A downhole phased array compound electromagnetic ranging system and method

Abstract

This invention discloses a downhole phased array composite electromagnetic ranging system and method, specifically relating to the field of downhole adjacent well detection technology. The system controls multiple circumferentially distributed transmitting array elements to be independently excited sequentially, acquiring independent response signals. A circumferential coupling imbalance map of the array elements is constructed, generating a compensated control sequence. Each array element is driven to form a scanning beam and a focusing beam, acquiring electromagnetic response signals under different beam modes. When the consistency of the response evolution is below a threshold, the true target well direction is confirmed based on peak displacement and phase difference reversal. After ranking the stability of each candidate direction, the distance and azimuth estimates are fused using a layered weighted method, outputting the relative distance and relative azimuth. This invention suppresses near-field distortion by constructing and dynamically compensating for the circumferential coupling imbalance map of the array elements; accurately identifies the true direction using multi-beam consistency discrimination and peak displacement and phase difference reversal; and improves ranging reliability by fusion of the stability ranking results using a layered weighted method.

Description

Technical Field

[0001] This invention relates to the field of downhole adjacent well detection technology, and more specifically, to a downhole phased array composite electromagnetic ranging system and method. Background Technology

[0002] In the field of downhole adjacent well distance measurement, an electromagnetic detection scheme using a single transmitter and a single receiver probe is a common approach. This scheme typically employs a longitudinally arranged transmitting coil to apply discontinuous alternating excitation, and two transverse receiving coils at both ends of the drill collar. The distance and azimuth of adjacent wells are calculated by measuring the changes in the induced electromotive force on the receiving coils. This method has a relatively simple structure and, under conditions of simple wellbore trajectory and relatively uniform distribution of downhole metal components, can provide acceptable ranging accuracy and azimuth indication.

[0003] In actual drilling operations, various asymmetrically distributed metallic objects often exist within the well, such as centralizers, stabilizers, adjacent well casing joints, screen pipes, and debris from fish that have fallen into the well. These metallic objects can cause near-field reflection, eddy current absorption, and magnetic circuit shunting of the primary magnetic field generated by the transmitting coil, resulting in a pseudo-enhanced response in the received signal that is highly similar to the actual electromagnetic response characteristics of the target well. At the same time, the continuous rotation of the drill string during rotary drilling causes the relative orientation between the metallic components and the transmitting probe to constantly change, further exacerbating the periodic distortion and phase jumps of the received signal.

[0004] Single-source structures, lacking the ability to acquire multi-view spatial information and beam pointing control, struggle to effectively distinguish between real target well signals and metallic interference signals under dynamic conditions of rotational propulsion and circumferential asymmetric metallic interference. Ranging results are also susceptible to near-field asymmetric coupling distortion. Therefore, improving the adaptability of single-source schemes to complex downhole electromagnetic environments while retaining their structural simplicity has become a focus of ongoing research for those skilled in the art. This invention proposes a downhole phased array composite electromagnetic ranging system and method to address the aforementioned problems. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides the following technical solution: A downhole phased array composite electromagnetic ranging method includes the following steps: Multiple transmitting array elements distributed circumferentially along the downhole tool body are controlled to be independently excited sequentially according to a preset test sequence, and the independent response signal of each transmitting array element in the current downhole environment is collected. Based on the preset array element circumferential coupling imbalance spectrum model, the array element circumferential coupling imbalance spectrum is constructed using independent response signals. Based on the array element circumferential coupling imbalance spectrum, the required phase compensation and amplitude compensation for each transmitting array element are calculated, and the compensated control sequence is generated. Based on the compensated control sequence, each transmitting array element is driven to form a scanning beam that deflects circumferentially and a focusing beam that focuses in a preset specified direction, and the corresponding electromagnetic response signals are collected in different beam modes. The response feature combination corresponding to each candidate direction is extracted from the electromagnetic response signal, namely response amplitude, phase dispersion, spatial gradient concentration and residual convergence. When the consistency of response evolution between different beam modes is lower than the preset consistency threshold, the true target well direction is confirmed from multiple candidate directions based on the peak displacement relationship and phase difference reversal relationship of the deflection beams on both sides of each candidate direction. Based on the combination of response features corresponding to each candidate direction, the candidate directions are ranked according to their stability. Based on the stability ranking results, the distance estimate and azimuth estimate of the target well are fused in a hierarchical weighted manner to output the relative distance and relative azimuth of the target well.

