KR800000004B1 - Radioactivity oil-water well logging utilizing neutron source - Google Patents

Abstract

Device for radioactivity logging for radiation which stemmed from a borehole through an examination by neutron for the logging of stratum. Radiation monitor is composed of the propertional gamma radiation which have the multi-channel pulse height analyser connected to a radiation monitor for the generating signal. 1st limits of energy were applicable to gamma radiation 1.3 MEV-3.0 MEV and 2nd were applicable to 40MEV or the level of the minimum neutron captured gamma radiation to be contained.

Description

Detection of Radioactive Well Using Neutral Resources

1 is a schematic front view of a borehole in which an exploration device manufactured according to the present invention is suspended.

2 is a diagram of a typical record formed in accordance with the principles of the present invention.

3 is a diagram illustrating information obtained in accordance with the present invention.

4 is a diagram illustrating the reaction of a device according to the present invention but without a preselected shielding material such as samarium.

FIG. 5 is a diagram of the reaction of the probe of the present invention comprising a preselected shielding material such as samarium oxide for the same strata as in FIG.

6 is a chart showing the shape of the samarium capture gamma-ray spectrum.

The present invention relates to measuring the properties of the strata by means of a borehole exploration device, and more particularly, to the improvement of a neutral resource exploration device for geodetic measurement of the presence of hydrocarbon oil or brine in the strata through which boreholes pass.

It is therefore an object of the present invention to improve a radioactive exploration device using neutral resources to produce a detectable and measurable observable effect indicating the presence of petroleum or brine in the strata along the borehole.

It is well known to analyze the strata in situ as the passage of the borehole, using various radiometric methods. For example, by using a method commonly referred to as pore exploration, it is possible to measure the presence of pore regions along the passage of boreholes to indicate the presence of hydrogen present as hydrocarbon oil or water in the pores of the strata. Such analysis is performed by using neutron-neutron or neutron-gamma measurements according to known methods. In addition, according to the conventional method, by using the nuclear chlorine exploration method to analyze whether chlorine is included as a component, it has been proposed to determine the presence of the brine in the strata as the borehole passes. According to such a known method, a neutral resource passes through a borehole, radiation is detected by two energy ranges, and two signals are emitted. The first signal is a layer reference signal representing hydrogen, and is called a hydrogen signal (H-Signal) and is substantially insensitive to chlorine in the detected layer. The second signal is a ground reference + chlorine signal, which is denoted as a hydrogen + chlorine signal (H + Cl signal) and represents hydrogen and is sensitive to chlorine in the explored strata. The two signals are recorded or shown in relation to the location of the probe in the borehole, e.g. the difference between the two signals is quantitatively indicating the chlorine content in the strata, and the corresponding change in the two signals is the hydrogen content in the strata. (Sometimes called porosity).

It is therefore an object of the present invention to improve methods and apparatus known in the art for the art. Another object of the present invention is to provide an improved borehole probe that simultaneously measures the hydrogen and chlorine content of the borehole passages, which uses a single proportional radiation detector with an associated multichannel wave height analyzer. will be.

It is another object of the present invention to provide an improved method and apparatus for quantitatively discriminating hydrocarbon oil and salt water contained in the pores of the boreholes through which the bore passes, and at the same time being relatively insensitive to the adverse effects of other interferences that may be present in the beds. It is.

Summary of the Invention The present invention is an improvement of the method and apparatus for neutron well exploration to be handled in the field of exploration, which includes a mechanism that passes through a borehole and also includes a neutral resource that surveys the strata along the borehole. Depending on the longitudinal axis of the borehole, the radiation detection unit is mounted at a predetermined distance from the neutral source, which combines a multi-channel crest signal analyzer that signals in proportion to at least two separate predetermined energy ranges. It includes a proportional radiation detector. In addition, the channel 1 of the two energy ranges, ie, the ground reference (FR) signal, indicates hydrogen, which is substantially insensitive to the chlorine content of the ground, and the other energy range, that is, the channel 2 or the ground reference and chlorine ( What is represented by the FR Cl) signal represents hydrogen and chlorine in adjacent strata. Around the radiation detector there is a preselected shielding material with a relatively high capture cross-sectional area for neutrons, which reacts significantly in the energy range of channel 1 to gamma rays generated by thermal neutrons and in the energy range of channel 2 Almost no response. Preferred shielding materials include samarium and other examples include europium or gadolinium. In a preferred embodiment, the preselected shielding material surrounds the casing of the probe in the vicinity of the probe such that the shielding material intercepts the neutrons so that neutrons are trapped in the iron of the probe and do not emit gamma rays representing iron.

