WO2023061940A1 - Dispositif d'évaluation en forage d'une teneur en uranium et d'une porosité hydrogène d'une région d'intérêt d'une formation géologique et procédé associé - Google Patents
Dispositif d'évaluation en forage d'une teneur en uranium et d'une porosité hydrogène d'une région d'intérêt d'une formation géologique et procédé associé Download PDFInfo
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- WO2023061940A1 WO2023061940A1 PCT/EP2022/078100 EP2022078100W WO2023061940A1 WO 2023061940 A1 WO2023061940 A1 WO 2023061940A1 EP 2022078100 W EP2022078100 W EP 2022078100W WO 2023061940 A1 WO2023061940 A1 WO 2023061940A1
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- WIPO (PCT)
- Prior art keywords
- neutrons
- interest
- region
- hydrogen
- uranium content
- Prior art date
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- 229910052770 Uranium Inorganic materials 0.000 title claims abstract description 91
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 title claims abstract description 91
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 77
- 239000001257 hydrogen Substances 0.000 title claims abstract description 77
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 76
- 238000005553 drilling Methods 0.000 title claims abstract description 17
- 230000015572 biosynthetic process Effects 0.000 title claims description 17
- 238000000034 method Methods 0.000 title claims description 13
- 239000000523 sample Substances 0.000 claims abstract description 43
- 238000011156 evaluation Methods 0.000 claims abstract description 32
- 230000004992 fission Effects 0.000 claims abstract description 18
- 230000003993 interaction Effects 0.000 claims abstract description 17
- 238000005259 measurement Methods 0.000 claims description 34
- 238000005755 formation reaction Methods 0.000 description 14
- 238000010521 absorption reaction Methods 0.000 description 4
- 238000004088 simulation Methods 0.000 description 4
- 230000002123 temporal effect Effects 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 3
- 239000006096 absorbing agent Substances 0.000 description 3
- 229910052796 boron Inorganic materials 0.000 description 3
- 229910052793 cadmium Inorganic materials 0.000 description 3
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 238000009434 installation Methods 0.000 description 3
- 238000012937 correction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 229910052805 deuterium Inorganic materials 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 229910052722 tritium Inorganic materials 0.000 description 2
- JFALSRSLKYAFGM-OIOBTWANSA-N uranium-235 Chemical compound [235U] JFALSRSLKYAFGM-OIOBTWANSA-N 0.000 description 2
- AETVBWZVKDOWHH-UHFFFAOYSA-N 2-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]-3-(1-ethylazetidin-3-yl)oxypyrazol-1-yl]-1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethanone Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C=1C(=NN(C=1)CC(=O)N1CC2=C(CC1)NN=N2)OC1CN(C1)CC AETVBWZVKDOWHH-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000011358 absorbing material Substances 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- SWQJXJOGLNCZEY-BJUDXGSMSA-N helium-3 atom Chemical compound [3He] SWQJXJOGLNCZEY-BJUDXGSMSA-N 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V5/00—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity
- G01V5/04—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging
- G01V5/08—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays
- G01V5/10—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays using neutron sources
- G01V5/107—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays using neutron sources and detecting reflected or back-scattered neutrons
Definitions
- the present invention relates, according to a first aspect, to a device for evaluating in drilling a uranium content and a hydrogen porosity of a region of interest of a geological formation.
- the invention relates to an associated method making it possible to evaluate in drilling the uranium content and the hydrogen porosity of the region of interest.
- Uranium content and hydrogen porosity are two important properties in mineral exploration. They are needed to build geological and hydraulic models, and to assess the uranium potential of a region or, when a deposit has been discovered, to enable the reserves to be assessed.
- Hydrogen porosity is the fraction of the pore volume of a formation occupied by water. It is directly related to the amount of hydrogen atoms present in the formation.
- the active neutron interrogation method consists in emitting neutrons towards the region of interest for which one wishes to know the hydrogen porosity and the uranium content.
