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M. 24, 1946.
g. M. SHOOK ETAL
2,413,116
SYSTEM FOR GEOPHYSICAL EXPLORATION
Filed Feb. 14, 1944
4 Sheets-Sheet 2
aduzlm mzOvEuw
INVENTORS.
Ear/2y M. Shoal: 0m!
Ruben‘ M. Olson.
5V J
'
5
W
#orney.
%¢.21,1916.
EMSHOOK “AL
V
2,413,111
. SYSTEM FOR GEOPHYSICAL EXPLORATION
Filed Feb. 14, 1944
)
4 Sheets-Sheet 3
mm4-
INVENTORS.
Ear/cg M. Shock and
Rob/arr‘ W Q/son.
BY
Dec. 24, 1946.
E_ M_ SHQOK EI-AL
2,413,136
SYSTEM FOR GEOPHYSICAL EXPLORATION
Filed Feb. 14, 1944 v
20
FIGURE'S
4 Sheets-Sheet 4
0
‘20A
FIGURE-7
INVENTORS.
Ear/cg M. Shock and
Eoéer/ W Olson.
Afforney.
2,413,116
Patented Dec. 24, 1946
UNITED sures PATENT OFFlCE
2,413,116
SYSTEM FOR GEOPHYSICAL EXPLORATION
Earley M. Shook and Robert W. Olson, Washing
ton, D. 0., assignors, by mesne assignments, to
Socony-Vacuum Oil Company, Incorporated,
New York, N. Y., a corporation of New York
Application February 1d, 1944, Serial No. 522,358
5 Claims. (Cl. 177-352)
1
2
This invention relates to geophysical explora
tion, more particularly to re?ection methods of
seismic surveying in which the time break, the
uphole geophone, and communication signals are
wires for the transmission of the time break, the
uphole geophone, and communication signals
from the shotpoint to the recording truck. The
to be transmitted from the shotpoint to a record
transmission by radio of these signals has been
proposed, but spurious signals superimposed upon
ing truck.
the carrier have made difficult the transmission
.
The seismograph method of exploration en
and recordation of the desired signals with su?i
ables geologists and geophysicists to determine‘
cient clarity so as to be easily recognized on the
the location and depths of geological structures
seismogram. Systems such as shown in Shook
favorable to the accumulation of petroleum and 10 et al. Patent No. 2,290,773 have been utilized, but
other subsurface deposits. In brief, at a suit
leave much to be desired in the faithful trans
able location in the area to ‘be explored or sur
mission and recordation of all or a selected por
veyed, a shothole of a few inches in diameter is
tion of the signals from the uphole geophone.
drilled into the ground to a suitable depth, of the
In carrying out the present invention in one
order of from 50 to 100 feet. In the shothole is. 15 form thereof, a frequency modulated carrier wave
inserted a suitable charge of a high-explosive
is utilized for the transmission of signals repre
such as dynamite. This hole is generally ?lled
sentative of the time break and the uphole break
with water in amount adequate for tamping. The
and the same carrier is amplitude modulated for
dynamite is exploded by a detonating cap con
the transmission of communication or voice sig
nected to an electrical blaster, preferably of the 20 nals. The combined AM-FM system which forms
type shown in Minton Patent No. 2,189,741. The
the subject matter of the present invention func
explosion creates. seismic waves which travel
tions faithfully to transmit an electrical impulse
through the earth in all directions from the shot
representative of the instant of creation of the
point. By means of a geophone placed at the top
seismic waves; it functions with extremely high
of the shothole, the time required for the vertical 25 ?delity. to transmit the exact character of the
travelling waves to reach the earth’s surface may
?rst seismic wave received and detected by the
be ascertained.
uphole geophone; and it functions to permit the
At a suitable distance from the shothole, from
simultaneous transmission of voice signals. A
one to ?ve thousand feet for reflection shooting,
minimum of equipment and power is utilized.
and up to 5 or 10 miles for refraction shooting,
The system further includes means automatically
geophones or detectors are distributed along a
operable after transmission of the desired uphole
line Or over a selected area. These geophones
geophone signal to disable the transmitting sys
known as the spread geophones may be from 5
tem as a whole in order that the same galvanome
to 50 in numberr They are connected through
ter at the recording truck may be used for one of
ampli?ers to a multi-element recording galva 35 the spread geophones. In this manner a single
nometer to produce a photographic record of the galvanometer records on a single trace of a‘seis
arrival of the seismic waves. They not only re-'
mogram the time break impulse, the uphole break,
cord the waves which travel directly from the
and the signals received by one of the. geophones
of the spread.
shothole to the spread geophones but they also re
cord re?ections of the seismic waves, which re 40
This invention further resides in features of
flections occur between each interface of strata
construction, combination and arrangement de
having materially different physical characteris
tics.
scribed hereinafter.
