Downhole natural gamma-ray spectrum logging device and method

Abstract

The invention provides an underground natural gamma-ray spectrum logging device and method, and belongs to the technical field of oil-gas exploration, and the device comprises a perovskite-based energy spectrum detector which is used for directly absorbing gamma rays from a stratum underground and converting the energy of the gamma rays into electric pulse signals with corresponding amplitudes; the temperature monitoring module is connected with the perovskite-based energy spectrum detector and used for providing stable bias voltage for the perovskite-based energy spectrum detector and monitoring and controlling the working temperature of the perovskite-based energy spectrum detector; the signal amplification module is electrically connected with the perovskite-based energy spectrum detector and is used for amplifying the electric pulse signal; and the multi-channel energy spectrum analysis module is used for carrying out amplitude analysis on the shaped electric pulse signal, carrying out channel counting according to the amplitude according to an analysis result, and generating natural gamma-ray energy spectrum data. By adopting the method, the efficiency and the accuracy of obtaining the energy spectrum data in complex underground environments such as deep wells and high-temperature wells can be improved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration technology, specifically to a device and method for downhole natural gamma ray spectroscopy logging. Background Technology

[0002] In the fields of oil and gas exploration and radiological geological assessment, natural gamma ray spectroscopy logging is a key technology for identifying specific radionuclides in formations. By analyzing the energy distribution of incident gamma photons, natural gamma ray spectroscopy logging can identify characteristic peaks of elements such as potassium (characteristic peak 1.46 MeV), uranium series (characteristic peak 1.76 MeV), and thorium series (characteristic peak 2.62 MeV). This technology enables quantitative analysis of the content of different radioactive elements in formations, thereby accurately calculating clay content, finely classifying lithology, identifying sedimentary environments, and assessing oil generation potential, significantly improving the geological interpretation accuracy of logging data. Currently, downhole natural gamma ray spectroscopy logging commonly employs an indirect detection system of "scintillator + photomultiplier tube (PMT)". In this system, gamma rays are first absorbed by a scintillator (such as NaI(Tl) crystal) and converted into visible light. Subsequently, this visible light is received by a photomultiplier tube and converted into an electrical signal, which is then analyzed by a multichannel analyzer.

[0003] In the process of realizing this invention, the inventors discovered that existing methods have at least the following problems: First, due to the multi-stage conversion process of "gamma photons, visible light, photoelectrons, and photomultiplier electrons," statistical fluctuations and noise are introduced at each stage, resulting in a severe limitation on the overall energy resolution of the system. This causes the characteristic peaks of uranium, thorium, and potassium to be severely broadened and overlapped in the energy spectrum, making it difficult to achieve high-precision nuclide identification and quantitative inversion; Second, poor environmental adaptability, the light output of the scintillator will significantly decrease with increasing temperature, and the gain of the photomultiplier tube is also extremely sensitive to temperature and magnetic field, causing the performance of the entire system to drop sharply or even fail in downhole high-temperature environments exceeding 125°C, failing to meet the operational requirements of deep wells, ultra-deep wells, and geothermal wells; Third, low mechanical reliability. Glass-encapsulated PMTs and brittle scintillation crystals suffer from high damage rates under harsh conditions such as logging while drilling, which involve strong vibrations (>10g RMS) and high impacts (>50g), severely affecting the continuity and economy of logging operations. In addition, the system is bulky, has low integration, and high power consumption, and the core components (high-performance PMTs and energy-level scintillation crystals) have long been dependent on imports, resulting in high costs.

[0004] In summary, as oil and gas exploration extends to deeper and more complex formations, existing natural gamma spectral logging technologies based on scintillators and photomultiplier tubes face severe challenges in terms of energy resolution, high-temperature stability, mechanical reliability, and production and maintenance costs. There is an urgent need for a downhole natural gamma spectral logging technology that can operate at low cost and high efficiency under complex geological conditions. Summary of the Invention

[0005] In view of this, it is necessary to provide a device and method for downhole natural gamma spectral logging to solve the technical problems of low detection efficiency and high cost caused by poor environmental adaptability, poor mechanical stability, poor energy resolution, high power consumption, and low integration in existing methods under complex geological conditions.

[0006] To address the aforementioned technical problems, in a first aspect, the present invention provides an apparatus for downhole natural gamma ray spectroscopy logging, comprising: A perovskite-based energy spectrum detector is used to directly absorb gamma rays from the formation downhole and convert the gamma ray energy into an electrical pulse signal of corresponding amplitude. The perovskite-based energy spectrum detector uses a perovskite semiconductor material with an adjustable bandgap as the sensing element. A temperature monitoring module, connected to the perovskite-based energy dispersive detector, is used to provide it with a stable bias voltage and monitor and control its operating temperature. The signal amplification module is electrically connected to the perovskite-based energy spectrum detector and is used to amplify and shape the electrical pulse signal. The multichannel energy spectrum analysis module is electrically connected to the signal amplification module. It is used to perform amplitude analysis on the shaped electrical pulse signal and count the channels according to the amplitude based on the analysis results to generate natural gamma energy spectrum data.

[0007] In one possible implementation, the perovskite semiconductor material is selected from CsPbBr3, At least one of MAPbI3 and FAPbBr3, or other semiconductor materials and their derivatives having a perovskite crystal structure.

[0008] In one possible implementation, the perovskite semiconductor material is modified by doping, passivation, or compositional modulation to optimize carrier lifetime, bandgap width, environmental operability, and energy resolution.

