Induced Electron Data Acquisition System and Method Based on Plasma Fiber Optic Sensor

Abstract

The induced polarization (IP) data acquisition system and method based on plasma fiber optic sensors provided by this invention can rapidly and cost-effectively detect the distribution patterns of formation complex resistivity and formation polarizability in underground three-dimensional work areas, as well as their relationship with underground oil, gas, and mineral resources. This significantly reduces interference from various anthropogenic noises on existing electronic IPI data acquisition devices, improving the signal-to-noise ratio of the IPI data. Because plasma resonance fiber optic sensors are used, the IPI data acquisition device no longer contains any electronic components or sensors. There is no mutual interference or crosstalk between plasma resonance fiber optic sensors or between the plasma resonance fiber optic sensors and the instrument host. The plasma resonance fiber optic sensors and the fiber optic host are also less susceptible to electromagnetic noise interference from the surrounding environment of the three-dimensional work area. Furthermore, the armored optical cables connecting the various plasma resonance fiber optic sensors enable high-speed, real-time transmission of large amounts of data across multiple channels and parameters.

Description

Technical Field

[0001] This invention belongs to the fields of geophysical exploration technology and ground-induced polarization exploration technology, specifically referring to an induced polarization data acquisition system and method based on a plasma fiber optic sensor. Background Technology

[0002] Geophysical exploration methods mainly include seismic methods, direct current methods, magnetic methods, gravity methods, electromagnetic methods, and radiometric methods. Among them, the electromagnetic method, also known as the "electromagnetic induction method," is a method of surface mineral exploration that utilizes the principle of electromagnetic induction based on the differences in electrical conductivity and magnetic permeability of rocks or ores. This is collectively referred to as the surface electromagnetic exploration method.

[0003] The application of surface electromagnetic exploration technology has played a crucial role in the joint interpretation of structural zones and special targets, as well as the joint detection and evaluation of oil and gas traps. After nearly two decades of research and development, surface electromagnetic exploration technology has become a relatively mature method. Electromagnetic field excitation methods can be divided into frequency domain excitation and time domain excitation. The limitation of frequency domain (continuous wave) excitation is the strong coupling between the transmitter and receiver, making the source field signal directly from the transmitter to the receiver much stronger than the signal from the formation, thus making it difficult to accurately measure the electromagnetic field signal received from the formation. Although multi-target processing techniques and methods combining multiple sets of measurement data can provide information about the target formation of interest, the net signal obtained is still small compared to the total measurement signal, and the useful information is negligible.

[0004] Time-domain electromagnetic method (TDEM), also known as transient electromagnetic method (TEM), utilizes the principle of electromagnetic induction and is essentially the same as frequency-domain electromagnetic method, but differs in the excitation and observation methods of the field. TDEM uses an ungrounded loop or a grounded source with a pulsed current (the transmitting field source uses a periodic pulse sequence, such as rectangular, trapezoidal, half-sine, and triangular waves) as the field source to excite the target and induce a secondary current. The response of the secondary field as a function of time is measured during the intervals between pulse currents. The time from the generation to the end of the secondary field is brief, hence the term "transient" or "transitional process."

[0005] From a methodological perspective, frequency domain methods and time domain methods are not fundamentally different. The former studies the characteristics of harmonic fields, while the latter studies the characteristics of unstable fields; the two can be linked using Fourier transforms. Under certain conditions, data from one method can be converted into data from another method.

[0006] Induced polarization (IP) is a set of electrical exploration methods that utilize the induced polarization effect of rocks and ores to locate metals and solve hydrogeological and engineering geological problems. It is further divided into DC induced polarization (time domain method) and AC induced polarization (frequency domain method (SIP)). Commonly used electrode arrangements include intermediate gradient arrangement, combined profile arrangement, fixed-point power supply arrangement, and symmetrical four-electrode sounding arrangement. Methods that directly or indirectly charge the ore body can also be used to delineate the extent of the ore body and increase the exploration depth.

[0007] When the power supply electrodes supply power to the ground, the supply current remains constant. The potential difference between the measuring electrodes increases over time and tends to a certain saturation value. After the power is cut off, a potential difference still exists between the measuring electrodes that decreases over time and gradually decays towards zero. This phenomenon is called the "induced polarization effect." The induced polarization method (IP) is the method for studying this effect. This process of electric field change over time due to the induced polarization effect is divided into charging and discharging processes. During the charging process after power is supplied, the electric field initially increases rapidly over time, then slows down, and finally tends to saturate. During the discharging process after power is cut off, the electric field decays rapidly over time, then slows down, and finally tends to zero.

[0008] When conducting resistivity measurements in the field or on indoor rock and mineral specimens, if a stable current is supplied to the ground or specimen through power supply electrodes while simultaneously measuring the potential difference across the measuring electrodes, under constant current intensity, the potential difference between the measuring electrodes can be observed to change over time, tending towards a stable saturation value after a considerable period. Upon disconnection of the current, the potential difference between the measuring electrodes decreases rapidly at the moment of power failure, then decreases slowly over time, decaying to near zero after a considerable period. This phenomenon, where an additional electric field slowly changes over time during charging and discharging, is called excited polarization. This phenomenon indicates that a secondary electric field is generated in the earth or rock and mineral specimen under the influence of an external current field. This secondary electric field is the result of a series of complex electrochemical interactions at the interface between the solid material (rock and mineral particles) in the rock and mineral and the electrolyte solution.

