March 19, 1929.
B. MCCOLLUM
Re. 17,242
'IETHOD AND _APPARATUS FOR DETERMINING THE CONTOUR OF SUBTERRANEAN STRATA
Original Eiled Aug. 14. 1922
FIG. 1.,
FIG. 4.
3 $heet$_$heet
FIG. 2.
FIG. 6.
INVENTOR.
4am
1
March 19, 1929.
a. MQCOLLUM
7
Re. 17,242
IETHOD AND APPARATUS FQR DETERMINING THE CONTOUR OF SUBTERRANEAN STRA'I'A
Original Filed Aug. 14. 1922
3 Sheets-Sheet
3
26
'
FIG. IO
27
gmuantoz
Mamaam
Re. 17,242
Reissued Mar. 19, 1929.
UNITED STATES
PATENT OFFICE.
BURTON IcOOLLUM, OF WASHINGTON, DISTRICT 0]‘ COLUMBIA, ABBIGNOB ‘.l‘O KC~
'COLL'UM GEOLOGICAL EXPLORATIONS, INC., A CORPORATION 01' DELAWARE.
METHOD AND APPARATUS FOR DETERMINING THE ‘CONTOUR OF SUBTERRANEAN
BTRA'I‘A.
Original No. 1,672,495, dated June 5, 1928, Serial No. 581,886, ?led Augult 14, 1922. Renewed March 5,
1928. Application for reissue ?ed January 11, 1928. Serial '80. 881,744.
My invention relates to methods of deter
mining the contour of subterranean strata or
the sound receiving device in contact with
the earth.
'
-
boundaries of geologic formations, and has
Fig. 11 shows an improved form of a sound
among its objects the study of the geological receiving device which is useful in connec
conditions at depths that cannot be conven
tion wit 1 my invention.
Figs. 12 and 13 show diagrammatic ar
means. In particular, I have found that by
the use of my invention it is possible to deter
mine the location of deposits of various ores,
mineral oils, and other valuable materials.
My invention depends on the well known
principle that if a sound wave be transmittted
rangements of microphonic devices which I
iently and economically reached by ordinary
10
have found useful in connection with my in
vention.
For the sake of clearness and brevity my in
vention is described below with articular
reference‘to but one of its practica applica
through the earth partial re?ection’ of the tions, namely, the location of deposits of min
15
60
'
65
wave takes place at t e boundary between any eral oil and natural gases. It will readily be
two masses which differ in'respect to certain seen, however, ‘that the method may be ap
of their physical properties. By properly plied‘to' determining the location of many
utilizing the transmitted and re?ected waves other kinds of mineral deposits.
20
I am able to determine accurately the loca-~
It is well known that in regions where de
tion. shape, and extent of such boundaries, posits of oil or gas may be encountered the
which information is of great value for the deposits are not distributed generally
purposes stated above. My invention is fur throughout the area, but are highly localized
ther described in the following speci?cation, in pools occupying a relatively small portion
reference being made to the accompanying of the total Votential oil bearing area. The
drawings.
75
location of t iese pools is governed by a well
Of the drawings:
known principle illustrated in Figs. 1. In
Fig. 1 is a diagram showing the relation this ?gure, (1) is the surface of the ground
between the contour of subsurface strata and and (2) a ‘dense subterranean stratum of ir
the occurrence of certain valuable mineral regular contour concave upward at (3) giv-v 80
deposits.
ing a synclinal fold, and convex upward at
Fig. 2 shows the principle of methods that (4) giving an anticlinal fold. It is well
have heretofore been unsuccessfully tried to known that in a potential oil bearing region
accomplish the object here sought. .
the oil and gas accumulate‘locally at (5) un
Figs. 3 and 4 are typical examples of rec der the anticlinal fold (4), it being forced
ords showing di?iculties confronting previous upward into this osition by the heavier salt
85
attempts to accomplish the results obtained water stratum (5‘ beneath it. The problem
by my invention.
of locating a pool of oil in a potential oil
Fig. 5 shows in diagrammatic form a prac bearing region is therefore, one of determin
tical embodiment of my invention.
ing the location of these anticlinal folds in
Fig.6 shows a typical record obtainable the subterranean rocks. This latter, as stated
through the use of my invention.
above, is one of the objects of my invention.
Heretofore, numerous investigators have
primiple of an acoustic shield which I use endeavored to determine the contour of sub
to improve the character of the graphic rec terranean strata by the use of sound waves
ords obtained in connection with the applica re?ected from them, but up to the present
Fig. 7 shows in diagrammatic form the
45
50
tion of my invention.
Fig. 8 shows a combination of sound receiv
time none of these methods has been success
ful. Fig. 2 illustrates some of the fundamen-'
ing devices which I have found particularly tal di?iculties that have confronted all these
valuable.
previous attempts and prevented their suc
Fig. 9 shows an arrangement of portions cessful application.
of the apparatus for determining the velocity
In their fundamental principles these
of sound in the earth.