In order to better explain the additional objects and advantages of the present invention, reference is made to the following description and attached drawings.

Referring to FIG. 1 of the drawings, a plurality of layers 11, 12, 13, and 14 and boreholes 10 passing through a fluid layer 15 such as brine or crude oil are shown. Is shown. In the borehole 10, a borehole exploration device 17 made in accordance with the principles of the present invention is shown suspended by a cable 16. The cable 16 is externally conductive with one or more internal conductors (not individually shown) to be a device for transmitting electrical signals between the device 17 and the electrical device on the surface. It has a covering.

The device of the indicator includes a device represented by the indicator electronic 18 that receives a signal transmitted from the probe 17 and amplifies and separates the received signal.

The indicator device includes a mechanism for amplifying the received signal and a multi-channel wave height analyzer or discriminator having separate channel output passages for signals of different pulse heights. The output passage from the indicator electronics 18 has a separate signal channel, one of which is transmitted to the first display device in the form of a channel 1 recorder 19 and the other to the channel 2 recorder 20. Is transmitted to the second display device in the form of. The two recording devices may be separate recorders, which are preferably composed of separate channels of the multi-channel recorder, such as the boxes 21 indicated by the dotted lines surrounding the recorders 19 and 20. In either case, the recorders 19 and 20 include a rate meter which is necessary for recording the intensity, that is, the rate of occurrence of the detected radiation. Although the discriminator has been described as part of the indicator device, it should be understood that this may also be included as part of the device in the probe 17.

In order to correlate the position of the probe 17 in the borehole 10, the surface is equipped with a surveying device 23, which is adapted to detect the movement of the cable 16 in or out of the borehole 10. The perimeter is shown schematically as wheels in contact with the cable 16.

The surveying device 23 can be of any known instrument of the type suitable for measuring the position of the probe 17 in the borehole 10 and correlates the recorded probe signal with the position of the probe of the borehole. In order to achieve this, it is suitable to generate an electrical output signal that can be transmitted to the recorders 19 and 20 by the conductive circuit 24.

The exploration device 17 is composed of an elongated shell-shaped casing 25 formed of conventional steel according to known methods, to withstand the pressures and temperatures typically encountered in an oil exploration process. The casing is suitably characterized to withstand the conditions it will receive in a borehole at depths of 10,000 to 20,000 feeds.

The casing 25 includes a neutral resource 26 for irradiating the strata along the borehole, together with a suitable radiation detector for detecting gamma rays induced in the strata as a result of irradiation with neutral resources. The casing contains suitable electrical circuitry for amplifying and processing the output signal from the radiation detection device, so that transmission is via the cable 16 to the indicator device. In particular, the neutral resource 26 is located in the casing 25 and is shown surrounded by a neutron permeable shield 27 made of lead to prevent gamma rays that are radiated and transmitted directly or indirectly to the detection device. .

Neutral resources 26 preferably have a relatively long half-life and relatively no incident gamma radiation for stability, such as a combination of arylnium 227 or plutonium or radium D or polonium or americium with beryllium. . On top of the instrument 17 there is a radiation detection unit 28 isolated from the neutral resource 26 at a predetermined distance, which unit 28 has first and second output signals with associated shielding material and associated circuitry. The first output signal of the two output signals is substantially insensitive to the chlorine content, and the second output signal is adjacent to the strata. Proportional to the chlorine content. The signal transmitted to channel 1 is proportional to the radiation emitted from the adjacent strata as a result of the interaction of the neutrons from the neutral resource with the strata described below. The first signal is derived from the channel 1 output of the discriminator, and is hereafter referred to as the stratum reference signal in the text. The second signal is proportional to the radiation emitted from the adjacent strata as a result of the neutrons derived from channel 2 and from the neutral source, indicating the hydrogen and chlorine content of the adjacent strata, and subsequently the reference and chlorine signals in the text. Is displayed.