[0009] Since both the total potential difference and the secondary potential difference are proportional to the supply current intensity, the polarizability, i.e., the ratio of the secondary potential difference to the total potential difference, can be used as a parameter characterizing the intensity of the induced polarization effect in a bulk polarized medium. The main factors affecting the polarizability of rocks and minerals are the content and structure of electronically conductive minerals (the size, shape, and connectivity of the electronically conductive mineral particles, etc.). When the particle size is constant, the polarizability increases with increasing electronically conductive mineral content.

[0010] Based on the type of induced polarization effect, induced polarization methods can be divided into two types: one is the time-domain induced polarization method, which observes the induced polarization effect of the electric field changing with time under steady current excitation; the other is the frequency-domain induced polarization method, which observes the induced polarization effect of the electric field changing with frequency under alternating current.

[0011] Excited polarization methods can utilize various electrode devices found in resistivity methods. Among these, the most widely used devices in time-domain induced polarization include intermediate gradient, combined profile, near-field source diode, and symmetrical quadrupole sounding. Frequency-domain induced polarization primarily uses dipole-dipole devices.

[0012] Spectral Induced Electrolysis (SIP) is a frequency-domain induced electrolysis method used in geophysical exploration. This method analyzes the spectral characteristics of the complex resistivity by performing multi-frequency apparent complex resistivity measurements in the ultra-low frequency band, thus solving geological problems. SIP employs a dipole-dipole device on the ground to sweep the radial electric field, making it a high-density geometric sounding method. The measured spectrum includes the near-field electromagnetic spectrum (EM) caused by conductivity and the induced electrostatic spectrum (IP) caused by polarization. These two spectra occupy different positions in the frequency band; fitting and inverting the measured video spectrum using different models can separate them, thereby achieving the removal of the electromagnetic spectrum (EM) response and obtaining four induced electrostatic spectrum (IP) parameters: r s (apparent geometric resistivity), m s (depending on charging rate), t s (apparent time constant), C s (Video rate correlation coefficient). These four induced polarization (IP) parameters reflect the electrical conductivity and polarization properties of anomalous underground geological bodies, and can make relatively accurate judgments on the properties of anomalous materials.

[0013] Currently, frequency-domain or time-domain electromagnetic data acquisition systems used in the industry typically include induction coil or fluxgate type single-component or three-component magnetic field sensors, one or two pairs of orthogonal non-polarized electrode pairs as electric field sensors, and modules for signal amplification, filtering and noise reduction, analog-to-digital conversion, long-distance transmission, or local storage. These traditional electromagnetic data acquisition systems suffer from high power consumption, high instrument noise floor, weak electromagnetic interference resistance, bulky electromagnetic sensors, high instrument costs, low production efficiency, and difficulty in large-scale mass production and rapid deployment during construction. The two pairs of non-polarized electrode pairs used for collecting electric field data must be separated by leads at a distance of 50 to 100 meters during construction. To avoid mutual interference and interference from the instrument host, the three-component magnetic field sensors must be buried separately at a distance of 5 to 10 meters, significantly reducing construction efficiency. Due to the weak electromagnetic interference resistance of electronic instruments and sensors, qualified electromagnetic field data are often not collected in environments with strong electromagnetic interference, such as high-voltage power lines. Summary of the Invention

[0014] The purpose of this invention is to overcome the shortcomings of the prior art. This invention provides an induced polarization data acquisition system and method based on a plasma fiber optic sensor.

[0015] To achieve the above objectives, the technical solution of the present invention is as follows:

[0016] The induced polarization data acquisition system based on plasma fiber optic sensor includes a ground-based transmitter and a ground-based fiber optic induced polarization signal receiving and acquisition device.

[0017] The ground transmitter is a time-domain pulse current transmitter or a frequency-domain sinusoidal current transmitter. It also includes a control device for the ground transmitter and a transmitting antenna. The control device provides a high-power excitation current to the transmitting antenna. The excitation current is a square wave pulse excitation current or a sinusoidal excitation current.

[0018] The ground-based fiber optic induced polarization signal receiving and acquisition device is distributed within the measurement area according to the pre-designed measurement points or lines;

[0019] The transmitting antenna includes a grounded long conductor or a loop transmitting coil; there are four grounded long conductors that surround the work area, and each conductor has a grounding electrode at both ends; the loop transmitting coil surrounds the work area and is either a square loop transmitting coil or a circular loop transmitting coil.

[0020] The ground-based fiber optic induced polarization signal receiving and acquisition device includes at least one optical system for detecting induced polarization signals. The optical system includes a broadband light source, a polarizer, a polarization controller, a fiber optic circulator, a plasma resonance fiber optic sensing probe, a fiber optic circulator, and a spectrometer connected in sequence.

[0021] The plasma resonance fiber optic sensing probe is a miniature and chemically inert fiber optic sensor. This sensor can be inserted into the measurement medium to perform in-situ and continuous monitoring of electrochemical reactions and interfacial dynamics changes near the sensor surface. By detecting the disturbance of surface plasma waves propagating on its surface, the sensor can measure and monitor its electrochemical dynamics characteristics without interfering with its normal operation.