\
methods have all comprised a source of sound
Fig. 10 shows a preferred method of ?xing (7 ) which has heretofore always been placed
95
2
17,242
either on or below the snrface of the earth. is entirely obscured so that the recordis en
Thetheory is that sound travels out radially tirely worthless for the purpose desired.
in all directions and is in part reflected from _ It. will be evident that this difficulty will
the boundary 2, 3, 4, 8, 10, and 12, “the part. be the greater the more remote is the detector
of the wave incident at the point (8) being at the point (11) from the source (7), and
.that it can be diminished by placing the dc~
tector close toth'e source. This isshown'by
comparing Figs. 3 and 4. These two records
re?ected to the point (9), that part incident
at (10) being re?ected ‘to the point (11) , and
so on, the angle of re?ection being equal to
the angle of incidence. It is evident that if
70
are the result of the same source of sound at
only this simple condition existed and if we (7) but in Fig. 3 the receiver was 150 feet 75
could clearly distinguish at any point of from the source, while 1n Fig. 4 it was but 50
15
known position such as at (11) ‘for example, feet away. Interchangmg receivers give
between the direct transmitted wave (14) identical effects showing that the difference
which goes either directly or through shal in form is not due to the influence of the re
low subsurface strata to the point (11), and ceivers. The sensitivity of the recording in 80
the wave re?ected to the point (11) from the strument was, of course, adjusted to give suit~
'
point (10)," we could by well known means. able sensitivit in the two cases.
calculate the depth of the point (10) on the
20
25
Although tfiese diffraction effects may be
Serious difficulties of a thus diminished by bringing the detector
practice. nature prevent the realization of closer to the source, the disturbances pro 85
this simple set of conditions. In the ?rst duced by the direct transmitted waves men
place, the velocity of sound in the rock layer . tioned above become much more violent in
(2) is practically always much greater than comparison with the re?ected waves so that
in the surface strata. On this account when if the distance is made short enough to sub
re?ectin
surface.
the slowly travelling‘sound wave reaches the stantially eliminate diffraction effects the
nearest point, as at (3), of the re?ecting rock transmitted waves completely obscure the ad
layer, a sound wave of relatively high veloc
vent of any re?ected waves.
90
It is evident,
30
ity moves along the rock layer as shown by therefore, that no location of the detector can
the arrows (15),,and all the while a portion be found that will permit it to distinguish
of the energy‘of the wave is being diffracted de?nitely between the true re?ected wave
and disturbances due to diffraction and direct
transmission. Similar disturbances result in
35
upward into the overlying strata as indicated
by the arrows (16), and this diffracted en
ergy moves upward and may reach the point
(11) before the arrival of the true re?ected»
wave from the point (10), since this latter,
be seen that this initial diffracted disturb
ably the latter, high up in the air and so ar
ance arriving at (11) ‘will be immediately
followed by others caused by the transmitted
wave striking portions of the rock layer (2)
at (8) and other points intermediate between
range the two that the direction of the re
the case wave trains are used in lieu of sin
gle pulses.
'
‘I have now invented a very simple ex
100
although travelling by a somewhat shorter pedient whereby .the foregoing troubles can
path, must travel all the way through the me be entirely obviated. I accomplish thisend
dium of low velocity. Furthermore, it will by placing the detector or the source, prefer
40
50
55
?ected waves reaching the detector makes
only a very small angle with the direction
of the transmitted waves. preferably not
(12) and (10), so that a continuous train of more than a few degrees. This angle is made
diffracted disturbances will be detected atv small, as in the arrangements hereinafter de
(11) which will completely obscure the ar scribed, by causing the distance, measured
rival of the true re?ected wave.
vertically between the shot or sound wave
Fig. 3 shows a typical record which reveals source and the detector, great as compared
‘clearly the seriousness of this difficulty in with the horizontal distance between the de
practice. This is a record of disturbances tector and the sound wave source or shot. By
received at the detector placed at a point cor_ keeping this angle small, the diffraction dis
responding to the point (11) due to a single turbances are avoided and by placing the
quick pulse of sound sent out from the source source at a considerable elevation above the
at the point (7). In consequence of the com surface of the earth the difficulties due to the
bined effect of the direct transmitted waves, direct transmitted wave are not only elimi
llf)
of which there are three distinct types, name nated, but this wave becomes very useful as
ly, a compression wave, a transverse wave,‘ will appear from the following detailed dc~
and a surface or Rayleigh wave, all of which scription of the essential features of my in—
travel at different velocities and therefore
reach the detector at different times, and fur
ther, the innumerable diffracted waves due to
the reaction on the two former by the subter~
ranean re?ecting surfaces as described above,
the record becomes so complex that the ef
65 fect of the arrival of any pure re?ected wave
60
vention.
My invention will be clearly understood by
reference to Fig. 5.
The source of sound
(17) is placedhigh up in the air. This
source may be of any suitable kind, but I
prefer to use a short abrupt sound such as
that produced by ?ring a charge of explosive
130
17,242
or by the sudden release of gas under pres
sure. Approximately below the source (17 )
and either on.or slightl below the surface
of the earth, I place a etector (18) which
may be of any type, such use microphone,
piezo-electric crystal, or electromagnetic de
3
and the intensity of the wave at any point is
goverened by the inverse square law. Sup
pose, for example, that the height of the
source ( 17 ) above the detector (18) is equal 1
to the depth of the re?ecting surface (21).
