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Патент USA US3037125

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United States Patent Office
1.
3,037,115
METHOD 0F WELL LOGGING
Leendert de Witte, Ponca City, Okla, assignor to Con
tinental Oil Company, Ponca City, Okla, a corporation
of Delaware
No Drawing. Filed Oct.14, 1954, .Ser. No. 462,370‘
4 Claims. (Cl. 250-435)
3,037,115
Patented May‘ 29, 1962
2.
?ected by or transmitted throughthe mixturev are then
detected, the intensity of the neutron stream detected will
vary as the relative ‘amounts of brine and crude oil in
the mixture vary.
When a method is used which utilizes'a neutron stream,
care must be exercised as to the‘ energy level of the neu
tron stream used, because, as is well known in the art, the'
effects produced on neutrons by, different substances vary.
This invention relates to a method of neutron logging,
greatly with the energy of the neutrons. Thus neutrons of.
of wells to deter-rnine‘therein point-s ofentry of different 10 a very high energy level may pass unaffected through a
?uids.
certain mixture whereas neutrons of. a slightly lower en
When different ?uids enter the producing stream of a
ergy level are affected selectively by the different com
well and the presence of one of said ?uids in the ?nal
ponents of such mixture
output of the well is undesirable, it is possible to elimi
The determination of the levels wherein oil and brine
mate the entry of the undesired ?uid if the depths at which 15 enter the producing stream of an oil well is accomplished
it enters the well bore can be accurately determined.
by the present invention by detecting the above mentioned
Quite often oil and brine are'both present in the produc
differences in the e?ect by oil and brine in‘scattering, re
ing stream of an oil well. It is desirable that the output
tarding, and absorbing a neutron stream. These differ
of the well be as rich in oil as possible so that the well
ences are most pronounced when theenergy level of the
pumping operation will be e?‘icient from the standpoint of 20 neutron stream at the point where it starts traversing the
producing oil, and so that the need for separating opera
sample is approximately 10,000 electron volts.
tions will be reduced. If the depths at which brine en
The apparatus which may be used in carrying out the
ters the stream of the well can be accurately determined;
method of this invention may consist of a wellknown
then by well known methods the walls of the well can be
form of tubular ‘well surveying tool, commonly referred
cemented over at these depths thus reducing the amount 25 to as a sonde, but 'which contains in ?xed spaced relation
of water contaminating the well stream.
a source of neutrons enclosed in a suitable shield and a
The determination of points of entry of different ?uids
detector of slow neutrons. The detector is connected to
into a well presents several distinct problems.
a suitable devicewhich records‘ the detected signals‘rela
Soon after the different ?uids enter the well bore they
tive to the depths at which they originated. The neutron
begin to mix. Therefore, the samples of the admixture 30 source and shield are mounted in the bottom of the
in the well stream must be large enough so that a fair
sonde. Just above the shield, means are provided for
representation of the relative quantities of the different
the passage of well ?uids into the sonde. The slow neu
?uids entering at that level is obtained. However, the
tron detector should be mounted in the sonde from 6 to
samples analyzed must not be too large because the pur
12 inches above the shield so that it detects the neutron
pose of analyzing samples is to ?nd distinct depth ranges 35 stream that has been transmitted for that distance through
wherein each ?uid enters the bore. If the samples are
the ?uids between the shield and the detector.
too large, i.e., are taken along too great a length of the
The particular detector used is not critical. Its func
well bore, accurate location of the interfaces between
tion is to detect only slow neutrons. Examples of suit
said ranges is impossible.
able detectors are a boron coated proportional counter
It is the principal object of this invention to provide a 40 and a 13-10 enriched boron~tri?uoride counter.
method of logging a well to determine therein points of
entry of different ?uids.
The particular neutron source used is not critical.
Ex
amples of suitable sources are the products resulting from
It is a more speci?c object of this invention to provide
the action of a radioactive element on one of the follow
a method of logging oil wells to determine points of entry
ing: aluminum, beryllium, boron, lithium, magnesium,
45 phosphorus, and sodium. The most likely used sources
therein of brine ‘and oil.
'Further objects and advantages of my invention will
appear more fully throughout the following speci?cation
and claims wherein the speci?c application of my in
vention to oil wells is described.
will be mixtures of radium-beryllium or poloniumberyl
lium.