[0022] It includes multiple plasma resonance fiber optic sensing probes arranged in an array on the ground and connected to an instrument vehicle on the ground via armored fiber optic cables. The instrument vehicle controls the array via the armored fiber optic cables and collects the data acquired by the array.

[0023] The distance between adjacent plasma resonance fiber optic sensing probes is 10 to 50 meters, and they are connected by armored fiber optic cables.

[0024] The array of plasma resonant fiber optic sensing probes is configured such that every two plasma resonant fiber optic sensing probes form a pair of induced polarization signal measurement probes, which sequentially measure the potential signal difference between the primary or secondary fields between the two plasma resonant fiber optic sensing probes.

[0025] The excitation current is a high-power square wave pulse excitation current, the waveform of which is a zero-duty half-duty bipolar square wave or a pseudo-random pulse sequence with a zero duty cycle and positive and negative polarities, and the square wave period or unit pulse width is 0.01 to 64 s; or the excitation current is a high-power sine wave excitation current, the waveform of which is a sine wave with positive and negative peaks at different frequencies.

[0026] The length of the grounding conductor is 5000m to 10000m, and the control device alternately supplies power to the grounding conductors in different directions through a reversing switch.

[0027] The square large loop transmitting coil has a side length of 5000m to 10000m, and the circular large loop transmitting coil has a diameter of 5000m to 10000m.

[0028] The induced polarization (IP) data acquisition method based on a plasma fiber optic sensor, employing the aforementioned IPI data acquisition system based on a plasma fiber optic sensor, includes the following steps:

[0029] S1. The control device of the ground-based transmitter continuously transmits high-power square wave pulse excitation current or sine wave excitation current, which is supplied to the ground through the grounding electrode of the transmitting antenna to excite the ground, or the square or circular large loop transmitting coil around the three-dimensional induced electromagnetic data acquisition area excites the electromagnetic field in the ground, causing the underground medium to generate induced eddy currents, which gradually diffuse and attenuate into the half-space underground.

[0030] S2. The plasma resonance fiber optic sensing probe in the ground fiber optic induced polarization signal receiving and acquisition device collects the time-domain induced polarization signal or frequency-domain induced polarization signal generated on the ground by the power supply current or induced eddy current continuously emitted by the control device in step S1 along the pre-designed measuring line at a certain point spacing. Each measuring point measures and records 10 to 50 cycles of time-domain induced polarization signal or frequency-domain induced polarization signal.

[0031] S3. The GPS or Beidou timing and positioning module on the top of the instrument vehicle on the ground provides timing for the time domain induced polarization signal or frequency domain induced polarization signal collected by each ground fiber optic induced polarization signal receiving and acquisition device each time.

[0032] S4. The plasma resonance fiber optic sensing probe array of the ground fiber optic induced polarization signal receiving and acquisition device transmits the ground time-domain induced polarization signal or frequency-domain induced polarization signal acquired in step S2 to the fiber laser signal modulation and demodulation instrument in the ground instrument vehicle in real time through armored fiber optic cable. Then, it is converted into time-domain induced polarization signal or frequency-domain induced polarization data at each measurement point location. Finally, it is stored in the computer in the instrument vehicle.

[0033] S5. Process the time-domain induced polarization data from step S4 in the time domain to obtain the apparent polarization parameter η at each measurement point. s The attenuation degree (D) and excitation ratio (J) were then used to extract mineral, lithological, reservoir, and fluid parameters related to the formation's electrical properties.

[0034] S6, the apparent polarizability η s It is a fundamental measurement parameter in DC (time domain) induced polarization method, and it comprehensively reflects the induced polarization effect of topography and various polarimetric bodies within the current's range of influence. Its expression is: η s =ΔU2(t) / ΔU(T)×100%, where ΔU(T) is the polarization field potential difference measured at power supply time T; ΔU2(t) is the secondary field potential difference measured at time t after power outage. η s Expressed as a percentage, its size and distribution reflect the presence and occurrence of polaritons within a certain depth range underground. (From η) s As can be seen from the expression, apparent polarizability is related to the power supply time T and the measurement delay time t. Therefore, when referring to polarizability, the corresponding power supply time T and measurement time t must be specified. For simplicity, we define apparent polarizability as the measurement result under long power supply (T→∞) and no delay (t→0).

[0035] The attenuation degree D is a measurement parameter reflecting the rate of decay of the secondary field (excited polarization field), expressed as a percentage. Its expression is: D = ΔU1(t) / ΔU2(t) × 100%, where ΔU1(t) is the average value of the secondary field potential difference over a certain period after power failure. The faster the secondary field decays, the smaller its attenuation degree.

[0036] The excitation ratio (J) is a comprehensive parameter combining apparent polarizability and attenuation, reflecting the magnitude of the secondary field and its attenuation characteristics. Its calculation formula is J = η. s ×D=ΔU1(t) / ΔU(T)×100%. For aquifers, generally η s Both D and D are high values, and multiplying them can amplify the anomaly and make the anomaly more obvious.