In that event when the sound wave reaches the
Wires extend from this detector to a detector (18) it has a certain intensity.
tector.
recording device (19) of a type to record the Suppose now that 100% ofthe energy of the
di?'erence in time between two or more events. wave is re?ected from the surface (21). 'It
10
The well known oscillograph having con will be evident that when the re?ected wave
stants adapting it to this particular work is front has travelled back again to the detector
typical of the recording devices which I have (18) the total distance which it will have
found suitable. It will be evident that'if a traversed from the source (17) will be three
sudden sound be produced at the source (17) times as great as the distance traversed by
the wave will travel downward and strike the direct wave in going from the source (17)
the surface of the earth (20) where a con
S0
to the detector ( 18) . The intensity of the re
siderable part of‘ the energy will be re?ected ?ected wave when it reaches the detector
and pass o?' into space. A part, however, would therefore be only one-ninth of the in—
will be transmitted to the earth and this por
tion immediatelv produces an effect on the
detector (18) w 1icl-1 is near the surface and
this e?ect is recorded on the recorder (19).
This point on the record is then used as the
zero of time to which subsequent recorded
events are referred. The wave then travels
tensity of the direct wave. If, as is usually
the case in practice, only a fraction of the
energy is re?ected from the surface (21) , the
intensity of the re?ected wave becomes still
further reduced. If new thesensitivity of the
arrangement is made great enough to give
a su?iciently large effect due to the re?ected
90
downward until it strikes the ?rst re?ecting wave, the disturbances due to the direct wave surface (21) where a part of its energy is re will be so great that they may interfere seri
?ected upward to the surface, where it again ously with the proper interpretation of the
affects the detector, and the time elapsing be records. It will be evident, therefore, that
tween the arrival of the re?ected wave. and in general will be necessary to take steps to 95
r the arrival of the transmitted wave will be increase the amplitude of the re?ected wave,
determined. The velocity of sound in the relative to that of the ‘direct wave. I have de
overl ing stratum can be determined and vised several means of accomplishing this
the ?pth ofthe-surface from which re?ec result, each and all of which comprise a part
tion takes place can be readily calculated of my invention.
from this velocity and the measured time in
One of the means whereby I increase the
terval between the arrival of. the direct trans intensity of the re?ected wave relative to that
mitted wave and the re?ected wave.' It will of the direct ‘wave, is by putting a source
40
be evident that if the depth of the re?ecting of sound very high up in the air as compared
surface be determined at a su?icient number to the depth of the stratum under investiga
of points the‘contour of this‘surface will be tion. As seen from the example given above,
if the depth of the stratum is substantially
It will be quite evident that with this ar equal to the height of, the source, then as
rangement of apparatus the effects on the suming 100% re?ection the intensity of the
known.
‘
-
‘
detector of both the Rayleigh wave and the re?ected wave at the receiver will be only lltl
transverse wave in the earth will be elimi one-ninth of the intensity of the direct wave.
nated, a'nd only those effects due to the com Suppose, however, that the source be put to
pression wave will be recorded in either the“ a height above the detector of say ?ve times
transmitted or re?ected wave. thereby great the depth of the re?ecting stratum under
' 1y simplifying__r the record. It- will also be study. In that case the re?ected wave travel
very evident that all di?raction c?'ccts, such ling back to the detector will have travelled '
as those described above. will not affect the about 40% farther from the source than the
detector.
In consequence of this a very sim
direct wave. when the two pass the detector.
ple form of record, like that shown in Fig. _6 Applying the inverse square law it will be
is obtained where the ditl'crent events can seen that in this case, assuming 100% re?ec
be clearly distinguished and the time inter
vals accurately measured.
A further consideration of very great prac
60
120
tion, as before. the intensity of the re?ected
wave at the detector will be 1/1.96. or ap
proximately one-half of that of the direct
tical importance has to do with the relative wave, as compared with the ratio one-ninth,
intensity as shown by the record of the direct when the source is placed‘ at the lesser ele 125v
wave, actuating the receiving device, and of vation. It will therefore be seen that by put
the re?ected wave coming back from the sur ting the source very high in the air in com
face under investigation. It will be seen that parison with the depth of the stratum under
the‘ sound wave emanating from the source investigation, it is possible, because of the in
(17) travels out spherically in all directions, verse square law of propagation of sound
130
4 .
17,242
waves, to greatly increase theintensity ofthe the reflected wave, and the detector will there
re?ected wave in comparison with that of the fore be actuated by the re?ected wave with
direct wave. In practice I prefer to elevate nearly as much intensity as if the acoustic
Cl
the source to a height at least as great as the shield (22) did not exist. At the same time
there will be very little effect due to the direct wave, since only a very small amount of the
ably to several times this height.