- the emitted neutrons interact both with the hydrogen nuclei and with the uranium nuclei present in the region of interest.
- Some of the neutrons emitted are backscattered by the hydrogen nuclei towards the probe retaining a high energy, typically greater than 0.5 eV, the cut-off energy of the cadmium surrounding the detector in some probes.
- Other neutrons emitted thermalize in the formation, i.e. they slow down following successive collisions with hydrogen nuclei present in the region of interest.
- Some of these thermal neutrons cause the fission of uranium 235 nuclei and the emission of 2 to 3 prompt neutrons per fission with an average energy of the order of 2 MeV
- a probe comprising a source of neutrons and at least two detectors sensitive to thermalized neutrons in the formation (or thermal neutrons) which have been backscattered and whose the energy is around 0.025 eV.
- the hydrogen porosity is determined from the ratio of the counting rates measured by the two detectors. This ratio first increases linearly with the porosity then converges at high porosity towards a limit value, which makes it difficult to accurately determine the porosity typically when it exceeds 40%.
- uranium content of the formation it is known to perform a count of prompt neutrons from fission of uranium 235 nuclei induced by thermalized neutrons from a pulsed generator of initially fast neutrons.
- a ratio is measured between a counting rate of the thermal neutrons coming from the generator and a counting rate of the so-called epithermal fission prompt neutrons, that is to say which have an energy greater than 0. .5 eV.
- An object of the invention is to propose a compact drilling device which makes it possible to jointly evaluate the uranium content and the hydrogen porosity of a region of interest of the geological formation in a reliable and precise manner.
- the invention relates to a device for evaluating in drilling a uranium content and a hydrogen porosity of a region of interest of a geological formation, the device comprising:
- the probe comprising a pulsed neutron generator configured to emit at least one pulse of neutrons, at least part of said neutrons being emitted towards the region of interest, a single neutron detector disposed away from the pulsed neutron generator, said neutron detector being adapted to detect a plurality of neutrons resulting from interactions between the neutrons emitted by the neutron generator and the region of interest, the probe further comprising a shielding device surrounding the neutron detector, the shielding device being adapted to absorb a plurality of neutrons having an energy lower than a cut-off energy, and resulting from interactions between the neutrons emitted by the generator of neutrons and the region of interest,
- - a neutron counting unit connected to the neutron detector, the neutron counting unit being at least configured to measure over time, during a first time interval, a number of neutrons backscattered by hydrogen nuclei of the region d interest and to measure over time, during a second time interval, a number of prompt fission neutrons resulting from interactions between the neutrons emitted by the neutron generator and uranium nuclei present in the region of interest, the second time interval being later than the first time interval, - a hydrogen porosity evaluation unit configured to evaluate the hydrogen porosity of the region of interest using a total number of neutrons measured during the first time interval,
- a uranium content evaluation unit configured to evaluate the uranium content of the region of interest using a total number of neutrons measured during the second interval.
- the invention from a probe equipped with a single detector and for example thanks to a single acquisition sequence, which comprises a plurality of cycles of neutron pulses and counting of the neutrons detected by the detector, and by applying the method described below, it is possible to determine two parameters, namely the uranium content and the porosity of a region of interest.
- the device comprises one or more of the following characteristics, taken separately or according to all the technically possible combinations:
- the probe comprises a moderation device arranged between the shielding device and the neutron detector, the moderation device being adapted to slow down the neutrons having passed through the shielding device;
- the pulsed neutron generator and the neutron detector extend in a direction substantially coincident with or parallel to a main direction of elongation of the probe;
- the uranium content evaluated by the uranium content evaluation unit is substantially proportional to the total number of neutrons measured during the second time interval;
- the uranium content evaluation unit is configured to determine the uranium content using the hydrogen porosity evaluated by the hydrogen porosity evaluation unit;
- the uranium content evaluation unit is configured to correct the uranium content evaluated by using a parameter representative of the variation over time of the number of neutrons measured during the second time interval;
- the hydrogen porosity evaluation unit is further configured to evaluate the hydrogen porosity using a distance between the probe and an internal wall of the borehole.