[0037] S7. Process the frequency domain induced polarization data from step S4 in the frequency domain to obtain the frequency domain excitation polarization parameter video divergence P at each measurement point. s Apparent phase φs Apparent complex resistivity spectrum ρ s (iω), and then extract mineral, lithological, reservoir and fluid parameters related to the formation electrical properties;

[0038] S8, the video dispersion P s It is a fundamental measurement parameter in the AC (frequency domain) excited polarization method, and its expression is: P s =(ΔU(f) D )-ΔU(f G )) / ΔU(f D )×100%,ΔU(f D ), ΔU(f G ) represent the ultra-low frequency band (n×10) －2 ~n×10 2 The total field potential difference formed by the low-frequency and high-frequency supply currents (Hz). And η s Similarly, P s It is also a comprehensive reflection of the topography and the polarization effect induced by various polarimetric bodies within the range of current action. Since time-domain induced polarization and frequency-domain induced polarization are physically consistent, under limiting conditions, i.e., ΔU(f D →0) and ΔU(f G When the value approaches infinity (→∞), both methods will produce exactly the same measurement results.

[0039] The induced polarization effect causes a phase shift in the total field potential difference relative to the supply current; this is the apparent phase φ of the complex resistivity. s All other things being equal, the stronger the induced polarization effect, the greater the φ. s The larger the absolute value, the greater the apparent phase φ. s It can also be used as a parameter to describe the strength of the induced polarization effect. In fact, the apparent phase φ caused by the induced polarization effect... s The dispersion factor P is approximately proportional to the slope of the amplitude-frequency curve or the rate of change of the electric field amplitude with frequency. s (f D f G It also corresponds to the amplitude-frequency response curve at frequency f. D and f G The average slope between frequencies is proportional. Therefore, the phase φ at a certain frequency f is proportional to the average slope between frequencies. s The dispersion rate P of the two frequencies before and after it s (f D f G It is approximately proportional to φ. s and P s (f D f G Like the (limiting) apparent polarizability η, it is also related to the apparent polarizability η. s They are directly proportional, and the latter can be used to represent them.

[0040] The induced electrostatic effect in an alternating current field is characterized by the frequency characteristics of the total field potential difference or complex resistivity. Therefore, the complex resistivity spectrum ρ across the entire (ultra-low frequency) frequency band where the induced electrostatic effect occurs... s (iω) should be the most comprehensive parameter describing the frequency domain induced polarization effect. The complex resistivity method, or spectral induced polarization method, studies underground geological conditions by observing the real and imaginary components, or amplitude and phase spectra of the apparent complex resistivity over a fairly wide (ultra-low frequency) band.

[0041] S9. Perform time-domain inversion imaging and frequency-domain inversion imaging on the time-domain excitation polarization parameters or frequency-domain excitation polarization parameters of each measuring point obtained in steps S5 and S7 respectively to obtain the distribution of the time-domain complex resistivity or the frequency-domain complex resistivity in the three-dimensional space of the strata under the three-dimensional induced polarization data acquisition area.

[0042] S10. Based on the relationship between the distribution variation law of the formation time domain complex resistivity obtained by the time domain processing method and the formation frequency domain complex resistivity obtained by the frequency domain processing method, the distribution variation law of formation polarizability is obtained.

[0043] S11. Based on the distribution patterns, ranges, and characteristics of the complex resistivity and polarizability of underground strata, and through comprehensive interpretation combined with other geological, structural, lithological, mineral, and geoscientific information, the geoelectric characteristics of underground strata or rock units can be delineated, potential enrichment or accumulation zones of metallic, non-metallic, or oil and gas resources can be identified, predicted, interpreted, and evaluated, and the distribution of oil and gas-bearing or highly polarizable minerals in the strata can be realized.

[0044] The induced polarization (IP) data acquisition system and method based on plasma fiber optic sensors provided by this invention can rapidly and cost-effectively detect the distribution patterns of complex resistivity and polarizability of formations in underground three-dimensional work areas, as well as their relationship with underground oil, gas, and mineral resources. It can also improve the resolution of target geological bodies, significantly reduce interference from various anthropogenic noises on existing electronic IPI data acquisition devices, improve the signal-to-noise ratio of IPI data, indicate the anisotropic characteristics of formation resistivity, provide information such as formation occurrence, and achieve comprehensive interpretation and evaluation of reservoir parameters. Because it uses plasma resonance fiber optic sensors, the IPI data acquisition device no longer contains any electronic components or induction coil or fluxgate magnetic field sensors. There is no mutual interference or crosstalk between plasma resonance fiber optic sensors or between the plasma resonance fiber optic sensors and the instrument host. The plasma resonance fiber optic sensors and the fiber optic host are also less susceptible to electromagnetic noise interference from the surrounding environment of the three-dimensional work area. Furthermore, the armored optical cables connecting the various plasma resonance fiber optic IPI signal receiving and acquisition devices can achieve high-speed, real-time transmission of multi-channel, multi-parameter, and large-data volumes, overcoming most of the shortcomings of conventional electronic IPI data acquisition instruments. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of an induced polarization data acquisition system based on a plasma fiber optic sensor.

[0046] Figure 2 This is a schematic diagram of the induced polarization data acquisition system and long wire emission structure of an induced polarization fiber optic sensor, which is one of the implementation methods.

[0047] Figure 3 This is a schematic diagram of the induced polarization data acquisition system and the square coil transmitting structure of the plasma fiber optic sensor according to the second implementation method.

