A preparation system for non-radioactive tracer ceramsite with stable signal-to-noise ratio

Abstract

The present invention discloses a preparation system for non-radioactive tracer ceramsite with stable signal-to-noise ratio, comprising: a tracer ceramsite green body preparation device, a detection unit, a control system, a database, and an adjustment and optimization module; a method for real-time online regulating the content of tracer elements contained in the tracer ceramsite based on the ζ o value is established, eliminating the phenomenon of low or high content of tracer elements caused by uneven mixing or other factors during the production process of the tracer ceramsite, and accurately controlling the content of tracer elements within the set threshold. According to the feedback of the measured data ζ 测 downhole, the set threshold ζ 阈 of the tracer ceramsite is adjusted in real time. With the linkage between the wellhead and the downhole, stable signal-to-noise ratio can be achieved when monitoring the fracture information by the neutron activation prompt gamma ray method of the in-use tracer ceramsite in a complex fracturing environment, and the sudden increase and decrease of the captured gamma signal during fracture logging such as different logging tool parameters, wellbore environment, and oil and gas reservoirs can be avoided, thereby improving the logging success rate.

Description

Technical Field

[0001] The present invention belongs to the field of oil and gas production aids, and particularly relates to a preparation system for non-radioactive tracer ceramsite with stable signal-to-noise ratio for accurately depicting hydraulic fracture cracks. Background Technique

[0002] The reserves of unconventional oil and gas resources such as shale oil and gas in China are very rich. In recent years, the production of unconventional oil and gas in China has continued to grow, and China has become the country with the fastest pace of shale oil and gas exploration and development after the United States, with remarkable results in increasing reserves and production. It is reported that the shale oil production in China exceeded 3 million tons in 2022, quadrupling compared with 2018; the shale gas production reached 24 billion cubic meters, a 122% increase compared with 2018. Therefore, strengthening the exploration and development of unconventional oil and gas such as shale oil and gas is of great significance for ensuring China's energy security and optimizing the energy structure. The 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 position of proppants and the height, width, azimuth, and dip angle of near-wellbore hydraulic fracture cracks is of great value for the design of fracture models, the evaluation and optimized production increase of unconventional oil and gas, and is an important support for China's resource efficient replacement strategy.

[0003] The near-wellbore fracture diagnosis technology is of great significance for evaluating the effect of hydraulic fracturing. At present, there are near-wellbore hydraulic fracture monitoring technologies such as caliper logging, array acoustic logging, and nuclear logging. Although the array acoustic logging is sensitive to fracture monitoring, its accuracy and precision are poor. Temperature logging cannot directly show the fracture height. The array acoustic logging has deficiencies in directly showing proppants. Compared with these technologies, nuclear logging has the advantages of a wide range of monitoring content, high monitoring accuracy, and high sensitivity. There are two technologies for near-wellbore hydraulic fracture nuclear logging: radioactive tracer logging and non-radioactive tracer logging. The radioactive measurement technology adds radioactive tracer isotopes such as antimony, scandium, and iridium to the proppant or fracturing fluid, then uses natural gamma or natural gamma ray spectroscopy logging for logging before and after fracturing, and then compares the differences in gamma counts before and after fracturing to obtain the downhole information of the fracture. Radioactive tracer logging uses substances with a certain radioactive intensity, which poses a radiation risk to the environment and people, does not meet the HSE requirements, and is easily restricted by safety, environmental protection, transportation, storage, and use requirements, making it difficult to promote.

[0004] Compared with radioactive tracer logging technology, the non-radioactive tracer ceramic particle neutron capture gamma tracer logging technology adds high neutron capture cross-section materials, such as gadolinium, boron, and samarium, to the proppant. By using the interaction between neutrons and proppants, before and after fracturing, a compensated neutron logging tool (CNL) or a pulsed neutron capture logging tool (PNC) is used for logging respectively. By comparing the changes in the thermal neutron count rates or capture cross-sections of the near and far detectors before and after, or by calculating the capture gamma counts generated by high thermal neutron capture cross-section elements, downhole information such as the location and height of the fracture is determined. It has the advantages of a wide range of monitoring content, accurate identification of fracture parameters, high sensitivity, and can be repeatedly measured for a long time. It meets the requirements of HSE and the development trend of nuclear logging, and is an important new means to evaluate the fracturing effect.