'
For a more detailed understanding of the in
'
From the foregoing, it will be seen that not
vention, reference shouldnow be had to the ac»
only must the photographic record, the seismo 45 companying drawings, in which:
gram, faithfully record the detected signals, but
Fig. 1 is a block diagram of the transmitting
also that the time of arrival of the differing waves
at the respective geophones is of paramount im
portance.
-
system;
.
'
Fig. 2 is a block diagram of a preferred receiv
.- ing system;
In areas to be surveyed, ?eld operations may 50
Fig. 3 illustrates the desired data as recorded
be exceedingly difficult. Between the shotpoint'
and the recording truck, there may be heavy un
on a single trace of a seismogram;
dergrowth, swampland or ?ooded areas. These
mitting system embodying the invention;
’
Fig. 5 is a sectional elevation of a frequency
greatly increase the cost of, if not preventing,
‘
Fig. 4 is a schematic wiring diagram of a trans
entirely, the stringing of the necessary telephone 55 modulating device; and
2,413,118
3
through the doubler 18, the quadrupler 20, the
Figs. 6 and 7 are views looking toward the crys
tal and actuating unit, respectively.
?nal ampli?er I3, is radiated from the antenna
l4.
Referring to the form of the invention illus
trated in Fig. 1, a blaster l0 includes a detonat
As before, the FM carrier is demodulated
at the receiver and the uphole geophone signals
ing system preferably of the type shown in Min
ton patent No. 2,189,741. During. preparation or
installation of the explosive charge in the shot
hole, and during the location of the spread of.
geophones, the crew at the shotpoint maintains
communication with the crew at the recorder by 10
means of a. microphone _II which through an
ampli?er [2 produces amplitude modulation at
the ?nal ampli?er [3 of the transmitting system.
are recorded, as shown at 23, Fig. 3, on the single
trace 2i of the seismogram. The instant of ?rst
arrival of the uphole signals is accurately deter
mined and the true character of the uphole break
is faithfully recorded.
The ?rst of the uphole signals, derived from
the ampli?er IT by way of line 25, initiates op
eration of a blocking means 28 for the applica
tion of a negative bias, by way of lines 21 and
28, to the ampli?ers l2 and II, which bias renders
each ampli?er inoperative or blocks the further
The amplitude modulated carrier is radiated
from an antenna l4. A radio transmitter of any
suitable type for transmitting voices at the re
cording truck and a radio receiver at the shot
point (neither shown) may be utilized to com
transmission
of signals therethrough.
This
blocking means 26 eliminates all further signals
from the recording galvanometer and makes it
possible for the trace 2| to be utilized for the
plete two-way communication between the ?eld
parties. When. all is in readiness at both loca 20 recordation of signals 28 from a selected geo
phone of the spread. Alternatively the blocking
tions, with the uphole geophone l5 located on the
means may be operated a time interval after pro
earth's surface adjacent the shothole, word is re
duction of the time break impulse.
.
ceived from the recording truck to detonate the
The preferred form of the receiving system is
charge of dynamite located in the shothole.
This is done by operation of the blaster Ill. Co 25 diagrammatically illustrated by the block dia
gram of Fig. 2. The carrier, frequency and
amplitude modulated, is received by an antenna
30 and is applied to a conventional mixer 32
which also receives a locally generated signal
incidentally with the explosion of dynamite, a
single time break impulse is produced by gen
erator I6, This single electrical impulse is ampli
?ed by ampli?er l1 and by means of the crystal
oscillator and frequency modulator as indicated 30 from a local oscillator 33.‘ In accordance with
at IS, a frequency modulated impulse is produced.
The frequency modulated impulse passes through
a frequency doubler l9, and frequency quad
rupler 20, the ?nal ampli?er l3, and to the
antenna I4. The frequency modulated carrier 35
is demodulated by a suitable receiver at the re
cording truck and the single time break impulse
is faithfully recorded on the seismogram by a
suitable galvanometer appropriately connected
to the receiver. , This time break impulse is in
conventional superheterodyne principles, the re
sult is an amplitude and frequency modulated
signal at an intermediate frequency, which is
then ampli?ed in two intermediate frequency
stages 34 and 35. The ampli?ed output from
the second IF stage 35 is applied by line 36 to
a demodulator or detector 31 of amplitude modu
lated signals and the audio output therefrom
passes through an ampli?er 38 and to a loud
40 speaker 39. The ampli?edoutput from the sec
trace of the seismogram coincidentally with the
instant of generation of the seismic waves, which
ond IF stage 35 is also applied to limiter 40. The
two limiters 40 and 4| function to provide an
output signal for a discriminator 42 of uniform
amplitude and in avoidance of interference by
are produced by the explosion of the dynamite.