[0048] Figure 4 This is a schematic diagram of the induced polarization data acquisition system and circular coil transmitting structure of the plasma fiber optic sensor according to the third embodiment. Detailed Implementation

[0049] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0050] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "longitudinal," "lateral," "horizontal," "inner," "outer," "front," "rear," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0051] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "have," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The embodiments of this invention are described in detail below with reference to the accompanying drawings, but these do not constitute a limitation of the invention and are merely examples. The advantages of this invention will become clearer and easier to understand through the explanation.

[0052] Figure 1This is a schematic diagram of the induced polarization data acquisition system based on a plasma fiber optic sensor according to the present invention. The induced polarization data acquisition system based on a plasma fiber optic sensor according to the present invention includes a ground-based transmitter 1 and a ground-based fiber optic induced polarization signal receiving and acquisition device 2;

[0053] The ground transmitter 1 is a time-domain pulse current transmitter or a frequency-domain sinusoidal current transmitter. It also includes a control device 3 and a transmitting antenna 4 for the ground transmitter 1. The control device 3 provides an excitation current 5 to the transmitting antenna 4. The excitation current 5 is a high-power square wave pulse excitation current or a sinusoidal excitation current.

[0054] The ground fiber optic induced polarization signal receiving and acquisition device 2 is distributed in the measurement area according to the pre-designed measurement points or measurement lines;

[0055] The transmitting antenna 4 includes a grounded long conductor 42 or a loop transmitting coil; there are four grounded long conductors 42 that surround the work area, and each conductor has a grounding electrode 41 at both ends; the loop transmitting coil surrounds the work area and is a square large loop transmitting coil 43 or a circular large loop transmitting coil 44.

[0056] The ground-based fiber optic induced polarization signal receiving and acquisition device 2 includes at least one optical system for detecting induced polarization signals. The optical system includes a broadband light source 22, a polarizer 23, a polarization controller 24, a fiber optic circulator 25, a plasma resonance fiber optic sensing probe 26, a fiber optic circulator 25, and a spectrometer 27, which are connected in sequence.

[0057] The plasma resonance fiber optic sensing probe 26 is a miniature and chemically inert fiber optic sensor. This sensor can be inserted into the measurement medium to perform in-situ and continuous monitoring of electrochemical reactions and interfacial dynamic changes near the sensor surface. By detecting the disturbance of surface plasma waves propagating on its surface, the sensor can measure and monitor its electrochemical dynamic change characteristics without interfering with its normal operation.

[0058] Figure 2 This is a schematic diagram of the induced polarization data acquisition system and long wire emission structure of an ionosphere fiber optic sensor, which is one of the implementation methods.

[0059] The multiple plasma resonance fiber optic sensing probes 26 of the ground fiber optic induced polarization signal receiving and acquisition device 2 can be arranged in an array on the ground and connected to the instrument vehicle 6 on the ground via armored fiber optic cable 28. The instrument vehicle 6 controls the array via the armored fiber optic cable 28 and transmits the data collected by the array in real time via the armored fiber optic cable 28.

[0060] Example 1

[0061] like Figure 2As shown, when there are multiple plasma resonance fiber optic sensing probes 26, the distance between adjacent plasma resonance fiber optic sensing probes 26 is 10 meters to 50 meters, and they are connected by armored fiber optic cables 28.

[0062] When in use, the plasma resonance fiber optic sensing probe array 26 is configured such that every two plasma resonance fiber optic sensing probes 26 form a pair of induced polarization signal measurement probes, and the potential signal difference between the primary or secondary fields between each pair of plasma resonance fiber optic sensing probes 26 is measured sequentially.

[0063] The excitation current 5 is a high-power square wave pulse excitation current, the waveform of which is a zero-duty half-duty bipolar square wave or a pseudo-random pulse sequence with a zero duty cycle and positive and negative polarities, and the square wave period or unit pulse width is 0.01 to 64s. Alternatively, the excitation current 5 is a high-power sine wave excitation current, the waveform of which is a sine wave with positive and negative peaks at different frequencies.

[0064] The grounding conductor 42 of the transmitting antenna 4 has a length of 5000m to 10000m. The control device 3 of the ground transmitting source 1 alternately supplies power to the grounding conductor 42 in different directions through a reversing switch.

[0065] Example 2

[0066] Figure 3 This is a schematic diagram of the induced polarization data acquisition system and the square coil transmitting structure of the plasma fiber optic sensor according to Embodiment 2. The side length of the square large loop transmitting coil 43 is 5000m to 10000m. When there are multiple plasma resonance fiber optic sensing probes 26, the distance between adjacent plasma resonance fiber optic sensing probes 26 is 10 meters to 50 meters, and they are connected by armored fiber optic cables 28.

[0067] Example 3

[0068] Figure 4 This is a schematic diagram of the induced polarization data acquisition system and circular coil transmitting structure of the plasma fiber optic sensor according to Embodiment 3. The diameter of the circular large loop transmitting coil 44 is 5000m to 10000m. When there are multiple plasma resonance fiber optic sensing probes 26, the distance between adjacent plasma resonance fiber optic sensing probes 26 is 10 meters to 50 meters, and they are connected by armored fiber optic cables 28.

