A gamma logging instrument principle demonstration simulation device and method

Abstract

The application discloses a gamma logging instrument principle demonstration simulation device and method, and belongs to the field of well logging principle demonstration. The device comprises a cylinder for simulating a formation model; the cylinder is arranged vertically and has different light transmittances at different heights of the cylinder; a photosensitive resistance device is arranged in the interior of the cylinder for replacing a gamma ray detector; the photosensitive resistance device is connected with driving devices for driving the photosensitive resistance device to move up and down; the photosensitive resistance device is also connected with a linear voltage-controlled oscillator through wires, the linear voltage-controlled oscillator is connected with a voltage comparator, the voltage comparator is connected with a counter, and the counter is connected with a single-chip microcomputer. The application can convert different light intensities into electric pulse signals with different frequencies, and then count square wave pulses output by the voltage comparator in a unit time through the counter, so that gamma logging simulation is realized. The application simplifies the structure and scale of a measuring device and a simulated formation in a demonstration process, and enhances the convenience and intuitiveness of relevant demonstration operations.

Description

Technical Field

[0001] The invention relates to the field of well logging principle demonstration, in particular to a simulation device and method for demonstrating the principles of a natural gamma ray logging instrument and an azimuthal gamma ray logging instrument used in resource exploration. Background Art

[0002] Natural gamma ray logging and azimuthal gamma ray logging are of great significance in fields such as oil exploration. They measure the intensity of natural gamma rays in the formation to obtain formation information. In training practitioners and related scientific research, an effective simulation device is needed to help trainees and researchers understand the logging principles of natural gamma ray logging and azimuthal gamma ray logging.

[0003] (1) Natural gamma ray logging tool and azimuthal gamma ray logging tool;

[0004] Natural gamma logging is mainly based on the gamma ray radiation of natural radioactive elements in the formation. The radioactive elements in the formation mainly include potassium-40 ( 40 K), uranium-238 ( 238 U) and thorium-232( 232 Th). These radioactive elements emit gamma rays during their decay process. The intensity of the gamma rays emitted varies depending on the radioactive element content in the formation. By measuring the intensity of gamma rays emitted by the formation surrounding the wellbore, we can infer the radioactive element content in the formation and, in turn, understand information such as the lithology and mud content of the formation. For example, mudstone formations with relatively high radioactive element content will have high natural gamma ray intensity; whereas pure sandstone formations with low radioactive element content will have low natural gamma ray intensity.

[0005] A natural gamma ray logging tool consists of a detector and a signal processing section. Commonly used natural gamma ray logging detectors include scintillation counters and semiconductor detectors. A scintillation counter primarily consists of a scintillation crystal and a photomultiplier tube. When gamma rays enter the scintillation crystal, they excite atoms within the crystal, which then de-excite and emit photons. These photons enter the photomultiplier tube, where they are amplified multiple times and form an electrical pulse signal. The detector is placed in the headstage of the logging tool and moves along the wellbore. When the detector receives gamma rays emitted by the formation, it generates a corresponding electrical signal. The amplitude and frequency of this electrical signal are related to the energy and intensity of the gamma ray. The electrical signal generated by the detector is typically very weak and requires amplification by an amplifier circuit. The amplified signal may have an irregular waveform and needs to be processed by a shaping circuit to form a regular pulse signal for subsequent counting and analysis. The processed pulse signal is fed into a counter, which counts the number of pulses per unit time. This pulse count represents the gamma ray intensity. The tool also records logging depth information, allowing a logging curve to be generated showing how natural gamma ray intensity varies with depth. Well logging curves can intuitively show the changes in the content of radioactive elements in the formation at different depths, providing an important basis for geological analysis.

[0006] In short, the stronger the formation radioactivity, the higher the frequency of the electrical pulse signal generated in the natural gamma ray logging instrument. By counting the number of pulses per unit time, the counting rate is used to reflect the radioactivity intensity of the formation.

