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Патент USA US2263097

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NQV. 18, _1941.
Filed May 8, 1939
Oámîj @w
' ‘Patented Nov. 1s, 1941u
-inurl-51D''*,S,Ta'r1zs¿ , PATENT Í 10F-FICE
GEornYsIcAL Paosrnc'rlNG
Joseph A. Marchand, Houston, Tex., assigner of
_ fifty-five per
cent to Bailey Balken, Houston,`
' Application 'May a, 193s, serial No. 2772.468
1 claim.
(c1. 17a-182)
ical prospecting for the location of subsurface
structures and deposits'such as gas and oil.
'I‘his invention- is based on the discovery that
l of desired polarity from the>` resistor 5 may be
_impressed upon the electrodes at the points l
and 2. In one manner of practicing the inven
tion this potential is varied until thegalvanom
eter 3 reads zero, at which time it is known that
directional indications are revealed by the mak
ing of `measurements about points in a prospect
ing _area land that such indications are inter
pretable in terms of »subsurface structures and
the applied potential'is equal and opposite to
that between the points l and 2. The ampli
deposits. While the inventionjisy not confined
thereto ` the necessary-measurements may >be 10
tude and polarity of the indicated potential ._is
made by the observation of potentials which are
set up by telluric currents which are known
to exist in the earth, such -measurements being
yReadings are also taken between the point l
and a predetermined number of polnts~2 there
about whereby the amplitude and direction of
` made in accordance with technique hereinafter
described in greater detail. It -has also been
the maximum and minimum potential gradients -
found that in making of resistivity -measure
ments in accordance with the invention, the de
are obtained.
A series of such _measurements is repeated
about >a plurality of points, as indicated by the v
sired directional indications are obtainable. The
perspective areal View of Fig. 1 in whichf the
principal object of the invention is'to provide a
ments is shown in Fig. 2-as comprising a po
tentiometer circuit whereby a variable potential
. The invention relates to methods for geophys
simple, rapid and effective method of directional 20 results at the individual .points 2 are indicated
vby the arrows 8 within the area l.
‘ information within the prospect area thru meas
It has been found that the directional indi- .
' cationsïin general constitute whorls of which
urements' made about a point or points within
Another object is to provide a method in which
the configuration varies in accordance with the
in order 'to,obtain directional information in
dicative of both the location of subsurface struc
tures and the area' in which more intensive in
vestigations should be carried out.
It is also an object to provide a method in 30
which variations in the potential gradient. pro
subsurface structure, which gives rise to the
directional indications. At points remote from
the structure the indications are such as toA lead
the prospector toward the structure about which
more complete information is desired.
Repeated tests Vhave revealed that while the
maximum or minimum amplitudes mayyary.
particularly with changes in moisture conditions
yet the direction does not change and repeatable
observations may thereforeV be obtained. It is
also found, however, >that when measurements
measurements are made about a point or points 25 nature and extent of the fault,- dome or other v
duced by telluric currents about points in the '
prospect area are measured for directional in
formation indicative of the sought structures.
The technique vconstituting the inventionv
whereby the, enumerated objects and others, are ,
- are made as above described and when direct
. current readings are made between the electrodes
_realized may be varied, the accompanying dis
'clœure being presented by way of illustration
and supplemented by the drawing in which:
-Fig. 1 is a dlagrammaticareal representation
of `directional information~ obtained in accord
ance-with the invention'.
at each' setting thereof, the product of the cur
rent and the measured potential for any posi~
tion of the electrodes is substantially constant ‘
regardless of vchanging terrestrial“ conditions.
Measurements of current, when" the product of
Fig. 2 illustrates the procedural operations at
an observation point and'embodiment of equip
potential and current are relied upon, may be
` ment which may be used for carrying out the 45 readily obtained by opening the key l0 in the
Referring first to Fig. 2 of the drawing. the
battery circuit and’moving the slider Il to the>
left upon the resistor 5l so that the millivoltmeter
reference character I indicates a-point about '
l2 is short-circuited. » The current is then read
upon the galvanometer 3, such current flowing
which observations or measurements are to be
made. An- electrode is embedded in the earth 50 thru Vthe circuit constituted by the earth be
tween the points l and 2, andthe ñxed~ resist
,at this point, such electrode being >one of a pair
ance of the circuit thru the galvanometer 3.
of which the other is embedded in the ground in
When using the technique iu'st described, the
succession, at points! equidistant from the- point »
l and arranged an'g‘ularly thereabout.
One form ci aDPmtU-S‘for making measure
current ñowing thru
stant is related to the
e> test circuit atany in
tivity of _the earth
between the >points at vwhich the electrodes are
infomation indicative of the location of sought
deposits is obtained. buried in the earth, since such test circuit cur-_
rent is due to the current nowing in the ,earth
What is claimed is:
. l
inthe area under investigation. The resistiv
,The vmethod of geophysical prospecting com
ity o! the earth is an important factor inthe 5 prising the steps ot measuring the potential
amplitude and distribution pattern oi' _the earth
'produced by telluric currents between a-point ~
current and hence interpretations may be made
and a.l plurality` of points spaced equidistant
in terms of resistivity.
thereabout, measuring the current which flows
While the applicant is uncertain 9s to theof
through a fixed resistance connected successively
vries. which Vmight explain ' phenomena `revealed 10 between said point and each of such plurality
in the practice of the invention as described,
yet repeated tests in producing areasV and in
areas where subsequent drilling has resulted in
.of points, and repeating said measurements
l about each of `a plurality of additional points
within a prospect area so that such measure
production, reveal the practicability and utility
ments of potential and’v current constitute‘in
of the invention ç'which broadly comprehends a 15 formation of the location and extent of sought
simple and eiîective method of exploration by/ Q
the making of observations about a plurality of
points in a prospect area. _whereby directional
subsurface structures. i
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