the amplitude modulated carrier. The frequency
dicated at 22, Fig. 3. As above explained, it is
known as the time break and it is recorded on a
modulated signals are detected or demodulated
It will be understood by those skilled in the
by the discriminator 42 and pass by way of an
art that a seismogram is produced by suitable
attenuator 43 to one of several recording gal~
means such as a multiple-element recording
vanometers 44 which produces the seismogram
galvanometer. Each” galvanometer produces a
single trace which may correspond with the seis 50 illustrated in Fig. 3. The output signal from the
discriminator 42 may also be utilized to initiate
mic waves received by a detector or geophone.
operation ,of a master controller 45 which, in co
The trace of Fig. 3 also records the time break
operation with one or more ampli?ers 46, con
22 as already described. Across each trace are
trols the gain in the signals from a plurality of
vertical timing lines. The horizontal distance
between adjacent lines is generally predetermined 55 geophones 41 comprising the geophones of the
and selected to equal one-hundredth of a second.
Since the uphole geophone may be but from .
50 to 100 feet from the seismic wave generating
means, the time required for the waves to reach
spread.
The master controller 45 may be of a
type like or similar to those described in United
States Letters Patent No. 2,301,739,v 2,306,991,
or‘ 2,312,934.
With the foregoing understanding of the-broad
the uphole geophone is exceedingly short. It 00
principles underlying our invention, reference
usually is of the order of from ?ve thousandths
may now be had to the wiring diagram of Fig. 4
wherein the blaster III, as above described, in
cludes a. circuit effective upon detonation of the
only operate to produce the single time break
impulse but Within that exceedingly short time 65 charge of the dynamite to apply a voltage im
pulse to the primary winding 48 of a transformer
it must be rendered inoperative for the produc
to two hundredths of a second. This means, of
course, that the impulse generator [6 must not
tion of other or additional impulses; otherwise, '
49. - The secondary winding 50 is connected
through coupling condensers 5i and 52 to the
control grids 53 and 54 of a pair of gas tubes 55
obscured and indeterminable on the seismogram.
The instant of ?rst arrival of the vertical travel 70 ‘and 58, each of which has the characteristic of
continued ?ow of anode or plate current once the
ling seismic waves at the uphole geophone I5 is
grid loses control. Tubes-of this type are also
detected and the resultant electrical signal ap
known by the trade name of “'I‘hyratron." Each
plied to the ampli?er I1, the output from which
of the control grids 53 and 54 has a negative
is utilized to produce at l8 frequency modulation
of a radio carrier wave which, after passing 75 bias derived from the negative end of a voltage
the signals from the uphole geophone would be
‘2,418,116
5
.
'
divider 58 which bias is applied by way 01' the
contact 58 of a double pole switch 88, conductor
BI and by resistor 62 to control grid 53 and by way
of resistor 53 to control grid 34. The cathodes
and suppressor grids of each of the gas tetrodes
55 and 58 are connected together and to con
ductor 84, which forms a common return circuit
to a tap 65 located at a position marked at zero
on the voltage divider 58. While gas tetrodes are
triode tube 88 includes the coupling condenser 88
and a tank circuit 88 which functions as a fre
quency doubling stage. The output from the ire
quency doubler is applied through grid leak con
denser 8| to the control grid of a tetrode tube 82,
the output circuit of which includes a coupling
condenser 83 and a tank circuit 84 which func
tions to quadruple the frequency. The output
from tube 82 is applied through the grid leak
illustrated, it will be understood gas triodes may 10 condenser 85 to the control grid of a thermionic
be used if desired.
tube 88, the anode or output circuit of which
By reason of the circuit connections including
includes a coupling condenser 81 and a tank cir
resistors 82 and 83, the negative ‘bias on one or
cuit 88. The inductor 88 forming a part of the
the other of control grids 53 or 54 is materially
tank circuit 88 is inductively associated with the
reduced in value by the'voltage impulse applied
coils I88 and MI. The coil I88 has one end con
by the blaster ‘I8, while the negative bias on the
nected to the exterior of a concentric transmis
other grid is materially increased. The exact op
sion line and its other end is connected to the
eration depends upon the polarity of the impulse
inner conductor or wire thereof, which leads to
as applied to the primary winding 48. Regard
the radiating antenna I83. The outside of the
less of polarity, however, any impulse from the 20 transmission line is also connected by conductor
blaster I8 makes one Or the other of grids 53 or
54 su?iciently less negative to cause a gas tube
to ?re or/to render it conductive. Plate current
immediately ?ows through a circuit which may '
be traced from a tap 85 on‘ the voltage divider 58 25
by conductor 66a, resistor 81, meter 68, conductor
59,‘ resistor 18, switch 1I, condenser 12, conductor
I82 to ground G.
'
The coil I8I comprises a single turn and forms
a part of a link circuit between the ?nal tank cir
cuit 98 and the tank coil of the frequency quad
rupler. This is accomplished by a second coil I84
comprising a single turn located in inductive re
lation with the' coil or inductor of the tank cir
13, (and assuming gas‘ tetrode 55 is ?red) re
cuit 95. Sumcient coupling of correct polarity is
sistor 14, the anode of tube 55 and from the oath
obtained to provide neutralization of the ?nal
ode by way of conductor 64 to tap 65 on the volt 30 stage.
