Preparation method of non-radioactive tracer ceramicite with stable signal-to-noise ratio

Abstract

This invention discloses a method for preparing non-radioactive tracer ceramsite with a stable signal-to-noise ratio, and designs a gamma capture value ζ per unit volume of tracer ceramsite green body. o The acquisition method establishes a ζ o This method, based on real-time online control of tracer element content in tracer ceramsite, eliminates the phenomenon of excessively low or high tracer element content caused by uneven mixing or other factors during tracer ceramsite production, precisely controlling the tracer element content within a set threshold. Based on downhole measured data... 测 Feedback is provided to adjust the set threshold ζ of the tracer ceramsite in real time. 阈 The wellbore and downhole linkage can achieve a stable signal-to-noise ratio when monitoring fracturing information using tracer ceramsite neutron-activated transient gamma ray method in complex fracturing environments. It can avoid the fluctuations in the captured gamma signal during fracturing fracture logging due to different logging tool parameters, wellbore environment and oil and gas reservoir, thereby improving the logging success rate.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas extraction additives, and in particular relates to a method for preparing non-radioactive tracer ceramsite with a stable signal-to-noise ratio for precise characterization of fracturing fractures. Background Technology

[0002] China possesses abundant reserves of unconventional oil and gas resources, including shale oil and gas. In recent years, China's unconventional oil and gas production has continued to grow, making it the country with the fastest pace of shale oil and gas exploration and development after the United States, with significant results in increasing reserves and production. Reports indicate that in 2022, China's shale oil production exceeded 3 million tons, quadrupling compared to 2018; shale gas production reached 24 billion cubic meters, a 122% increase compared to 2018. Therefore, increasing the exploration and development of unconventional oil and gas, such as shale oil and gas, is of great significance for ensuring my country's energy security and optimizing its energy structure. Hydraulic fracturing technology can significantly improve the overall permeability of oil and gas reservoirs and is the most effective way to develop unconventional oil and gas reservoirs such as shale oil and gas and tight gas. Accurately evaluating the location of proppant and the height, width, azimuth, and dip angle of near-wellbore fracturing fractures is of great value for fracturing model design, unconventional oil and gas assessment, and optimized production enhancement, providing crucial support for the efficient replacement of resources in my country.

[0003] Near-wellbore fracture diagnosis technology is of great significance for evaluating the effectiveness of hydraulic fracturing. Currently, there are several near-wellbore fracture monitoring technologies, including caliper logging, array sonic logging, and nuclear logging. While array sonic logging is sensitive for fracture monitoring, its accuracy and precision are somewhat lacking. Temperature logging cannot directly display fracture height. Array sonic logging also has limitations in directly displaying proppant information. Compared to these technologies, nuclear logging offers advantages such as a wide range of monitoring capabilities, high accuracy, and high sensitivity. Near-wellbore fracturing nuclear logging includes two techniques: radioactive tracer logging and non-radioactive tracer logging. Radioactive measurement technology involves adding radioactive tracer isotopes such as antimony, scandium, and iridium to the proppant or fracturing fluid, followed by pre- and post-fracturing logging using natural gamma ray or natural gamma ray spectroscopy. The difference in gamma counts before and after fracturing is then compared to obtain downhole information about the fractures. Radioactive tracer logging uses substances with a certain level of radioactivity, posing radiation risks to the environment and people. It does not meet HSE requirements and is subject to restrictions on safety, environmental protection, transportation, storage, and use, thus limiting its widespread adoption.

[0004] Compared to radioactive tracer logging, non-radioactive tracer ceramic particle neutron capture gamma tracer logging incorporates high-capture-section materials, such as gadolinium, boron, and samarium, into the proppant. Utilizing the interaction between neutrons and the proppant, logging is performed before and after fracturing using a compensated neutron (CNL) instrument or a pulsed neutron capture instrument (PNC). By comparing changes in the thermal neutron count rate or capture cross-section of the near- and far-field detectors before and after fracturing, or by calculating the captured gamma count generated by elements with high thermal capture cross-sections, downhole information such as the location and height of the fracturing fractures can be determined. This method offers advantages such as broad monitoring scope, accurate fracture parameter identification, and high sensitivity. It allows for repeated measurements over extended periods, meeting HSE requirements and aligning with the trend of nuclear logging development, making it a new and important means of evaluating fracturing effectiveness.

[0005] Precise control of the concentration of tracer elements in the neutron capture cross section is crucial and a prerequisite for the success of neutron capture gamma tracer logging technology using non-radioactive tracer ceramic particles. Both excessively high and low tracer element content will hinder the application of this technology in logging. Excessive tracer element content leads to a significant increase in the cost of the tracer ceramic particles, resulting in substantial resource waste. Insufficient tracer element content results in a low signal-to-noise ratio for captured gamma, leading to logging failure. In current tracer ceramic particle preparation processes, if tracer elements are not thoroughly mixed with the base material, or in the early stages of large-scale tracer ceramic particle production, the tracer element content will deviate significantly from its set value. Furthermore, different logging tool parameters, wellbore environment, and oil and gas reservoirs during the logging process can cause the logging tool detector to receive different neutron capture signals, even if the tracer element content within the tracer ceramic particles is the same, potentially resulting in vastly different signal-to-noise ratios.