[0005] The precise control of the concentration of tracer elements with high neutron capture cross-sections contained is the key and prerequisite for the success of the non-radioactive tracer ceramic particle neutron capture gamma tracer logging technology. Too high or too low content of tracer elements will impede the logging application of this technology. If the content of tracer elements is too high, it will lead to a significant increase in the cost of tracer ceramic particles, resulting in a large waste of resources. If the content of tracer elements is too low, it will cause a low signal-to-noise ratio of capture gamma, leading to logging failure. In the current preparation process of tracer ceramic particles, in the initial stage of mixing trace tracer elements with the base material and in large-scale production of tracer ceramic particles, the content of tracer elements will deviate significantly from its set value. In addition, during the logging process, different logging tool parameters, wellbore environments, and oil and gas reservoirs will also cause different neutron capture signals to be obtained by the detectors of the logging tool. Even if the content of tracer elements in the tracer ceramic particles is the same, different signal-to-noise ratios may be generated.

[0006] Therefore, the precise real-time control of the content of tracer elements in tracer ceramic particles and whether a neutron capture signal with a stable signal-to-noise ratio can be obtained during logging are prominent problems faced by the current development of downhole fracture tracer logging technology. Summary of the Invention

[0007] The object of the present invention is to provide a preparation system for non-radioactive tracer ceramic particles with a stable signal-to-noise ratio in view of the deficiencies of the prior art.

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

[0009] A preparation system for non-radioactive tracer ceramic particles with a stable signal-to-noise ratio, comprising: a tracer ceramic particle green body preparation device, a detection unit 9, a control system 12, a database, and an adjustment and optimization module;

[0010] The detection unit 9 is located in a shielding box 25. The detection unit 9 includes a moderator thickness measurement device, a neutron activation effective radius R measurement device for tracer ceramic particle green bodies, and a unit volume capture gamma value acquisition device. These three devices are all equipped with logging tools, which are respectively defined as the first logging tool, the second logging tool, and the third logging tool;

[0011] The moderator thickness measuring device includes a first logging tool and a moderator; the fast neutrons emitted by the neutron source 19 of the first logging tool are converted into thermal neutrons or epithermal neutrons by the moderator; the thermal neutron detector of the first logging tool is used to monitor the change of the thermal neutron count rate, and the optimal value of the moderator thickness can be determined accordingly; the moderators in the neutron activation effective radius R measuring device and the unit volume capture gamma value obtaining device both adopt this thickness value;

[0012] The device for measuring the neutron activation effective radius R of the tracer ceramsite green body includes a second logging tool, a slide rail 26, a second conveyor belt 27, a fourth discharge valve 28, a vibration device 29, a third conveyor belt 31, a level gauge 32, and a moderator; the tracer ceramsite green body 30 is added to the silo of the device for measuring the neutron activation effective radius R of the tracer ceramsite green body through the third conveyor belt 31. A level gauge 32 is provided at the top of the silo, and the moderator is located at the bottom of the silo and above the second logging tool. When the fourth discharge valve 28 at the bottom discharges to the second conveyor belt 27, the thickness of the overlying tracer ceramsite green body will gradually become thinner; the fast neutrons emitted by the neutron source of the second logging tool are moderated to form thermal neutrons or epithermal neutrons, which are captured by the elements with high capture cross-sections contained in the tracer ceramsite, generating prompt gamma rays; the near-well gamma detector 20 and the far-well gamma detector 21 of the second logging tool are used to detect the magnitude of this signal value, and the change in its magnitude can be used for the calculation of the neutron activation effective radius R;

[0013] The device for obtaining the capture gamma value per unit volume includes: a third logging tool, a moderator, a rotating device 33, a fifth discharge valve 34, a fourth conveyor belt 35, a fifth conveyor belt 36, a cable 37, and a lifting device 38; the tracer ceramsite green body 30 enters the simulated wellbore of the device for obtaining the capture gamma value per unit volume through the fifth conveyor belt 36; the third logging tool 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 tool. The neutron source 19 of the third logging tool horizontally emits neutrons to irradiate the tracer ceramsite green body in the simulated wellbore, and its effective action radius is R; the lifting device 38 controls the lifting of the third logging tool, and the neutron activation reaction height h can be obtained, and then the effective neutron activation volume V can be calculated to obtain the capture gamma value ζ per unit volume o ;

[0014] If the capture gamma value ζ per unit volume o exceeds the set threshold ζ 阈 , it is considered that the content of the tracer element contained in the tracer ceramsite product does not meet the standard. The control system 12 will automatically calculate the deviation value of the concentration of the tracer solution in the mixing and homogenizing device 14 and issue an instruction to control the tracer ceramsite green body preparation device in real time to adjust the concentration of the tracer solution, so as to achieve real-time online precise control of the content of the tracer element in the tracer ceramsite green body;

[0015] If the gamma capture value ζ per unit volume o falls within the set threshold ζ 阈 , it is considered that the content of the tracer elements in the tracer ceramsite product meets the standard. At this time, the green tracer ceramsite is conveyed into the tunnel kiln for high-temperature calcination, and finally the tracer ceramsite for hydraulic fracture monitoring is prepared. The gamma capture value per unit volume is ζ 陶 ;

