Gamma logging instrument principle demonstration simulation device and method

Abstract

The invention discloses a gamma logging instrument principle demonstration simulation device and method, and belongs to the field of logging principle demonstration. The apparatus includes a cylinder for simulating a formation model; the cylinder is vertically arranged, and different light transmission properties are achieved at different heights of the cylinder; a photoresistor device is arranged in the cylinder and is used for flatly replacing the gamma ray detector; the photoresistor device is connected with a driving device for driving the photoresistor device to move up and down; the photoresistor device is further connected with the linear voltage-controlled oscillator through a wire, the linear voltage-controlled oscillator is connected with the voltage comparator, the voltage comparator is connected with the counter, and the counter is connected with the single-chip microcomputer. Different illumination intensities can be converted into electric pulse signals with different frequencies, square wave pulses output by the voltage comparator in unit time are counted through the counter, and gamma logging simulation is achieved. The structure and the scale of the measuring device and the simulated stratum in the demonstration process are simplified, and the convenience and the intuition of related demonstration operation are enhanced.

Description

Technical Field

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

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

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

[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 the decay process. The content of radioactive elements in the formation is different, and the intensity of the emitted gamma rays is also different. By measuring the intensity of gamma rays emitted by the formation around the wellbore, the content of radioactive elements in the formation can be inferred, and then the lithology, mud content and other information of the formation can be understood. For example, the content of radioactive elements in mudstone formations is relatively high, and the intensity of natural gamma rays is large; while the content of radioactive elements in pure sandstone formations is low, the intensity of natural gamma rays is small.

[0005] The natural gamma logging instrument includes a detector part and a signal processing part. Common natural gamma logging detectors include scintillation counters and semiconductor detectors. The scintillation counter is mainly composed of scintillation crystals and photomultiplier tubes. When gamma rays enter the scintillation crystal, the atoms in the crystal are excited and then de-excited to emit photons. The photons enter the photomultiplier tube and form an electrical pulse signal after multiple amplification. The detector is placed in the probe part of the logging instrument and moves along the wellbore. When the detector receives the gamma rays emitted by the formation, a corresponding electrical signal is generated. The amplitude and frequency of this electrical signal are related to the energy and intensity of the gamma rays. The electrical signal generated by the detector is usually very weak and needs to be amplified by an amplifier circuit. The amplified signal may have problems such as irregular waveforms, and it needs to be processed into a regular pulse signal by a shaping circuit for subsequent counting and analysis. The processed pulse signal is sent to the counter. The counter records the number of pulses per unit time, and this pulse count represents the intensity of the gamma ray. At the same time, the instrument also records the logging depth information, so that a logging curve of the natural gamma ray intensity changing with depth can be obtained. Well logging curves can intuitively show the changes in the content of radioactive elements in the strata 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 unit of the natural gamma logging output curve is API (American Petroleum Institute). API unit is a relative measurement unit, which is obtained by comparing the instrument reading in a standard calibration well with a formation with known radioactivity. There is a formation model with known radioactivity content in the calibration well. The instrument reading in a low-radioactive formation model is defined as 0API, and the reading in a high-radioactive formation model is defined as 200API.

[0008] Compared with ordinary natural gamma logging tools, azimuth gamma logging tools have an additional azimuth measurement function, which can measure the difference in formation radioactivity in different directions around the wellbore. The simple principle is to cover the gamma detector with a shield with a window in a fixed direction, which only allows gamma rays in a specific direction to enter the detector and convert them into voltage pulses. The window shield rotates in the well to achieve 360° azimuth scanning measurement of formation radioactivity.

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

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

[0011] The length of industrial natural gamma logging instruments is more than 3 meters. If you want to demonstrate a continuous natural gamma logging curve that reflects the natural radioactivity of formations of different properties, you need a huge simulated formation model (preliminary estimates show that the thickness of the simulated formation should reach more than 10 meters), or place the instrument in a real downhole environment. This demonstration method requires large-scale equipment, high cost, and poor flexibility. Especially when scientific research activities need to explore the impact of different geological environments on instrument response, the formation model needs to be replaced, and the engineering difficulty involved is very large. For azimuthal gamma logging instruments, the difficulty and scale of making formation models with different radioactivity in different azimuths are even greater.