[0006] Therefore, the precise real-time control of the tracer element content within the tracer ceramic particles and the acquisition of a neutron capture signal with a stable signal-to-noise ratio during logging are prominent challenges currently facing the development of downhole fracturing tracer logging technology. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing non-radioactive tracer ceramic particles with a stable signal-to-noise ratio, addressing the shortcomings of existing technologies.

[0008] The present invention adopts the following technical solution:

[0009] A method for preparing non-radioactive tracer ceramsite with a stable signal-to-noise ratio includes the following steps:

[0010] Step 1: The raw ore weighed by weight is coarsely crushed and then added to the ball mill to be ground into mixed powder. After being ground to the target fineness, the powder is transferred to silo 1. The powder in silo 1 is weighed on belt scale 3 through first discharge valve 2. The weighed mixed powder is then transferred to pellet mill 5 through second discharge valve 4.

[0011] Step 2: ζ阈 The threshold range for capturing gamma values ​​per unit volume is set; the control system 12 calculates the amount of water and tracer liquid required for the preparation of tracer ceramsite based on the threshold. The water in the water tank 17 and the tracer liquid in the tracer liquid tank 16 enter the mixing and homogenizing device 14 through the third flow valve 18 and the second flow valve 15, respectively, to form a uniformly mixed tracer solution.

[0012] Step 3: The tracer liquid in the mixing homogenizer 14 is atomized and sprayed into the granulator 5 through the first flow valve 13 to prepare the tracer ceramsite preform 30. Then, it is transferred to the first conveyor belt 7 through the third discharge valve 6, dried and sieved, and finally the tracer ceramsite preform that meets the particle size requirements is selected.

[0013] Step 4: The tracer ceramsite blank is transferred to the detection unit 9, which includes a moderator thickness measuring device, a neutron activation effective radius R measuring device for the tracer ceramsite blank, and a unit volume captured gamma value acquisition device. Fast neutrons emitted by the neutron source 19 of the first logging tool are converted into thermal neutrons or hyperthermal neutrons by the moderator 23; the thermal neutron detector 24 is used to monitor the change in the thermal neutron count rate and can determine the optimal value of the moderator thickness accordingly.

[0014] Step 5: The tracer ceramsite blank 30 is added to the tracer ceramsite blank neutron activation effective radius R determination device via the third conveyor belt 31; when the fourth discharge valve 28 discharges, the thickness of the tracer ceramsite blank covering the moderator 23 in the tracer ceramsite blank neutron activation effective radius R determination device will gradually become thinner.

[0015] Step 6: The level gauge 32, located at the top of the device, measures the distance h between it and the upper surface of the tracer ceramic pellet green body coated with the moderating body. i Fast neutrons emitted from neutron source 19 are slowed down to form thermal or ultrathermal neutrons, which are captured by the high-capture-section elements contained in the tracer ceramic particles, producing transient gamma rays; near-well gamma detector 20 and far-well gamma detector 21 are used to detect the magnitude of this signal value, and the change in its magnitude is used to calculate the effective radius R of neutron activation.

[0016] Step 7: The tracer ceramic blank 30 enters the device for obtaining the unit volume captured gamma value via the fifth conveyor belt 36; the rotating device 33 controls the rotation of the logging instrument, and the neutron source 19 horizontally emits neutrons to irradiate the tracer ceramic blank around the simulated wellbore, with an effective radius of action of R; the lifting device 38 controls the lifting of the logging instrument to obtain the neutron activation reaction height h, and then calculates the effective neutron activation volume V to obtain the unit volume captured gamma value ζ. o ;

[0017] Step 8: If the gamma value captured per unit volume is ζ o Exceeded the set threshold ζ 阈If the content of tracer elements in the tracer ceramsite product is not up to standard, the control system 12 will automatically calculate the deviation value of the tracer solution concentration in the mixing and homogenizing unit 14 and issue an instruction to adjust the ratio of water and tracer liquid entering the mixing and homogenizing unit 14 by controlling the third flow valve 18 and the second flow valve 15, thereby achieving the purpose of real-time control of the tracer solution concentration in the mixing and homogenizing unit 14, and thus realizing real-time online precise control of the tracer element content in the tracer ceramsite green body;

[0018] Step 9: If the gamma value captured per unit volume is ζ o Falling at the set threshold ζ 阈 If the tracer element content of the tracer ceramsite product meets the standard, the tracer ceramsite blank is then conveyed into a tunnel kiln for high-temperature calcination, ultimately producing tracer ceramsite for monitoring hydraulic fracturing fractures. The gamma capture value per unit volume is ζ. 陶 ;

[0019] Step 10: ζ 陶 The value is used to guide the design and construction of downhole fracturing schemes, and has ζ. 陶 The tracer ceramic particles were used in actual well logging of fracturing fractures; the logging tool used a gamma detector to obtain the downhole neutron-activated transient gamma ray value, thus obtaining the downhole measured value ζ. 测 Its value varies depending on different logging tool parameters, wellbore environment, and oil and gas reservoirs;

[0020] Step 11: Establish ζ under different well conditions 测 The database is used to adjust and optimize the set threshold ζ during the preparation of tracer ceramsite in real time. 阈 Through continuous iteration and optimization, the precise control of the tracer element content in the high neutron capture section of the tracer ceramsite is finally achieved, and the gamma detector can consistently obtain a stable signal-to-noise ratio under complex downhole fracturing conditions, thereby achieving the goal of fine characterization of downhole fracturing fractures during hydraulic fracturing.