[0009] In one possible implementation, the multichannel energy spectrum analysis module includes an analog-to-digital converter and a multichannel pulse amplitude analyzer. The analog-to-digital converter is used to convert pulse amplitudes into digital channel addresses, and the multichannel pulse amplitude analyzer is used to count and statistically analyze pulses with different digital channel addresses.

[0010] In one possible implementation, the temperature monitoring module includes a high-voltage power supply and a temperature sensor. The temperature sensor is used to monitor the temperature of the perovskite-based energy dispersive spectroscopy detector and adjust the output of the high-voltage power supply through feedback control, or activate heating and cooling devices, so that the temperature control range of the perovskite-based energy dispersive spectroscopy detector is -20°C to 300°C.

[0011] In one possible implementation, the perovskite-based energy spectrum detector is encapsulated within a metal shock-resistant and pressure-resistant housing.

[0012] In one possible implementation, the device further includes a data acquisition and transmission system connected to the multichannel energy spectrum analysis module, for receiving and transmitting the natural gamma energy spectrum data to a ground system.

[0013] On the other hand, the present invention also provides a method for downhole natural gamma ray spectral logging, which is applied to the aforementioned downhole natural gamma ray spectral logging apparatus, comprising: The temperature monitoring module provides bias voltage and regulates the operating temperature of the perovskite-based energy spectrum detector. The perovskite-based energy spectrum detector directly absorbs gamma rays from the strata and converts the gamma ray energy into electrical pulse signals of corresponding amplitude. The electrical pulse signal is amplified by the signal amplification module. Based on the multi-channel energy spectrum analysis module, amplitude analysis and channel counting are performed on the shaped electrical pulse signal to generate natural gamma energy spectrum data; The characteristic peaks corresponding to each radioactive element in the natural gamma energy spectrum data are identified and analyzed to obtain the analysis results. Each radioactive element includes at least one of potassium, uranium, and thorium. Based on the analysis results, qualitative and quantitative analysis of the radioactive elements in the strata was performed.

[0014] In one possible implementation, before application, an energy calibration is performed using a standard radiation source to ensure that the linear relationship between the amplitude of the electrical pulse signal and the energy of the gamma photons has an error of no more than 0.5%.

[0015] In one possible implementation, the identification and analysis of characteristic peaks corresponding to each radioactive element in the natural gamma-ray spectrum data to obtain analysis results includes: The characteristic peaks of each radioactive element are counted and identified by methods such as peak position fitting and background subtraction algorithms (usually a combination of one or more of these methods) to obtain the identification results. The peak area of ​​the characteristic peak corresponding to each radioactive element in the identification results is calculated, and the content of each element is quantitatively analyzed based on the calculation results to obtain the analysis results.

[0016] The beneficial effects of this invention are as follows: The downhole natural gamma spectral logging device provided by this invention consists of a signal processing chain formed by sequentially connecting a perovskite-based energy spectrum detector, a temperature monitoring module, a signal amplification module, and a multi-channel energy spectrum analysis module. This chain achieves linear conversion of gamma photon energy into electrical signals, and subsequent modules work together to stabilize, amplify, shape, and generate digital energy spectra. The direct energy conversion path and the controlled working environment (combined with measures such as thermos bottles) jointly ensure the ultra-high fidelity of the signal source. The modular solid-state architecture achieves comprehensive advantages such as strong shock resistance, compact structure, and controllable cost, significantly improving the efficiency and reliability of acquiring high-precision natural gamma spectral data under complex working conditions such as deep wells, ultra-deep wells, and logging while drilling. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of an embodiment of the downhole natural gamma ray spectroscopy logging device provided by the present invention; Figure 2 for Figure 1 A schematic diagram of an embodiment of a multichannel energy dispersive spectroscopy (EDS) module; Figure 3 for Figure 1 A schematic diagram of an embodiment of the medium temperature monitoring module; Figure 4 A schematic flowchart of another embodiment of the downhole natural gamma ray spectroscopy logging device provided by the present invention; Figure 5 A schematic flowchart of an embodiment of the downhole natural gamma ray spectroscopy logging method provided by the present invention; Figure 6 for Figure 5 A schematic diagram of an embodiment of step S505. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] In the description of the embodiments of the present invention, unless otherwise stated, "multiple" means two or more. "And / or" describes the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0021] The terms "first," "second," etc., used in the embodiments of this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a technical feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] Before demonstrating the embodiments, the following terms will be explained.

[0024] Perovskite is a type of functional material with an ABX3 crystal structure (A site is usually an organic cation or cesium ion, B site is a lead ion, and X site is a halide ion). It has excellent photoelectric properties and a tunable band gap.

[0025] A perovskite-based spectrometer is a radiation detector that uses perovskite semiconductor material as the sensing element. Its working principle is direct detection, which can linearly convert the energy of a single incident gamma photon into an electrical signal pulse, thereby providing high-fidelity raw data for subsequent spectrometer analysis.

[0026] The Sensitive Volume is the core functional region inside the detector that directly interacts with radiation and generates the initial signal. In this embodiment, it specifically refers to the part made of perovskite semiconductor material.

[0027] Direct detection is a radiation detection mechanism. High-energy photons (such as gamma rays) directly generate electron-hole pairs within a semiconductor sensor, which are then collected as electrical signals. Unlike indirect detection using a scintillator and photomultiplier tube, this mechanism theoretically offers higher energy resolution.