[0016] ζ 陶 value is used to guide the design and construction of downhole fracturing programs. The tracer ceramsite with ζ 陶 value is used for actual logging of hydraulic fracture cracks; the logging tool obtains the downhole neutron activation prompt gamma ray value with the help of a gamma detector to obtain the downhole measured value ζ 测 , and its value varies with different logging tool parameters, wellbore environments, and oil and gas reservoirs, etc.;

[0017] ζ under different well conditions 测 is stored in the database, and the adjustment and optimization module adjusts and optimizes the set threshold ζ during the preparation of tracer ceramsite in real time according to ζ 测 under different well conditions in the database 阈 , so as to continuously iterate and optimize, finally realizing the precise control of the content of the tracer elements with high neutron capture cross-section in the tracer ceramsite, and enabling the gamma detector to always obtain a stable signal-to-noise ratio under complex downhole fracturing environments, so as to achieve the purpose of accurately depicting downhole fracturing cracks during hydraulic fracturing production.

[0018] For the system described above, the green tracer ceramsite preparation device includes a ball mill, a storage bin 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 and homogenizing device 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 added into the ball mill after coarse crushing, ground into a mixed powder, and after being ground to the target fineness, the powder is transferred to the storage bin 1; the powder in the storage bin 1 passes through the first discharge valve 2 to the belt scale 3 for weighing, and the weighed mixed powder is then transferred to the granulator 5 through the second discharge valve 4; 阈 is the set threshold range of the gamma capture value per unit volume; the control system 12 calculates the amounts of water and tracer liquid required for the preparation of tracer ceramsite according to this 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; the tracer liquid in the mixing and homogenizing device 14 is atomized and sprayed into the granulator 5 through the first flow valve 13 to prepare the green tracer ceramsite 30, and then is transferred to the first conveyor belt 7 through the third discharge valve 6, dried and sieved, and finally the green tracer ceramsite meeting the particle size requirements is screened out.

[0019] For the system described above, the vibration devices 29 are located on both sides of the silo; the vibration devices include an ultrasonic generator, a transducer, and a waveguide rod. By controlling the vibration time, amplitude, frequency, and power, the upper surface of the tracer ceramsite green body in the device is always kept in a state tending to be horizontal, thereby achieving accurate measurement of the thickness of the tracer ceramsite green body in the device.

[0020] For the system described above, the tracer liquid is one or any combination of ionic solutions containing elements with high neutron capture cross-sections such as gadolinium, boron, samarium, etc., such as gadolinium nitrate and boric acid.

[0021] For the system described above, the optimal value of the thickness of the moderator is as follows: increasing the thickness of the moderator, 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. At this time, the thickness of the corresponding moderator is the optimal value of the design thickness of the moderator in the detection unit.

[0022] For the system described above, the vibration devices include an ultrasonic generator, a transducer, and a waveguide rod. By controlling the vibration time, amplitude, frequency, and power, the upper surface of the tracer ceramsite green body in the device can be always kept in a state tending to be horizontal, thereby achieving accurate measurement of the thickness of the tracer ceramsite green body in the device.

[0023] For the system described above, the discrimination principle of the neutron activation effective radius R is as follows: when the fourth discharge valve 28 starts to discharge materials, the thickness of the overlying tracer ceramsite green body is relatively large, and the upper-layer tracer ceramsite green body cannot be neutron-activated due to the long distance. At this time, the neutron activation effective radius R is less than the thickness of the overlying green body, and the neutron activation region has been stable within the limited neutron activation effective radius R. At this time, the gamma values obtained by the near-well gamma detector of the second logging tool and the far-well gamma detector of the second logging tool are the highest and stable; as the fourth discharge valve 28 further discharges materials, 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 neutron activation effective radius R is greater than the thickness of the overlying green body, and the gamma values obtained by the near-well gamma detector of the second logging tool and the far-well gamma detector of the second logging tool gradually decrease; when the gamma value just starts to decrease from the stable highest value, the thickness of the corresponding moderator at this time corresponds to the neutron activation effective radius R of the tracer ceramsite green body.

[0024] For the system described above, the rotating device includes a stepping motor, an encoder, a driving gear, a driven gear, a coupling, and a support structure; the support structure is a telescopic ring. When rotating, the ring support extends to closely adhere to the simulated wellbore, and after the rotation work is completed, the ring support contracts appropriately without affecting the lifting of the detection unit.

[0025] In the described system, the lifting device includes a stepper motor, an encoder, a screw rod, a guide rail, and a steering wheel; the stepper motor drives the screw rod to achieve horizontal movement, and the cable is connected to the screw rod through the steering wheel, finally driving the detection unit to achieve vertical lifting.