‘
It is not to be understood that there is a energy of the direct wave will be diffracted
depthof the reflecting stratum, and prefer
critical height of the source 17 of the sound directly from the edges of the acoustic shield
energy utilized which under all circumstances to the source (18) . I have found that in this
is to be exceeded, nor is it necessar to know way I can reduce the intensity of the direct
either the height of the source 1 ‘nor the wave at the receiver to a small fraction of
. depth of the re?ecting stratum.v In actual what it would‘ be without the shield, and at the
practice the procedure is substantially as same'time secure nearly as much effect on
the detector from the reflected wave as if the
follows:
- A sound'wave is produced at any conven shield did’ not exist.
10
80
A third method which ‘I have devised for
or 2,000 feet above the earth’s surface, and a reducing the amplitude of the direct wave in
suitable record, as photographic, 'is taken of comparison‘ with that of the re?ected wave is
the waves actuating or‘in?uencing the de shown in Fig. 8. .It is Well known that be
tector. If upon examination of the record cause of the very great difference in the
so taken there is revealed a re?ectedv event ‘acoustic properties-of the earth and air, a
ient height, as by a charge exploded, say, 1,000
clearly distinguishable from the after ef
fects of the direct wave, it shows that the ex
sound wave travelling either in the air or in
the earth reaching the surface of the earth
plosion occurred at a sufficient height. The
signi?cant fact is the time interval‘ between
‘the arrival at the detector of the direct and
re?ected waves, and it is only necessary to
will be nearly all reflected back into the
the source of sound at a greater elevation.
the effect of the direct wave on the detector
medium in which it is travelling,"thus, as 90
pointed out above, the wave coming from the
source (17) up in the air, has most of its
knowr this time interval, which, when multi Jenergy re?ected at the surface of the earth
plied by the velocity of sound in the overlying bacli again intov the air and off into the at
medium, gives a distance which is twice the mosphere. Similarly, that part of the.
depth of the re?ecting stratum. If, on the energy which goes into the earth and is re
other hand, the record shows no re?ected ?ected back toward the surface from the re
event clearly distinguishable from the after fleeting surface (21‘), will on arrival at the
effects of the direct wave, it is proof that the surface be again re?ected downward, only‘ a
source of the sound energy was not sufficiently small fraction of its energy returning again 100..
high above. the detector, and in such case it to the air. ' By taking. advantage of‘this
is only necessary to take another record with principle I am able to reduce the intensity ofv
to any desired degree without materially re
creased ratio of the intensity of the re?ected ducing the intensity of the re?ected disturb
A second means whereby I secure an in
40
and direct waves,‘is by the use of 'an acoustic ance which it is desired to record. This is
shield interposed between a source and the accon'lplished by the use of two receiving de
detector. One form of this is shown in Fig. vices as shown in Fig. 8. ' Here one receiving
7. The acoustic shield (22) which can be device (18) is placed in the earth as pre
made up in any form to be substantially sound viously described, in which case it is actuated
I10
proof, is placed between the source (17) and only by that part of the sound energy passing
the detector (18) and preferably close to the into the earth. The second receiving device
latter. In practice I prefer to put the shield (24) is placed to be responsive to the direct
' (22) near or on the surface of the earth. as‘ air wave to a much greater degree than to the
shown in Fig. 7. It will now be seen that re?ected ground wave, and very close to the
the sound energy travelling downward from detector (18). In order to make clear the
the source (17) strikes the shield and the method offnnctioning of this‘ arrangement,
earth all around it. The shield (22) may be let us assume that the sensitivity of the de
designed either to reflect or absorb the energy tector (24) bears to the sensitivity of the de
‘ striking it, in which event it .will be seen that tector (18) the same numerical ratio as the 120
no sound energy travels directly into the sound energy transmitted to the earth bears
earth at the detector (18). However, in the ‘ to the total sound energy incident on the sur
(it)
region all around the shield, the energy passes face of the earth from the source (17). In
downward into the earth as will readily be that case it is obvious that the total effect
seen, and is gradually diffracted inward un produced on the detector (24) will be just
derneath the shield into the region (23). equal to the total effect produced on the de
'By the time the reflected wave from the sur tector (18), dueto the ‘direct wave coming
face (21) reaches the'detector (18) the dif-__ from the source (17). Consider now what
fraction will have been sufficient to giye happens when the re?ected wave arrives again
nearly a uniform dlstribution of energy 1n at the surface after ‘having been re?ected
130
17,942
from
the
subsurface
(21) .
This
wave
travelling in the earth give full effect on the
detector (18) embedded in the earth, but on
reaching the surface nearly all of its energy
is again turned back in a downward direction,
only a small fraction of it being transmitted
selves, it is desirable to have the microphones
very ?rmly ?xed in contact with the earth.
Thiscan be done by making a hole, placing
the mlcrophone in 1t ?lled either with earth
of other suitable binding material and
thoroughly tampin the ?lling material in
to the air where it can affect the detector (24) . place around and a ove the detector.
10
5
This
It will be seen, therefore, that the e?ect of the procedure, however, is di?icult and time con
re?ected wave will be enormously greater on sumlng and renders very di?icult the recovery
the detector (18) than it is on the detector of the indicating device, especially when
(24) , whereas the effect of the direct wave on buried to a considerable depth,‘ after the
the two detectors will be substantially equal. records have been taken.