[0021] In the preparation method described above, the tracer solution in step (2) is one or any combination of ionic solutions containing high neutron capture cross-section elements such as gadolinium, boron, and samarium, for example, gadolinium nitrate and boric acid.

[0022] In the preparation method described above, the optimal value of the moderator thickness in step (4) is: as the moderator thickness increases, the thermal neutron count will also increase continuously; when fast neutrons are almost completely converted into thermal neutrons, the reading of the thermal neutron detector 24 tends to be stable and unchanged, and at this time the corresponding moderator thickness is the optimal value of the designed moderator thickness in the detection unit.

[0023] The preparation method described above, in step (6), the principle for determining the effective radius R of neutron activation is as follows: When the fourth unloading valve 28 begins to unload, the thickness of the upper tracer ceramic blank is relatively large. Because the upper tracer ceramic blank is far away, it cannot be activated by neutrons. At this time, the effective radius R of neutron activation is smaller than the thickness of the upper blank, and the neutron activation region remains stable within a limited effective radius R. At this time, the gamma values ​​obtained by the near-well gamma detector 20 and the far-well gamma detector 21 are the highest and most stable. As the fourth unloading valve 28 further unloads, all the tracer ceramic blanks in the device are activated by neutrons, and the total number of activated blanks continuously decreases. At this time, the effective radius R of neutron activation is greater than the thickness of the upper blank, and the gamma values ​​obtained by the near-well gamma detector 20 and the far-well gamma detector 21 gradually decrease. When the gamma value begins to decrease from its stable highest value, the thickness of the moderator corresponds to the effective radius R of neutron activation of the tracer ceramic blank.

[0024] The preparation method described above, in step (6), calculates the effective radius of neutron activation as follows: R = h0 - h i h0 is the distance between the level gauge 32 and the slowing agent 23, which is a fixed value.

[0025] The preparation method described above, step (7) involves capturing a gamma value ζ per unit volume. o For: ζ o =η / V, V = πR 2 H and η represent the total captured gamma value.

[0026] The preparation method described above, step (9) involves capturing a gamma value ζ per unit volume. 陶 For: ζ 陶 =kζ o Where k is the correction coefficient, k = V 烧结 / V 素坯 The reason why k is less than 1 is that the volume of tracer ceramic particles after high-temperature sintering will shrink to a certain extent compared with the tracer ceramic particle blank. For example, in the preparation process of 20 / 40 mesh tracer ceramic particles, the screen selected before firing is 0.95 mm and 0.71 mm, and the screen of the finished product after firing is within the range of 0.85 mm and 0.50 mm.

[0027] The preparation method described above, step (10) describes the measured value ζ. 测 The neutron activation transient gamma signal value or signal-to-noise ratio detected during well logging can vary significantly due to different logging tool parameters, wellbore environment, and oil and gas reservoir. Therefore, the measured value ζ 测 It should also be constantly changed according to different logging environments and objects.

[0028] This invention proposes a method for preparing tracer ceramsite with a stable signal-to-noise ratio for precise characterization of hydraulic fracturing fractures, and designs a gamma capture value ζ per unit volume of tracer ceramsite green body.o The acquisition method establishes a ζ o This method, based on a value-based real-time online control of the tracer element content in tracer ceramsite, eliminates the phenomenon of excessively low or high tracer element content caused by uneven mixing or other factors during the production process, precisely controlling the tracer element content within a set threshold. After high-temperature calcination, the total gamma captured per unit volume of the tracer ceramsite is ζ. 陶 This is used to guide the design and construction of downhole fracturing schemes. Based on downhole measured data... 测 Feedback is provided to adjust the set threshold ζ of the tracer ceramsite in real time. 阈 This method, which integrates both surface and downhole monitoring, enables stable signal-to-noise ratios when using tracer-based ceramsite neutron-activated transient gamma-ray logging to monitor fracturing fracture information in complex fracturing environments. It avoids the fluctuating gamma-ray signals captured during fracturing fracture logging due to varying logging tool parameters, wellbore environment, and oil and gas reservoir conditions, thereby improving logging success rates, reducing logging costs, and making measurements more accurate and efficient. This gives the logging technology a broader market application prospect and greater viability. The entire preparation process is program-controlled, highly automated, and continuously monitored, eliminating human error and saving manpower. Attached Figure Description

[0029] Figure 1 A simplified flowchart of a method and system for preparing tracer ceramsite with a stable signal-to-noise ratio for precise characterization of hydraulic fracturing fractures;

[0030] Figure 2 A method for preparing tracer ceramsite with real-time online precise control of tracer element content in high-molecular-weight neutron capture cross-section;

[0031] Figure 3 Method for measuring the thickness of moderating bodies;

[0032] Figure 4 A method for determining the effective neutron activation radius R;

[0033] Figure 5 A method for determining the total gamma captured per unit volume;