[0012] Secondly, it is difficult to demonstrate the calibration process of the instrument when using industrial logging instruments for training demonstrations.

[0013] As mentioned above, the natural gamma logging tool uses relative measurement units and needs to be calibrated in high-radioactivity and low-radioactivity formation models. This requires that the calibration demonstration must be carried out on-site at the calibration well, which causes inconvenience to the training of new practitioners.

[0014] Finally, the safety risks involved in training demonstrations using industrial logging tools are high.

[0015] Training demonstrations using industrial natural gamma logging instruments need to be carried out at the well site, which poses a high safety risk. On the other hand, even if a small-scale logging instrument is developed, formation models with different radioactivity levels need to be made, and high-radioactivity formation models involve nuclear radiation safety protection issues. Summary of the invention

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

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

[0018] A gamma logging instrument principle demonstration simulation 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;

[0019] A photoresistor device is arranged 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;

[0020] 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.

[0021] Preferably, the wire is also connected to a first adjustable resistor for adjusting the voltage variation range across the photoresistor device;

[0022] The voltage comparator is also 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 formed by a transparent acrylic cylinder, on which paints of different colors and thicknesses are applied to change the light transmittance of different positions of the cylinder.

[0024] Preferably, the driving device includes a lifting 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 lifting rope is connected to the photoresistor device, the other end of the lifting 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 arranged on the outer edge of the turntable, the transmission tooth is meshed with a power gear arranged adjacent to the turntable, the power gear is connected to the second stepping motor, and the second stepping 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 arranged 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 gamma logging tool principle demonstration simulation method, using the above-mentioned device, comprising the following steps:

[0030] (1) The single chip microcomputer controls the speed and direction of the first stepper motor to drive the drum to wind or release the lifting rope, and then the lifting rope pulls the photoresistor device through the fixed pulley to achieve lifting and lowering in the cylinder, thereby obtaining the photoresistor device as a simulated gamma ray probe to measure 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, and 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, and 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 per unit time and transmits the result to the single chip microcomputer, which is further uploaded to the host computer for processing and display, thus completing the simulation measurement to demonstrate the principle of natural gamma logging.

[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 value 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, and the resistance value of the photoresistor device is only affected by the light intensity shining in from 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, and 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 transparent window on the cylinder, the intensity of light irradiated onto the photoresistor device through the hollow window on the light shield is strong, while when the hollow window on the light shield is not aligned with the strip transparent window on the cylinder, the intensity of light irradiated onto the photoresistor device is weak, and as the strip transparent window gradually moves away from the hollow window, the intensity of light irradiated onto 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 simulated stratum with the strongest 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 as Nmax;

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

[0044] Following the calibration method of industrial instruments, the count rate N in the simulated measurement process is calibrated to the value GRa in the simulated API unit; the calibration relationship is: GRa = (N-Nmin) / (Nmax-Nmin)×200API.

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

[0046] (1) The present invention uses a photoresistor device to replace the gamma-ray detector, uses cylinders with different light transmittances at different heights to simulate the formation model, and then combines a linear voltage-controlled oscillator and a voltage comparator to convert different light intensities into electrical pulse signals of different frequencies. The square wave pulses output by the voltage comparator per unit time are counted by a counter to achieve gamma logging simulation. The present invention simplifies the structure and scale of the measuring device and the simulated formation in the demonstration process on the basis of simulating the measurement principle of industrial instruments to the greatest extent, and enhances the convenience and intuitiveness of the relevant demonstration operations.

[0047] (2) The simulation demonstration of the present invention is rich in functions and easy to operate. The natural gamma logging and azimuthal gamma logging modes can be easily switched by simply loading or removing the shielding cover and starting or disabling some components. The demonstration of the principles of the two logging methods can be realized through a set of simulation devices.