[0007] The units of the gamma ray log output curve are API (American Petroleum Institute). API units are a relative measurement unit, determined by comparing the instrument reading in a standard calibrated well with a formation with known radioactivity. The calibrated well contains a formation model with known radioactivity content. The instrument reading in the low-radioactive formation model is defined as 0 API, and the reading in the high-radioactive formation model is defined as 200 API.

[0008] Compared to conventional natural gamma logging tools, azimuthal gamma logging tools offer an additional azimuthal measurement capability, enabling the measurement of formation radioactivity differences in different directions around the wellbore. The basic principle is to cover the gamma detector with a shield with windows in fixed directions, allowing only gamma rays from specific directions to enter the detector and be converted into voltage pulses. The windowed shield rotates within the wellbore, enabling 360° azimuthal scanning of formation radioactivity.

[0009] (2) Limitations of using industrial logging tools for training demonstrations;

[0010] First, using industrial natural gamma ray logging tools for training demonstrations is costly, large-scale, and inflexible.

[0011] The length of the industrialized natural gamma ray logging instrument is more than 3m, if the continuous natural gamma ray logging curve of the reaction of different properties of the natural radioactivity of the formation is to be demonstrated, a large simulation formation model (it is estimated that the thickness of the simulation formation is more than 10m) is needed, or the instrument is placed in a real downhole environment. The equipment needed for this demonstration is large in scale, high in cost and poor in flexibility. Especially when the influence of different geological environments on the instrument response needs to be explored in scientific research activities, the formation model needs to be replaced, and the engineering difficulty involved is very large. For the azimuthal gamma ray logging instrument, it is more difficult and larger in scale to make a formation model corresponding to the different azimuthal radioactivity.

[0012] Secondly, it is difficult to demonstrate the calibration process of the instrument using the industrialized logging instrument.

[0013] As described above, the natural gamma ray logging instrument uses relative measurement units, and needs to be calibrated in high and low radioactivity formation models in sequence. Therefore, the calibration demonstration must be carried out in the calibration well site, which causes inconvenience to the training of new employees.

[0014] Finally, the training demonstration using the industrialized logging instrument involves high safety risks.

[0015] The training demonstration using the industrialized natural gamma ray logging instrument needs to be carried out in the well site, which involves high safety risks. On the other hand, even if a small-scale logging instrument is developed, different radioactivity formation models need to be made, and the high radioactivity formation model involves nuclear radiation safety protection problems. SUMMARY

[0016] Based on the above technical problems, the present application provides a gamma ray logging instrument principle demonstration simulation device and method.

[0017] The technical solution adopted by the present application is:

[0018] A gamma ray logging instrument principle demonstration simulation device, comprising a cylinder for simulating a formation model; the cylinder is arranged vertically and has different light transmittances at different heights of the cylinder;

[0019] A photosensitive resistance device is arranged in the interior of the cylinder to replace the gamma ray detector; the photosensitive resistance device is connected with a driving device for driving the up and down movement thereof;

[0020] The photosensitive resistance device is further connected with a linear voltage-controlled oscillator through a wire, the linear voltage-controlled oscillator is connected with a voltage comparator, the voltage comparator is connected with a counter, and the counter is connected with a single-chip microcomputer.

[0021] Preferably, the wire is further connected with a first adjustable resistor for adjusting the voltage variation range of the photosensitive resistance device;

[0022] The voltage comparator is further connected to a second adjustable resistor for adjusting the threshold voltage.

[0023] Preferably, the cylinder is formed by connecting acrylic cylinders with different light transmittances; or the cylinder is a transparent acrylic cylinder, and paints of different colors and thicknesses are applied on the transparent acrylic cylinder to change the light transmittance of different positions of the cylinder.

[0024] Preferably, the driving device includes a pulling rope, a fixed pulley, a drum and a first stepper motor. The fixed pulley is arranged at one end of the top of the cylinder. One end of the pulling rope is connected to the photoresistor device. The other end of the pulling rope passes around the fixed pulley and is wound around the drum. The drum is connected to the first stepper motor for driving its rotation, and the first stepper motor is connected to the single-chip microcomputer.