[0026] The tracer ceramsite preparation system for accurately depicting hydraulic fracture with stable signal-to-noise ratio proposed by the present invention designs the capture gamma value ζ per unit volume of the tracer ceramsite green body. o Acquisition method, and a method for real-time online regulating the content of tracer elements contained in the tracer ceramsite based on the ζ o value is established, eliminating the phenomenon of low or high content of tracer elements caused by uneven mixing or other factors during the production process of the tracer ceramsite, and accurately controlling the content of tracer elements within the set threshold. After high-temperature calcination, the total capture gamma value per unit volume of the tracer ceramsite is ζ 陶 for guiding the design and construction of downhole fracturing schemes. According to the feedback of the measured data ζ 测 downhole, the set threshold ζ 阈 of the tracer ceramsite is adjusted in real time. With the linkage between the wellhead and the downhole, it is possible to achieve a stable signal-to-noise ratio when monitoring fracturing fracture information by the neutron activation prompt gamma ray method of the tracer ceramsite in a complex fracturing environment, avoiding the high and low capture gamma signals during logging of fracturing fractures due to different logging tool parameters, wellbore environments, and oil and gas reservoirs, etc., thereby improving the logging success rate, reducing the logging cost, making the measurement more accurate and efficient, and endowing the logging technology with a broader market application prospect and vitality. The entire preparation process is controlled by a program, with a high degree of automation and continuous monitoring, eliminating human errors and saving manpower. Brief Description of the Drawings

[0027] Figure 1 It is a flow diagram of a preparation method and system for tracer ceramsite for accurately depicting hydraulic fracture with stable signal-to-noise ratio;

[0028] Figure 2 It is a preparation method for tracer ceramsite in which the content of tracer elements with high neutron capture cross-section is accurately controlled in real time online;

[0029] Figure 3 It is a method for measuring the thickness of the moderator;

[0030] Figure 4 It is a method for measuring the effective neutron activation radius R;

[0031] Figure 5 It is a method for measuring the total capture gamma per unit volume;

[0032] In the figure: 1. Silo; 2. First discharge valve; 3. Belt weigher; 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. Far-well gamma detector; 22. Shield; 23. Moderator; 24. He3 thermal neutron detector; 25. Shield box; 26. Slide rail; 27. Second conveyor belt; 28. Fourth discharge valve; 29. Vibration device; 30. Tracer ceramsite green body; 31. Third conveyor belt; 32. Level gauge; 33. Rotating device; 34. Fifth discharge valve; 35. Fourth conveyor belt; 36. Fifth conveyor belt; 37. Cable; 38. Lifting device. Detailed implementation mode

[0033] The present invention will be described in detail below in conjunction with specific embodiments.

[0034] Reference Figure 1-2 , a preparation system for non-radioactive tracer ceramsite with stable signal-to-noise ratio, the system includes: a tracer ceramsite green body preparation device, a detection unit 9, a control system 12, a database, and an adjustment and optimization module;

[0035] The tracer ceramsite green body preparation device includes a ball mill, a silo 1, a first discharge valve 2, a belt weigher, 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 and homogenizing device 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 added into the ball mill after coarse crushing, ground into mixed powder, and after being ground to the target fineness, the powder is transferred to the silo 1. The powder in the silo 1 passes through the first discharge valve 2 to the belt weigher 3 for weighing, and the weighed mixed powder is then transferred to the granulator 5 through the second discharge valve 4. ζ 阈 is the set threshold range of the capture gamma value per unit volume. The control system 12 calculates the required amounts of water and tracer liquid for the preparation of tracer ceramsite according to this 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, forming a uniformly mixed tracer solution. The tracer liquid in the mixing and homogenizing device 14 is atomized and sprayed into the granulator 5 through the first flow valve 13 to prepare the tracer ceramsite green body 30, and then is transferred to the first conveyor belt 7 through the third discharge valve 6, dried and sieved 8, and finally the tracer ceramsite green body meeting the particle size requirements is screened out.

[0036] The detection unit 9 is located inside the shielding box 25. The detection unit 9 includes a moderator thickness measurement device, a tracer ceramsite green body neutron activation effective radius R measurement device, and a unit volume capture gamma value acquisition device. Each of these three devices has a logging tool, which are respectively defined as the first logging tool, the second logging tool, and the third logging tool;

[0037] As Figure 3 shown, the moderator thickness measurement device includes the first logging tool and the moderator 23; the first logging tool includes a neutron source 19, a near-well gamma detector 20, a far-well gamma detector 21, a shielding body 22, and a He3 thermal neutron detector 24; the fast neutrons emitted by the neutron source 19 are converted into thermal neutrons or epithermal neutrons by the moderator 23. The thermal neutron detector 24 is used to monitor the change in the thermal neutron count rate, and the optimal value of the moderator thickness can be determined based on this; the moderators in the tracer ceramsite green body neutron activation effective radius R measurement device and the unit volume capture gamma value acquisition device both use this thickness value.