[0028] Electron-hole pairs occur when a semiconductor absorbs radiation energy, causing electrons to be excited from the valence band to the conduction band, while simultaneously leaving a positively charged hole in the valence band. These charge carriers, under the influence of an electric field, form a detectable electrical signal, the number of which is proportional to the energy of the incident photon.

[0029] The band gap is the energy difference between the top of the valence band and the bottom of the conduction band in a semiconductor. The band gap of perovskite materials can be flexibly tuned by changing the composition of A, B, and X-site ions, thereby optimizing their detection efficiency for different energy rays and their temperature resistance.

[0030] Natural Gamma Ray Spectrum Logging is a geophysical logging method that analyzes the energy distribution (spectrum) of natural gamma rays in the formation to identify specific radionuclides such as uranium, thorium, and potassium and calculate their content, for the purpose of fine-grained formation evaluation.

[0031] A characteristic peak, on a gamma-ray spectrum, is a peak in the count rate formed by gamma rays of characteristic energy emitted by a specific radionuclide (such as 1.46 MeV for potassium-40, 1.76 MeV for uranium series, and 2.62 MeV for thorium series). It is a marker for identifying the element.

[0032] Energy resolution is a key performance indicator characterizing a detector's ability to distinguish minute differences in the energy of incident particles. It is typically expressed as the percentage of the full width at half maximum (FWHM) of a specific energy peak to the peak energy. The lower the value, the higher the resolution.

[0033] The count rate (Counts Per Second, cps) is the number of electrical pulse signals recorded by the detector per unit time, corresponding to the intensity of the incident radiation.

[0034] Channel address, in multichannel pulse amplitude analysis, is the digital value output by the analog-to-digital converter (ADC). It corresponds to the amplitude (i.e., energy) of the input pulse and is the "number" or "index" of the energy spectrum data storage unit, with the horizontal axis as the reference.

[0035] The Multi-channel Spectrum Analysis Module (MCA) contains circuit units for analog-to-digital converters (ADCs) and multi-channel pulse amplitude analyzers (MCAs). It is used to classify and statistically analyze pulse signals of different amplitudes according to channel addresses, and finally form the energy spectrum distribution curve.

[0036] An analog-to-digital converter (ADC) is a circuit module that converts analog voltage signals into digital signals. In this scheme, it is used to accurately measure the peak voltage of each pulse and convert it into a digital address.

[0037] Bias voltage is a DC operating voltage applied between the two electrodes of the detector to create a strong electric field for collecting charges within the sensitive body.

[0038] A low-noise preamplifier is the first-stage amplifier circuit that follows the detector output. Its core task is to amplify the weak electrical pulses output by the detector while minimizing the noise it introduces. Charge-sensitive amplifiers are a commonly used type.

[0039] Pulse shaping filters and shapes the pulse signal output from the preamplifier (e.g., to form a Gaussian wave) to improve the signal-to-noise ratio and standardize its shape, making it easier for subsequent circuits to perform accurate amplitude analysis.

[0040] API Units are standardized units of measurement used in natural gamma logging. They were developed by the American Petroleum Institute to unify and compare measurement results from different instruments.

[0041] Logging While Drilling (LWD) is a logging technology performed simultaneously during the drilling process, which places extremely high demands on the high temperature resistance, shock resistance, and reliability of the instruments.

[0042] High-temperature stability refers to the ability of a detector to maintain its key performance without significant degradation when operating for extended periods in high-temperature downhole environments (such as >125℃ or even 200℃).

[0043] Shock / Vibration Resistance refers to the ability of a detector to resist strong vibrations and mechanical shocks (such as >10g RMS acceleration) generated by downhole drilling tools.

[0044] Dark current, the background current generated inside the detector due to thermal excitation and other reasons when there is no radiation exposure, is one of the main noise sources and affects detection sensitivity and energy resolution.

[0045] This invention provides an apparatus and method for downhole natural gamma ray spectral logging. The technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0046] Figure 1 This is a schematic diagram of an embodiment of the downhole natural gamma ray spectral logging device provided by the present invention. The device includes a perovskite-based energy spectrum detector 101, a temperature monitoring module 102, a signal amplification module 103, and a multichannel energy spectrum analysis module 104, as detailed below: The perovskite-based energy spectrum detector 101 is used to directly absorb gamma rays from the formation downhole and convert the gamma ray energy into an electrical pulse signal of corresponding amplitude. The perovskite-based energy spectrum detector 101 uses a perovskite semiconductor material with an adjustable bandgap as the sensing element. Temperature monitoring module 102 is connected to perovskite-based energy spectrum detector 101 to provide it with a stable bias voltage and to monitor and control its operating temperature. The signal amplification module 103 is electrically connected to the perovskite-based energy spectrum detector 101 and is used to amplify and shape the electrical pulse signal. The multichannel energy spectrum analysis module 104 is electrically connected to the signal amplification module 103. It is used to perform amplitude analysis on the shaped electrical pulse signal and count the channels according to the amplitude based on the analysis results to generate natural gamma energy spectrum data.

[0047] Specifically, the downhole natural gamma ray energy spectrum logging device provided in this embodiment works in concert through four sequentially connected modular units to realize the entire process from gamma ray sensing to energy spectrum data generation.