[0069] The data acquisition method of the induced polarization data acquisition system based on plasma fiber optic sensors includes the following steps:

[0070] S1. The control device 3 of the ground transmitter 1 continuously transmits excitation current 5, namely high-power square wave pulse excitation current or sine wave excitation current, which is supplied to the ground through the grounding electrode 41 of the transmitting antenna 4 to excite, or the square large loop transmitting coil 43 or the circular large loop transmitting coil 44 surrounding the three-dimensional induced electromagnetic data acquisition area excites and induces an electromagnetic field in the ground, so that induced eddy currents are generated in the underground medium, and the induced eddy currents gradually diffuse and attenuate in the half-space underground.

[0071] S2. The plasma resonance fiber optic sensing probe 26 in the ground fiber optic induced polarization signal receiving and acquisition device 2 collects the time-domain induced polarization signal or frequency-domain induced polarization signal generated on the ground by the power supply current or induced eddy current continuously emitted by the control device 3 of the high-power pulse ground transmitter 1 in step S1 at a certain point spacing along the pre-designed measurement line. Each measurement point measures and records 10 to 50 cycles of time-domain induced polarization signal or frequency-domain induced polarization signal.

[0072] S3. The GPS or Beidou timing and positioning module on the top of the instrument vehicle 6 on the ground provides timing for each time domain induced polarization signal or frequency domain induced polarization signal collected by each ground fiber optic induced polarization signal receiving and acquisition device 2.

[0073] S4. The plasma resonance fiber optic sensing probe 26 array of the ground fiber optic induced polarization signal receiving and acquisition device 2 transmits the ground time-domain induced polarization signal or frequency-domain induced polarization signal acquired in step S2 to the fiber laser signal modulation and demodulation instrument in the ground instrument vehicle 6 in real time through the armored fiber optic cable 28. Then, it is converted into time-domain induced polarization data or frequency-domain induced polarization data at each measurement point location. Finally, it is stored in the computer in the instrument vehicle 6.

[0074] S5. Process the time-domain induced polarization data from step S4 in the time domain to obtain the apparent polarization parameter (η) of each measurement point. s The parameters of attenuation (D) and excitation ratio (J) are then used to extract mineral, lithological, reservoir, and fluid parameters related to the formation's electrical properties.

[0075] S6, the apparent polarizability η s It is a fundamental measurement parameter in DC (time domain) induced polarization method, and it comprehensively reflects the induced polarization effect of topography and various polarimetric bodies within the current's range of influence. Its expression is: η s =ΔU2(t) / ΔU(T)×100%, where ΔU(T) is the polarization field potential difference measured at power supply time T; ΔU2(t) is the secondary field potential difference measured at time t after power outage. η s Expressed as a percentage, its size and distribution reflect the presence and occurrence of polaritons within a certain depth range underground. (From η) sAs can be seen from the expression, apparent polarizability is related to the power supply time T and the measurement delay time t. Therefore, when referring to polarizability, the corresponding power supply time T and measurement time t must be specified. For simplicity, we define apparent polarizability as the measurement result under long power supply (T→∞) and no delay (t→0).

[0076] The attenuation degree D is a measurement parameter reflecting the rate of decay of the secondary field (excited polarization field), expressed as a percentage. Its expression is: D = ΔU1(t) / ΔU2(t) × 100%, where ΔU1(t) is the average value of the secondary field potential difference over a certain period after power failure. The faster the secondary field decays, the smaller its attenuation degree.

[0077] The excitation ratio (J) is a comprehensive parameter combining apparent polarizability and attenuation, reflecting the magnitude of the secondary field and its attenuation characteristics. Its calculation formula is J = η. s ×D=ΔU1(t) / ΔU(T)×100%. For aquifers, generally η s Both D and D are high values, and multiplying them can amplify the anomaly and make the anomaly more obvious.

[0078] S7. Process the frequency domain induced polarization data from step S4 in the frequency domain to obtain the frequency domain excitation polarization parameter video divergence P at each measurement point. s Apparent phase φ s Apparent complex resistivity spectrum ρ s (iω), and then extract mineral, lithological, reservoir and fluid parameters related to the formation electrical properties;

[0079] S8, the video dispersion P s It is a fundamental measurement parameter in the AC (frequency domain) excited polarization method, and its expression is: P s =(ΔU(f) D )-ΔU(f G )) / ΔU(f D )×100%,ΔU(f D ), ΔU(f G ) represent the ultra-low frequency band (n×10) －2 ~n×10 2 The total field potential difference formed by the low-frequency and high-frequency supply currents (Hz). And η s Similarly, P s It is also a comprehensive reflection of the topography and the polarization effect induced by various polarimetric bodies within the range of current action. Since time-domain induced polarization and frequency-domain induced polarization are physically consistent, under limiting conditions, i.e., ΔU(f D →0) and ΔU(f G When the value approaches infinity (→∞), both methods will produce exactly the same measurement results.