,
age divider 58. Current continues to ?ow until
By means of a microphone I05 voice currents
the condenser 12 is charged. This occurs very
may be produced in the primary winding I86 of
rapidly and when condenser 12 is charged, the
a transformer I81 when a normally open switch
e?ect is to remove the voltage from the anodes of
I 88 is moved to closed position. This circuit may
the tubes 55 and 56 and neither tube may ?re 35 also include battery I89, if desired. From the
upon reversal of or production of subsequent im
secondary H8 of transformer I81, voice signals
pulses from the blaster I8. This fact is important‘
are applied directly to the control grids of a
inasmuch as the blaster ordinarily-includes wires
double triode tube III, the respective electrodes
which are ruptured by the explosion of the dyna
of which are connected in parallel with each
mite. In many cases the wiresare not only blown 40 other. The grid circuits may be traced through
apart but are also blown upwardly and possibly
winding H8, the conductor 69, meter 68, resistor
out 'of the shothole. During their travel-they may
61, conductors 86a and II 2, and the resistor'l I4,
repeatedly engage and disengage. In many cases
which is connected to the two cathodes of tube
there are a number of impulses following the one
III. The grid biasing resistor H8 is provided
indicative of the instant of creation of the seismic 45 with the usual bypass condenser I I5. The out
waves. By providing the foregoing circuit ar
put from tube I I I is applied through transformer
-angements for the two gas tubes, but a single
III; to the control grids of a double triode tube
impulse is generated-the one that coincides with
II1. In this case, the respective cathodes are
Ihe instant of creation of the seismic wave.
connected by conductor H8 to a midtap of the
It will be observed one side of the series com 50 secondary winding of transformer H6. The re
.)ination of meter 68 and resistor 81 is connected
spective trlodes of the tube II1 are connected in
by conductor 15, resistor 16 and by conductor 11
to the control grid of a thermionic pentode ampli
9
push-pull relation, the output circuit including
the primary winding of a transformer I28, having
t‘ying tube 18, while the other side of the resistor
a conductor I 2| leading from a midtap thereof
51 and meter 68 is connected by conductor 19 55 through a. resistor I 22 to the source of anode
and resistance 88 to the cathode of tube 18. In
potential, including voltage divider 58. The sec
consequence, the current impulse through the re
ondary winding of the transformer I28 is in series
sistor 61 and meter 68 produces a potential dif
' with the source of anode potential for tube 96.
ference or IR drop which is applied to the control
Thus, one end of the secondary is connected
grid of pentode 18. The result is the production 60 through an RF choke coil I24 to the anode‘ of the
in the output circuit including the primary wind_
tube_96, while its other end is connected by con
ing 8| of transformer‘ 82 of a voltage impulse of
ductor I88 to B plus on voltage divider 58, the
ampli?ed magnitude. This is applied by sec
return being by way of ground connection G and
ondary winding 83 to an operating coil 88 of a
conductor I82 to the cathode of tube 86.
'frequency modulating device 85, the details of 65
As previously pointed out, the transmitting sys
which will be later set forth. The application of
the ampli?ed impulse to the device 85 produces
a change in the frequency of the crystal oscil
lator which includes the ?rst stage of a, double
tem may frequently be operated in a region quite
remote from good roads and usual power facili
ties. Hence the design requirements are some
triode thermionic tube 86, whose output circuit
sumption. Ordinarily, storage batteries are uti
lized, with a vibrator, and suitable transformers,
includes the coupling condenser 81 and the tank
circuit 88. The output of the crystal oscillator
stage is applied through grid leak condenser 81a
to the control grid of the second section of the
what severe as regards weight and power con
and ?lter circuits to provide the required poten
tial for the supply of anode current. The tube
H1 is preferably operated as a class B ampli?er
double triode 86. The second stage of the double 75 and a relatively large condenser I28 is connected
2,413,110
so as to supply the peak demands of class B.
modulation.