- the invention also relates to a method for evaluating, in drilling, a uranium content and a hydrogen porosity of a region of interest of a geological formation, using an evaluation device as described above. , the method comprising the following steps: - emitting at least one pulse of neutrons with the neutron generator, at least part of said neutrons being emitted towards the region of interest,
- the first measurement comprising a measurement during the first time interval of a number of backscattered neutrons resulting from interactions between neutrons of the pulse and hydrogen nuclei of the region of interest
- the second measurement comprising a measurement during the second time interval of a number of prompt fission neutrons resulting from interactions between neutrons of the pulse and uranium nuclei present in the region of 'interest
- the method comprises one or more of the following characteristics, taken in isolation or according to all technically possible combinations:
- the evaluation of the hydrogen porosity is carried out using a distance between the probe and a wall of the borehole.
- FIG. 1 is a schematic representation of a device according to the invention
- FIG. 2 is an example of a timing diagram showing the time evolution of the neutron count after a pulse of fast neutrons from the generator recorded with the device of Figure 1,
- Figure 3 represents modeled curves showing the relationship between the hydrogen porosity of the region of interest and the total number of neutrons measured during the first time interval by the device of Figure 1 for different uranium contents
- Figure 4 represents modeled curves showing the relationship between the uranium content of the region of interest and the total number of neutrons measured during the second time interval by the device of Figure 1 for different porosities, and
- figure 5 represents chronograms showing the temporal evolution of the neutron count recorded with the device of figure 1 for different uranium contents and hydrogen porosities.
- FIG. 1 schematically represents a device 10 for evaluating in drilling the uranium content and the hydrogen porosity of a region of interest 12 of a geological formation.
- the region of interest 12 is crossed by a borehole 14.
- the borehole 14 is represented in FIG. 1 vertically, that is to say with a dip equal to 90°.
- the borehole 14 is not vertical and has any dip and azimuth.
- Drilling 14 is carried out through a plurality of geological formations. For example, drilling 14 is carried out for exploration purposes to search for a possible uranium deposit. As a variant, drilling 14 is carried out for the purposes of developing an identified deposit. The information collected in borehole 14 is then used to estimate the deposit's uranium reserves. The borehole 14 is filled with fluid, for example water, at least opposite the region of interest 12.
- fluid for example water
- the device 10 comprises a probe 16 intended to be inserted into the borehole 14 opposite the region of interest 12, a surface installation 18 making it possible to move the probe 16 along the borehole 14 upwards and downwards according to the direction of extension of the borehole 14.
- the surface installation 18 comprises a winch 20 and a device 22 suitable for knowing the position of the probe 16 inside the borehole 14, for example an encoder wheel.
- the probe 16 is connected by a cable 24 to the surface installation 18.
- the cable 24 allows both the displacement of the probe 16 inside the borehole 14, the electrical supply of the probe 16 and the transfer to the surface of the measurements made by the probe 16.
- the device 10 further comprises a neutron counting unit 26 connected to the probe 16, a hydrogen porosity evaluation unit 28 and a uranium content evaluation unit 30.
- a neutron counting unit 26 connected to the probe 16
- a hydrogen porosity evaluation unit 28 and a uranium content evaluation unit 30.
- These units 26, 28, 30 are by example integrated in the probe 16 or remote on the surface as illustrated schematically in FIG.
- the device 10 further comprises an eccenter 32 adapted to press the probe 16 against a wall 34 of the borehole 14.
- the probe 16 includes a pulsed neutron generator 36, a single neutron detector sensitive primarily to thermal neutrons 38, and a shielding device 40 made of a thermal neutron absorbing material surrounding the neutron detector 38.
- probe 16 includes a moderating device 42 disposed between shielding device 40 and neutron detector 38.
- the probe 16 extends along a main direction of elongation L.