The detection unit 28 detects the photon output wave from the luminophor and transmits an electrical signal proportional thereto, so as to be located adjacent to the luminophore 30. And, a suitable proportional fluorescence detector comprising a gamma-ray sensitive luminopor 30 in the form of thallium-activated sodium iodide crystals. The photomultiplier tube is shown adjacent to the preamplifier 32, which amplifier (not individually shown) transmits the output signal derived from the photomultiplier tube 31 to the indicator device by the cable 16. And electrical connection to an additional electrical device, represented by the electronic device 33. The photomultiplier tube 31 obtains energy by a high voltage source (not shown), which includes a battery located in the probe or, more typically, as an alternating current from the surface to the probe in the borehole. A power source consisting of a transformer and a rectifier in the probe can be used to obtain a suitable dc operating voltage from the power supplied. The electronic device 33 may additionally include a circuit for transmitting the signal material to the indicator according to principles known in the art.

For example, the radiation detector signal is transmitted to the indicator as an amplitude-modulated signal, or in the form of a frequency-modulated signal according to a known method. When so-called single conductive cables are used, each signal transmitted from a separate detector channel can be transmitted simultaneously as pulses with different polarities or as different wave heights, or as frequency-modulated signals on carriers with different frequencies, for example. Can be. Luminopor 30 is shown as being located in a conventional aluminum container 30a, which serves to protect it from moisture and physical damage. The luminopores 30 are preferably surrounded by a thin boron shield plate 30b located around the outside of the container 30a to absorb thermal neutrons to prevent their activation. The upper end of the container 30a facing the photomultiplier 31 is shown to be open while the luminopores 30 are in direct contact with the photomultiplier 31. However, the container 30a may be sealed with a transparent cover of glass or plastic by methods known in the art. In the vicinity of the detector having the luminopores 30 in the container 30a, a shielding material 50 of neutron-absorbing material is provided around the casing 25 of the probe 17, and the neutron-absorbing material is oxidized. Samarium in the form of a coating of samarium (Sm ₂ O ₃ ), preferably contained in the adhesive or matrix of the epoxy resin. Samarium shielding material 50 is a neutron-absorbing material that, when trapping neutrons, emits gamma rays within the channel 1 detector energy range and is also combined with other elements of the present invention, including a multi-channel discriminator, as described below. It serves to represent neutron-gamma radiation signals (stratum reference signals) induced by channel 1, which are mainly sensitive to hydrogen and relatively insensitive to the effects of chlorine, as described below. The channel 1 discriminator is responsible for excluding most of the inappropriate low energy gamma rays, so that the channel 1 signals are sensitive to gamma rays generated mainly by neutrons and are not sensitive to inappropriate low energy naturally occurring gamma rays or gamma rays scattered from neutral sources. It must be biased. Preferably, the discriminator should be biased so that the measured radiation signal exhibits a gamma ray in the range having energy of about 1.3 MEV (millionelectron Volt) or higher. This special bias level is the epoxy shield of the neutron-absorbing material 50 surrounding the luminopores 30 at the probe location at 15.75 inches from the neutral source with 2 "x 4" sodium iodide crystals. In combination with samarium oxide within, it produces a very satisfactory stratified reference signal, which is primarily sensitive to hydrogen in the strata under radiation resulting from irradiation by neutrons from the neutral source 26. Furthermore, by biasing the detector to exclude low-energy gamma rays, most of the gamma rays scattered from the natural gamma rays and neutral sources present in the strata are removed from the detected signals. Because both natural and scattered gamma rays are at relatively low energy levels.

By so-called neutron-gamma measurement, neutral resources pass through the borehole to irradiate the strata along the borehole crossing. Neutrons from neutral resources are slowed down by the fluids in the strata and boreholes, mainly due to the slowing effect of hydrogen, and after being decelerated into the thermal range, the neutrons are trapped by the strata's material upon the release of gamma rays. These neutron-gamma rays are detected and their intensity, ie the rate of occurrence, is measured as a measure of the hydrogen content of the strata (indicated here as porosity).

When a thermal neutron is captured by hydrogen, specific gamma rays are released by hydrogen. When only hydrogen is present in the pores of the irradiated area, the intensity of the detected gamma ray, that is, the rate of generation, quantitatively indicates the hydrogen content of the strata. However, other materials that may be present in the strata may adversely affect neutron-gamma recording devices and may also prevent the exploration as a hydrogen measurement to be credible. Of particular importance is the presence of chlorine having a capture cross section of relatively high thermal neutrons compared to hydrogen.