’
If now the two detectors (l8) and (24) are
I have devised a very simple and convenient
coupled together in such manner that‘ they means of ?rmly attaching thereceiving de
tend to neutralize each other as regards their vice to the earth which eliminates these
. effect on the recording device, then the direct troubles. This is shown in Fig. 10, where the
80
wave will produce no effect on the records pro
recelvlng device is mounted inside of a rigid
vided the two detectors are adjusted to give case (26) which‘ may be of metal or other
equal and opposite impulses, Whereas the re suitable material. In the base of this case
?ected wave will be recorded through the dc» is ?rmly attached a large screw (27), suitable
tector (18) at almost its full value. In prac for ‘screwing into the earth. To place a re
tice I prefer not to completely eliminate the ce‘iving device in position I ?rst bore a small
25
30
35
direct wave on the record so that I do not ad hole, large enough to accommodate the re
just the detectors (18) and (24) so that they celver and extending to the desired depth,
exactly neutralize each other. ‘I prefer to ad after which the receiver is placed down in the
just them so that the resultant e?'ect of the
two, due to the direct wave, is only a small
fraction of the effect produced on either in-.
strument alone, as this gives an indication on
the record showing the time of arrival of the
direct Wave, which is useful as a basis of
reference for the time scale. It will be seen,
85
90
hole with the screw downward and by means
of a suitable long handled wrench the receiver
case is turned so as to drive the screw ?rmly
into the earth. After the records have been
taken the receiver can readily be unscrewed
from its position and brought to the surface.
As stated above, any one of the usual types
therefore, that by proper adjustment of the of receiving devices may be used. I have
relative sensitivity of the two detectors in found, however, that instead of using a single
Fig. 8, the relative intensity as shown on the receiving element it is often desirable to use
record of the direct and re?ected waves can‘ a considerable number of such elements
be controlled to any desired extent. In prac grouped in a single unit in order to increase
100
tice any one of the above described means for the sensitivity and reliabilit of the receiving
controlling the relative intensity of the effects apparatus. This is particu arly true in case
of the direct and re?ected waves may be used, carbon microphones are used as receiving de
vices. ' These microphones, when used singly
bination if desired.
exhibit certain inherent instabilities fre
In order to measure the velocity of sound quently called frying, which gives rise to
in the stratum between the surface of the earth ‘more or less erratic pulsations of current
or any two or all of them may be used in com
and the re?ecting surface under investigation flowing in the microphone, which in turn pro
I place two receiving devices in the earth as duces disturbances on the record, especially
shown in Fig. 9. one (18) at a suitable distance where a very sensitive recorder is used. This
below the surface, and the second (25) a trouble is especially serious if one attempts to
110
known distance below it, substantially in line use a very large current in the microphone in
with the direction of propagation of the sound order to increase the sensitivity. This diffi
wave. The difference in time of arrival of culty can be greatly minimized by using a
a the sound wave at the two receivers is large number of microphone elements con~
, measured by means of a recorder from which, nected- in parallel, but such a simple arrange
and the known distance between the re ment cannot be used in practice. It is well
55
ceivers, the velocity is readily obtainable.
In some cases where there is reason to believe
known that in order to use a microphone suc 120
cessfully and secure good sensitivity in detect
that'the velocity of sound in the overlying ing disturbances of relatively low frequencies,
it is necessary to use it in conjunction with a
cating devices may be placed at_ various mutual inductance having an iron core, and
depths in orderthat the law of varlation of further, that the current ?owing through the 125
velocity with‘ depth may be determined.
primary of this mutual inductance, which of
I have found that in order to secure a good course is the current ?owing through the
sensitivity in the indicating devices and also microphone, must be kept small enough so
stratum may vary with depth, several indi
60
in order to eliminate spurious disturbances as not to produce saturatlon in the iron core.
due to vibrations of receiving devices them This fact placesa limit on the number of
130
6
17,242
microphones that can be‘ used in parallel on sired. The second arrangement and the one
a single mutual induct-ance, and ' with the which I prefer to use,'is shown in Fig. 13.
usual forms of inductance practically noth
Here a mutual inductance is used, préferabl
ing is gained by the use of more than one or one having an iron core (33) provided wit
two microphones in this way. .. I have, how two primary windings (34) and (35) differ 70
10
ever, devised an arrangement whereby the entially connected, the winding (34) being
ordinary forms of iron core mutual in in series with the group of microphone ele
ductance may be used effectively with a large ments (29), (29') etc., and the winding (35)
number of microphone elements in proper being in series wit the grou (30), (30') etc.
\Vith this arrangement a arge number of 75.
combination.