- the main direction of elongation L is substantially coincident with the main direction of elongation of the borehole 14.
- the pulsed neutron generator 36 is configured to emit at least one pulse of neutrons. At least some of the neutrons are emitted towards the region of interest 12, the pulsed neutron generator 36 emitting the neutrons isotropically. Preferably, neutron generator 36 is configured to emit a plurality of neutron pulses forming a periodic signal.
- the frequency of the emission signal is for example between 100 Hz and 10 kHz, for example equal to 200 Hz.
- the pulsed neutron generator 36 preferably has an average emission of neutrons greater than 10 7 neutrons per second, for example 10 8 neutrons per second.
- the duration of each pulse is for example between 5 ps and 500 ps.
- the duty cycle also called work rate, which corresponds to the ratio between the duration of the pulse and the period of the signal emitted by the neutron generator 36, is for example less than 10%, preferably less than 1%.
- the pulsed neutron generator 36 is for example of the Deuterium-Tritium or Deuterium-Deuterium type adapted to emit a flux of neutrons having an energy greater than 2 MeV, for example 14 MeV for a generator of the Deuterium-Tritium or 2.5 MeV type. for a Deuterium-Deuterium generator.
- the neutron detector 38 is adapted to detect a plurality of neutrons resulting from interactions between the neutrons emitted by the neutron generator 36 and the region of interest 12.
- the neutron detector 38 is arranged away from the pulsed neutron generator 36.
- the neutron detector 38 and the neutron generator 36 preferably extend substantially in the same direction coincident with or parallel to the main direction of elongation L of probe 16.
- neutron detector 38 is disposed relative to neutron generator 36 so that when probe 16 is inserted into borehole 14, neutron detector 38 is above the generator. of neutrons 36 in an elevation direction.
- neutron detector 38 is disposed below neutron generator 36 in the elevation direction.
- the neutron detector 38 is for example a helium-3 gas proportional counter.
- the neutron detector 38 is a boron deposit proportional counter.
- the shielding device 40 is adapted to absorb a plurality of low-energy neutrons having an energy lower than a cut-off energy, and resulting from interactions between the emitted neutrons and the region of interest 12.
- the shielding device 40 completely surrounds the neutron detector 38, i.e. it defines a closed internal volume receiving the neutron detector 38.
- the shielding device 40 is for example made of cadmium or boron.
- the shielding device 40 has for example a thickness of between 1 mm and 1 cm depending on the material used.
- the cut-off energy depends on the nature of the material of the shielding device 40.
- the cut-off energy is between 0.1 eV and 10 eV, for example 0.5 eV for cadmium.
- low energy neutrons with energy below the cut-off energy are absorbed by shielding device 40 and not detected by neutron detector 38.
- High energy neutrons with energy above cut-off energy contribute to the signal measured by the neutron detector 38.
- the neutrons absorbed by the shielding device 40 will be qualified as “thermal neutrons” or “low energy neutrons” and the neutrons which cross the shielding device 40 to the neutron detector 38 of "epithermal neutrons" or "high energy neutrons”.
- a moderation device 42 is arranged inside the shielding device receiving the neutron detector 38 to slow down the fission neutrons having passed through the shielding device 40, that is to say the epithermal neutrons. This makes it easier to count the neutrons by the neutron detector 38.
- Moderation device 42 completely surrounds neutron detector 38.
- moderation device 42 is formed by a layer of polyethylene interposed between shielding device 40 and neutron detector 38.
- moderation device 42 is formed by a compound of the polyolefin type.
- the neutron counting unit 26 is configured to count over time a number of high energy neutrons passing through the shielding device 40 detected by the neutron detector 38, in particular after the neutron generator 36 has emitted a pulse of neutrons.
- FIG. 2 represents several modeled chronograms showing the temporal evolution of the number of neutrons measured by the neutron counting unit 26 for different average uranium contents of the region of interest 12.