[0048] The perovskite-based energy spectrum detector 101 is a sensor made of perovskite semiconductor material (such as CsPbBr3 single crystal). When gamma rays from the strata are incident, the material utilizes its direct bandgap characteristic to directly convert the energy of a single gamma photon into a proportional electron-hole pair, thereby forming an initial electrical pulse signal under an applied electric field. This step eliminates the optical conversion step required in traditional technologies.

[0049] The temperature monitoring module 102 is connected to the perovskite-based energy dispersive spectroscopy detector 101. On one hand, it applies a stable DC high voltage of several hundred volts to form a strong electric field for collecting charges within the sensitive element. On the other hand, through temperature monitoring and feedback control (such as connecting a micro heater), it precisely regulates the temperature of the perovskite-based energy dispersive spectroscopy detector 101 within a predetermined range to ensure the stability of its physical and electrical properties. The preset range can be selected according to the actual application requirements. The signal amplification module 103 is used to process the weak nanovolt or microvolt level signal output from the perovskite-based energy spectrum detector 101. Preferably, the signal amplification module 103 includes a low-noise preamplifier (such as a charge-sensitive amplifier) ​​and subsequent pulse shaping circuitry to amplify the weak charge pulses into standard voltage pulses at the volt level and shape them into regular waveforms (such as Gaussian waveforms) to optimize the signal-to-noise ratio and facilitate subsequent accurate amplitude measurements.

[0050] The multichannel energy spectrum analysis module 104 performs digital and statistical analysis on the shaped pulses. It measures the peak voltage (corresponding to photon energy) of each pulse and classifies them into different channels according to their magnitude for counting and accumulation. Finally, it outputs a digital energy spectrum with energy as the horizontal axis and count rate as the vertical axis, which includes characteristic peak information of elements such as potassium, uranium, and thorium.

[0051] This embodiment employs a signal processing chain consisting of a perovskite-based energy spectrum detector, a temperature monitoring module, a signal amplification module, and a multichannel energy spectrum analysis module connected sequentially. The perovskite sensor directly achieves a linear conversion of gamma photon energy into an electrical signal, with subsequent modules collaboratively stabilizing, amplifying, shaping, and generating a digital energy spectrum. The direct energy conversion path and the controlled operating environment (high-voltage temperature control module) jointly ensure ultra-high fidelity at the signal source. Secondly, end-to-end optimization, from detector intrinsic characteristics and electrical conditions to each stage of signal processing, minimizes noise and interference, allowing for clear separation of uranium, thorium, and potassium characteristic peaks in the energy spectrum. Finally, the modular solid-state architecture fundamentally overcomes the performance degradation at high temperatures, mechanical fragility under vibration, and sensitivity to magnetic fields inherent in traditional scintillation optoelectronic systems, facilitating the acquisition of stable, reliable, and high-precision energy spectrum data in complex downhole environments such as deep wells and high-temperature wells.

[0052] In some embodiments of the present invention, the perovskite semiconductor material is selected from at least one of CsPbBr3, MAPbI3, and FAPbBr3, or is other semiconductor materials and their derivatives having a perovskite crystal structure.

[0053] Specifically, the all-inorganic CsPbBr3 crystal, with its excellent chemical and thermal stability, is suitable for downhole environments where long-term device reliability is extremely important. Meanwhile, MAPbI3 exhibits a high absorption coefficient over a wide spectral range, which helps improve the detection efficiency of low-energy gamma rays. Furthermore, other semiconductor materials and their derivatives with perovskite crystal structures provide space for new compounds formed through A-site substitution (e.g., partially replacing cesium ions with rubidium ions), B-site substitution, or X-site ion substitution. These materials maintain the ABX3-type perovskite lattice framework and its direct bandgap semiconductor characteristics, ensuring the effectiveness of the direct detection mechanism.

[0054] In some embodiments of the present invention, perovskite semiconductor materials are modified by doping, passivation, or compositional modulation to optimize carrier lifetime, bandgap width, environmental operability, and energy resolution.

[0055] To further improve the performance of perovskite-based energy dispersive detectors, this embodiment employs materials engineering techniques to modify the aforementioned perovskite semiconductor materials. Specific methods include doping, passivation, or compositional modulation, aiming to specifically improve the microstructure and electrical properties of the materials. For example, a small amount of strontium ions are incorporated into the preparation of CsPbBr3 crystals. These ions, with ionic radii similar to lead ions, enter the crystal lattice, effectively suppressing the formation of deep-level defects such as lead vacancies. This synergistic application of ion doping and lattice passivation. The common goal of these modifications is to optimize the carrier transport performance of the material: reducing the trapping and non-radiative recombination of photogenerated carriers by lattice defects, thereby significantly extending the effective lifetime of carriers; simultaneously, reducing the thermally excited dark current caused by defect states, thereby suppressing background noise.

[0056] This embodiment significantly reduces the probability of carrier recombination or trapping before collection by selecting and modifying the material, enabling the complete and consistent collection of the total charge generated by a single gamma photon. This improved uniformity of charge collection efficiency significantly enhances energy resolution. Simultaneously, material doping and other methods improve the intrinsic thermal stability of the material, suppressing ion migration and phase transitions at high temperatures. The reduction of defect states directly lowers dark current noise dominated by thermal excitation. This allows the perovskite-based energy dispersive detector to maintain low noise levels and stable energy response in downhole environments reaching 125°C or even above 200°C, overcoming the bottleneck of high-temperature failure in traditional photomultiplier tubes.

[0057] In some embodiments of the present invention, the perovskite-based energy spectrum detector 101 is encapsulated in a metal shock-resistant and pressure-resistant housing.