In particular, chlorine has a neutron capture cross section of about 32 Barns, while hydrogen has a neutron capture cross section of about 0.33 Barns. Thus, chlorine is about 100 times more effective than hydrogen in capturing thermal neutrons. When the thermal neutrons are captured by chlorine and not by hydrogen, one gamma ray is emitted when one neutron is captured by the hydrogen atom, while about 3.1 gamma rays are emitted (on average). In addition to the foregoing, many of the gamma rays emitted by chlorine are about 4-8 MEV in the high energy range compared to the characteristic 2.2 MEV by hydrogen. As can be seen from the foregoing, the presence of chlorine increases the intensity of the gamma rays detected by the neutron-gamma device even at a very small amount, resulting in an incorrect hydrogen content in the final exploration. When measuring neutron-gamma radiation, the adverse effects of chlorine on one channel's hydrogen signal, ie, ground-layer signal, can be neutralized by subjecting the gamma-ray detector to radiation that reverses the effect of the detector on the presence of chlorine. Chlorine has a relatively high capture cross section corresponding to the capture of each neutron and emits a large number of gamma rays (photons). Therefore, the count ratio of the gamma ray detector increases with the presence of chlorine. To neutralize the chlorine effect, a gamma ray signal is generated which decreases with the presence of chlorine. This is done by generating a gamma ray signal whose intensity is proportional to the thermal neutron flow near the probe. This phenomenon is due to the fact that chlorine absorbs or removes thermal neutrons from around the probe in response to relatively high capture cross sections. As such, the thermal neutron flow near the detector decreases with the presence of chlorine. In the vicinity of the probe will emit a large number of neutron capture gamma rays. Using sodium iodide probes, the thickness of samarium oxide needs to be sufficient to absorb at least most of the thermal neutrons, and the balance is achieved by adjusting the channel 1 discriminator vias. Except in the absence of chlorine, when the exploration instrument passes from the same area to a chlorine-containing area, the counting ratio of the gamma ray detector increases with an increase in the number of captured gamma rays (photons) directly caused by chlorine. In this case, however, around the detector, the number of thermal neutrons available for capture by the neutron absorbing material is reduced, thus reducing the ratio of counting in the gamma ray detector. By means of a suitable instrument, these two effects can be canceled out from each other, so that an exploration device using this method can be separated from chlorine-containing strata, with the same porosity, stratification and hydrogen content, but without chlorine. If it passes, the result remains constant.

Samarium acts as a neutron absorber and as an anti-gamma preventer to extract the thermal neutron stream near the NaI (Tl) probe. Most of the samarium gamma rays are at relatively low energy, many of which are strata reference signals, which are preferably measured at channel 1 by adjusting the discriminator to accept all gamma rays detected between 1.30-2.92 MEV. .

The ground reference signal and the chlorine signal are obtained in channel 2 by measuring all gamma rays with energy above the lower limit of 3.4 MEV. This signal includes gamma rays from chlorine as well as iron, calcium and silicon, while the ground reference signal for channel 1 also contains gamma rays from hydrogen and samarium sleeves.

인치 일때 채널 1 변별기를 1.30-2.92MEV로 조정 시킴으로써 열중성자 성분에 대하여 균형화 될수 있다.In the apparatus shown in FIG. 1, the above-described two effects of neutralizing the effect of chlorine on the stratum reference signal of channel 1 can be adjusted by adjusting the bias of the discriminator or by adjusting the amount of neutron absorbing material 50. Or by combining the two methods described above. For example, the neutron-absorbing material 50 may be a coating of samarium oxide surrounding the probe, and may be a crystal having a thickness that substantially captures all the thermal neutrons that diffuse into the samarium oxide layer. Elevation of capture gamma-rays causes gaps between neutral resources and detectors.

In inches, the channel 1 discriminator can be balanced against the thermal neutron component by adjusting the channel to 1.30-2.92 MEV.

The lower limit of the channel 1 discriminator vias will be in the range of 0.8-1.8 MEV depending on the distance between the probe and neutral resources, the size of the crystal, the thickness of the case, the case material, the diameter of the borehole and the salinity of the fluid.