'
i
The essential elements are shown in Fig. microphone elements maybe used in each
11. Inside the receiver case (26) is mounted group, and correspondingly large currents
a rigid plate (28), preferably tilted at an sent through the two differentially wound
angle with respect tothe axis of the case ‘primary coils (34) and (35) without'danger
(26). I prefer to make this angle between of saturating the magnetic circuit. When
30° and 60°, but larger or smaller angles may the current in one circuit lncreases While that
80
be used if desired. A terminal of each of the in the other decreases, the effects are cumu
microphone elements (29) and (30) is gen ' lative in causing changes in the ma netiza
erally attached to the plate (28), and inter 111011 of the iron core (33), and hence 1n actu
posed between this plate and the other termi ating the oscillograph (19’), which is con~
nal of each microphone is placed a cushion nected to the single secondary coil (36). 'As
of suitable fabric, such as cloth or other ma here shown, the microphone elements (29),
terial, to serve as a damping agent to pre-' (29’), etc., are grouped in series. It will be
vent vibrations in the microphone when it evident that parallel or series multiple group
is actuated. Any desired number of such ing may be used with equal effect, provided 90
pairs of microphone elements may be mount the number of turns in the primary coils (34)
ed inside the case (26). The receiver case is and (35) of the mutual inductance are made
?xed to the ground with its‘axis in the direc to correspond to the number of microphone
tion of the earth displacement which it is elements in series. '
A careful consideration of the foregoing ~
sought to record, in this case being vertical.
It will be evident that when the earth _vi discussion reveals that one of the funda
brates due to the passage of a sound wave or mental features of my invention comprises
40
pulse, the receiver case is moved up and down the placing ofa source of sound and a re
with the earth while the heavy case of the ceiver in such relation toeach other and to 100
microphone elements (29) and (30) tend to the re?ecting surface, the depth or contour
stand practically stationary. In consequence of which is to be studied, that the angle be
of this, it will be seen that the pressure on the tween the direct transmitted and the re?ected
microphone elements (29) and (30) will vary waves‘ affecting the receiver is small, where
as the wave passes, thus causing vibrations by the disturbance due to the surface waves,
in their resistance. It will be noted that when transverse waves, and the innumerable dif~
the pressure on the microphone element (29) fraction effects above discussed, are made to
is increased due to thedownward movement disappear. This might, of course, be done by
of the case (26), the microphone (30) will placing both source and receiver in the earth,
'
decrease so that the pulsations of resistance provided one is placed‘ at a considerable 110
on the two microphone elements will be op depth, in order to have the receiver remote
posite. In order to make the elfects‘of the from the source. - It is, however, very dif
two groups cumulative on the recording in ?cult, expensive, and time‘ consuming to place
strument, either of two arrangements may the instruments at a great enough depth to
be used, one of which is shown in Fig. 12. be effective. Furthermore, experience has
Here all of the microphone elements (29), shown that if the source be placed in the
(29’) ' etc., which are similarly mounted earth the available sources of a quick, sharp
with respect to the plate (28), are placed in pulse, such as the ?ring of a charge of ex~
one arm of a Wheatstone bridge while all
those (30), (30’), etc., which are so mounted
as to give resistance variations opposite to
the ones in group (29) , (29’) etc., are placed
in the adjacent arm of the bridge. It will
plosive, produce a violent disruptive effect
in the earth immediately surrounding it,
which in turn tends to change the character 120
of the disturbance from a quick, simple pulse
to a complex and greatly prolonged disturb
be obvious that as the resistance of one group ance, thus defeating the object of the arrange
60
increases and that of the other decreases, the ment. I'have found, however, that if the
two effects are cumulative in disturbing the source of sound be placed high up in the air,
balance of the bridge, and therefore in ef preferably high enough so that the wave front
fecting the indications of the oscillograph or striking the earth will be practically a plane
other instrument (19') coupled across the wave, this difficulty will be entirely avoided.
diagonal of the bridge. The mutual induct If the wavefront striking the earth be nearly
ance (32) may or may not be used, as de
plane, the subsequent diminution of intensity
7
, 17,949
with distance, both before and after re?ec known pointat a distance from said source
10
tion, will be relatively slight so that the ratio
of the intensity of the transmitted and of the
re?ected waves will be much smaller than if
the wave front striking the earth has a
small radius of curvature. For this reason
.\ if the source be placed high up in the air,
- and the passage of the re?ected wave over
the intensity of the shock imparted to the
earth at any point may be very slight, and
nowhere sufficient to cause permanent de
formation of the medium, and still give a re
?ected wave of ample intensity for detec
tion. On the other hand, if the source be
placed on the surface or imbedded withinthe
earth, the intensity of the shock at points
um from the said time interval and the said
velocity, the said source and the said known
the same point, measuring the velocity of
sound in the medium between the said known
point and the said subterranean stratum and 70.
calculating the distance between the said
known point and the said subterranean'strat
point being so placed with respect to the said
subterranean stratum that the path traversed
by the direct wave is substantially identical
with the path traversed by the re?ected wave.