[0034] In the diagram: 1. Silo; 2. First discharge valve; 3. Belt scale; 4. Second discharge valve; 5. Granulator; 6. Third discharge valve; 7. First conveyor belt; 8. Drying and sieving; 9. Detection unit; 10. Sintering; 11. Tracer ceramsite; 12. Control system; 13. First flow valve; 14. Mixing and homogenizing device; 15. Second flow valve; 16. Tracer liquid tank; 17. Water tank; 18. Third flow valve; 19. Neutron source; 20. Near-well gamma detector ; 21. Remote well gamma detector; 22. Shielding body; 23. Moderator; 24. He3 thermal neutron detector; 25. Shielding box; 26. Slide rail; 27. Second conveyor belt; 28. Fourth unloading valve; 29. ​​Vibration device; 30. Tracer ceramic blank; 31. Third conveyor belt; 32. Level gauge; 33. Rotation device; 34. Fifth unloading valve; 35. Fourth conveyor belt; 36. Fifth conveyor belt; 37. Cable; 38. Lifting device. Detailed Implementation

[0035] The present invention will be described in detail below with reference to specific embodiments.

[0036] refer to Figure 1-2 A system for preparing non-radioactive tracer ceramsite with a stable signal-to-noise ratio includes: a tracer ceramsite green body preparation device and a detection unit 9, a control system 12, a database, and an adjustment and optimization module;

[0037] The tracer ceramsite green body preparation device includes a ball mill, a silo 1, a first discharge valve 2, a belt scale, a second discharge valve 4, a granulator 5, a third discharge valve 6, a first conveyor belt 7, a control system 12, a first flow valve 13, a mixing homogenizer 14, a second flow valve 15, a tracer liquid tank 16, a water tank 17, and a third flow valve 18. The raw ore, weighed by weight, is coarsely crushed and then added to the ball mill to be ground into a mixed powder. After grinding to the target fineness, the powder is transferred to the silo 1. The powder in the silo 1 is weighed on the belt scale 3 via the first discharge valve 2, and the weighed mixed powder is then transferred to the granulator 5 via the second discharge valve 4. 阈 A threshold range for capturing gamma values ​​per unit volume is set. The control system 12 calculates the required amounts of water and tracer solution for preparing the tracer ceramsite based on this threshold. The water in the water tank 17 and the tracer solution in the tracer solution tank 16 enter the mixing and homogenizing unit 14 via the third flow valve 18 and the second flow valve 15, respectively, to form a uniformly mixed tracer solution. The tracer solution in the mixing and homogenizing unit 14 is atomized and sprayed into the granulator 5 through the first flow valve 13 to prepare tracer ceramsite preforms 30. These preforms are then transferred to the first conveyor belt 7 via the third discharge valve 6, dried, and sieved through the sieve 8, ultimately selecting tracer ceramsite preforms that meet the particle size requirements.

[0038] The detection unit 9 is located inside the shielded box 25. The detection unit 9 includes a moderator thickness measuring device, a tracer ceramic blank neutron activation effective radius R measuring device, and a unit volume captured gamma value acquisition device. Each of these three devices has a logging instrument, which are respectively defined as the first logging instrument, the second logging instrument, and the third logging instrument.

[0039] like Figure 3 As shown, the moderator thickness measuring device includes a first logging instrument and a moderator 23. The first logging instrument includes a neutron source 19, a near-wellbore gamma detector 20, a far-wellbore gamma detector 21, a shield 22, and a He3 thermal neutron detector 24. Fast neutrons emitted by the neutron source 19 are converted into thermal neutrons or ultrathermal neutrons by the moderator 23. The thermal neutron detector 24 is used to monitor changes in the thermal neutron count rate and can determine the optimal value of the moderator thickness accordingly. This thickness value is used for the moderator in both the neutron activation effective radius R measuring device and the unit volume captured gamma value acquisition device.

[0040] like Figure 4 As shown, the device for determining the effective radius of neutron activation (R) of tracer ceramsite blanks includes a second logging instrument, a slide rail 26, a second conveyor belt 27, a fourth unloading valve 28, a vibration device 29, a third conveyor belt 31, a level gauge 32, and a moderator 23. The second logging instrument includes a neutron source 19, a near-wellbore gamma detector 20, a far-wellbore gamma detector 21, and a shield 22. The tracer ceramsite blank 30 is added to the hopper of the device for determining the effective radius of neutron activation (R) of tracer ceramsite blanks via the third conveyor belt 31. A level gauge 32 is installed at the top of the hopper, and the moderator 23 is located at the bottom of the hopper, above the second logging instrument. When the fourth unloading valve 28 at the bottom unloads the blank onto the second conveyor belt 27, the thickness of the tracer ceramsite blank covering it gradually decreases.

[0041] The second logging instrument is mounted on the slide rail 26, which is used to adjust the horizontal position of the second logging instrument. The level gauge 32 is used to measure the distance h between itself and the upper surface of the tracer ceramic blank coated on the moderating body 23. i .

[0042] The fast neutrons emitted by the neutron source 19 of the second logging tool are slowed down to form thermal or ultrathermal neutrons, which are captured by the high-capture-section elements contained in the tracer ceramic particles, producing transient gamma rays. The near-wellbore gamma detector 20 and the far-wellbore gamma detector 21 are used to detect the magnitude of this signal, and the change in its magnitude can be used to calculate the effective neutron activation radius R.