There are many more thermal neutron components than necessary for low bias adjustment, and lower than required amount for high bias adjustment. Thus, according to one feature of the present invention, low channel 1 is adjusted to 1.0 MEV, for example, and the thickness of the samarium oxide shield 50 can be adjusted to vary the amount of samarium so that both effects are offset. Once this is done, an additional neutron-absorbing material, such as boron or lithium, must be placed between the crystal and samarium to a thickness sufficient to absorb the thermal neutrons that have passed through samarium. Since boron or lithium do not emit neutron capture gamma rays above 1.0 MEV and crystals are not activated by thermal neutrons, it is appropriate to operate as described above. This feature is accomplished by adding a layer of neutron-trapping material, such as boron, between the neutron interaction material 50 and the luminopores 30.

Samarium is preferred as a material for trapping thermal neutrons near the detector to neutralize the effect of chlorine on the channel 1 strata reference signal, but other materials other than samarium may be used, and may also be used with samarium. In the present case where samarium is used in an exploration device having a steel casing, a sleeve of material such as samarium substantially reduces iron capture gamma rays from the exploration signal.

It is important that the iron in the probe has a thermal neutron capture cross section of 2.43 Barns, compared to a samarium capture cross section of about 5,800 Barns. Iron emits neutron capture gamma rays up to the 9.3 MEV range, while samarium emits gamma rays up to 7.89 MEV when it captures thermal neutrons.

Uto earth or gadolinium may also be used to practice the present invention. Gadolinium has a capture cross section of 47,000 Barns and emits neutron capture gamma rays up to 7.78 MEV. As described above, chlorine results in balanced effects and detection of neutron capture gamma rays up to about 8.55 MEV from the detected gamma rays signal.

Samarium or other materials with similar characteristics are applied, or the total amount of the materials used, whether or not a combination of these materials, such as those containing samarium and steel casings, has a predetermined net effect, which is the very It is important to generate a gamma ray signal in the vicinity corresponding to the thermal neutron concentration, and it is important that the detector directly cancels the capture gamma ray effect according to the presence of chlorine in the borehole and the presence of the strata near the probe.

인치 거리로 중성자원으로 부터 위치된 4인치 길이 및 2인치 직경의 플로토늄 배릴륨, 탈륨-활성요드화나트륨 결정의 방사선 검지기로 구성되고, 10⁷중성자/초의 중성자원 강도를 이용하는 바람직한 실시예에 있어서는, 검지기 근처에서 산화사마륨 슬리브로 포위된 강철 케이싱에 대하여 상술한 바와 같이 1.30-2.92MEV 범위의 감마선 만을 검지 하도록 채널 1 바이아스를 조성시킴에 의하여 채널 1의 암층기준 신호에 미치는 염소의 역효과를 만족 스럽게 상쇄시킬 수 있다.From center to center

In a preferred embodiment, which consists of a radiation detector of 4 inches long and 2 inches diameter plutonium baryllium and thallium-activated sodium iodide crystals located from the neutral source at inches distance, using a neutral resource intensity of 10 ⁷ neutrons / sec. , By satisfying the adverse effects of chlorine on the channel reference signal by creating a channel 1 vias to detect only gamma rays in the range of 1.30-2.92MEV, as described above for steel casings surrounded by samarium oxide sleeves near the detector. Can be offset.

In a preferred embodiment, the channel 1 vias in the 1.3-2.92 MEV range not only moderates the chlorine's effect on the stratum reference signal but also minimizes other petroleum adverse effects on the detected signal. However, if the channel 1 bias range is slightly changed, for example, if the channel 1 bias extends in the range of approximately 1.0-3.0 MEV, a satisfactory operation can be achieved. Similarly, with a special range of 3.43 MEV and properly tuned to adequately remove the petroleum adverse effects, channel 2 can be biased to detect about 4.5 MEV and more radiation if inaccurate. The upper limit of channel 2 bias has no special cutoff, which is fixed to fully accept neutron gamma spectra above a certain lower limit (appropriately 3.43 MEV). In practice, the neutron gamma-ray spectrum rises to about 8 or 9 MEV, so the critical upper limit of channel 2 bias is adjusted to the above general range in a given case. It is important, however, that the channel 2 bias is adjusted to detect the most prevalent neutron gamma rays generated by trapping thermal neutrons by chlorine in the strata. This is made possible by adjusting the channel 2 bias as described above.