[0038] As Figure 4 shown, the tracer ceramsite green body neutron activation effective radius R measurement device includes the second logging tool, a slide rail 26, a second conveyor belt 27, a fourth discharge valve 28, a vibration device 29, a third conveyor belt 31, a level gauge 32, and a moderator 23. The second logging tool includes a neutron source 19, a near-well gamma detector 20, a far-well gamma detector 21, and a shielding body 22; the tracer ceramsite green body 30 is added to the silo of the tracer ceramsite green body neutron activation effective radius R measurement method device through the third conveyor belt 31. A level gauge 32 is provided at the top of the silo. The moderator 23 is located at the bottom of the silo and above the second logging tool. When the fourth discharge valve 28 at the bottom discharges to the second conveyor belt 27, the thickness of the overlying tracer ceramsite green body will gradually become thinner.

[0039] The second logging tool is installed on the slide rail 26, and the slide rail 26 is used to adjust the horizontal position of the second logging tool. The level gauge 32 is used to measure the distance h between it and the upper surface of the overlying tracer ceramsite green body on the moderator 23 i .

[0040] The fast neutrons emitted by the neutron source 19 of the second logging tool are moderated to form thermal neutrons or epithermal neutrons, which are captured by the elements with high capture cross-sections contained in the tracer ceramsite, generating prompt 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 can be used for the calculation of the neutron activation effective radius R.

[0041] The 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 green body in the device can be kept in a state tending to be horizontal all the time, thereby realizing the accurate measurement of the thickness of the tracer ceramsite green body in the device.

[0042] As Figure 5 shown, the gamma capture value per unit volume acquisition device includes: a third logging tool, a moderator 23, a rotating device 33, a fifth discharge valve 34, a fourth conveyor belt 35, a fifth conveyor belt 36, a cable 37, and a lifting device 38; the third logging tool includes: a neutron source 19, a near-well gamma detector 20, a far-well gamma detector 21, and a shield 22; the tracer ceramsite green body 30 enters the simulated wellbore of the gamma capture value per unit volume acquisition method device through the fifth conveyor belt 36. The third logging tool 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 tool. The neutron source 19 of the third logging tool horizontally emits neutrons to irradiate the tracer ceramsite green body around the simulated wellbore horizontally, and its effective action radius is R. The lifting device 38 controls the lifting of the third logging tool, and the neutron activation reaction height h can be obtained, and then the effective neutron activation volume V can be calculated to obtain the gamma capture value ζ per unit volume. o The cable 37 is used for power supply and signal transmission.

[0043] If the gamma capture value ζ per unit volume o exceeds the set threshold ζ 阈 , it is considered that the content of the tracer element in the tracer ceramsite product does not meet the standard. The control system 12 will automatically calculate the deviation value of the tracer solution concentration in the mixing and homogenizing device 14 and issue an instruction to adjust the ratio of water and tracer liquid entering the mixing and homogenizing device 14 by controlling the third flow valve 18 and the second flow valve 15 in the tracer ceramsite green body preparation device, so as to achieve the purpose of real-time regulating the tracer solution concentration in the mixing and homogenizing device 14, thereby realizing the real-time online precise control of the tracer element content in the tracer ceramsite green body;

[0044] Example of the automatic calculation method of the control system 12: The control system 12 can obtain the concentration of the tracer element contained in the actual sample according to the gamma capture value ζ per unit volume o , and can obtain the designed concentration of the tracer element according to the threshold ζ 阈 . Combining the volume V of the tracer ceramsite green body in the granulator 5, the deviation amount of the tracer element from the requirement can be obtained.

[0045] If the gamma capture value ζ per unit volume o falls within the set threshold ζ 阈 , it is considered that the content of the tracer element in the tracer ceramsite product meets the standard. At this time, the tracer ceramsite blank is conveyed into the tunnel kiln for high-temperature calcination, and finally the tracer ceramsite for fracture monitoring in hydraulic fracturing is prepared, and the gamma capture value per unit volume is ζ 陶 .

[0046] ζ 陶 The value is used to guide the design and construction of downhole fracturing schemes and has ζ陶 The tracer ceramsite of the value is used for the actual logging of the fracturing crack. The logging tool obtains the value of the prompt gamma ray of neutron activation in the wellbore with the help of a gamma detector, and obtains the measured value ζ in the wellbore. 测 Its value varies with different logging tool parameters, wellbore environments, oil and gas reservoirs, etc.