[0025] Preferably, a strip-shaped transparent window is provided on the cylinder, and the strip-shaped transparent window is arranged along the length direction of the cylinder;

[0026] The bottom end of the cylinder is fixed on the turntable, and a transmission tooth is provided on the outer edge of the turntable. The transmission tooth is engaged with a power gear arranged adjacent to the turntable. The power gear is connected to the second stepper motor, and the second stepper motor is connected to the single chip microcomputer.

[0027] The photoresistor device is also equipped with a light shield, and the photoresistor device is placed in the light shield when needed. A hollow window is also provided on one side of the light shield.

[0028] Preferably, the single chip microcomputer is connected to a host computer.

[0029] The present invention also provides a method for demonstrating the principle of a gamma logging tool, which uses the above-mentioned device and includes the following steps:

[0030] (1) The single chip microcomputer controls the speed and direction of the first stepper motor, drives the reel to wind or release the pull rope, and then the pull rope pulls the photoresistor device through the fixed pulley to achieve the lifting and lowering of the photoresistor device in the cylinder, thereby obtaining the photoresistor device as a simulated gamma ray probe to measure the simulated strata at different depths;

[0031] (2) When the photoresistor device is placed at different positions in the cylinder, its corresponding resistance value changes with the light intensity at its position, which in turn causes the control voltage of the linear voltage-controlled oscillator to change;

[0032] The linear voltage-controlled oscillator outputs AC signals of different frequencies. The frequency of the output AC signal is linearly related to the magnitude of the input control voltage. Therefore, the change in the resistance of the photoresistor device caused by the light intensity will cause the frequency of the AC signal output by the linear voltage-controlled oscillator to change.

[0033] (3) The voltage comparator compares the AC signal output by the linear voltage-controlled oscillator with the threshold voltage and outputs a square wave pulse signal related to the frequency of the AC signal. When the voltage of the AC signal is lower than the threshold voltage, the voltage comparator outputs a low level. When the voltage of the AC signal is higher than the threshold voltage, the voltage comparator outputs a high level. In this way, the square wave signal output by the voltage comparator simulates a pulse signal reflecting the radioactivity of different strata.

[0034] (4) The counter counts the square wave pulse signal output by the voltage comparator in unit time and transmits the result to the single chip microcomputer, which is further uploaded to the host computer for processing and display, completing the simulation measurement of the natural gamma logging principle demonstration.

[0035] Preferably, in step (2), the resistance value of the first adjustable resistor connected in series with the photoresistor device is adjusted, thereby adjusting the voltage variation range across the photoresistor device;

[0036] In step (3), the resistance of the second adjustable resistor is adjusted, thereby adjusting the magnitude of the threshold voltage.

[0037] Preferably, the simulation method further comprises the following steps:

[0038] (5) Cover the photoresistor device with a light shield. The resistance value of the photoresistor device is only affected by the light intensity shining through the hollow window on the light shield;

[0039] (6) The second stepper motor is controlled by the single chip microcomputer to rotate at a constant speed. The second stepper motor drives the turntable to rotate through the power gear, thereby causing the cylinder to rotate synchronously;

[0040] When the hollow window on the light shield is aligned with the strip-shaped transparent window on the cylinder, the intensity of light shining on the photoresistor device through the hollow window on the light shield is strong. When the hollow window on the light shield is not aligned with the strip-shaped transparent window on the cylinder, the intensity of light shining on the photoresistor device is weak. As the strip-shaped transparent window gradually moves away from the hollow window, the intensity of light shining on the photoresistor device gradually weakens. Therefore, at the same simulated depth, the resistance value of the photoresistor device can reflect the difference in light intensity in different azimuths, and is reflected in the difference in the number of square wave pulses per unit time counted by the counter during the rotation of the cylinder, thereby realizing the measurement simulation of azimuthal gamma logging.

[0041] Preferably, the simulation method further comprises a simulation scale demonstration step:

[0042] First, without a light shield, suspend the photoresistor device in the most light-transmitting simulated stratum in the simulated stratum model represented by the cylinder. Record the number of square wave pulses per unit time output by the counter at this moment as Nmax.