-
‘
Members of the crew at .the shotpoint may
utilize the microphone I05 to communicate with
' bered the resistor 61' was also utilized in conjunc
‘ tion with the capacitor ‘I2 to produce the single
impulse representative of the time break. This
impulse. resulted from the momentary ?ow of
current through the resistor 61, a ?ow'which per
sisted only long enough for the capacitor’ ‘I2 to
seismogram is to be made, the blaster I0 is oper
be charged. ~
ated and a single impulse produced by ?owof
As shown in 'Fig. -3, this time break impulse,
current through one of the gas triodes 54’or 55
which begins at 22, is of extremely short duration.
is applied to the ampli?er ‘I8 and to device“
and a frequency modulated signal is radiated‘ 10 For that‘ reason, though this‘ impulse is also ap
plied to the grids of tube III, it does not inter
from the antenna I03. Almost immediately, the
fere with operation of the microphone I05 even
uphole geophone I5 applies an" electrical signal
though-the impulse may be heard at the receiving
by way of transformer I25 to a pentode amplify—
station.
ing tube I30, the output of which is’ coupled in
It will further be observed that the tap 66 of
conventional manner to the amplifying tube ‘I8, 15
the voltage divider 58 is utilized as the source of
and in like manner frequency modulation in ac
anode ‘supply. for the gas tubes 56, 55 and I33,
cordance with the uphole signal is produced by
while this same tap 66 is connected by conductor
device 85 which is also, radiated from antenna
H2 and resistor II4 to the cathode of the tube
I03. It may here be observed the polarity of the
geophone I5 is determined and the connections 20 III. The tap 66 is connected by conductors 6611,
‘I9, and resistor 80 to the cathode of the tube ‘I8.
to ampli?er tube I30 are such that the ?rstv
The‘anode supply for tubes ‘I0 and I II is derived
seismic wave arriving at geophone I5 produces in
from a higher-voltage tap, the one nearer B+.
the output circuit of tube I 30 an electrical impulse
In consequence, the tubes ‘I8 and I II operate with
of negative polarity. The ?rst impulse of ‘nega
tive polarity from the geophone I5, as it'appears 25 their cathodes well above ground potential, in
fact, at a voltage substantially equal to that _of
in the output circuit of the amplifying tube I30,
tap 66. By arranging the circuits-in this man- _
is also7 applied by way of conductor I3I through
ner, and asfurther pointed out herein, the single
a condenser I32 to the control‘ grid of a gas
source of potential indicated by B— and 3+ ade
tube I33.
‘,
.
This gas tube I33 is negatively biased to a non 30 quately serves to supply the’ various tubes and
thus avoids the need for thepresence of separate
conducting condition through a circuit which in
sources of supply. '
‘
cludes the resistor I 34, contact I35 of switch 60,
and by conductor I36 to the negative end (minus
It. will therefore be seen that the tube I33
?ve volts) of the voltage divider 58.. The return
provides a’ means ,for blocking translation of
the men at the recording truck. ‘ At the time a »
circuit is by way of tap 65, conductor-s 64 and I38, 85 .further signals through both of tubes ‘I8 and
and to the cathode of gas tube I33. Because the >
III, the net result of which isthe elimination
?rst impulse or half cycle of the uphole geophone
of radiation from the antenna I03 of modulated
signal is of negative polarity as it appears in the
signals of any character. All subsequent dis
output circuit of tube I30, the application of that
turbances of the uphole geophone and micro
half cycle to the control grid of gas tube I30 ren 40 phone cannot produce modulation of the carrier.
ders it more negative. Hence it does not ?re and
In consequence, at the receiving'station, there
is accurately recorded by one of the galvanom
‘ does not interfere with the transmission of said
half cycle to the recorder where the true char
eters M, Fig. 2, on the trace of the seismogram
acter thereof is recorded on the seismogram.
a time break impulse 2.2, Fig. '3, indicative of
the instant of creation of the seismic waves. On
However, upon the appearance of the subse
quent half cycle of opposite or positive polarity,
the same'trace of the seismogram there are re
corded the ‘uphole geophone signals 23 repre
the application thereof through the circuit in
cluding condenser I32 reduces the negative bias
sentative of the uphole break. By operation of
on the control grid of gas tube I33. Hence this‘
the tube I33, all further signals ‘from the shot
tube immediately ?res or becomes conductive and
pointare blocked, but a geophone 41 of the spread
current ?ows through a circuit which may bev
such as shown in Fig. 2 is connected to the same
traced from its cathode by way of conductors I38‘
galvanometer and on the same trace there may
and 64, taps 65 and 66 of voltage divider 58, con
be recorded seismic signals 28 detected by the
geophone 41. As further shown in Fig. 3, after
ductor 66a, resistor 61, meter 68, conductor 69,
‘ the uphole'break 23 has been recorded, the sig
resistor ‘I0, switch ‘II, and to the anode of tube
nals generated by the geophone 41 as indicated
I33. Because of the characteristic of gas tube I33
at :28, are recorded. The accuracy and the high
current continues to ?ow in this, circuit and the
?delity with which the time break and uphole
voltage drop across the resistor 61 and meter 68,
signals are recorded is accomplished in the pres
which is included in the grid circuit of tube ‘I8,
is immediately effective to bias the tube ‘I8 to‘an 60 ence of spurious‘ noise or signals such as are
produced by static, commutator ripple, or other
4 inoperative condition through a circuit which in
' cludes conductor ‘I5, resistor ‘I6, conductor 11, re
sistor 80, and conductor ‘I9. At the same time
the voltage drop across resistor 61 and meter 68
extraneous sources of electrical energy which
have heretofore played havoc with radio trans-~
mitting systems utilizing amplitude modulation '
negatively biases the amplifying tube III to an 65 of a- carrier 'for the transmission of seismic
inoperative or non-conductive condition, through
It will be recalled that the time break or‘ shot
a circuit including conductor 69, and through the
instant was determined or represented by a single
secondary winding IIO to the grids, the return
electrical impulse produced by the ?ow of a surge
circuit being from the cathodes, ‘resistor H4, and
by way of conductors II2 and'66a to the othe 70 of current through one of the gas tubes 55 and
56 while charging the condenser ‘I2. .Further im
side of resistor 61.