[0058] In this embodiment, to ensure long-term reliable operation in extreme downhole environments, the perovskite-based energy spectrum detector 101 is encapsulated in a specially designed metal shock-resistant and pressure-resistant housing, and a multi-layer composite shielding structure is further integrated on the outer layer of the housing.

[0059] Specifically, the metal shock-resistant and pressure-resistant shell is usually made of high-strength and high-toughness materials (such as special stainless steel or titanium alloy). Its structure is optimized by mechanical simulation, effectively absorbing and dispersing the strong vibration (>10g RMS) and high impact (>50g) energy generated during logging while drilling, providing a robust physical protection space for the internal brittle perovskite crystals and precision electrodes.

[0060] Outside this shell, functional shielding layers laid in sequence form a multi-layered shielding structure: the inner layer is usually a high atomic number metal material (such as lead or tungsten alloy) to absorb and attenuate stray gamma rays from the formation around the wellbore and from non-target directions in the drilling fluid, reducing background noise; the middle layer is often a high permeability alloy material (such as permalloy) to guide and shield low-frequency electromagnetic interference generated by downhole motors, cables, etc.; the outermost layer is a grounded conductive shielding layer to suppress high-frequency electromagnetic noise.

[0061] The structure adopted in this embodiment uses a metal shell to directly protect the perovskite-based energy spectrum detector from physical damage, which is expected to reduce its annual damage rate to be much lower than that of traditional glass PMT systems. This meets the requirements of harsh working conditions such as logging while drilling and significantly improves the mechanical reliability and environmental adaptability of the perovskite-based energy spectrum detector. Secondly, the multi-layer shielding structure physically optimizes the detection signal-to-noise ratio and signal purity. The radiation shielding layer reduces the interference of non-target signals, making the characteristic peaks obtained by subsequent energy spectrum analysis more accurate. The electromagnetic shielding layer effectively avoids the coupling interference of external electric and magnetic fields on the detector's weak analog signal circuit. Together, these two provide crucial external environmental protection, providing hardware support for obtaining accurate and repeatable natural gamma energy spectrum data under complex well conditions.

[0062] In some embodiments of the present invention, such as Figure 2 As shown, the multichannel energy spectrum analysis module 104 includes an analog-to-digital converter 201 and a multichannel pulse amplitude analyzer 202. The analog-to-digital converter 201 is used to convert pulse amplitudes into digital channel addresses, and the multichannel pulse amplitude analyzer 202 is used to count and statistically analyze pulses with different digital channel addresses.

[0063] In this embodiment, the input terminal of the analog-to-digital converter 201 receives analog voltage pulses from the pre-amplifier module and performs high-precision amplitude-to-digital conversion. This involves accurately measuring the peak voltage of each input pulse and linearly mapping it to a discrete digital value, which is the digital channel address. For example, a high-speed analog-to-digital converter with 16-bit resolution can divide the input voltage range of 0 to 10V into 65,536 discrete channels, thereby achieving amplitude resolution at the microvolt level.

[0064] The multichannel pulse amplitude analyzer 202 works in conjunction with the analog-to-digital converter 201, and internally contains a series of memory cells that correspond one-to-one with digital channel addresses. Whenever the analog-to-digital converter 201 outputs a digital channel address, the multichannel pulse amplitude analyzer 202 increments the count value of the memory cell corresponding to that address by 1. Through long-term accumulation, a histogram distribution is eventually formed, with the horizontal axis representing the digital channel address (corresponding to gamma photon energy) and the vertical axis representing the accumulated count; this is the final required natural gamma energy spectrum data.

[0065] The high linearity and low differential nonlinearity of the analog-to-digital converter in this embodiment ensure minimal loss of energy information during conversion, while the precise counting of the multichannel analyzer provides the foundation for energy spectrum formation, achieving high-precision digitization and statistical analysis of gamma photon energy. Secondly, this approach provides a standardized data interface for subsequent automated spectral analysis, resulting in a unified format for the output digital energy spectrum data. The digitization process is far less affected by temperature drift and electromagnetic interference than a purely analog system, helping to maintain the stability of the energy scale over long periods in complex downhole environments. This ensures the comparability of energy spectrum data obtained at different times and from different wells, and the consistency of geological interpretation.

[0066] In some embodiments of the present invention, such as Figure 3 As shown, the temperature monitoring module 102 includes a high-voltage power supply 301 and a temperature sensor 302. The temperature sensor 302 is used to monitor the temperature of the perovskite-based energy spectrum detector 101 and adjust the output of the high-voltage power supply 301 through feedback control, or activate the heating and cooling devices, so that the temperature control range of the perovskite-based energy spectrum detector 101 is -20℃ to 300℃.

[0067] In this embodiment, a temperature sensor 302 (such as a platinum resistance thermometer or thermocouple mounted close to the detector's casing) monitors the temperature of the detector body in real time and feeds this signal back to the control circuit. Based on this, the module executes two active control strategies: First, it dynamically adjusts the output voltage of the high-voltage power supply 301 through feedback control. This is because the charge collection efficiency and leakage current of the semiconductor detector are closely related to its internal electric field strength, which is determined by the bias voltage. Adjusting the bias voltage can compensate for changes in parameters such as carrier mobility when the temperature changes, thus maintaining optimal and stable electric field conditions. Second, when the temperature exceeds a predetermined operating window, an integrated heating device (such as a surface-mount heating resistor) or a cooling device (such as a miniature thermoelectric cooler) is activated to directly manage the detector's thermal performance, strictly controlling its core temperature within a wide range of -20°C to 300°C.