- the first curve 200 is a chronogram for an average content in uranium equal to 250 ppmu.
- the second curve 210 is a chronogram for an average uranium content equal to 2000 ppmu.
- the third curve 220 is a chronogram for an average content equal to 10,000 ppmu.
- the fourth curve 230 represents the active background noise (0 ppmu) generated by the neutron generator 36.
- Each timing diagram corresponds to the sum of the neutrons measured over a plurality of pulse emission cycles by the neutron generator 36, for example more than 30,000 cycles.
- the origin of the times of each of the chronograms corresponds to the start of each neutron pulse. In the example shown, the duration of the pulse is 50 ps.
- the fastest neutrons i.e. those measured during and just after the pulse, correspond in particular to the neutrons backscattered by the hydrogen nuclei present in the region of interest. They form the first part of the measured signal.
- the measured signal corresponding to the backscattered neutrons is independent of the uranium content of the region of interest.
- the signal is also independent of the temperature of the fluid present in the borehole (usually water) and the salinity of this fluid.
- the neutron counting unit 26 is at least configured to perform a count over time, during a first time interval 240 (FIG. 2), of a plurality of neutrons backscattered by hydrogen nuclei from the region of interest which have been detected by the detector 38. During the first time interval, the plurality of neutrons backscattered by the hydrogen nuclei of the region of interest 12 form the main contribution of the measured signal.
- the first time interval 240 is synchronized with the pulse of the neutron generator 36, that is to say that the measurement of the number of backscattered neutrons starts from the start of the pulse.
- the duration of the first time interval 240 is preferably between the start of the pulse and a few tens of ps after the end of the pulse, i.e. for example between 50 and 200 ps as represented in FIG. 2.
- the second part of the chronogram shows the prompt fission neutrons resulting from the interactions between the neutrons emitted by the neutron generator 36 and the uranium nuclei present in the region of interest 12. Indeed, after the pulse and for a few hundred of microseconds, the active background noise 230 due to the neutrons of the neutron generator 36 being slowed down but not yet fully thermalized remains predominant. However, this signal contribution decreases very rapidly.
- the number of fission prompt neutrons measured depends on the uranium content of the region of interest 12. The higher the uranium content in the region of interest 12, the higher the number of fission prompt neutrons.
- the neutron counting unit 26 is also suitable for counting over time, during a second time interval 250, a plurality of prompt fission neutrons resulting from interactions between the neutrons emitted by the neutron generator 36 and nuclei of uranium present in the region of interest 12 which were detected by the detector 38.
- the second time interval 250 is later than the first time interval 240. It begins a few hundred microseconds after the pulse, for example 900 ps after the pulse, as represented in FIG. 2.
- the start of the second time interval 250 is for example chosen so that the signal ratio (coming from prompt fission neutrons) to active background noise 230 is high, that is to say for example greater than 7.
- the duration of the second time interval 250 is chosen so to be as long as possible in order to increase the counting statistic.
- the duration of the second time interval 250 is preferably between 1 ms and 10 ms, for example 4 ms.
- the hydrogen porosity evaluation unit 28 is configured to evaluate the hydrogen porosity of the region of interest 12 using a total number of neutrons measured during the first time interval 240.
- Figure 3 presents curves relating the total number of neutrons measured during the first time interval 240 to the hydrogen porosity for three distinct uranium contents (10000 ppmu, 2000 ppmu and 250 ppmu). It is observed that the three curves are substantially merged. This confirms that the total number of neutrons measured during the first time interval 240 is independent of the uranium content in the region of interest 12. Over the range of porosity represented, that is to say between 0 and 40%, the curves are perfectly one-to-one, ie a value of the total number of neutrons measured during the first time interval 240 corresponds to a single value of hydrogen porosity.
- the relationship between the total number of neutrons measured during the first time interval 240 and the porosity depends on the geometry of the device 10 which can be determined for example via numerical simulations with the MCNP code.