1
pulses from the blaster I0 were blocked or pre
Since the resistor 61 and the meter 68 are both
vented from affecting the tubes 55 and 56 by
included in the grid circuits of tubes ‘I8.and III,
operation of the condenser ‘I2 to remove the
the foregoing current ?ow is effective to block
both tubes. In this connection, it will be remem 75 voltage ,from the anodes thereof. Further im
signals.
.
.
v
>
9
pulses from the uphole geophone and‘ micro
10
crystal 200 mounted on a metal back plate 20I
which is itself carried on a support 202 of in- ‘
phone are blocked by a constant bias resulting
sulating material such as “Bakelite.” An elec
from the IR drop across resistor 61 and meter
trical connection 203 leads to the metal plate
83 when tube I33 is conducting.
20I. The crystal 200 is rectangular in shape and
It is seen that during the process of making
is preferably cut so as to be stable in operation
a seismogram, the transmission of time break,
even with temperature variations. As shown in
‘uphole and voice signals was interrupted. The
Fig. 6 both the crystal 200 and back plate 20I
circuit arrangement as shown provides complete
have the same rectangular shape.
restoration of the circuit to its original condi
A cooperating metallic plate 204 is carried by
tion by the operator at the shotpoint when he is 10
a metallic diaphragm 205 operatively connected
compelled to reset the circuit to reestablish
byv linkage 206 to an electromagnetic operating
communication.
unit 201. This unit is provided with operating
To restore the circuit to its original condition
coils 84, cooperating magnetic structure 208 and
and in readiness for the next ?eld operations,
the switch ‘II, normally spring biased to its il 15 an armature 200. The’ diaphragm 205 is pref
lustrated position, is momentarily depressed.‘
erably provided with several corrugations to
This opens the anode circuit of tube I33 and
completes a discharge circuit for the condenser
minimize resistance to movement by the arma
vide proper tuning for the selected resting
tube 92, Fig. 4, also multiply frequency changes
produced by device 85.
ture 209 and linkage 206. The corrugations also
insure return of the diaphragm to its original
‘I2. Upon return of the switch ‘II to its original
position the negative bias on the grid of gas 20 position after movement therefrom in either‘
direction. >
tube I33 prevents further current ?ow until the
To provide easy adjustment and rigid secure
application to its grid of the next positive im
ment of all parts in desired ?nal positions, the
pulse; and the condenser ‘I2 having lost its charge
outer frame, annular in shape, consists of inter
is in readiness to assist in producing one im
pulse representative of the shot instant or time 25 iorly threaded members 2I0 and '2“ locked to
gether by a series of screws, two of which, the
break and for blocking all subsequent impulses
screws 2I2 and M3 are shown. The housing
which may appear in the blaster I0 and which
2I-4 threadedly engages frame member 2I0 and
may be applied to the control grids of tubes 55
is locked in position by threaded ring 2I-5. The
and 56.
For testing purposes, the spring biased switch 30 insulated support 202 threadedly engaging frame
member 2“ is held in position by a locking ring
60 may be momentarily operated from its illus_
2I6. The frame 2I0--2II is mounted from a
trated position. The contacts 59 and‘ I35 serve
part of a chassis or stationary member 2I‘I by
not only to remove the negative bias on tubes
means of an upright support 2I8 and a base
55, 56 and I33 but also to apply a positive bias
plate 2 I 9 which by means of screws 1220 is secured
thereto.
to member 2 I1.
'
Circuit elements not described in detail repre
The diaphragm 205 is clamped by a'locking.
sent conventional practice. For example, the
ring 22I against the inner’ edge of the housing
plate or anode circuits of tubes 86, 92 and 96 are
2M.
shunt fed with RF choke coils included in each
As shown in Fig. 4, the device 05 which in
circuit. The anode voltage for tube I30 is ob 40
cludes crystal 200 and plate 20I is connected in
tained from B plus by way of conductor I00
the grid circuit of the tube 86;. In manner under
and conventional resistors. The cathode of tube
stood by those skilled in the art, the crystal 200
I30 is connected‘ directly to B minus and to
is ‘connected to the ?rst section of tube 86 which
ground. The tube ‘I8 has its anode connected
through primary winding 8I to conductor- I60 - makes up a conventional crystal controlled oscil
lator.
and to B plus while its cathode is connected
Upon application of signals to the operating
through resistor 80 and conductors ‘I9 and 66a
coil 80 the armature 209 through linkage 208
to tap 68. Similarly tubes III and II? have
moves the diaphragmecarried metallic plate 200
their cathodes connected to tap 56 with their
anodes connected to B plus. In this manner the v .toward and away from the face of crystal 200.