[0043] Then, the photoconductive resistor device is suspended in the simulated formation with the worst light transmittance in the simulated formation model represented by the cylinder, and the number of square wave pulses output by the counter per unit time at this moment is recorded as Nmin;

[0044] The count rate N in the simulation measurement process is scaled as a value GRa in simulated API units in the manner of scaling of the scale of the industrial instrument; the scaling relationship is: GRa=(N-Nmin) / (Nmax-Nmin) * 200 API.

[0045] The beneficial technical effects of the present application are as follows:

[0046] (1) The present application replaces the gamma ray detector with a photoconductive resistor device, uses a cylinder with different light transmittances at different heights to simulate a formation model, and combines a linear voltage-controlled oscillator and a voltage comparator, so that different light intensities can be converted into electrical pulse signals with different frequencies, and the square wave pulses output by the voltage comparator per unit time are counted by a counter to realize gamma logging simulation. The present application simplifies the structure and scale of the measurement device and the simulated formation in the demonstration process to the greatest extent on the basis of simulating the measurement principle of the industrial instrument, and enhances the convenience and intuitiveness of the related demonstration operation.

[0047] (2) The present application has rich simulation demonstration functions and is convenient to operate. Natural gamma logging and azimuthal gamma logging modes can be easily switched by loading or removing the shielding cover and starting or disabling part of the components. The principle of two logging methods can be demonstrated by one set of simulation device.

[0048] (3) The present application reduces the safety protection risk in the demonstration process. The device is small in scale and light in quality, and does not involve radioactive components, so compared with the demonstration in the actual well site using the industrial instrument, the risk of mechanical injury and nuclear radiation injury to the participants in the demonstration process is greatly reduced.

[0049] (4) The present application can also perform simulation calibration demonstration; compared with the real industrial instrument demonstration, it has the advantages of convenient operation, strong demonstration and safety and environmental protection. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 The structural principle diagram of the gamma logging instrument principle demonstration simulation device of the present application is shown in the figure;

[0051] Figure 2 The structural schematic diagram of the light shield in the gamma logging instrument principle demonstration simulation device of the present application is shown in the figure.

[0052] In the figure: 1-cylinder, 2-photoresistor device, 3-pulling rope, 4-fixed pulley, 5-reel, 6-first stepper motor, 7-single-chip microcomputer, 8-wire, 9-linear voltage-controlled oscillator, 10-first adjustable resistor, 11-voltage comparator, 12-second adjustable resistor, 13-counter, 14-host computer, 15-strip transparent window, 16-turntable, 17-power gear, 18-second stepper motor, 19-light shield, 20-hollow window; 101-upper area, 102-middle area, 103-lower area. DETAILED DESCRIPTION

[0053] Aside from using industrial logging instruments, there is currently no experimental device that can obtain continuous logging curves and fully demonstrate the principles, response characteristics, and influencing factors of natural gamma logging and azimuthal gamma logging. Directly using industrial logging instruments or small-scale scaled-down devices has limitations: (1) large scale and lack of flexibility; (2) difficulty in demonstrating instrument calibration; and (3) limited by nuclear radiation safety protection requirements, it is impossible to simulate the response of highly radioactive formations.

[0054] Therefore, a small-scale, safe and convenient demonstration simulation device can demonstrate the principle response characteristics and influencing factors of natural gamma logging and azimuthal gamma logging, which can significantly improve the capacity building of new practitioners and support services for scientific research activities.

[0055] Based on this, the present invention proposes a gamma logging tool principle demonstration simulation device and method. Figure 1 As shown, a gamma logging instrument principle demonstration simulation device includes a cylinder 1 for simulating a formation model. The cylinder 1 is arranged vertically and has different light transmittances at different heights of the cylinder 1. The cylinder 1 can be made of acrylic cylinders with different light transmittances connected up and down. Of course, the cylinder 1 can also be made of a transparent acrylic cylinder, and by applying paint of different colors and thicknesses on the transparent acrylic cylinder, the light transmittance of different positions of the cylinder can be changed. Specifically, as Figure 1 As shown, the cylinder 1 is divided into an upper region 101 , a middle region 102 and a lower region 103 , and the upper region 101 , the middle region 102 and the lower region 103 have different light transmittances.