[0047] ζ under different well conditions 测 is stored in the database, and the adjustment and optimization module adjusts and optimizes the set threshold ζ during the preparation of the tracer ceramsite in real time according to ζ under different well conditions in the database. 测 By continuously iterating and optimizing in this way, the accurate control of the content of the tracer element with a high neutron capture cross section contained in the tracer ceramsite is finally realized, and the gamma detector can always obtain a stable signal-to-noise ratio under the complex downhole fracturing environment, so as to achieve the purpose of accurately depicting the downhole fracturing crack during hydraulic fracturing production. 阈 According to the above system, a method for preparing non-radioactive tracer ceramsite for accurately depicting fracturing cracks with a stable signal-to-noise ratio includes the following steps:

[0048] Step 1: Prepare the green body of the tracer ceramsite;

[0049] Step 4: The green body of the tracer ceramsite is conveyed to the detection unit 9, and the detection unit 9 includes a moderator thickness measurement device, a device for measuring the effective radius R of neutron activation of the green body of the tracer ceramsite, and a device for obtaining the capture gamma value 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 the 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.

[0050] Step 5: The green body of the tracer ceramsite 30 is added to the device for measuring the effective radius R of neutron activation of the green body of the tracer ceramsite through the third conveyor belt 31. Figure 3 .

[0051] When the fourth discharge valve 28 discharges, the thickness of the tracer ceramsite green body covering the moderator 23 in the device for measuring the effective radius R of neutron activation of the tracer ceramsite green body will gradually become thinner. Figure 4 .

[0052] 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 ceramsite green body covering the moderator. i The slide rail 26 is used to adjust the horizontal position of the logging tool. The fast neutrons emitted by the neutron source 19 are moderated to form thermal neutrons or epithermal neutrons, which are captured by the elements with a high capture cross section contained in the tracer ceramsite, generating prompt gamma rays. The near-well gamma detector 20 and the far-well gamma detector 21 are used to detect the magnitude of the signal value, and the change of its magnitude can be used for the calculation of the effective radius R of neutron activation.

[0053] Step 7: The tracer ceramsite blank 30 enters the unit volume capture gamma value acquisition method device through the fifth conveyor belt 36. Figure 5 The rotating device 33 controls the rotation of the logging instrument, and the neutron source 19 horizontally emits neutrons to horizontally irradiate the tracer ceramsite blanks around the simulated wellbore, and its effective action radius is R. The lifting device 38 controls the lifting of the logging instrument, and the neutron activation reaction height h can be obtained, and then the effective neutron activation volume V can be calculated to obtain the unit volume capture gamma value ζ o The cable 37 is used for power supply and signal transmission.

[0054] Step 8: If the unit volume captures the gamma value ζ o Exceeded the set threshold 阈 , it is considered that the tracer element content contained in the tracer ceramsite product does not meet the standard, and the control system 12 will automatically calculate the deviation value of the tracer solution concentration in the mixing homogenizer 14, and issue a command 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, so as to achieve the purpose of real-time regulation of the tracer solution concentration in the mixing homogenizer 14, thereby realizing real-time online and precise control of the tracer element content in the tracer ceramsite blank.

[0055] Step 9: If the unit volume capture gamma value ζ o Falling below the set threshold 阈 If the content of tracer elements in the tracer ceramsite product is within the standard, the tracer ceramsite blank is transported into the tunnel kiln for high-temperature calcination, and finally the tracer ceramsite for fracturing crack monitoring is prepared. The unit volume capture gamma value is ζ 陶 .

[0056] Step 10: ζ 陶 The value is used to guide the design and construction of downhole fracturing schemes and has 陶 The value of tracer ceramsite is used for actual logging of fracturing fractures. The logging instrument uses the gamma detector to obtain the value of neutron activation prompt gamma ray in the well and obtain the measured value ζ 测 Its value varies with different logging instrument parameters, wellbore environment and oil and gas reservoirs.

[0057] Step 11: Establish ζ under different well conditions 测 The database is used to adjust the threshold value ζ in real time to optimize the preparation of tracer ceramsite. 阈 Through continuous iterative optimization, we can eventually achieve precise control of the content of tracer elements in the high neutron capture cross-section of the tracer expanded clay, and enable the gamma detector to always obtain a stable signal-to-noise ratio in the complex downhole fracturing environment, thereby achieving the purpose of fine characterization of downhole fracturing cracks during hydraulic fracturing.

[0058] Step (2) 阈For setting the threshold value, which is a theoretically calculated value, and referring to the existing actual logging data ζ 测 Optimize and adjust accordingly.

[0059] The tracer solution described in step (2) is one or any combination of ionic solutions containing elements with high neutron capture cross-sections such as gadolinium, boron, samarium, etc., such as gadolinium nitrate, boric acid.

[0060] The detection unit 9 described in step (4) includes three devices: a method for measuring the thickness of the neutron moderator, a method for measuring the effective radius R of neutron activation of the tracer ceramsite green body, and a method for obtaining the capture gamma value per unit volume.