[0043] Vibration device 29 is located on both sides of the silo; the vibration device includes an ultrasonic generator, a transducer, and a waveguide rod. By controlling the vibration time, magnitude, frequency, and power, the upper surface of the tracer ceramsite blank inside the device can be kept in a horizontal state, thereby achieving accurate measurement of the thickness of the tracer ceramsite blank inside the device.

[0044] like Figure 5 As shown, the device for obtaining the unit volume captured gamma value includes: a third logging instrument, a moderator 23, a rotating device 33, a fifth unloading valve 34, a fourth conveyor belt 35, a fifth conveyor belt 36, a cable 37, and a lifting device 38. The third logging instrument includes: a neutron source 19, a near-wellbore gamma detector 20, a far-wellbore gamma detector 21, and a shield 22. The tracer ceramic blank 30 enters the simulated wellbore of the device via the fifth conveyor belt 36. The third logging instrument is located in the middle of the simulated wellbore and is fixedly installed on the rotating device 33 and the lifting device 38. The rotating device 33 controls the rotation of the third logging instrument. The neutron source 19 of the third logging instrument horizontally emits neutrons to irradiate the tracer ceramic blank around the simulated wellbore with a horizontal neutron irradiation radius of R. The lifting device 38 controls the lifting and lowering of the third logging instrument to obtain the neutron activation reaction height h, and then calculates the effective neutron activation volume V to obtain the unit volume captured gamma value ζ. o Cable 37 is used for power supply and signal transmission.

[0045] If the gamma value captured per unit volume is ζ o Exceeded the set threshold ζ 阈 If the content of tracer elements in the tracer ceramsite product is not up to standard, the control system 12 will automatically calculate the deviation value of the concentration of tracer solution in the mixing homogenizer 14 and issue an instruction to adjust the ratio of water and tracer liquid entering the mixing homogenizer 14 by controlling the third flow valve 18 and the second flow valve 15 in the tracer ceramsite green body preparation device, thereby achieving the purpose of real-time control of the concentration of tracer solution in the mixing homogenizer 14, and thus realizing real-time online precise control of the tracer element content in the tracer ceramsite green body;

[0046] Example of automatic calculation method of control system 12: control system 12 will capture the gamma value ζ per unit volume. o The concentration of tracer elements in the actual sample can be obtained, based on the threshold ζ. 阈 The design concentration of the tracer element can be obtained. Combined with the volume V of the tracer ceramsite green body inside the pellet mill 5, the deviation of the tracer element from the required concentration can be obtained.

[0047] If the gamma value captured per unit volume is ζ o Falling at the set threshold ζ 阈 If the tracer element content of the tracer ceramsite product meets the standard, the tracer ceramsite blank is then conveyed into a tunnel kiln for high-temperature calcination, ultimately producing tracer ceramsite for monitoring hydraulic fracturing fractures. The gamma capture value per unit volume is ζ. 陶 .

[0048] ζ 陶 The value is used to guide the design and construction of downhole fracturing schemes, and has ζ.陶 The tracer ceramic particles were used in actual well logging for fracturing fractures. The logging tool used a gamma detector to obtain the downhole neutron-activated transient gamma ray value, thus obtaining the downhole measured value ζ. 测 Its value varies depending on different logging tool parameters, wellbore environment, and oil and gas reservoir.

[0049] ζ under different well conditions 测 Stored in the database, the adjustment and optimization module adjusts the ζ based on different well conditions in the database. 测 The set threshold ζ during the preparation of tracer ceramsite is adjusted and optimized in real time. 阈 Through continuous iteration and optimization, the precise control of the tracer element content in the high neutron capture section of the tracer ceramsite is finally achieved, and the gamma detector can consistently obtain a stable signal-to-noise ratio under complex downhole fracturing conditions, thereby achieving the goal of fine characterization of downhole fracturing fractures during hydraulic fracturing.

[0050] The method for preparing non-radioactive tracer ceramsite with a stable signal-to-noise ratio for precise characterization of hydraulic fracturing fractures according to the above system includes the following steps:

[0051] Step 1: The raw ore, weighed according to weight, is coarsely crushed and then added to a ball mill to be ground into a mixed powder. After grinding to the target fineness, the powder is transferred to silo 1. The powder in silo 1 is discharged through the first discharge valve 2 to a belt scale 3 for weighing. The weighed mixed powder is then transferred through the second discharge valve 4 to a pellet mill 5. Step 2: ζ 阈 A threshold range for capturing gamma values ​​per unit volume is set. The control system 12 calculates the required amounts of water and tracer solution for preparing the tracer ceramsite based on this threshold. The water in water tank 17 and the tracer solution in tracer solution tank 16 enter the mixing and homogenizing unit 14 via the third flow valve 18 and the second flow valve 15, respectively, to form a uniformly mixed tracer solution. Step 3: The tracer solution in the mixing and homogenizing unit 14 is atomized and sprayed into the granulator 5 through the first flow valve 13 to prepare tracer ceramsite preforms 30. These preforms are then transferred to the first conveyor belt 7 via the third discharge valve 6, dried, and sieved to finally select tracer ceramsite preforms that meet the particle size requirements.