[0056] Inside the cylinder 1, a photoresistor 2 is installed to replace the gamma-ray detector. The photoresistor 2 is connected to a drive mechanism for its vertical movement. The drive mechanism includes a pull rope 3, a fixed pulley 4, a drum 5, and a first stepper motor 6. The fixed pulley 4 is located at the top end of the cylinder 1. One end of the pull rope 3 is connected to the photoresistor 2. The other end of the pull rope 3 passes around the fixed pulley 4 and is wound around the drum 5. The drum 5 is connected to the first stepper motor 6 for rotational drive. The first stepper motor 6 is connected to a single-chip microcontroller 7.

[0057] The photoresistor device 2 is also connected to a linear voltage-controlled oscillator 9 via a wire 8. This wire 8 is also connected to a first adjustable resistor 10 for adjusting the voltage variation range across the photoresistor device. The first adjustable resistor 10 is connected in series with the photoresistor device 2. The linear voltage-controlled oscillator 9 is connected to a voltage comparator 11, which is further connected to a second adjustable resistor 12 for adjusting the threshold voltage. The voltage comparator 11 is connected to a counter 13, which is connected to a single-chip microcomputer 7. The single-chip microcomputer 7 is connected to a host computer 14.

[0058] The primary function of a natural gamma logging instrument is to convert gamma rays of varying intensities into electrical pulse signals of varying frequencies. Ultimately, the intensity of the natural gamma rays generated by the formation is measured by measuring the number of electrical pulse signals per unit time. This demonstration simulation device uses a photoresistor as a replacement for a gamma-ray detector. Using the photoresistor in conjunction with a voltage-controlled oscillator and a voltage comparator, the device converts varying light intensities into electrical pulse signals of varying frequencies, simulating the electrical pulse signals generated by a natural gamma detector. In this method, the response of the gamma-ray probe to gamma rays is simulated by the photoresistor's response to light intensity, thereby simulating natural gamma logging.

[0059] Since the gamma-ray detectors have been replaced with photoresistors, the instrument's stimulus information has shifted from gamma rays to light signals of varying intensities. Therefore, acrylic cylinders with varying light transmittances can be used as simulated formation models. For example, different colors and thicknesses of paint can be applied to a transparent acrylic tube to alter the light transmittance of the simulated formation model, thereby simulating formations of varying "radioactivity."

[0060] The present invention also provides a method for demonstrating the principle of a gamma logging tool, which uses the above-mentioned device and includes the following steps:

[0061] (1) The single chip microcomputer 7 controls the speed and direction of the first stepper motor 6, drives the reel 5 to wind or release the pulling rope 3, and then the pulling rope 3 pulls the photoresistor device 2 through the fixed pulley 4 to achieve lifting and lowering in the cylinder 1, thereby obtaining the photoresistor device 2 as a simulated gamma ray probe to measure simulated strata at different depths.

[0062] (2) When the photoresistor device 2 is placed at different positions in the cylinder 1, its corresponding resistance value changes with the light intensity at the position where it is located, which in turn causes the control voltage of the linear voltage-controlled oscillator 9 to change. The resistance value of the first adjustable resistor connected in series with the photoresistor device 2 is adjusted, thereby adjusting the voltage variation range across the photoresistor device.

[0063] The linear voltage-controlled oscillator 9 outputs AC signals of varying frequencies, with the frequency of the output AC signal being linearly related to the magnitude of the input control voltage. Therefore, changes in the resistance of the photoresistor 2 caused by light intensity will cause changes in the frequency of the AC signal output by the linear voltage-controlled oscillator 9.