The resultant changes in the air gap between
single voltage divider 58 and the one source of
~p1ate 204 and. crystal 200 produce a change in
potential indicated by B minus and B plus serve '
the frequency proportional to the change in the
. the various tubes in manner already described
air gap and in amount adequate for transmis
in detail.
The antenna I03 may be of the “whip" type; In Ll sion and reproduction with high ?delity of the
time break and uphole geophone signals. The
that is, it may comprise telescopic tubes which
frequency multipliers, second section tube 86 and
may-be elevated to the desired height to pro
frequency.
_
When the uphole geophone is not to be used,
the normally open switch I12 in shunt with the
capacitor 12 is closed. Hence, the current ?ow
ing to the gas tube 55 or 56- which ?res continues
to ?ow through resistor 01 and the meter. The
tubes ‘I8 and III are blocked in manner already
described to prevent further transmission of
voice signals or any further signals from an
It will now be realized that a signal electrical
impulse representing the time break or the in
stant of creation of the seismic waves produces
frequency modulation and at the recorder pro
duces a photographic record coincidentally with
--the instant of their generation. Almost instan
taneously thereafter, within as little as about one
hundredth of a second an electrical signal is pro
duced in response to arrival at the earth's surface
of seismic waves from the shotpoint. This signal
ing the frequency modulation of the carrier 70 likewise produces frequency modulation of the
carrier and the true character of the uphole
radiated from antenna I03. It also serves ‘to
gcophone signal is faithfully recorded on the
‘determine the resting frequency, or the frequency
same trace of the seismogram as the uphole
of the carrier in the absence of frequency modu
break. Thereafter seismic waves and their re
lation. It may take various forms, but the one
preferred, the device 85, comprises, Fig. 5, a 75 ?ections are detected by a geophone of the spread
tenna I03.
'
'
The device 85 has been described as produc
2,418,116
11
12
which is wire-connected to the recorder and these
location for recording on‘ a. single trace said im
pulse and said seismic waves after travel through
the earth. demodulating means responsive to the
frequency modulated carrier for actuating said
recorder to record said impulse and said signal,
said demodulating means including signal-limit-q
too are recorded on said trace of said seismo
gram.
Before and during the frequency modulation of
' said carrier, the voice modulating means is oper
able to produce amplitude modulation of the car
rier but as soon as the uphole geophone signal
ing means for preventing operation of said re
cording means by amplitude modulation of said
has been transmitted, both the amplitude and
frequency modulating means are rendered inop
carrier, means operable immediately after said
erative until the manually operable switch ‘H has 10 impulse produces said frequency modulation for
been operated.
‘
so biasing said ampli?ers as to prevent further
frequency and amplitude modulation of said car
rier during the period of recording of said seismic
signal produce frequency modulation of said car
waves at said receiving location, and means for
rier without interference between them. And the 15 rendering said biasing means ineffective thereby
to render effective said frequency and amplitude
invention further embraces the features of con
modulating means for subsequent modulation of
current amplitude modulation of the carrier
said carrier.
without interference with the frequency modu
3. In a system for geophysical exploration in
lated signals and the other features already de
scribed in detail.
20 which seismic waves are created below the earth's
surface and their travel time through the earth
While we have illustrated a preferred embodi
measured, the combination of a single radio
ment of our invention, it is to be understood We
transmitter for radiating a carrier from a sending
intend by the claims to cover all modi?cations
which fall within the true spirit and scope of our
location, means for producing a single electrical
invention.