2. The method of locating a subterranean
stratum, which comprises producing an
very close to the source must be very great aperiodic sound wave, causing said wave to
in order that the re?ected wave may be of be transmitted through the earth to the sub~
su?icient intensity, and in practice it is terranean stratum and to be re?ected there
found that permanent deformation of the from, measuring the time interval elapsing
earth very close to the source always occurs, between the passage of said wave past a
thus giving rise to the increased complexity known point and the passage of the re?ected
and prolongation of the wave above de wave past the same point, determining the
scribed. It will therefore be apparent that velocity of sound in the medium between said
the placing of the source up in the air at a known point and said stratum, and determin
considerable distance from I the earth, as ing the distance between said known point,
hereinabove described, is of fundamental im~ and said stratum from said time interval and
portance in eliminating certain of the prac said velocity, the place of production of said
tical difficulties that have heretofore been sound wave and said known point being so
encountered in attempting to explore sub positioned with respect to said stratum that
terranean strata through the medium of the paths traversed by the direct and re?ected
75
85
90
95
sound waves. Any suitable means may be waves are substantially identical.
used for placing the source at a proper eleva
3. In the art of exploring subterranean
tion. .Where circumstances are such that a
height of ‘not more than about 100 feet is
su?icient, a light telescoping pole or tower
can be used successfully. As a rule, however,
I have found that it is desirable to place the
source at a considerably greater elevation,
regions, the method which comprises produc
ing sound at a distance above the surface of
the earth, and detecting at a point whose dis
tance horizontally from the source of said
sound is small compared with its distance
vertically therefrom, the sound re?ected
and when this is desired some other means from a subterranean formation.
can be conveniently used for putting the
130
,
4. In the art of exploring subterranean
source up in the air. Any one‘of a number of regions, the method which comprises pro
devices may be used if desired, such as a ducing sound at a substantial distance above
captive balloon, a kite, an airplane, or re the surface of the earth, and detecting the
course may be had to projecting a charge of sound re?ected from a subtcrrrmcan fiirma;
1...?
explosive into‘ the air, the same being fired tion at a point through which both the direct‘: 34‘
by a time fuse in accordance With principles and re?ected waves pass.
well known to military ballistics.
5. In the art of exploring subterranean
For the sake of brevity in the appended regions, the method which comprises produc
claims, the term “aperiodic’7 as applied to ing sound at a distance above the surface of
the sound produced by the source includes the earth, and detecting, at a point adjacent
an abrupt sound wave or a sound wave 1m
11C
the earth’s surface and whose distance hori
zontally from the source of said sound is
pulse or rapidly decadent sound waves, pro
duced by a shot, explosion or equivalent means small compared with its distance vertically
herein described, as distinguished from sus therefrom the sound re?ected from a sub
tained, continuous or undamped sound
waves.
_
>
terranean formation.
>
120
6. In the art of exploring subterranean
regions, the method Wl11Cl1 comprises prod uc
I claim:
1. The method of determining the contour ing sound at a distance above the surface of
hf)
of a subterranean stratum which consists of the earth, and detecting at a point adjacent
sending out a sound wave from a source of
the earth’s surface the sound re?ected from a
sound, causing the said sound wave to be subterranean formation, said point being
transmitted through the earth to the said sub located adjacent substantially identical paths
terranean stratum and re?ected therefrom, in which the direct ‘and re?ected waves are
measuring the time interval elapsing between
the passage of the said sound wave over a
transmitted._
125
‘
‘7. In the artof exploring subterranean
130
8
' 1am
regions, the method which comprises ' roduc-I' re?ected therefrom, producing a plurality of v ‘
effects‘ by the direct and reflected sounds, and
above the surface of the earth, and detecting, producin a composite‘ indication by said ef
at a point whose distance horizontally from ects, sai effects being roduced at pointsv
_ ing an aperiodic sound wave at a ' ista'nce
the source of said sound is small compared adjacent substantially 1 entical paths over 70
with its distance vertically therefrom the, whlch the direct and re?ected sounds-‘are
sound re?ected from a subterranean forma
15. In a system of the character described,
tion.
8. In the art of exploring “subterranean re means for transmitting sound through the
gions, the method which comprises producing earth to a subterranean formation to be re 75
an aperiodic sound wave at a distance above ?ected therefrom, a plurality of detectors
‘the surface of the earth, and detecting, at a affected to greater extents, respectively, 'by
point, adjacent the earth’s surface and whose direct ‘and re?ected sound, Indicating means, ’
distance horizontally from the source of said and means for causing said detectors to affect
80
sound is small compared with its distance sald indicating means in opposite senses.
,16. In a system of the character described,
vertically therefrom the sound re?ected from
transmitted.
10
'
a
a subterranean formation.
means for transmitting sound through the '
ing sound at a distance above the surface of
affected to greater extents respectively, by as
9. In the art of‘ exploring subterranean earth to a subterranean formation to e re
_ regions, the method which comprises produc ?ected therefrom, a plurality of detectors
20
the .earth, and detecting, at a point whose direct and re?ected sound, indicating means,
distance horizontally from the source of said and means for causing said detectors to affect
sound is small compared with its distance ver said indicating means in opposite senses, said
tically therefrom the sound transmitted to
detectors disposed adjacent substantially
and re?ected from a subterranean formation. identical paths over which the direct and re
10.‘ In the art of exploring subterranean
?ected sound is transmitted.
.