[0068] This embodiment stabilizes the detector temperature at a set point, eliminating energy spectrum drift caused by drastic well temperature changes. This ensures the absolute position of the characteristic peaks of uranium, thorium, and potassium remains constant. Through voltage-temperature-responsive compensation, the detector operates at the bias point with the highest charge collection efficiency and lowest noise at different temperatures. This achieves near-experimental energy resolution in low-temperature well sections at -20℃ or ultra-deep well sections at 300℃. The detector no longer passively withstands ambient temperature but actively maintains its optimal operating conditions. This makes the perovskite-based energy spectrum logging device adaptable to a wide range of scenarios with extreme temperature differences, from shallow wells in cold regions to ultra-deep wells and geothermal wells, thus improving environmental adaptability.

[0069] In some embodiments of the present invention, such as Figure 4 As shown, the downhole natural gamma ray spectral logging device also includes a data acquisition and transmission system 401, which is connected to a multichannel energy spectrum analysis module 104 and is used to receive and transmit natural gamma ray spectral data to the surface system.

[0070] This embodiment further integrates a data acquisition and transmission system 401. This system connects to the output of the multichannel energy spectrum analysis module 104, receiving digitized natural gamma ray energy spectrum data generated downhole in real time. It reliably transmits the energy spectrum data stream, containing channel address and count information, to the surface computer system via cable telemetry or downhole wireless short-range transmission. This data acquisition and transmission system 401 serves as a standard interface between downhole instruments and the surface control terminal, ensuring the feasibility and compatibility of engineering implementation. The data acquisition and transmission system provided in this embodiment enables real-time transmission of energy spectrum data and instant transmission from the surface, allowing bottom-side engineers to simultaneously observe the distribution changes of formation radioactive elements during logging, thereby making timely engineering decisions and significantly improving operational efficiency. Simultaneously, as the endpoint of the data link, it provides a complete and continuous data source for subsequent data storage, depth correlation, spectral analysis, and geological inversion, which is beneficial for improving the accuracy of downhole natural gamma ray energy spectrum logging results.

[0071] Figure 5 This is a schematic flowchart illustrating an embodiment of the downhole natural gamma ray spectral logging device provided by the present invention. The method, applied to the aforementioned downhole natural gamma ray spectral logging device, specifically includes: S501: Provides bias voltage and adjusts operating temperature for the perovskite-based energy spectrum detector through a temperature monitoring module; S502: A perovskite-based energy spectrum detector is used to directly absorb gamma rays from the strata and convert the gamma ray energy into an electrical pulse signal of corresponding amplitude. S503, amplifies the electrical pulse signal through the signal amplification module; S504. Based on the multi-channel energy spectrum analysis module, the amplitude analysis and channel counting of the shaped electrical pulse signal are performed to generate natural gamma energy spectrum data. S505. Identify and analyze the characteristic peaks corresponding to each radioactive element in the natural gamma energy spectrum data to obtain the analysis results. Each radioactive element usually includes at least one of potassium, uranium, and thorium. S506. Based on the analysis results, qualitative and quantitative analysis of the radioactive elements in the strata is performed.

[0072] First, step S501 is executed. In this stage, the temperature monitoring module begins operation, establishing the external conditions necessary for the normal operation of the perovskite-based energy dispersive spectroscopy detector (hereinafter referred to as the detector). Specifically, this module applies a stable DC bias voltage of several hundred to several thousand volts between the two electrodes of the detector to create the strong electric field required for charge collection within the perovskite sensing element inside. Simultaneously, the temperature sensor monitors the detector temperature in real time and, through feedback control mechanisms—such as activating a micro-heater when the temperature is below a set value or guiding the well fluid to dissipate heat when the temperature is too high—precisely controls the detector core temperature within a predetermined operating range (e.g., -20°C to 300°C). In deep wells with large temperature gradients, this approach helps maintain measurement consistency.

[0073] Next, in step S502, as the instrument moves within the wellbore, natural gamma rays from radioactive nuclides such as uranium, thorium, and potassium in the formation penetrate the instrument's outer casing and are directly absorbed by the sensitive element of the perovskite-based energy spectrum detector. Unlike the indirect conversion of traditional scintillators, perovskite semiconductor materials utilize their direct bandgap characteristics to efficiently convert the energy of a single incident gamma photon into a large number of electron-hole pairs. These charge carriers, driven by the bias electric field applied in step S501, are rapidly collected and form a current pulse. The integrated charge of this pulse (i.e., the amplitude of the final voltage pulse) is proportional to the energy of the incident photon. This direct conversion mechanism, in principle, avoids the statistical errors caused by the secondary conversion between "gamma-light" and "photo-electricity" in traditional techniques.

[0074] Then, in step S503, the weak electrical pulse signal output by the detector, with an amplitude of only millivolts, is fed into the signal amplification module. This module typically consists of a low-noise charge-sensitive preamplifier and subsequent main amplifier and filtering / shaping circuitry. The charge-sensitive preamplifier converts the charge packet into a voltage signal, and its excellent signal-to-noise ratio characteristics preserve the original energy spectrum information to the greatest extent possible; the subsequent circuitry amplifies and shapes the pulse (e.g., shaping it into a Gaussian waveform) to suppress noise and prevent pulse accumulation.