25, impulse coincidentally with the instant of crea
What is claimed is:
tion of said seismic waves, means including an
1. In a system for geophysical exploration in
ampli?er operable by said single impulse for fre
which seismic waves are created and their travel
quency modulating said carrier substantially dur
time through the earth measured, .the combina
ing the period of said impulse, means including
tion of a single radio transmitter for radiating 30 an uphole geophone for producing an electrical
a single carrier from a sending location; means
signal indicative of the arrival at the earth's sur
for producing a single electrical impulse coinci
face of seismic waves which have travelled
dentally with the instant of creation of said
through at least a part of the weathered layer
seismic waves, means including an ampli?er and
of the earth's surface, means inicluding said
operable by said single impulse for frequency
ampli?er for applying said signal to said fre
In its broader aspect the invention embraces
the system by which the time break and uphole
modulating said carrier substantially during the
period of said impulse, means including an uphole
geophone for producing an electrical signal indi
cative of the arrival at the earth’s surface of
seismic waves which have travelled through at
least a part of the weathered layer of the earth's
surface, means including said ampli?er for ap
plying said signal'to said frequency modulating
means to produce frequency modulation of said
carrier during the period of said signal, .a second
ampli?er, sound responsive means including said
second ampli?er and concurrently operable for
producing amplitude modulation of said carrier,
means including a seismic recorder at a receiving
location for recording on a single trace said im
pulse said signal and seismic waves after travel
through the earth, and means operable imme
diately after said geophone signal produces said
quency modulating means to produce frequency
modulation of said carrier substantially during
40
the period of said signal, a second ampli?er,
sound responsive means including said second
ampli?er and concurrently operable for produc
ing amplitude modulation of said carrier, means
including a seismic recorder at a receiving loca
tion for recording said impulse and said seismic
waves after travel through the earth, demodulat
ing means responsive to the frequency modulated
carrier for actuating said recorder to record said
impulse and said signal, said demodulating means,
including signal-limiting means for preventing
operation of said recording means by amplitude
modulation'of said carrier, means operable im
mediately after said geophone signal produces
said frequency modulation for so biasing said
ampli?ers as to prevent further frequency and.
frequency modulation for rendering said ampli
amplitude modulation of said carrier during the
?ers inoperative thereby to prevent further fre
period of recording of said seismic waves, and
quency and amplitude modulation of said carrier
manually operable means for rendering said bias
thereby to prevent application to said recorder of
ing means ineffective thereby. to render effective
further signals and impulses during the period of
said frequency and amplitude modulating means
recording of the seismic waves which have trav~
for subsequent modulation of said carrier.
elled through the earth to said recorder.
00
4. In a system for geophysical exploration in
2. In a system for geophysical exploration in
which seismic waves are created below the earth's
which seismic waves are created below the earth's
surface and their travel time through the earth
surface and their travel time through the earth
measured, the combination of a single radio
measured, the combination of a single radio
transmitter for radiating a carrier from a send
transmitter for radiating a carrier from 2. send
ing location, means for producing a single elec
ing location, means for producing a single elec
trlcal impulse co-incidentally with the instant
trical impulse'coincidentally with the instant of
of creation of said seismic waves, means includ
creation of said seismic waves, means including
ing an ampli?er operable by said single impulse
an ampli?er operable by said single impulse for
for frequency modulating said carrier substan
frequency modulating said carrier substantially
tially during the period of said impulse, a second
during the period of said impulse, a second am
ampli?er, sound responsive means including said
pli?er, sound responsive means including said
second ampli?er and ‘concurrently operable with
second ampli?er and concurrently operable for
said frequency modulating means for producing
producing amplitude modulation of said carrier,
amplitude modulation of said carrier, means in
means including a seismic recorder at a receiving
cluding a seismic recorder at a receiving location
2,418,116
13 '
for recording on a single trace said impulse and
seismic waves after travel through the earth, an
14
bination of a transmitter for generating and
radiating a single electromagnetic carrier, a ?rst
ampli?er and gain’ control means for producing
ampli?er including an amplifying tube operable
variable gain of said ampli?er during the period
upon creation of said seismic signals for ire-y
of recording of seismic waves, demodulating 5 quency.-modulating said carrier, a second amph
means responsive to the .frequency modulated
?er having an amplifying tube operable by voice
carrier for applying to said ampli?er. and recorder ‘ _ signals for amplitude-modulating said carrier, a
a signal representative of said impulse, means
gas tube normally biased to a non-conducting
operable by said signal for initiating operation of
condition, a ‘single source of supply for the anodes
said control means, said demodulating means 10 of said amplifying tubes and said gas tube, circuit
including‘ signal-limiting means for preventing
connections for operating said amplifying tubes
operation of said recording means by amplitude
with their cathodes substantially at the same
modulation of said carrier, means operable im
potential as the anode of said gas tube, a re
mediately after said geophone signal produces
sistor, means connecting said resistor in series
said frequency modulation for ‘so biasing said 15 circuit relation with said gas tube and for con-_
?rst-named ampli?er as to prevent further fre
>. necting it in the grid circuits of said amplifying
quency modulation of said carrier during the
tubesfor the development, upon current ?ow
period of recording of said seismic waves, and '
through said resistor, of a negative bias to pre
means for rendering said biasing means ine?’ec
vent conduction of current by said “ampli?er
tive thereby to render e?ective said frequency 20 tubes, and means operable within a short time
modulating means for subsequent modulation of
interval after creation of said seismic waves for
said carrier.
'
rendering said gas tube‘conductive thereby to
5. In a system for geophysical exploration in ' > produce said negative bias.
which seismic signals produced at a shotpoint
EARLEY M. BHOOK.
are recorded at a receiving location, the com- 25
ROBERT W. OLSON.
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