[0080] The induced polarization effect causes a phase shift in the total field potential difference relative to the supply current; this is the apparent phase φ of the complex resistivity. s All other things being equal, the stronger the induced polarization effect, the greater the φ. s The larger the absolute value, the greater the apparent phase φ. s It can also be used as a parameter to describe the strength of the induced polarization effect. In fact, the apparent phase φ caused by the induced polarization effect... s The dispersion factor P is approximately proportional to the slope of the amplitude-frequency curve or the rate of change of the electric field amplitude with frequency. s (f D f G It also corresponds to the amplitude-frequency response curve at frequency f. D and f G The average slope between frequencies is proportional. Therefore, the phase φ at a certain frequency f is proportional to the average slope between frequencies. s The dispersion rate P of the two frequencies before and after it s (f D f G It is approximately proportional to φ. s and P s (f D f G Like the (limiting) apparent polarizability η, it is also related to the apparent polarizability η. s They are directly proportional, and the latter can be used to represent them.

[0081] The induced electrostatic effect in an alternating current field is characterized by the frequency characteristics of the total field potential difference or complex resistivity. Therefore, the complex resistivity spectrum ρ across the entire (ultra-low frequency) frequency band where the induced electrostatic effect occurs... s (iω) should be the most comprehensive parameter describing the frequency domain induced polarization effect. The complex resistivity method, or spectral induced polarization method, studies underground geological conditions by observing the real and imaginary components, or amplitude and phase spectra of the apparent complex resistivity over a fairly wide (ultra-low frequency) band.

[0082] S9. Perform time-domain and frequency-domain inversion imaging on the time-domain or frequency-domain excitation polarization parameters of each measuring point obtained in steps S5 and S7 respectively to obtain the distribution of the time-domain complex resistivity or the frequency-domain complex resistivity in the three-dimensional space of the underground strata in the three-dimensional induced polarization data acquisition area.

[0083] S10. Based on the relationship between the distribution variation law of the formation time domain complex resistivity obtained by the time domain processing method and the formation frequency domain complex resistivity obtained by the frequency domain processing method, the distribution variation law of formation polarizability is obtained.

[0084] S11. Based on the distribution patterns, ranges, and characteristics of the complex resistivity and polarizability of underground strata, and through comprehensive interpretation combined with other geological, structural, lithological, mineral, and geoscientific information, the geoelectric characteristics of underground strata or rock units can be delineated, potential enrichment or accumulation zones of metallic, non-metallic, or oil and gas resources can be identified, predicted, interpreted, and evaluated, and the distribution of oil and gas-bearing or highly polarizable minerals in the strata can be realized.

[0085] All other parts not described in detail are existing technology.

Claims

1. An induced polarization data acquisition system based on a plasma fiber optic sensor, comprising a ground transmitter (1) and a ground fiber optic induced polarization signal receiving and acquisition device (2). The ground transmitter (1) is a time-domain pulse current transmitter or a frequency-domain sinusoidal current transmitter, and also includes a control device (3) and a transmitting antenna (4) for the ground transmitter (1). The control device (3) provides an excitation current (5) to the transmitting antenna (4). The ground fiber optic induced polarization signal receiving and acquisition device (2) is distributed in the measurement area according to the pre-designed measurement points or measurement lines; The ground fiber optic induced polarization signal receiving and acquisition device (2) includes at least one optical system for detecting induced polarization signals. The optical system includes a broadband light source (22), a polarizer (23), a polarization controller (24), a fiber optic circulator (25), and a plasma resonance fiber optic sensing probe (26) connected in sequence. The fiber optic circulator (25) and the spectrometer (27) are connected. The array includes multiple plasma resonance fiber optic sensing probes (26) arranged in an array on the ground. The array of plasma resonance fiber optic sensing probes (26) is arranged such that every two plasma resonance fiber optic sensing probes (26) form a pair of fiber optic induced polarization signal measurement probes, and the potential signal difference between the primary or secondary fields between the two plasma resonance fiber optic sensing probes (26) is measured in sequence. The transmitting antenna (4) includes a grounded long conductor (42) or a loop transmitting coil; there are four grounded long conductors (42) that surround the work area, and each conductor has a grounding electrode (41) at both ends; the loop transmitting coil surrounds the work area and is a square large loop transmitting coil (43) or a circular large loop transmitting coil (44).

2. The induced polarization data acquisition system based on a plasma fiber optic sensor according to claim 1, characterized in that, The plasma resonance fiber optic sensing probe (26) is a miniature and chemically inert fiber optic sensor.

3. The induced polarization data acquisition system based on a plasma fiber optic sensor according to claim 1, characterized in that, The plasma resonance fiber optic sensing probe (26) is connected to an instrument vehicle (6) on the ground via an armored fiber optic cable (28). The instrument vehicle (6) controls the array via the armored fiber optic cable (28) and collects data from the array.

4. The induced polarization data acquisition system based on a plasma fiber optic sensor according to claim 3, characterized in that, The adjacent plasma resonance fiber optic sensing probes (26) are spaced 10 to 50 meters apart and connected by armored fiber optic cables (28).

5. The induced polarization data acquisition system based on a plasma fiber optic sensor according to claim 1, characterized in that, The excitation current (5) is a high-power square wave pulse excitation current, the waveform of which is a zero-duty half-duty bipolar square wave or a pseudo-random pulse sequence with a zero duty cycle and positive and negative polarities, and the square wave period or unit pulse width is 0.01~64s; or the excitation current (5) is a high-power sine wave excitation current, the waveform of which is a sine wave with positive and negative peaks at different frequencies.