The shield should be of such thickness and composi
tion that the neutron stream entering the ?uid mixture
50 has an energy level of about 10,000 electron volts. It
Broadly stated, my invention comprises:
The method of determining the respective points of
may be made of lead or a suitable plastic.
entry into a well of different ?uids which signi?cantly
In operation, the sonde is lowered into the well so that
differently affect a neutron stream which comprises pro
the ?uids produced by the well, substantially at the levels
gressively establishing in local areas in the well a neutron
where they enter the well bore, may ?ow into the sonde
stream and making ‘a log indicative of variations in a 55 just above the shield. The ?uids then flow through the
parameter of the a?ected neutron stream at a fixed dis
sonde upwards around the detector and out of the top of
tance from its source.
the sonde. As the ?uids produced by the well pass
through the neutron stream emanating from the shield,
they scatter, absorb and retard the neutrons of said
60
level, the different components of the mixture may affect
stream. The degree to which the brine produced by the
the neutrons in various ways. ‘Some substances will scat
well affects the neutron stream is sufficiently distinct from
ter neutrons. Some substances will retard the neutrons’
the ‘degree to which the oil a?ects the neutron stream that
velocity. Some substances will absorb neutrons, and some
when an unusual amount of oil or water is present at any
substances will exert combinations of these effects on
point which the sonde passes, the recording device con
When a mixture of certain ?uids is bombarded by neu
trons, and when the neutron stream has the proper energy
the neutrons. When a mixture of several substances is 65 nected to the detector of slow neutrons will indicate a
rapid change in one direction or the other. The sonde
bombarded by ‘a stream of neutrons it is possible to readi
is lowered throughout the well while the recording device
ly determine the relative ‘amounts of the various sub
makes a trace of the detector signals on a depth log.
stances present in the mixture if the effects they produce
As a separate operation the sonde should be placed in
on a neutron stream are signi?cantly different. Thus,
70 a ?ask of brine which has been separated \from the well
when a neutron stream of a given energy level bombards
output, and the effect of the pure brine on the neutron
a mixture of brine vand crude oil and the neutrons re
3,037,115
A
3
a
areas of entry of different ?uids into a well bore, each of
said ?uids having a signi?cantly different effect upon a
stream of slow neutrons, which comprises emitting a
Stream of slow neutrons at different locations along the
stream recorded. Similarly, the sonde should be placed
in a ?ask of substantially pure oil separated from the well
output, and the e?ect of the pure oil on the neutron stream
recorded. These two records can then be used to cali
Well bore, passing the ?uids produced by the well through
brate the depth log, to directly indicate quantitatively the
relative amounts of brine and oil present in each local
the neutron stream, and logging, at a ?xed distance from
the source of said slow neutrons, the variations at each
location in that parameter of said slow neutron stream
area throughout the well.
It is not essential that the apparatus of this invention
be constructed speci?cally as described above. Rather
than measuring the intensity of the neutron stream trans
which has passed directly through and been affected by
the well ?uids at said location.
2. The method of claim 1 characterized further in that
mitted through the well ?uids, similar accurate informa
the energy level of said slow neutron stream is approxi
tion can be obtained by measuring the intensity of the
mately 10,000 electron volts.
neutron stream re?ected by the well ?uids.
3. The method of claim 1 in which the slow neutron
This method of locating points of water entry into wells
producing oil and water has several pronounced advan 15 stream is transmitted through the ?uids for a distance of
approximately 6 to 12 inches.
tages.
4. The method of claim 3 characterized further in that
‘The signal detected by the detector of slow neutrons is
the energy level of said neutron stream is approximately
independent of the way in which the oil and water are
10,000 electron volts.
mixed.
Furthermore, this method indicates the points of entry
References Cited in the ?le of this patent
of the water and the points of entry of the oil. Because
the points of ?uid entry are so indicated, that is, because
the points of oil entry are also known, the chance that the
oil output of the well would be reduced by subsequent
UNITED STATES PATENTS
2,335,409
2,463,733
2,544,412
2,726,338
2,735,944
2,738,426
cementing operation, is substantially eliminated.
Other modes of applying the principle of the invention
may be employed, change being made as regards the de
tails described, provided the ‘features stated in any of the
following claims or the equivalent of such be employed.
I, therefore, particularly point out and distinctly claim
as my invention:
1. A method for determining the location of respective
30
2,744,199
2,813,980
2,926,259
Hare ________________ __ Nov. 30,
Albaugh ______________ __ Mar. 8,
Bird _________________ __ Mar. 6,
Goodman ____________ __ Dec. 6,
Greer ________________ __ Feb. 21,
Hurst _______________ __ Mar. 13,
1943
1949
1951
1955
1956
1956
Juterbock et a1. ________ __ May 1, 1956
De Witte _____________ __ Nov. 19, 1957
Dewan _______________ _- Feb. 23, 1960
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