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

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

[0050] Figure 1 This is a structural principle block diagram of a simulation device for demonstrating the principle of a gamma-ray logging tool according to the present invention;

[0051] Figure 2 The present invention is a schematic diagram of the structure of the light shield in the gamma logging instrument principle demonstration simulation device.

[0052] In the figure: 1-cylinder, 2-photoresistor device, 3-lifting rope, 4-fixed pulley, 5-reel, 6-first stepper motor, 7-single chip microcomputer, 8-conductor, 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] Except for the use of 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 instruments and azimuthal gamma logging instruments. Direct use of industrial logging instruments or small-scale scaled-down devices has limitations: (1) large scale and insufficient flexibility; (2) difficulty in demonstrating instrument calibration; (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 a transparent acrylic cylinder, and the light transmittance of different positions of the cylinder can be changed by applying paints of different colors and thicknesses on the transparent acrylic cylinder. 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] A photoresistor device 2 is arranged inside the cylinder 1 to replace the gamma-ray detector. The photoresistor device 2 is connected to a driving device for driving it to move up and down. The driving device includes a pull rope 3, a fixed pulley 4, a reel 5 and a first stepper motor 6. The fixed pulley 4 is arranged at one end of the top of the cylinder 1. One end of the pull rope 3 is connected to the photoresistor device 2. The other end of the pull rope 3 passes around the fixed pulley 4 and is wound around the reel 5. The reel 5 is connected to the first stepper motor 6 for driving it to rotate. The first stepper motor 6 is connected to a single-chip microcomputer 7.

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

[0058] The main function of the gamma ray of the natural gamma logging instrument is to convert gamma rays of different intensities into electrical pulse signals of different frequencies, and finally characterize the intensity of the natural gamma rays generated by the formation by measuring the number of electrical pulse signals per unit time. The demonstration simulation device of the present invention uses a photoresistor device to replace the gamma ray detector, and converts different light intensities into electrical pulse signals of different frequencies through a photoresistor combined with a voltage-controlled oscillator and a voltage comparator to simulate the electrical pulse signals generated by the natural gamma detector. In the present invention, the response of the gamma ray probe to gamma rays is simulated by the response of the photoresistor to light intensity, thereby realizing the simulation of natural gamma logging.

[0059] Since the gamma-ray detector has been replaced by a photoresistor device, the instrument excitation information has changed from gamma rays to light signals of different intensities. Therefore, acrylic cylinders with different 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 change the light transmittance of the simulated formation model, thereby simulating formations with different "radioactivity".

[0060] The present invention also provides a gamma logging tool principle demonstration simulation method, using the above-mentioned device, comprising the following steps:

[0061] (1) The single chip microcomputer 7 controls the speed and direction of the first stepper motor 6, driving the reel 5 to wind or release the lifting rope 3, and then the lifting 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, thereby causing 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 of both ends of the photoresistor device.

[0063] The linear voltage controlled oscillator 9 outputs AC signals of different frequencies, and the frequency of the output AC signal is linearly related to the magnitude of the input control voltage. Therefore, the change in resistance of the photoresistor device 2 caused by the light intensity will cause the frequency of the AC signal output by the linear voltage controlled oscillator 9 to change.

[0064] (3) The voltage comparator 11 compares the AC signal output by the linear voltage-controlled oscillator with a fixed level of 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 signal output by the voltage comparator 11 per unit time, and transmits the result to the single chip microcomputer 7, which is further transmitted to the host computer 14 for processing and display, thus completing the simulation measurement for demonstrating the principle of natural gamma 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 single-chip microcomputer, receives the measurement data uploaded by the single-chip microcomputer and displays it to the user in a visual form.

[0067] As a further design of the present invention, a strip transparent window 15 is also provided on the cylinder 1. The strip transparent window 15 is arranged along the length direction of the cylinder and has high light transmittance, thereby causing the illumination intensity of the simulated well to be different in a specific direction. The bottom end of the cylinder 1 is fixed on the turntable 16. A transmission tooth is provided on the outer edge of the turntable 16. The transmission tooth is meshed with a power gear 17 arranged adjacent to the turntable. The power gear 17 is connected to the second stepper motor 18 in a transmission manner. The second stepper motor 18 is connected to the single-chip computer 7. The photoresistor device is also equipped with a light shield 19. When necessary, 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 with the photoresistor device 2 inside the light shield.