[0064] (3) The voltage comparator 11 compares the AC signal output by the linear voltage-controlled oscillator with a fixed-level DC voltage (threshold voltage) and outputs a square wave pulse signal related to the frequency of the AC signal. When the voltage of the AC signal is lower than the threshold voltage, the voltage comparator 11 outputs a low level, and when the voltage of the AC signal is higher than the threshold voltage, the voltage comparator outputs a high level. Therefore, a sinusoidal signal of one cycle can output a square wave signal. The resistance value of the second adjustable resistor 12 is adjusted to adjust the threshold voltage. The more AC signals the linear voltage-controlled oscillator 9 outputs, the more square wave pulses the voltage comparator 11 outputs per unit time. In this way, the square wave signal output by the voltage comparator 11 simulates a pulse signal reflecting the radioactivity of different strata. That is, the higher the transmittance of the simulated stratum, the stronger the radioactivity of the stratum, and the more pulses the voltage comparator 11 outputs per unit time.

[0065] (4) The counter 13 counts the square wave pulse signals output by the voltage comparator 11 per unit time, and transmits the result to the single chip microcomputer 7, which is further uploaded to the host computer 14 for processing and display, thus completing the simulation measurement for demonstrating the principle of natural gamma ray logging.

[0066] In the above principle demonstration simulation method, the host computer provides a human-computer interaction interface, uses the communication bus to send measurement commands to the microcontroller, receives the measurement data uploaded by the microcontroller and displays it to the user in a visual form.

[0067] As a further design of the present invention, a strip-shaped transparent window 15 is also provided on the cylinder 1. The strip-shaped transparent window 15 is arranged along the length of the cylinder and has high light transmittance, thereby causing the simulated well to have different light intensities in specific directions. The bottom end of the cylinder 1 is fixed to a turntable 16. A transmission tooth is provided on the outer edge of the turntable 16. The transmission tooth is engaged with a power gear 17 arranged adjacent to the turntable. The power gear 17 is connected to a second stepper motor 18 for transmission. The second stepper motor 18 is connected to the single-chip microcomputer 7. The photoresistor device is also equipped with a light shield 19. When needed, the photoresistor device is placed in the light shield 19. A hollow window 20 is also provided on one side of the light shield 19. Of course, a number of threading holes are also provided on the light shield 19 to facilitate the wire 8 and the pull rope 3 to pass through the light shield and connect to the photoresistor device 2 inside the light shield.

[0068] The above configuration enables the demonstration simulation device to also perform azimuthal gamma logging demonstration simulations. Specifically, in this simulation measurement mode, while the natural gamma logging simulation measurement mode operates normally, the geared turntable 16, power gear 17, second stepper motor 18, and light shield 19 are activated. Light shield 19 covers the photoresistor 2, and the resistance of the photoresistor 2 is affected only by the intensity of light entering through the hollow window 20 in the light shield.

[0069] The single chip microcomputer 7 controls the second stepping motor 18 to rotate at a constant speed. The second stepping motor 18 drives the turntable 16 to rotate through the power gear 17, thereby causing the cylinder 1 to rotate.

[0070] When the hollow window 20 on the light shield 19 is aligned with a highly transparent strip-shaped window 15 on the cylinder 1, the intensity of light shining through the hollow window 20 on the light shield 19 onto the photoresistor 2 is high. When the hollow window on the light shield 19 and the strip-shaped window are not aligned, the intensity of light shining onto the photoresistor 2 is low. Furthermore, as the strip-shaped window 15 gradually moves away from the hollow window 20, the intensity of light shining onto the photoresistor 2 gradually decreases. Therefore, at the same simulated depth, the resistance value of the photoresistor 2 can reflect the difference in light intensity at different azimuths, and is reflected in the difference in the number of square wave pulses counted per unit time by the counter during the simulated formation rotation, thereby achieving measurement simulation of azimuthal gamma logging.

[0071] Here, the simulated stratum is rotated while the simulated gamma ray probe represented by the photoresistor device 2 and the light shield 19 remains unchanged for the convenience of the measurement system. This does not change the relative motion relationship between the two.

[0072] The gamma logging tool principle demonstration simulation method of the present invention further includes a simulation scale demonstration step, which is specifically as follows:

[0073] First, the photoresistor device 2 (without the light shield 19) is suspended in the simulated stratum with the highest light transmittance in the simulated stratum model represented by the cylinder 1, and the number of square wave pulses per unit time output by the counter at this moment is recorded as Nmax.