[0075] In step S504, the shaped, amplitude-normalized pulses are fed into the core of the multichannel energy spectrum analysis module—the analog-to-digital converter (ADC). The ADC precisely measures the peak voltage of each pulse and linearly converts it into a digital channel address. For example, a pulse corresponding to a 1.46 MeV potassium characteristic energy might be assigned to channel 1460. The multichannel pulse amplitude analyzer continuously counts all pulses by channel address, ultimately forming a natural gamma energy spectrum with channel address (corresponding energy) on the x-axis and count rate on the y-axis.

[0076] In step S505, the acquired energy spectrum data is processed. First, based on the energy calibration performed using a standard radioactive source before logging, the digital address is accurately converted into energy values. Subsequently, through energy spectrum processing algorithms, such as Sandel-Vicao peak search, Gaussian fitting, and background subtraction techniques, characteristic peaks of radioactivity at 1.46 MeV (potassium), 1.76 MeV (uranium), and 2.62 MeV (thorium) are clearly identified in the energy spectrum.

[0077] Step S506 then, based on this, calculates the relative or absolute content of various radioactive elements such as potassium, uranium, and thorium in the formation by calculating the net peak area of ​​each characteristic peak (total count minus background count). These quantitative elemental abundance data are the direct basis for subsequent accurate calculation of mud content, lithology identification, and analysis of sedimentary environment and oil generation potential.

[0078] This embodiment combines active temperature control with the inherent high-temperature stability of perovskite materials, ensuring that the energy scale remains stable even at extreme downhole temperatures up to 300°C, overcoming the shortcomings of traditional photomultiplier tube systems that experience rapid performance degradation at high temperatures. Furthermore, since the detection mechanism does not involve the photomultiplication process sensitive to vibration and magnetic fields, and the circuit system does not require complex real-time gain compensation, this approach exhibits stronger adaptability and reliability in downhole environments with strong vibrations and magnetic interference (such as logging while drilling). It reduces the complexity of measurement interruptions or data corrections caused by instrument instability, thereby improving the quantitative accuracy of logging.

[0079] In some embodiments of the present invention, before application, an energy calibration is performed using a standard radiation source to ensure that the linear relationship error between the amplitude of the electrical pulse signal and the energy of the gamma photon does not exceed 0.5%.

[0080] To ensure the absolute accuracy of the measurement results, this embodiment calibrates the entire detection system using a standard gamma radiation source with known energy before the well logging operation begins. This step establishes and verifies a precise and traceable linear correspondence between the amplitude of the electrical pulse signal output from the perovskite-based energy spectrum detector and the energy of the incident gamma photon, and controls the error of this linear relationship to within 0.5%.

[0081] Specifically, this calibration operation is typically performed in a standard environment in a laboratory or well site. During implementation, standard radioactive sources with single or discrete characteristic peaks, such as ^137Cs (characteristic energy 0.662 MeV) and ^60Co (characteristic energies 1.173 MeV and 1.332 MeV), are sequentially placed at the standard geometric positions of the detector for irradiation. The system records the energy spectrum generated by each standard source and uses spectral analysis software to precisely determine the channel address of each characteristic peak within the energy spectrum. Subsequently, a least-squares linear fit is performed with the known gamma photon energy (in MeV) as the ordinate and the measured peak address as the abscissa to obtain an "energy-channel address" conversion scale curve. The slope of this curve represents the system's energy conversion gain, and its intercept is related to the system's zero-point noise. Through repeated calibration and circuit fine-tuning (such as adjusting amplifier gain), it is ensured that within the effective energy measurement range (e.g., 0.2 MeV to 3.0 MeV), the maximum deviation between the actual data points and the best-fit line is limited to within 0.5%.

[0082] The initial calibration used in this embodiment establishes a traceable benchmark. In subsequent logging operations or periodic maintenance, the stability of the calibration curve can be monitored by re-examining the standard source. If necessary, recalibration or software correction can be performed to ensure that the uranium, thorium, and potassium content data obtained from different times and wells have high comparability and long-term consistency.

[0083] like Figure 6 As shown, the characteristic peaks corresponding to each radioactive element in the natural gamma-ray spectrum data were identified and analyzed, and the analysis results include: S601. Count and identify the characteristic peaks of each radioactive element to obtain the identification results; S602. Calculate the peak area of ​​the characteristic peak corresponding to each radioactive element in the identification results, and quantitatively analyze the content of each element based on the calculation results to obtain the analysis results.

[0084] This embodiment further refines the energy spectrum analysis step in the method for downhole natural gamma ray spectral logging. This step takes the natural gamma ray spectral data generated in the previous process and accurately extracts the characteristic information of radioactive elements such as potassium, uranium, and thorium from the energy spectrum curve containing statistical fluctuations and background noise. It then converts this information into quantitative elemental content data, where each radioactive element typically includes at least one of potassium, uranium, and thorium.

[0085] Step S601 involves the precise identification of characteristic peaks. Specifically, the system first calls a pre-established energy-channel address calibration curve using a standard radioactive source to convert the abscissa of the energy spectrum data from "channel address" to "energy (MeV)". Subsequently, peak position fitting and background subtraction algorithms are implemented in the neighborhoods of energy values ​​of approximately 1.46 MeV, 1.76 MeV, and 2.62 MeV, respectively. A typical implementation method is to use a nonlinear least squares method to fit the data of each characteristic peak region into a superposition model of a Gaussian function (simulating peak shape) and a low-order polynomial (simulating continuous background).