It is important that the shielding material of the neutron-reactive substance around the probe has a relatively large capture cross section for the thermal neutron and has a neutron capture gamma-ray spectrum that is predominantly within the channel 1 vias and outside the channel 2 vias. Shielding materials such as samarium have a capture gamma-ray spectrum that differs substantially from the capture gamma-ray spectrum for chlorine, so that high energy chlorine capture gamma rays are detected in channel 2 and excluded from channel 1 and the predominant neutron capture gamma rays emitted by the sleeve It can be detected on channel 1 and excluded from channel 2.

Combining these various features in this manner can provide a chlorine system that is optimal for the needs described herein.

In order to stabilize and protect the scintillation probe against the effects of the high borehole temperature and its changes, the luminophore 30 and the optoelectronic plumbing 31 as well as the preamplifier 32 are located in the insulation chamber 34. This insulation chamber is preferably in the form of a Deer Flask defined by an outer wall 35 separated from the inner wall 36 by a vacuum space.

The insulation chamber 34 is provided with the insulation cover plug 37 which can be removed suitably in the insulation chamber 34 comprised of a dewar flask. A cooling chamber having a wall structure 39 is advantageously installed in the insulated cover plug 37, which is formed of a thermally conductive material such as thin aluminum and contains a certain amount of ice 40. The cooling chamber 38 containing the ice 40 maintains the fluorescence detection intensity in the insulating chamber 34 at a stable and low temperature due to the temperature stability that occurs as the ice is changed from the solid state to the liquid state during exploration. It becomes a mechanism to make it.

Other known methods of stabilizing the temperature of the device may also be used.

In order to enhance the sensitivity of the channel 2 strata and chlorine signals, the discriminator circuit associated with channel 2 is such that high energy gamma rays due to the presence of chlorine in the strata irradiated by neutrons from the neutral source 26 are well detected in channel 2. Should be biased to detect gamma rays above 3.43 MEV.

Despite the removal of 2.2 MEV hydrogen capture gamma rays from the channel 2 signal (according to 3.43MEV bias limits), the gamma rays detected in the channel 2 strata and chlorine markers are affected by the hydrogen content of the rock layer as well as the chlorine content. Proportional. The fast neutrons from the neutron resources must be slowed down before they can be captured and emit neutron-induced gamma rays. The hydrogen sensitivity of the rock layers and the chlorine signal channel is due to the fact that the lightest hydrogen of the element plays a role of mainly slowing down or thermally neutronizing fast neutrons from neutral sources.

The chlorine sensitivity of the channel 2 signal is due to the fact that most of the measured gamma rays are emitted upon the capture of thermal neutrons by chlorine.

In order to stabilize the position of the probe during exploration, a distributed arch spring 45 having upper and lower ends 46 and 47, respectively, is located in the probe 17, and the spring is provided with a probe borehole 10. It is positioned to be able to flex freely when moving due to irregularities in the sides. This is typically done by placing the upper and lower ends of the arch spring 45 in the device 17 in an active connection by means of a long slot (not shown) in the arch spring 45.

The nuclear chlorine exploration system is based on chlorine's thermal neutron capture cross-section, which is an amount greater than that of other major elements present in soil sediments. According to the present chlorine exploration system, a strata chlorine (FRCl) signal (also referred to herein as strata reference and chlorine signals). Two measurements are taken at the same time in succession for length, recording each ground reference (FR) signal. The interpretation of the chlorine content and the saturation of the water in the strata is made by comparing the two curves which are different functions of the measured chlorine content of the strata. Comparison and interpretation are generally performed by superimposing the two curves to observe the deviation of the FRCl from the FR curve or by cross-drawing in Cartesian coordinates. As the crossover method, a model such as that shown in FIG. 3 appears. All points representing the explored strata are on nearly parallel curves or between parallel curves. These two curves have the highest and lowest strata salinity, that is, trajectories of strata, filled with brine and filled with fresh water or oil. The region of intermediate fluid salinity is shown between these two curves. The curve of the median salinity can be made between the highest and lowest salinities and then can support the salinity for each of the explored strata.

Ideally, the salinity of the measured strata should not be affected by the porosity, shale (boron content) and rock formation of the strata.