6. The induced polarization data acquisition system based on a plasma fiber optic sensor according to claim 1, characterized in that, The length of the grounding long conductor (42) is 5000m~10000m, and the control device (3) alternately supplies power to the grounding long conductor (42) in different directions through a reversing switch; The square large loop transmitting coil (43) has a side length of 5000m~10000m, and the circular large loop transmitting coil (44) has a diameter of 5000m~10000m.

7. A method for acquiring induced polarization data based on a plasma fiber optic sensor, characterized in that, The induced polarization data acquisition system based on a plasma fiber optic sensor as described in any one of claims 1 to 6 includes the following steps: S1. The control device (3) of the ground transmitter (1) continuously transmits excitation current (5), namely high-power square wave pulse excitation current or sine wave excitation current, which is supplied to the ground through the grounding electrode (41) of the transmitting antenna (4) to excite, or through the square large loop transmitting coil (43) or the circular large loop transmitting coil (44) surrounding the three-dimensional induced electromagnetic data acquisition area to excite and induce electromagnetic fields in the ground, so that induced eddy currents are generated in the underground medium, and the induced eddy currents gradually diffuse and attenuate in the half-space underground. S2, the plasma resonance fiber optic sensing probe (26) in the ground fiber optic induced polarization signal receiving and acquisition device (2) collects the time-domain induced polarization signal or frequency-domain induced polarization signal generated on the ground by the control device (3) continuously transmitting the power supply current or induced eddy current along the pre-designed measuring line at a certain point spacing in step S1. Each measuring point measures and records 10 to 50 cycles of time-domain induced polarization signal or frequency-domain induced polarization signal. S3, the GPS or Beidou timing and positioning module on the top of the instrument vehicle (6) on the ground provides timing for each ground fiber optic induced polarization signal receiving and acquisition device (2) for each time domain or frequency domain induced polarization signal acquired. S4. The plasma resonance fiber optic sensing probe (26) array of the ground fiber optic induced polarization signal receiving and acquisition device (2) transmits the ground time-domain or frequency-domain induced polarization signal acquired in step S2 to the fiber laser signal modulation and demodulation instrument in the ground instrument vehicle (6) in real time through the armored fiber optic cable (28), and then converts it into time-domain induced polarization data or frequency-domain induced polarization data at each measurement point; finally, it is stored in the computer in the instrument vehicle (6). S5. Process the time-domain induced polarization data from step S4 in the time domain to obtain the apparent polarization parameter η at each measurement point. s The attenuation degree D and the excitation ratio J are used to extract mineral, lithological, reservoir and fluid parameters related to the formation's electrical properties. S6, the apparent polarizability η s It is a basic measurement parameter of the time-domain DC excitation polarization method. It is a comprehensive reflection of the topography and various polarimetric bodies in the range of current action. The attenuation degree is a measurement parameter that reflects the rate of attenuation of the excitation polarization field and is expressed as a percentage. The faster the secondary field decays, the smaller its attenuation degree. The excitation ratio J is a comprehensive parameter that is a combination of apparent polarizability and attenuation degree. S7. Process the frequency domain induced polarization data from step S4 in the frequency domain to obtain the frequency domain excitation polarization parameter video divergence P at each measurement point. s Apparent phase φ s Apparent complex resistivity spectrum ρ s (iω), and then extract mineral, lithological, reservoir and fluid parameters related to the formation electrical properties; S8, the video dispersion P s It is a fundamental measurement parameter in the frequency domain AC excited polarization method, and η s Similarly, P s It is also a comprehensive reflection of the topography and the polarization effect induced by various polarimetric bodies within the range of current action; the induced polarization effect causes a phase shift in the total field potential difference relative to the supply current, which is the apparent phase φ of the complex resistivity. s Under the same conditions, the stronger the induced polarization effect, the greater the φ. s The larger the absolute value, the greater the apparent phase φ. s As a parameter describing the strength of the induced polarization effect; the induced polarization effect in an alternating current field is characterized by the frequency characteristics of the total field potential difference or complex resistivity. Therefore, the complex resistivity spectrum ρ across the entire ultra-low frequency band where the induced polarization effect occurs... s (iω) is the parameter that most comprehensively describes the frequency domain induced polarization effect; S9. Perform time-domain inversion imaging and frequency-domain inversion imaging on the time-domain excitation polarization parameters or frequency-domain excitation polarization parameters of each measuring point obtained in steps S5 and S7 respectively to obtain the distribution of the time-domain complex resistivity or the frequency-domain complex resistivity in the three-dimensional space of the strata under the three-dimensional induced polarization data acquisition area. S10. Based on the relationship between the distribution variation law of the formation time domain complex resistivity obtained by the time domain processing method and the formation frequency domain complex resistivity obtained by the frequency domain processing method, the distribution variation law of formation polarizability is obtained. S11. Based on the distribution patterns, ranges, and characteristics of the complex resistivity and polarizability of underground strata, through comprehensive interpretation combining geological, structural, lithological, mineral, and geoscientific information, the geoelectric characteristics of underground strata or rock units are delineated, potential enrichment or accumulation zones of metallic, non-metallic, or oil and gas resources are identified, predicted, interpreted, and evaluated, and the distribution of oil and gas-bearing or highly polarizable minerals in the strata is realized.

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