[0061] The optimal value of the thickness of the moderator described in step (4) is as follows: increasing the thickness of the moderator, 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. At this time, the corresponding thickness of the moderator is the optimal value of the designed thickness of the moderator in the detection unit.

[0062] The vibration device described in step (5) includes an ultrasonic generator, a transducer, and a waveguide rod. By controlling the time, magnitude, frequency, and power of the vibration, the upper surface of the tracer ceramsite green body in the device can always be kept in a state close to horizontal, thereby achieving accurate measurement of the thickness of the tracer ceramsite green body in the device.

[0063] The level gauge described in step (6) includes, but is not limited to, an ultrasonic level gauge;

[0064] The discrimination principle of the effective radius R of neutron activation described in step (6) is as follows: when the fourth discharge valve 28 starts to discharge materials, the thickness of the overlying tracer ceramsite green body is relatively large, and the upper-layer tracer ceramsite green body cannot be neutron-activated due to the long distance. At this time, the effective radius R of neutron activation is less than the thickness of the overlying green body, and the neutron activation region has always been stable within a limited effective radius R of neutron activation. 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 materials, 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 radius R of neutron activation 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 corresponding thickness of the moderator at this time is the effective radius R of neutron activation of the tracer ceramsite green body.

[0065] The calculation method of the effective radius R of neutron activation described in step (6) is: R = h0 - h i , where h0 is the distance between the level gauge 32 and the moderator 23, which is a fixed value.

[0066] The capture gamma value ζ per unit volume described in step (7) o is: ζ o= η / V, V = πR 2 H, where η is the total captured gamma value.

[0067] The rotating device described in step (7) consists of a stepper motor, an encoder, a driving gear, a driven gear, a coupling, a support structure, etc. The support structure is a telescopic ring. When rotating, the ring support extends to closely adhere to the simulated wellbore. After the rotation operation ends, the ring support shrinks appropriately without affecting the lifting of the detection unit.

[0068] The lifting device described in step (7) consists of a stepper motor, an encoder, a screw, a guide rail, a steering wheel, etc. The stepper motor drives the screw to achieve horizontal movement. The cable is connected to the screw through the steering wheel, and finally drives the detection unit to achieve vertical lifting.

[0069] The gamma value ζ captured per unit volume described in step (9) 陶 is: ζ 陶 = kζ o , where k is a correction factor, k = V 烧结 / V 素坯 . k is less than 1 because the volume of the tracer ceramsite after high-temperature sintering will shrink by a certain proportion compared to the tracer ceramsite green body. For example, in the preparation process of 20 / 40 mesh tracer ceramsite, the pre-firing screen meshes selected are 0.95 mm and 0.71 mm, and the post-firing finished product screen meshes are in the range of 0.85 mm and 0.50 mm.

[0070] The measured value ζ described in step (10) 测 , the neutron activation prompt gamma signal value or signal-to-noise ratio detected during logging will vary greatly due to different logging tool parameters, wellbore environments, and oil and gas reservoirs, etc. Therefore, the measured value ζ 测 should also change continuously according to different logging environments and objects.

[0071] It should be understood that for those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A preparation system for non-radioactive tracer ceramsite with stable signal-to-noise ratio, characterized in that Comprising: A tracer ceramsite green body preparation device, a detection unit (9), a control system (12), a database, and an adjustment and optimization module; The detection unit (9) is located inside a shielding box (25). The detection unit (9) includes a moderator thickness measurement device, a tracer ceramsite green body neutron activation effective radius R measurement device, and a unit volume capture gamma value acquisition device. All three of these devices have logging tools, which are respectively defined as the first logging tool, the second logging tool, and the third logging tool; The moderator thickness measurement device includes the first logging tool and a moderator; the fast neutrons emitted by the neutron source (19) of the first logging tool are converted into thermal neutrons or epithermal neutrons by the moderator; the thermal neutron detector of the first logging tool is used to monitor the change in the thermal neutron count rate, and the optimal value of the moderator thickness can be determined based on this; the moderators in the tracer ceramsite green body neutron activation effective radius R measurement device and the unit volume capture gamma value acquisition device both use this thickness value; The tracer ceramsite green body neutron activation effective radius R measurement device includes the second logging tool, a slide rail (26), a second conveyor belt (27), a fourth discharge valve (28), a vibration device (29), a third conveyor belt (31), a level gauge (32), and a moderator; the tracer ceramsite green body (30) is added to the silo of the tracer ceramsite green body neutron activation effective radius R measurement method device via the third conveyor belt (31). A level gauge (32) is provided at the top of the silo. The moderator is located at the bottom of the silo and above the second logging tool. When the fourth discharge valve (28) at the bottom discharges to the second conveyor belt (27), the thickness of the overlying tracer ceramsite green body will gradually become thinner; the fast neutrons emitted by the neutron source of the second logging tool are moderated to form thermal neutrons or epithermal neutrons, which are captured by the elements with high neutron capture cross-sections contained in the tracer ceramsite, generating prompt gamma rays; the near-well gamma detector (20) and the far-well gamma detector (21) of the second logging tool are used to detect the magnitude of the signal value of the prompt gamma rays, and the change in its magnitude can be used for the calculation of the neutron activation effective radius R; The gamma capture value per unit volume acquisition device includes: a third logging tool, a moderator, a rotating device (33), a fifth discharge valve (34), a fourth conveyor belt (35), a fifth conveyor belt (36), a cable (37), and a lifting device (38); the tracer ceramsite green body (30) enters the simulated wellbore of the gamma capture value per unit volume acquisition device through the fifth conveyor belt (36); the third logging tool 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 tool. The neutron source (19) of the third logging tool horizontally emits neutrons to irradiate the tracer ceramsite green body in the simulated wellbore horizontally, and its effective action radius is R; the lifting device (38) controls the lifting of the third logging tool, and the neutron activation reaction height h can be obtained, and then the effective neutron activation volume V can be calculated to obtain the gamma capture value ζ per unit volume o .