- the uranium content evaluation unit 30 is configured to evaluate the uranium content of the region of interest 12 using a total number of neutrons measured during the second time interval 250.
- FIG. 4 represents the relationship between the total number of neutrons measured during the second time interval 250 and the uranium content of the region of interest 12 for a hydrogen porosity of 0% (curve 400) and for a hydrogen porosity of 40% (curve 410). It can be seen that in each case, for a given hydrogen porosity, the total number of neutrons measured during the second time interval is linearly related to the uranium content of the region of interest 12. In other words, the uranium content evaluated by the uranium 30 content evaluation unit is substantially proportional to the total number of neutrons measured during the second time interval 250.
- the relationship between the total number of neutrons measured during the second time interval 250 and the uranium content of the region of interest 12 can be modeled, still using for example the MCNP modeling code. Then, from the total number of neutrons measured during the second time interval 250, the uranium content of the region of interest 12 can be determined.
- the uranium content evaluation unit 30 is configured to determine the uranium content using the hydrogen porosity evaluated by the hydrogen porosity evaluation unit 28.
- the probe 16 is lowered into the borehole 14 so as to place it opposite the region of interest 12.
- At least one neutron pulse is then emitted, part of which is directed towards the region of interest 12 using the neutron generator 36.
- a plurality of neutron pulses are emitted in the form of a periodic signal.
- a number of neutrons crossing the shielding device 40 is then measured as a function of time, after each pulse, using the neutron counting unit 26.
- a first measurement is carried out, during the first time interval 240, by measuring a number of neutrons backscattered by hydrogen nuclei of the region of interest, and a second measurement is then carried out by measuring, during the second time interval 250, a number of prompt fission neutrons resulting from interactions between the neutrons emitted by the neutron generator and uranium nuclei present in the region of interest.
- a first measurement is successively carried out which consists in measuring, during the first time interval 240, the number of backscattered neutrons, and a second measurement which consists in measuring, during the second time interval 250, the number of prompt fission neutrons.
- the hydrogen porosity of the region of interest 12 is then evaluated using the series of first measurements. Indeed, as indicated above, the relationship between the total number of neutrons measured during the first time interval 240 and the hydrogen porosity of the region of interest 12 is one-to-one. This relationship is independent of the uranium content of region of interest 12.
- the uranium content of the region of interest is then assessed using the series of second measurements.
- the relationship between the total number of neutrons measured during the second time interval 250 and the uranium content of the region of interest 12 is one-to-one and linear.
- the evaluation of the uranium content is carried out using the hydrogen porosity evaluated with the first count.
- the hydrogen porosity evaluation unit 28 is configured to correct the uranium content which has been evaluated by using a parameter representative of the variation over time of the number of neutrons during the second interval temporal 250.
- the neutron absorbers include in a non-exhaustive manner the elements present in the region of interest 12, such as, for example, hydrogen, boron, chlorine, and uranium at high concentration (>10000 ppm).
- FIG. 5 represents the temporal variation of the number of neutrons measured by the neutron counting unit 26 for regions of interest 12 having different uranium contents and different porosities.
- the curves 510, 520 and 530 represent the number of neutrons measured for zero porosity and respectively a uranium content equal to 10000 ppmu, 2000 ppmu and 250 ppmu.
- Curves 540, 550 and 560 represent the number of neutrons measured for a porosity equal to 40% and respectively a uranium content equal to 10000 ppmu, 2000 ppmu and 250 ppmu.
- the only neutron absorber in the region of interest 12 is the hydrogen present in the water. It is observed that in FIG. 5, in which the number of neutrons measured is represented on a logarithmic scale, the slope of the curves 510 to 560 over the second time interval 250 is identical for the same value of hydrogen porosity, regardless of the content of uranium from region of interest 12.
- the time variation of the number of neutrons is an exponential decrease.
- the number of neutrons on the second time interval 250 is related to time by the equation:
- a o is a constant.
- t is time.
- T(O) is the time constant.
- o is the total neutron absorption cross section.