[0052] Step 4: The tracer ceramsite blank is transferred to detection unit 9, which includes a moderator thickness measuring device, a neutron activation effective radius R measuring device for the tracer ceramsite blank, and a unit volume captured gamma value acquisition device. Fast neutrons emitted from the neutron source 19 of the first logging tool are converted into thermal neutrons or ultrathermal neutrons by the moderator 23. The thermal neutron detector 24 is used to monitor changes in the thermal neutron count rate and can determine the optimal value for the moderator thickness accordingly. Figure 3 .

[0053] Step 5: The tracer ceramsite green body 30 is added to the apparatus for determining the neutron activation effective radius R of the tracer ceramsite green body via the third conveyor belt 31. Figure 4 When the fourth discharge valve 28 discharges material, the thickness of the tracer ceramic blank covering the moderator 23 inside the apparatus for determining the effective radius R of neutron activation in tracer ceramic blanks will gradually become thinner.

[0054] Step 6: The level gauge 32, located at the top of the device, measures the distance h between it and the upper surface of the tracer ceramic pellet green body coated with the moderating body. i The slide rail 26 is used to adjust the horizontal position of the logging tool. Fast neutrons emitted from the neutron source 19 are slowed down to form thermal or hyperthermal neutrons, which are captured by the high-capture-section elements contained in the tracer ceramic particles, producing transient gamma rays. The near-wellbore gamma detector 20 and the far-wellbore gamma detector 21 are used to detect the magnitude of this signal, and its magnitude change can be used to calculate the effective neutron activation radius R.

[0055] Step 7: The tracer ceramic pellet blank 30 enters the unit volume gamma value acquisition device via the fifth conveyor belt 36. Figure 5 Rotating device 33 controls the rotation of the logging tool, while neutron source 19 horizontally emits neutrons to irradiate the tracer ceramic blanks surrounding the simulated wellbore, with an effective radius of action of R. Lifting device 38 controls the lifting of the logging tool, allowing the acquisition of the neutron activation reaction height h, and subsequently calculating the effective neutron activation volume V, thus obtaining the gamma ray trapping value ζ per unit volume. o Cable 37 is used for power supply and signal transmission.

[0056] Step 8: If the gamma value ζ is captured per unit volume o Exceeded the set threshold ζ 阈 If the content of tracer elements in the tracer ceramsite product is deemed to be substandard, the control system 12 will automatically calculate the deviation value of the tracer solution concentration in the mixing homogenizer 14 and issue an instruction to adjust the ratio of water and tracer liquid entering the mixing homogenizer 14 by controlling the third flow valve 18 and the second flow valve 15, thereby achieving the purpose of real-time control of the tracer solution concentration in the mixing homogenizer 14, and thus realizing real-time online precise control of the tracer element content in the tracer ceramsite green body.

[0057] Step 9: If the gamma value captured per unit volume is ζ o Falling at the set threshold ζ 阈 If the tracer element content of the tracer ceramsite product meets the standard, the tracer ceramsite blank is then conveyed into a tunnel kiln for high-temperature calcination, ultimately producing tracer ceramsite for monitoring hydraulic fracturing fractures. The gamma capture value per unit volume is ζ. 陶 .

[0058] Step 10: ζ 陶 The value is used to guide the design and construction of downhole fracturing schemes, and has ζ. 陶The tracer ceramic particles were used in actual well logging for fracturing fractures. The logging tool used a gamma detector to obtain the downhole neutron-activated transient gamma ray value, thus obtaining the downhole measured value ζ. 测 Its value varies depending on different logging tool parameters, wellbore environment, and oil and gas reservoir.

[0059] Step 11: Establish ζ under different well conditions 测 The database is used to adjust and optimize the set threshold ζ during the preparation of tracer ceramsite in real time. 阈 Through continuous iteration and optimization, the precise control of the tracer element content in the high neutron capture section of the tracer ceramsite is finally achieved, and the gamma detector can consistently obtain a stable signal-to-noise ratio under complex downhole fracturing conditions, thereby achieving the goal of fine characterization of downhole fracturing fractures during hydraulic fracturing.

[0060] Step (2) 阈 The threshold value is a theoretically calculated value, referencing existing actual well logging data. 测 Optimize and adjust.

[0061] The tracer solution in step (2) is one or any combination of ionic solutions containing high neutron capture cross-section elements such as gadolinium, boron, and samarium, for example, gadolinium nitrate and boric acid.

[0062] The detection unit 9 in step (4) includes three devices: a method for measuring the thickness of a neutron moderator, a method for measuring the effective radius R of neutron activation in tracer ceramic blanks, and a method for obtaining the gamma value captured per unit volume.

[0063] The optimal value for the moderator thickness in step (4) is: increasing the moderator thickness will continuously increase the thermal neutron count. When fast neutrons are almost completely converted into thermal neutrons, the reading of the thermal neutron detector 24 tends to stabilize and remain unchanged. At this time, the corresponding moderator thickness is the optimal value for the designed moderator thickness in the detection unit.

[0064] The vibration device described in step (5) includes an ultrasonic generator, a transducer, and a waveguide rod. By controlling the vibration time, magnitude, frequency, and power, the upper surface of the tracer ceramsite blank inside the device can be kept in a horizontal state, thereby achieving accurate measurement of the thickness of the tracer ceramsite blank inside the device.