[0086] The perovskite-based detector used in this embodiment, due to its high energy resolution characteristics, enables the characteristic peaks of radioactive elements such as potassium, uranium, and thorium to be fully separated and have sharp peak shapes, providing a prerequisite for high-precision fitting and avoiding the peak overlap problem commonly found in traditional low-resolution energy spectra.

[0087] Step S602 completes the quantitative calculation based on the identification. In this step, the system calculates the integral area under the Gaussian fitting curve for the net spectral data of each characteristic peak obtained in S601. This "peak area" corresponds to the total count rate of gamma rays of that characteristic energy, which is proportional to the content of the corresponding element in the formation.

[0088] This embodiment achieves high-precision conversion from raw energy spectrum data to geological application parameters. Based on accurate peak position fitting of high-resolution energy spectrum, it minimizes the calculation errors caused by inter-peak interference and background contribution, making the final obtained data on the content of radioactive elements such as potassium, uranium, and thorium more accurate.

[0089] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware (such as a processor, controller, etc.), and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0090] The above provides a detailed description of the device and method for downhole natural gamma ray spectral logging provided by the present invention. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A device for downhole natural gamma ray spectroscopy logging, characterized in that, include: A perovskite-based energy spectrum detector is used to directly absorb gamma rays from the formation downhole and convert the gamma ray energy into an electrical pulse signal of corresponding amplitude. The perovskite-based energy spectrum detector uses a perovskite semiconductor material with an adjustable bandgap as the sensing element. A temperature monitoring module, connected to the perovskite-based energy dispersive detector, is used to provide it with a stable bias voltage and monitor and control its operating temperature. The signal amplification module is electrically connected to the perovskite-based energy spectrum detector and is used to amplify and shape the electrical pulse signal. The multichannel energy spectrum analysis module is electrically connected to the signal amplification module. It is used to perform amplitude analysis on the shaped electrical pulse signal and count the channels according to the amplitude based on the analysis results to generate natural gamma energy spectrum data.

2. The device for downhole natural gamma ray spectral logging according to claim 1, characterized in that, The perovskite semiconductor material is selected from at least one of CsPbBr3, MAPbI3, and FAPbBr3, or other semiconductor materials and their derivatives having a perovskite crystal structure.

3. The device for downhole natural gamma ray spectral logging according to claim 2, characterized in that, The perovskite semiconductor material is modified through doping, passivation, or compositional modulation to optimize carrier lifetime, bandgap width, environmental operability, and energy resolution.

4. The device for downhole natural gamma ray spectral logging according to claim 1, characterized in that, The multichannel energy spectrum analysis module includes an analog-to-digital converter and a multichannel pulse amplitude analyzer. The analog-to-digital converter is used to convert pulse amplitudes into digital channel addresses, and the multichannel pulse amplitude analyzer is used to count and statistically analyze pulses with different digital channel addresses.

5. The device for downhole natural gamma ray spectral logging according to claim 1, characterized in that, The temperature monitoring module includes a high-voltage power supply and a temperature sensor. The temperature sensor is used to monitor the temperature of the perovskite-based energy dispersive spectroscopy detector and adjust the output of the high-voltage power supply through feedback control, or activate the heating and cooling devices, so that the temperature control range of the perovskite-based energy dispersive spectroscopy detector is -20℃ to 300℃.

6. The device for downhole natural gamma ray spectral logging according to claim 1, characterized in that, The perovskite-based energy spectrum detector is encapsulated in a metal shock-resistant and pressure-resistant housing.

7. The apparatus for downhole natural gamma ray spectral logging according to any one of claims 1 to 6, characterized in that, The device further includes a data acquisition and transmission system connected to the multichannel energy spectrum analysis module, used to receive and transmit the natural gamma energy spectrum data to the ground system.

8. A method for downhole natural gamma ray spectral logging, characterized in that, An apparatus for downhole natural gamma ray spectral logging according to any one of claims 1 to 7, wherein the method comprises: The temperature monitoring module provides bias voltage and regulates the operating temperature of the perovskite-based energy spectrum detector. The perovskite-based energy spectrum detector directly absorbs gamma rays from the strata and converts the gamma ray energy into electrical pulse signals of corresponding amplitude. The electrical pulse signal is amplified by the signal amplification module. Based on the multi-channel energy spectrum analysis module, amplitude analysis and channel counting are performed on the shaped electrical pulse signal to generate natural gamma energy spectrum data; The characteristic peaks corresponding to each radioactive element in the natural gamma energy spectrum data are identified and analyzed to obtain the analysis results. Each radioactive element usually includes at least one of potassium, uranium, and thorium. Based on the analysis results, qualitative and quantitative analysis of the radioactive elements in the strata was performed.

9. The method for downhole natural gamma ray spectral logging according to claim 8, characterized in that, Before application, energy calibration is performed using a standard radiation source to ensure that the linear relationship between the amplitude of the electrical pulse signal and the energy of the gamma photon has an error of no more than 0.5%.

10. The method for downhole natural gamma ray spectral logging according to claim 8, characterized in that, The identification and analysis of the characteristic peaks corresponding to each radioactive element in the natural gamma-ray spectrum data yields the following results: The characteristic peaks of each radioactive element are counted and identified to obtain the identification results; The peak area of ​​the characteristic peak corresponding to each radioactive element in the identification results is calculated, and the content of each element is quantitatively analyzed based on the calculation results to obtain the analysis results.

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