[0074] Then, the photoresistor device 2 (without the light shield 19) is suspended in the simulated stratum with the worst light transmittance in the simulated stratum model represented by the cylinder 1, and the number of square wave pulses per unit time output by the counter at this moment is recorded as Nmin.

[0075] Following the scale of industrial instruments, the count rate N during the simulated measurement process is scaled to a value GRa in simulated API units. The scale relationship is: GRa = (N - Nmin) / (Nmax - Nmin) × 200API.

[0076] The principle of the voltage comparator adopted in the present invention is supplemented below.

[0077] (1) The linear voltage-controlled oscillator outputs a sinusoidal AC voltage, the frequency of which depends on the voltage divided by the first adjustable resistor to the voltage-controlled oscillator, further depends on the resistance value of the photoresistor device, and further depends on the light intensity of the environment in which the photoresistor device is located.

[0078] (2) The voltage comparator compares the magnitudes of two input voltages: the sinusoidal AC voltage output by the voltage-controlled oscillator and the DC threshold voltage. The magnitude of the DC threshold voltage can be controlled by adjusting the resistance of the second adjustable resistor.

[0079] (3) When the sinusoidal AC voltage output by the voltage-controlled oscillator is greater than the DC threshold voltage, the output of the voltage comparator is high, otherwise the output is low.

[0080] (4) The sinusoidal alternating current is converted into voltage pulses through a voltage comparator. The higher the frequency of the sinusoidal alternating current, the more voltage pulses there are per unit time.

[0081] In summary, this invention simplifies the structure and scale of the measurement device and simulated formation during demonstrations while maximally simulating the measurement principles of industrial instruments, enhancing the convenience and intuitiveness of the demonstration operations. The simulation demonstrations presented in this invention offer rich functionality and convenient operation, enabling easy switching between natural gamma logging and azimuthal gamma logging modes. The device is also compact and lightweight, and lacks radioactive components, reducing safety risks during demonstrations.

Claims

1. A gamma logging tool principle demonstration simulation device, characterized by: The invention comprises a cylinder for simulating a stratum model; the cylinder is arranged vertically, and has different light transmittance at different heights of the cylinder; A photoresistor device is provided inside the cylinder to replace the gamma ray detector; the photoresistor device is connected to a driving device for driving the photoresistor device to move up and down; The photoresistor device is also connected to a linear voltage-controlled oscillator through a wire, the linear voltage-controlled oscillator is connected to a voltage comparator, the voltage comparator is connected to a counter, and the counter is connected to a single-chip microcomputer.

2. A gamma logging tool principle demonstration simulation device according to claim 1, characterized in that: The wire is also connected to a first adjustable resistor for adjusting the voltage variation range across the photoresistor device; The voltage comparator is further connected to a second adjustable resistor for adjusting the threshold voltage.

3. A gamma logging tool principle demonstration simulation device according to claim 1 or 2, characterized in that: The cylinder is formed by connecting acrylic cylinders with different light transmittances; or the cylinder is a transparent acrylic cylinder, and paints of different colors and thicknesses are applied on the transparent acrylic cylinder to change the light transmittance of different positions of the cylinder.

4. A gamma logging tool principle demonstration simulation device according to claim 1, characterized in that: The driving device includes a pulling rope, a fixed pulley, a reel and a first stepper motor. The fixed pulley is arranged at one end of the top of the cylinder. One end of the pulling rope is connected to the photoresistor device. The other end of the pulling rope passes around the fixed pulley and is wound around the reel. The reel is connected to the first stepper motor for driving its rotation, and the first stepper motor is connected to the single-chip microcomputer.

5. The gamma logging tool principle demonstration simulation device according to claim 1, characterized in that: A strip-shaped transparent window is provided on the cylinder and is arranged along the length direction of the cylinder; The bottom end of the cylinder is fixed on the turntable, and a transmission tooth is provided on the outer edge of the turntable. The transmission tooth is engaged with a power gear arranged adjacent to the turntable. The power gear is connected to the second stepper motor, and the second stepper motor is connected to the single chip microcomputer. The photoresistor device is also equipped with a light shield, and the photoresistor device is placed in the light shield when needed. A hollow window is also provided on one side of the light shield.