[0065] The level gauge mentioned in step (6) includes, but is not limited to, ultrasonic level gauges;

[0066] The principle for determining the effective radius R of neutron activation in step (6) is as follows: When the fourth unloading valve 28 begins to unload, the thickness of the overlying tracer ceramic blank is relatively large. Because the upper layer of tracer ceramic blank is far away, it cannot be activated by neutrons. At this time, the effective radius R of neutron activation is smaller than the thickness of the overlying blank, and the neutron activation area remains stable within a limited effective radius R. At this time, the gamma values ​​obtained by the near-well gamma detector 20 and the far-well gamma detector 21 are the highest and most stable. As the fourth unloading valve 28 further unloads, all the tracer ceramic blanks in the device are activated by neutrons, and the total number of activated blanks continuously decreases. At this time, the effective radius R of neutron activation is greater than the thickness of the overlying blank, and the gamma values ​​obtained by the near-well gamma detector 20 and the far-well gamma detector 21 gradually decrease. When the gamma value begins to decrease from its stable highest value, the thickness of the moderator corresponds to the effective radius R of neutron activation for the tracer ceramic blank.

[0067] The calculation method for the effective radius of neutron activation in step (6) is: R = h0 - h i h0 is the distance between the level gauge 32 and the slowing agent 23, which is a fixed value.

[0068] Step (7) describes the capture of gamma value ζ per unit volume. o For: ζ o =η / V, V = πR 2 H and η represent the total captured gamma value.

[0069] The rotating device described in step (7) comprises a stepper motor, an encoder, a drive gear, a driven gear, a coupling, and a support structure. The support structure is a retractable ring. During rotation, the ring support extends to fit tightly against the simulated well shaft. After the rotation is completed, the ring support retracts appropriately without affecting the lifting and lowering of the detection unit.

[0070] The lifting device described in step (7) consists of a stepper motor, an encoder, a screw, a guide rail, and a steering wheel. The stepper motor drives the screw to achieve horizontal movement, and the cable is connected to the screw through the steering wheel, ultimately driving the detection unit to achieve vertical lifting.

[0071] Step (9) describes the capture of gamma value ζ per unit volume. 陶 For: ζ 陶 =kζ o Where k is the correction coefficient, k = V 烧结 / V 素坯 The reason why k is less than 1 is that the volume of tracer ceramic particles after high-temperature sintering will shrink to a certain extent compared with the tracer ceramic particle blank. For example, in the preparation process of 20 / 40 mesh tracer ceramic particles, the screen selected before firing is 0.95 mm and 0.71 mm, and the screen of the finished product after firing is within the range of 0.85 mm and 0.50 mm.

[0072] The measured value ζ in step (10)测 The neutron activation transient gamma signal value or signal-to-noise ratio detected during well logging can vary significantly due to different logging tool parameters, wellbore environment, and oil and gas reservoir. Therefore, the measured value ζ 测 It should also be constantly changed according to different logging environments and objects.