인치(중심대 중심)에 위치한다.The system of the present invention measures thermal neutron capture gamma rays in the two gamma ray energy ranges of 1.3-2.92 MEV and all gamma rays above 3.43 MEV. The probe is a NaI fluorescence detector, 2 inches to 4 inches long, from a plutonium beryllium neutral source that emits 107 neutrons per second.

Located in inches (center).

Lead is used as a shield between the thick stock and the detector. Neutral resources and probes are contained in steel casings covered with samarium oxide (Sm ₂ O ₃ ) sleeves. Sm ₂ O ₃ sleeves combined with a high gamma ray energy range eliminates porosity and shale (boron) effects on water saturation measurements. Petrological impacts are also minimized.

4 shows the results of an embodiment of the inventive chlorine system without Sm ₂ O ₃ sleeves for limestone layers with medium and high porosity. This figure shows the effect of boron in the strata on exploration. This effect is the result of changes in borehole and stratum components, indicating the presence of salt water in the strata filled with fresh water, combined as a vector, resulting in incorrect results.

In Figs. 4 and 5, the same symbol is used to denote boron in lime saturated with fresh water, lime saturated with brine and lime saturated with water. In FIG. 5 the results of the same system with Sm ₂ O ₃ are shown for the same strata as in FIG. As can be seen from this figure, the addition of boron does not misrepresent the presence of water or oil in the strata. This feature is achieved by vectors parallel to each other in the direction of increasing porosity in the borehole and in the strata component.

Note that in Figs. 4 and 5, the direction of the strata component vector is the same, and the direction of the borehole component vector is rotated in the strata component vectorer direction by the addition of the Sm ₂ O ₃ sleeve in the case of Fig. 5. In FIG. 5, contrary to FIG. 4, the borehole and the strata boron addition vector compete with the line of chlorine and water.

The function of the Sm ₂ O ₃ sleeve is to redirect the thermal neutrons near the detector to gamma rays that can be detected by a NaI (Cl) scintillator.

The shape of the samarium trap gamma ray spectrum is shown in FIG. As can be seen from this figure, most of the samarium gamma rays are in the 1.3-2.92 MEV range of the signal and the fractions are in the range of the FlCl signal.

It is inefficient to detect NaI (Tl) and energy gamma rays, so the number of improved samarium gamma rays in the range 1.3-2.92 is about 10 times higher than that in the range above 3.43 MEV. Other elements with larger capture cross-sections and thermal neutron capture gamma spectra similar to samarium are europium, gadolinium and other rare earth elements. The thickness of the sleeve made from these elements should be sufficient to capture most of the incidental thermal neutrons.

To conduct radiological exploration to precisely and quantitatively measure the chlorine content of boreholes through which the bore passes, the salinity percentage of water contained in the boreholes and strata is based on a sample of or at least a predetermined data indicating the expected salinity. It is preferable to determine. Salinity information is the standard data for calibration and adjustment of probes and evaluation of the exploration records obtained.

The probes can be calibrated for wells saturated with a given chlorine content by placing probes on opposite sides of the strata saturated at 100% saturated or otherwise known by brine and observing the measured radiation response. Can be. This reaction can then be adjusted to the desired position on the chart. Similarly, the probe should be located at the opposite layer in the strata with 100% petroleum saturated or other known percentages, preferably with the same percentage as selected for the calibration of the brine reaction, and then the exploration plots will provide the desired values. It should be adjusted to indicate. For convenience of explanation, the recording device of the exploration system should be adjusted so that the channel 1 strata reference signal, the channel 2 strata reference signal, and the chlorine signal are tracked in various strata. This makes both the reference signal detector and the reference and chlorine signal detectors substantially equal to the chlorine content (porosity) whether present as a component of petroleum or as a component of water. The next probe is located relative to the area containing the brine, so all the differences between the two signals are due to the presence of chlorine as a component of the brine. For these calibrated devices, the indicated reference or porosity signal indicates the petroleum or water content of the strata, while the separation or deviation between the reference signal and the reference and chlorine signals indicates that the ground reference or porosity signal is between the two signals. Indicate that it is due to brine to a degree proportional to the deviation. If the stratum reference signal exhibits high processability, eg hydrogen concentration, while the reference and chlorine signals are substantially consistent, if the petroleum is present in the rock, the exact amount thereof is also present. If the reference signal shows a high value and at the same time the reference and chlorine signals are separated from it, it indicates that the strata are mostly filled with saline, and the degree of separation between these two signals indicates the amount of saline over the total saturation. .