6. A gamma logging tool principle demonstration simulation device according to claim 1, characterized in that: The single chip microcomputer is connected to a host computer.

7. A method for demonstrating the principle of a gamma logging tool, using the device according to any one of claims 1 to 6, characterized in that The following steps are involved: (1) The single chip microcomputer controls the speed and direction of the first stepper motor, drives the reel to wind or release the pull rope, and then the pull rope pulls the photoresistor device through the fixed pulley to achieve the lifting and lowering of the photoresistor device in the cylinder, thereby obtaining the photoresistor device as a simulated gamma ray probe to measure the simulated strata at different depths; (2) When the photoresistor device is placed at different positions in the cylinder, its corresponding resistance value changes with the light intensity at its position, which in turn causes the control voltage of the linear voltage-controlled oscillator to change; The linear voltage-controlled oscillator outputs AC signals of different frequencies. The frequency of the output AC signal is linearly related to the magnitude of the input control voltage. Therefore, the change in the resistance of the photoresistor device caused by the light intensity will cause the frequency of the AC signal output by the linear voltage-controlled oscillator to change. (3) The voltage comparator compares the AC signal output by the linear voltage-controlled oscillator with the threshold voltage and outputs a square wave pulse signal related to the frequency of the AC signal. When the voltage of the AC signal is lower than the threshold voltage, the voltage comparator outputs a low level. When the voltage of the AC signal is higher than the threshold voltage, the voltage comparator outputs a high level. In this way, the square wave signal output by the voltage comparator simulates a pulse signal reflecting the radioactivity of different strata. (4) The counter counts the square wave pulse signal output by the voltage comparator per unit time and transmits the result to the single chip microcomputer, which is further uploaded to the host computer for processing and display, completing the simulation measurement of the natural gamma logging principle demonstration.

8. A gamma logging tool principle demonstration simulation method according to claim 7, characterized in that: In step (2), the resistance value of the first adjustable resistor connected in series with the photoresistor device is adjusted, thereby adjusting the voltage variation range across the photoresistor device; in step (3), the resistance value of the second adjustable resistor is adjusted, thereby adjusting the magnitude of the threshold voltage.

9. A gamma logging tool principle demonstration simulation method according to claim 7, characterized in that The following steps are also included: (5) Cover the photoresistor device with a light shield. The resistance value of the photoresistor device is only affected by the light intensity shining through the hollow window on the light shield; (6) The second stepper motor is controlled by the single chip microcomputer to rotate at a constant speed. The second stepper motor drives the turntable to rotate through the power gear, thereby causing the cylinder to rotate synchronously; When the hollow window on the light shield is aligned with the strip-shaped transparent window on the cylinder, the intensity of light shining on the photoresistor device through the hollow window on the light shield is strong. When the hollow window on the light shield is not aligned with the strip-shaped transparent window on the cylinder, the intensity of light shining on the photoresistor device is weak. As the strip-shaped transparent window gradually moves away from the hollow window, the intensity of light shining on the photoresistor device gradually weakens. Therefore, at the same simulated depth, the resistance value of the photoresistor device can reflect the difference in light intensity in different azimuths, and is reflected in the difference in the number of square wave pulses per unit time counted by the counter during the rotation of the cylinder, thereby realizing the measurement simulation of azimuthal gamma logging.

10. A gamma logging tool principle demonstration simulation method according to claim 7, characterized in that: Also included are the steps for demonstrating analog scales: First, without a light shield, suspend the photoresistor device in the most light-transmitting simulated stratum in the simulated stratum model represented by the cylinder. Record the number of square wave pulses per unit time output by the counter at this moment as Nmax. Then, suspend the photoresistor device in the simulated stratum with the worst light transmittance in the simulated stratum model represented by the cylinder, and record the number of square wave pulses per unit time output by the counter at this moment as Nmin; Following the scale method of industrial instruments, the count rate N in the simulated measurement process is scaled to the value GRa in simulated API units; the scale relationship is: GRa = (N-Nmin) / (Nmax-Nmin)×200API.

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