[0073] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing non-radioactive tracer ceramsite with a stable signal-to-noise ratio, characterized in that, It includes the following steps: Step (1): The raw ore weighed by weight is added into a ball mill after coarse crushing, ground into a mixed powder. After grinding to the target fineness, the powder is transferred to a silo (1). The powder in the silo (1) passes through a first discharge valve (2) to a belt scale (3) for weighing. The weighed mixed powder is then transferred to a granulator (5) through a second discharge valve (4). Step (2): ζ 阈 The threshold range for capturing gamma values ​​per unit volume is set; the control system (12) calculates the amount of water and tracer liquid required for the preparation of tracer ceramsite based on the threshold. The water in the water tank (17) and the tracer liquid in the tracer liquid tank (16) enter the mixing homogenizer (14) through the third flow valve (18) and the second flow valve (15) respectively to form a uniformly mixed tracer solution. Step (3): The tracer liquid in the mixing homogenizer (14) is atomized and sprayed into the granulator (5) through a first flow valve (13) to prepare a tracer ceramsite green body (30), and then transferred to a first conveyor belt (7) through a third discharge valve (6), dried and sieved, and finally the tracer ceramsite green bodies meeting the particle size requirements are screened out. Step (4): The tracer ceramsite green bodies are transferred to a detection unit (9). The detection unit (9) includes a moderator thickness measurement device, a device for measuring the effective neutron activation radius R of the tracer ceramsite green body, and a device for obtaining the gamma value captured per unit volume. The fast neutrons emitted by the neutron source (19) of the first logging tool are converted into thermal neutrons or epithermal neutrons by a moderator (23). The thermal neutron detector (24) is used to monitor the change of the thermal neutron count rate, and the optimal value of the moderator thickness can be determined accordingly. Step (5): The tracer ceramsite green bodies (30) are added into the device for the method of measuring the effective neutron activation radius R of the tracer ceramsite green body through a third conveyor belt (31). When the fourth discharge valve (28) discharges, the thickness of the tracer ceramsite green body covering the moderator (23) in the device for the method of measuring the effective neutron activation radius R of the tracer ceramsite green body will gradually become thinner. Step (6): The level gauge (32), located at the top of the device, measures the distance h between itself and the upper surface of the tracer ceramic blank coated on the modulator. i The fast neutrons emitted by the neutron source (19) are slowed down to form thermal neutrons or hyperthermal neutrons, which are captured by the high neutron capture section elements contained in the tracer ceramic particles, producing transient gamma rays; the near-well gamma detector (20) and the far-well gamma detector (21) are used to detect the magnitude of this signal value, and the change in its magnitude is used to calculate the effective radius R of neutron activation. Step (7): The tracer ceramic blank (30) enters the unit volume gamma capture value acquisition device via the fifth conveyor belt (36); the rotating device (33) controls the rotation of the logging instrument, and the neutron source (19) horizontally emits neutrons to irradiate the tracer ceramic blank around the simulated wellbore with an effective radius of R; the lifting device (38) controls the lifting of the logging instrument to obtain the neutron activation reaction height h, and then calculates the effective neutron activation volume V to obtain the unit volume gamma capture value ζ. o ; Step (8): If the gamma value captured per unit volume is ζ o Exceeded the set threshold ζ 阈 If the tracer element content in the tracer ceramsite product is not up to standard, the control system (12) will automatically calculate the deviation value of the tracer solution concentration in the mixing homogenizer (14) and issue an instruction to adjust the ratio of water and tracer liquid entering the mixing homogenizer (14) by controlling the third flow valve (18) and the second flow valve (15), thereby achieving the purpose of real-time control of the tracer solution concentration in the mixing homogenizer (14), and thus realizing real-time online precise control of the tracer element content in the tracer ceramsite blank; Step (9): If the gamma value captured per unit volume is ζ o Falling at the set threshold ζ 阈 If the tracer element content of the tracer ceramsite product meets the standard, the tracer ceramsite blank is then conveyed into a tunnel kiln for high-temperature calcination, ultimately producing tracer ceramsite for monitoring hydraulic fracturing fractures. The gamma capture value per unit volume is ζ. 陶 ; Step (10): ζ 陶 The value is used to guide the design and construction of downhole fracturing schemes, and has ζ. 陶 The tracer ceramsite with a value of [value missing] was used in actual well logging of fracturing fractures; The logging tool uses a gamma detector to obtain the downhole neutron activation transient gamma ray value, thus obtaining the downhole measured value ζ. 测 Its value varies depending on different logging tool parameters, wellbore environment, and oil and gas reservoir; Step (11): Establish ζ under different well conditions 测 The database is used to adjust and optimize the set threshold ζ during the preparation of tracer ceramsite in real time. 阈 Through continuous iteration and optimization, the precise control of the tracer element content in the high neutron capture section of the tracer ceramsite is finally achieved, and the gamma detector can consistently obtain a stable signal-to-noise ratio under complex downhole fracturing conditions, thereby achieving the goal of fine characterization of downhole fracturing fractures during hydraulic fracturing.

2. The preparation method according to claim 1, characterized in that, The tracer liquid in Step (2) is one or any combination of ionic solutions containing elements with high neutron capture cross-sections such as gadolinium, boron, and samarium.

3. The preparation method according to claim 1, characterized in that, The optimal value of the moderator thickness in Step (4) is as follows: when the moderator thickness is increased, the thermal neutron count will also continuously increase; when the fast neutrons are almost completely converted into thermal neutrons, the reading of the thermal neutron detector (24) tends to be stable and unchanged, and the thickness of the moderator corresponding at this time is the best value of the moderator design thickness in the detection unit.

4. The preparation method according to claim 1, characterized in that, The discrimination principle of the effective neutron activation radius R in Step (6) is as follows: when the fourth discharge valve (28) starts to discharge, the thickness of the tracer ceramsite green body covering is large, and the upper tracer ceramsite green body cannot be neutron-activated due to the long distance. At this time, the effective neutron activation radius R is less than the thickness of the overlying green body, and the neutron activation region is always stable within a limited effective neutron activation radius R. At this time, the gamma values obtained by the near-well gamma detector (20) and the far-well gamma detector (21) are the highest and stable. As the fourth discharge valve (28) further discharges, all the tracer ceramsite green bodies in the device are neutron-activated, and the total number of activated ones is continuously decreasing. At this time, the effective neutron activation radius R is greater than the thickness of the overlying green body, and the gamma values obtained by the near-well gamma detector (20) and the far-well gamma detector (21) gradually decrease accordingly. When the gamma value just starts to decrease from the stable highest value, the thickness of the moderator corresponding at this time is the effective neutron activation radius R of the tracer ceramsite green body.

5. The preparation method according to claim 1, characterized in that, The calculation method for the effective radius of neutron activation in step (6) is: R = h0 - h i h0 is the distance between the level gauge (32) and the moderating body, which is a fixed value.

6. The preparation method according to claim 1, characterized in that, Step (7) describes the capture of gamma value ζ per unit volume. o For: ζ o =η / V, V= πR 2 H and η represent the total captured gamma value.

7. The preparation method according to claim 1, characterized in that, Step (9) describes the capture of gamma value ζ per unit volume. 陶 For: ζ 陶 =kζ o Where k is the correction coefficient, k=V 烧结 / V 素坯 k is less than 1.

8. The preparation method according to claim 1, characterized in that, The measured value ζ in step (10) 测 The neutron activation transient gamma signal value or signal-to-noise ratio detected during well logging can vary significantly depending on different logging tool parameters, wellbore environment, and oil and gas reservoir; measured value ζ 测 It should also be constantly changed according to different logging environments and objects.

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