[0068] Through the above settings, the demonstration simulation device can also perform azimuth gamma logging demonstration simulation. Specifically, in this simulation measurement mode, while the natural gamma logging simulation measurement mode is operating normally, the geared turntable 16, the power gear 17, the second stepping motor 18 and the light shield 19 are enabled. The light shield 19 covers the photoresistor device 2, and the resistance value of the photoresistor device 2 is only affected by the light intensity of the light shining in from the hollow window 20 on 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 transparent window 15 on the cylinder 1, the light intensity irradiated onto the photoresistor device 2 through the hollow window 20 on the light shield 19 is high, while when the hollow window on the light shield is not aligned with the strip-shaped transparent window, the light intensity irradiated onto the photoresistor device 2 is weak. Moreover, as the strip-shaped transparent window 15 gradually moves away from the hollow window 20, the light intensity irradiated onto the photoresistor device 2 gradually weakens. Therefore, at the same simulated depth, the resistance value of the photoresistor device 2 can reflect the difference in light intensity in different directions, and is reflected in the difference in the number of square wave pulses per unit time counted by the counter during the simulated formation rotation process, thereby realizing the 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 also includes a simulation scale demonstration step, which is as follows:

[0073] First, the photoresistor device 2 (without the light shield 19) is suspended in the simulated stratum with the strongest 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 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.

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

[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 value 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 a high level, otherwise the output is a low level.

[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 greater the number of voltage pulses per unit time.

[0081] In summary, the present invention simplifies the structure and scale of the measuring device and the simulated formation during the demonstration process on the basis of simulating the measurement principle of industrial instruments to the greatest extent, and enhances the convenience and intuitiveness of the relevant demonstration operations. The simulation demonstration of the present invention is rich in functions and easy to operate, and can easily switch between the natural gamma logging and azimuthal gamma logging modes. The device of the present invention is small in scale, light in weight, and does not involve radioactive components, which reduces the safety protection risk during the demonstration process.

Claims

1. A gamma logging tool principle demonstration simulation device, characterized in that: 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 arranged 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 of both ends of the photoresistor device; The voltage comparator is also 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 formed by connecting a transparent acrylic cylinder, and coatings 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 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.

5. A gamma logging tool principle demonstration simulation device according to claim 1, characterized in that: A strip-shaped transparent window is arranged on the cylinder, and the strip-shaped transparent window 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 arranged on the outer edge of the turntable, the transmission tooth is meshed with a power gear arranged adjacent to the turntable, the power gear is connected to the second stepping motor, and the second stepping 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 arranged 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 as claimed in 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 to drive the drum to wind or release the lifting rope, and then the lifting rope pulls the photoresistor device through the fixed pulley to achieve lifting and lowering in the cylinder, thereby obtaining the photoresistor device as a simulated gamma ray probe to measure 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, and 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, and 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, thus completing the simulation measurement to demonstrate the principle of natural gamma logging.

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, and the resistance value of the photoresistor device is only affected by the light intensity shining in from 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, and 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 transparent window on the cylinder, the intensity of light irradiated onto the photoresistor device through the hollow window on the light shield is strong, while when the hollow window on the light shield is not aligned with the strip transparent window on the cylinder, the intensity of light irradiated onto the photoresistor device is weak, and as the strip transparent window gradually moves away from the hollow window, the intensity of light irradiated onto 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 analog scale demonstration: First, without a light shield, suspend the photoresistor device in the simulated stratum with the strongest 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 as Nmax; Then, the photoresistor device is suspended in the simulated stratum with the worst light transmittance in the simulated stratum model represented by the cylinder, and the number of square wave pulses per unit time output by the counter at this moment is recorded as Nmin; Following the calibration method of industrial instruments, the count rate N in the simulated measurement process is calibrated to the value GRa in the simulated API unit; the calibration relationship is: GRa = (N-Nmin) / (Nmax-Nmin)×200API.

Images