- the representative parameter used to correct the uranium content is for example a parameter representative of the time constant T(O). Indeed, the time constant depends on the total neutron absorption cross section of the region of interest 12 which, at low uranium concentration ( ⁇ 10000 ppm), does not depend on the uranium content.
- a correction coefficient is determined by numerical simulation allowing the value of the uranium content evaluated to be corrected to take account of the total neutron absorption cross section.
- the probe 16 is pressed against the internal wall 34 of the borehole 14, for example by means of the eccenter 32.
- the hydrogen porosity is evaluated by also using a measurement of the distance between the probe 16 and the internal wall 34 of the borehole. 14.
- the distance between the probe 16 and the inner wall 34 of the borehole 14 linearly affects the hydrogen porosity value evaluated.
- the device according to the invention is particularly advantageous because it makes it possible to evaluate the uranium content and the hydrogen porosity in drilling with a single tool from measurements over one or two time intervals.
- the measurements obtained are reliable and precise because the acquisition geometry is identical for the two measurements.
- the device is compact and allows for example to add other detectors close to the neutron generator to perform additional characterization measurements.
- the use of a single tool to perform both a porosity measurement and a measurement of the uranium content reduces acquisition times.
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Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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AU2022362643A AU2022362643A1 (en) | 2021-10-11 | 2022-10-10 | Device for evaluating a uranium content and a hydrogen porosity of a particular region in a geological formation when drilling and associated method |
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Application Number | Priority Date | Filing Date | Title |
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FR2110722A FR3128017B1 (fr) | 2021-10-11 | 2021-10-11 | Dispositif d’évaluation en forage d’une teneur en uranium et d’une porosité hydrogène d’une région d’intérêt d’une formation géologique et procédé associé |
FRFR2110722 | 2021-10-11 |
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WO2023061940A1 true WO2023061940A1 (fr) | 2023-04-20 |
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PCT/EP2022/078100 WO2023061940A1 (fr) | 2021-10-11 | 2022-10-10 | Dispositif d'évaluation en forage d'une teneur en uranium et d'une porosité hydrogène d'une région d'intérêt d'une formation géologique et procédé associé |
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AU (1) | AU2022362643A1 (fr) |
FR (1) | FR3128017B1 (fr) |
WO (1) | WO2023061940A1 (fr) |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3264477A (en) * | 1962-03-30 | 1966-08-02 | Texaco Inc | Epithermal neutron well logging |
US4209694A (en) * | 1977-01-17 | 1980-06-24 | Mobil Oil Corporation | Assaying for uranium-bearing ore |
US4625110A (en) * | 1983-10-24 | 1986-11-25 | Halliburton Company | Epithermal neutron porosity measurement |
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2021
- 2021-10-11 FR FR2110722A patent/FR3128017B1/fr active Active
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2022
- 2022-10-10 AU AU2022362643A patent/AU2022362643A1/en active Pending
- 2022-10-10 WO PCT/EP2022/078100 patent/WO2023061940A1/fr active Application Filing
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3264477A (en) * | 1962-03-30 | 1966-08-02 | Texaco Inc | Epithermal neutron well logging |
US4209694A (en) * | 1977-01-17 | 1980-06-24 | Mobil Oil Corporation | Assaying for uranium-bearing ore |
US4625110A (en) * | 1983-10-24 | 1986-11-25 | Halliburton Company | Epithermal neutron porosity measurement |
Non-Patent Citations (1)
Title |
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HUMPHREYS D R ET AL: "Uranium Logging with Prompt Fission Neutrons", INTERNATIONAL JOURNAL OF APPLIED RADIATION AND ISOTOPES,, vol. 34, no. 1, 1 January 1983 (1983-01-01), pages 261 - 268, XP001351717 * |
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FR3128017A1 (fr) | 2023-04-14 |
AU2022362643A1 (en) | 2024-04-18 |
FR3128017B1 (fr) | 2023-11-10 |
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