usage when
placed in a common transverse plane on the rotating
assembly, the apparatus of this invention and the method
of opera$ion are equally valid for any type of multiple
25 T/RTS whether placed in vertical arrays or circumferential
arrays, or any combination of the two.
While I have shown and described methods and
apparatus for processing multiple ESS so as to permit
transmission of multiple ESS over presently available low
30 frequency transmission channels to the surface, these sig-
nals could of course be transmitted to the surface without
processing, where the cable provides single or multiple
high frequency channels, and the same processing done at
the surface. The point being that the processing is
35 important in the utilization of the multiple ESS~ whether
done in the sonde, or at the surface. It is also impor-
tant as a basis for transmission over low frequency chan-
nels. So, when I speak of processing ESS I mean either
processing in the sonde or at the surface, as appropriate.
S~
-~7-
This invention makes possible three-dimensional
imagery of the rock response surrounding the borehole.
This concept is considered useful in application to any
logging parameter that can be focused and beam steered.
While the invention has been described with a
certain degree of particularity, it is manifest that many
changes may be made in the details of construction and the
arrangement of components without departing from the
spirit and scope of this disclosure. It is understood
10 that the invention is not limited to the exemplified
embodiments set forth herein but is to be limited only by
the scope of the attached claim or claims, including the
full range of equivalency to which each element thereof is
entitled.