90
‘
regions, the method which comprises produc
17. In a system of the character described,
identical paths over which .the direct and re
the direct and re?ected sound, and indicating
ing sound at a distance above the surface _of means for transmitting sound through the
the earth, and detecting the sound transmit earthto a subterranean fornriitiion to be- re
ted to and re?ected from a subterranean ?ected therefrom, a plurality of detectors
formation at a point adjacent substantially affected to greateraextents, respectively, by
means controlled by said detectors, the source
11. In the art of exploring subterranean of said sound disposed at a distance above
regions, the method which comprises produc the surface of the earth.
18. In a system of the character described,
ing an aperiodic sound wave at a dlstance
above the surface of the earth, and detecting, means for transmitting sound through the
at a point whose distance horizontally from earth to a subterranean formation to be re
the source of said sound is small compared ?ected therefrom, a plurality of detectors
with its distance vertically therefrom the affected to greater extents, respectively, by
?ected waves are transmitted.
35
40
sound transmitted to and re?ected from a direct and re?ected sound, indicating means,
and means for causing‘ said detectors to af
_
12. In the art of exploring subterranean foot said indicating means in opposite senses,
regions, the method which comprises produc the source of said sound disposed at a distance
ing an aperiodic‘ sound wave at a distance above the surface of the earth.
100
subterranean formation.
110
19. In a system of the character described,
- the sound transmitted to and reflected from a means for transmitting sound through. the
above the surface of the earth, and detecting
' subterranean formation at a point adjacent earth to a subterranean formation to be re
substantially identical paths over which the ?ected therefrom, a- plurality of detectors
affected to greater extents, respectively, by
direct and re?ected waves are transmitted.
13. In the art of exploring subterranean the direct and re?ected sound, and indicating
. regions, the method which comprises trans means controlled by said. detectors, the sound
produced by said means consisting, of an
aperiodic
sound wave.
nean ‘formation and reflecting it therefrom,
20. In a system of the character described,
producing an effect by the direct sound wave,
115
mitting sound from a source to a subterra
120
for transmitting sound through the
producing a'second effect by the re?ected means
earth to a ‘subterranean formation to be re
sound ‘wave at a point Whose distance hori
zontally from said source is small compared ?ected therefrom, a plurality of detectors
. with its distance vertically therefrom, and affected to greater extents, respectively, by
producing a composite indication by said ef the direct and re?ected 'sound, indicating
fects.
means, and means for causing. said detectors
14. In the art of exploring subterranean to affect said indicating means in opposite
senses, the sound produced by said means
regions, the method which comprises trans consisting
of an aperiodic sound wave.
,
mitting sound originating at a dlstance above
65
the earth to a subterranean formatlon to be
21. In a system of the character described,
125
17,242
9 v
I means for transmittin sound through the tance greater than the depth of the subter
earth'to and causing re ection of sound from ranean stratum, placing the detectors in con
a subterranean formation, a plurality of tact with the earth substantially in line with
sound detectors respectively in?uenced prin the normal extending from the subterranean
cipally by the direct and re?ected sound, a stratum through said source, and coupling
45
time-indicating, device, a transformer in the time measuring device to said detectors
whose secondary circuitsaid device is con to measure the time interval elapsing between
nected, and said detectors connected in cir the arrival of successive sound waves at said
cuit with the primary windings of said
10
transformer, said primaries being di?eren
tially related.
detectors.
,
o
_
24. A system for determining the contour
50
of a subterranean stratum comprising a '
22. In a system comprising a device for de- - source of sound, a time recording device, mi
termining the contour of a subterranean crophonlc devices, and means for mounting
stratum and comprising a source of sound, said m1crophon1c devices to e?'ect opposite
15
sound detectors, and a sound measurmg de
' vice, the method which comprises placing
said source in the air above the surface of the
"earth, disposing certain of the sound detectors in contact with the earth at points
20 intermediate said sound source and the sub
phase relation-of pulsating change of their
55
resistances in their e?'ect upon said record
ing device.
, '
7 25. A system for determining the contour
of a subterranean stratum comprising a
source of sound, a time recording device, mi
terranean stratum, and substantially in line crophonic devices electrically connected in
with the normal extending from the subter parallel, a differentially wound transformer
60
be actuated substantially only by an air wave, a secondary connected to the time recording
and so associated that its effect is opposed device, and means for mounting said micro
to that of sound detectors in contact with phonic devices to effect opposite phase re
the earth, and coupling the time measuring lation of the pulsations of their resistances in
65
ranean stratum through said source, and having primary coils connected respectively
placing other of the sound detectors so as to in series with said microphonic devices and
30
‘
device to said detectors in such manner as to their effect upon said recording device.
26. In the art of exploring subterranean 70
measure the time interval elapsing between
the arrival ofa direct sound wave at the de regions, the method which comprises trans
tectors in earth and air, and of one or more mitting sound to a subterranean formation
re?ected sound waves at the detectors in to e?ect re?ection therefrom, producing a
plurality of e?fects at points adjacent sub!
earth.
23. In a system for determining the con stantially identical paths over which the 75
tour of a subterranean stratum and compris— direct and re?ected sounds are transmitted,
ing a source of sound, sound detectors, and a and producing a composite indication by
time measuring device, the method which said e?ects.
comprises placing the source of sound in the
air above the surface of ‘the earth ata dis—
BURTON MoCOLLUM.