Referring to FIG. 2, there is shown a cross-sectional view of a typical multiple layer through which a borehole can pass and be explored by the probe of the present invention as shown in FIG. The diagram illustrates the typical natural gamma rays and their voltages along with the short normal resistivity of the adjacent layers. Also shown are two typical nuclear chlorine explorations that can be made by the probe 17. For the sake of brevity, it is assumed that the second chlorine exploration record is carried out after the first chlorine probe and changes as the petroleum-water contact is temporarily exhausted, for example as described below. This recording represents the first curve H representing the radiation intensity measured in channel 1 (increased to the right as recorded) and the hydrogen content of the strata and the radiation intensity measured in channel 2 (also increased to the right). The second curve H & Cl is shown, and the hydrogen and chlorine content of the strata are also shown. The reaction of the H curve indicates the amount of hydrogen, that is, the porosity of the strata. The corresponding deviation region of the two curves indicates the presence of petroleum or water and the region where the H & Cl signal exceeds the H signal indicates the presence of brine. Thus, oil or possibly water appears just below 2705 feet.

After a period of time, the petroleum-brine content at the bottom of this area shifted from 2760 feet shown in the first chlorine exploration record to 2725 feet shown in the next second logging operation. Salt saturation appears just below 4080 feet. In the region just below 2490 feet, H, H, and Cl are relatively low, resulting in low porosity. In the area just below 2650 feet, it appears to be thought of as a mixture of brine and petroleum in the first chlorine exploration record, which would be understood only as brine in the second exploration record.

Although two exploration signals representing hydrogen content and hydrogen and chlorine content, respectively, are shown and recorded on the same chart, these records can be recorded as separate curves in separate exploration records, and the two records correspond to the correspondence between the individual probes. It can be explained by looking at each other overlapping each other to explain the change and the deviation. In this case, it should be noted that the two exploration signals are adjusted so that the exploration system exhibits deviations in the same accumulation value.

Instead of recording the hydrogen signal and the hydrogen and chlorine signals separately, only one of the two signals, preferably only the hydrogen content signal, is recorded with a second related signal representing the ratio or difference between the hydrogen signal and the hydrogen and chlorine signals. can do. The hydrogen content signal can be shown for hydrogen and chlorine content in which case the straight line represents petroleum or water and the deviation from this straight line represents the chlorine content.

The channel 1 and 2 probes can be recorded magnetically, and can also be recorded in an analog or digital computer, to generate a signal indicating a difference or other deviation between the channel 1 and 2 signals. Appropriate mathematical methods or computer techniques may be used, or this signal may represent one signal to another.

In order to perform the exploration by the apparatus described herein, the exploration device 17 is lowered down the well to be explored and drawn out through the well at a predetermined constant speed, while the output of the two detector channels is connected to the cable 16. It is preferable to transmit them to the indicator device through which they are transmitted to the recorder. The intensity, ie the rate of occurrence of radiation detected in these two channels, is recorded in relation to the position of the probe in the borehole.

Claims (1)

A radioactive exploration device comprising: a rapid source of neutrons for irradiating strata along a borehole; and a radiation detector for detecting radiation generated in the boreholes upon irradiation with neutrons from said neutron source. The detector is configured as a proportional gamma radiation detector having a multi-channel wave analyzer connected to it for generating output signals in at least two energy ranges, the first range of energy ranges corresponding to gamma radiation of 1.3MEV-3.0MEV. Range 2 corresponds to gamma radiation ranging from about 4 MEV to at least a neutron capture gamma radiation of high energy chlorine, wherein a preselected shielding material substantially encompasses the active volume of the probe of the probe; The material has a relatively high trapping cross section for thermal neutrons, Predominantly within the energy range of the first channel and substantially outside the second channel range, the characteristic neutron capture gamma radiation is emitted, so that the signal derived from the first channel comprises a stratum reference signal representing mostly hydrogen, The signal derived from the second channel is a radioactive well logging method using a neutral resource as a device characterized in that it comprises a stratum reference and chlorine signal indicating mostly both hydrogen and chlorine.

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