2. The system according to claim 1, wherein: 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 and homogenizing device (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 added into the ball mill after coarse crushing, ground into mixed powder, and after being ground to the target fineness, the powder is transferred to the silo (1); the powder in the silo (1) passes through the first discharge valve (2) to the belt scale (3) for weighing, and the weighed mixed powder is then transferred to the granulator (5) through the second discharge valve (4); ζ 阈 ζ is the set threshold range of the gamma value captured per unit volume; the control system (12) calculates the amounts of water and tracer liquid required for preparing the tracer ceramsite according to this 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) respectively through the third flow valve (18) and the second flow valve (15) to form a uniformly mixed tracer solution; the tracer liquid in the mixing and homogenizing device (14) is atomized and sprayed into the granulator (5) through the first flow valve (13) to prepare the tracer ceramsite green body (30), which is then transferred to the first conveyor belt (7) through the third discharge valve (6), dried and sieved, and finally the tracer ceramsite green body meeting the particle size requirements is selected.

3. The system according to claim 1, wherein: The 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 green body in the device can always be kept in a state tending to be horizontal, thereby realizing the accurate measurement of the thickness of the tracer ceramsite green body in the device.

4. The system according to claim 2, wherein: The tracer liquid is one or any combination of ionic solutions containing elements with high neutron capture cross-sections such as gadolinium, boron, and samarium, including gadolinium nitrate and boric acid.

5. The system according to claim 1, wherein: The optimal value of the moderator thickness is as follows: increasing the moderator thickness, 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. At this time, the corresponding thickness of the moderator is the best value of the moderator design thickness in the detection unit.

6. The system according to claim 1, wherein: 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 green body in the device can always be kept in a state tending to be horizontal, thereby realizing the accurate measurement of the thickness of the tracer ceramsite green body in the device.

7. The system according to claim 1, characterized in that: The discrimination principle of the neutron activation effective radius R is as follows: When the fourth discharge valve (28) starts discharging for the first time, the thickness of the overlying tracer ceramsite green body is relatively large, and the upper-layer tracer ceramsite green body cannot be neutron-activated due to the long distance. At this time, the neutron activation effective radius R is less than the thickness of the overlying green body, and the neutron activation region has been stable within the limited neutron activation effective radius R. At this time, the gamma values obtained by the near-well gamma detector of the second logging tool and the far-well gamma detector of the second logging tool 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 neutron activation effective radius R is greater than the thickness of the overlying green body, and the gamma values obtained by the near-well gamma detector of the second logging tool and the far-well gamma detector of the second logging tool gradually decrease accordingly. When the gamma value just starts to decrease from the stable highest value, the thickness of the corresponding moderator at this time is the neutron activation effective radius R of the tracer ceramsite green body.

8. The system according to claim 1, wherein: The rotation device includes a stepping motor, an encoder, a driving gear, a driven gear, a coupling, and a support structure; the support structure is a telescopic ring. During the rotation operation, the ring support extends to closely adhere to the simulated wellbore, and after the rotation operation ends, the ring support contracts appropriately without affecting the lifting of the detection unit.

9. The system according to claim 1, wherein: The lifting device includes a stepping motor, an encoder, a screw rod, a guide rail, and a steering wheel; the stepping motor drives the screw rod to achieve horizontal movement, and the cable is connected to the screw rod through the steering wheel, and finally drives the detection unit to achieve vertical lifting.

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