[0006] In a preferred embodiment, the response feature combination is extracted in the following way: For each candidate direction, the received signal amplitude in that direction is extracted from the electromagnetic response waveform of the corresponding beam mode as the response amplitude; The phase dispersion is calculated as follows: traverse multiple measurement positions adjacent to the candidate direction, extract the received signal phase at each position, and calculate the standard deviation of these phases. This standard deviation is the phase dispersion. The spatial gradient concentration is calculated as follows: perform a second-order difference operation on the response amplitude of the candidate direction and its two adjacent directions before and after, take the reciprocal of the absolute value of the second-order difference and normalize it to obtain the spatial gradient concentration. The residual convergence is calculated as follows: the measured response amplitude is calculated by subtracting the preset theoretical amplitude to obtain the residual, and the negative value of the rate of change of the residual at multiple continuous scanning angles is taken as the residual convergence.

[0007] In a preferred embodiment, the independent response signal of each transmitting element in the current downhole environment is acquired, specifically referring to: Set a preset test sequence that iterates through all transmitting elements, where the excitation duration of each transmitting element is a fixed duration and a silent interval is set between adjacent excitations; During the excitation of each transmitting element, the electromagnetic response waveforms of each receiving channel are synchronously acquired through a multi-channel receiving array; For each set of acquired waveforms, perform quadrature demodulation to obtain in-phase and quadrature components. Calculate the amplitude of the independent response signal of the transmitting array element under the current environment by taking the square root of the sum of squares, and calculate the phase of the independent response signal by taking the arctangent of the ratio of the quadrature components. Record the amplitude sequence and phase sequence corresponding to all transmitting array elements, where the length of both the amplitude sequence and the phase sequence is equal to the total number of transmitting array elements. The amplitude sequence and the phase sequence together constitute an independent response signal.

[0008] In a preferred embodiment, the circumferential coupling imbalance map of the array elements is constructed using independent response signals, specifically referring to: Under an ideal equilibrium state, the ideal amplitude of each transmitting element is the average of the actual amplitudes of all transmitting elements, and the ideal phase is zero degrees. The amplitude imbalance coefficient of each transmitting element is obtained by comparing the actual amplitude with the ideal amplitude. The phase imbalance deviation of each transmitting element is obtained by calculating the difference between the actual phase and the ideal phase. The amplitude imbalance coefficient and phase imbalance deviation of each transmitting array element are combined in circumferential order to form a set of circumferentially distributed two-element group sequences, which is the array element circumferential coupling imbalance map. Among them, an amplitude imbalance coefficient greater than one indicates that there is gain distortion in that direction, and less than one indicates that there is attenuation distortion. The positive or negative sign of the phase imbalance deviation indicates whether the phase is leading or lagging.

[0009] In a preferred embodiment, generating the compensated control sequence specifically includes the following steps: Extract the amplitude imbalance coefficient and phase imbalance deviation of each transmitting element from the circumferential coupling imbalance map of the array elements; The amplitude compensation amount of each transmitting array element is set to the reciprocal of its corresponding amplitude imbalance coefficient, wherein when the amplitude imbalance coefficient is zero, the amplitude compensation amount of the transmitting array element is set to one. The phase compensation amount of each transmitting element is set to the negative of its corresponding phase imbalance deviation; The amplitude compensation and phase compensation required for each transmitting element are multiplied and added one by one according to the original excitation parameters of the corresponding transmitting element to obtain the compensated excitation amplitude and excitation phase. All compensated excitation amplitudes and excitation phases are arranged into a compensated control sequence according to the circumferential arrangement of the transmitting array elements.

[0010] In a preferred embodiment, driving each transmitting array element to form a scanning beam deflected circumferentially includes the following steps: From the compensated control sequence, obtain the compensated excitation amplitude and excitation phase of each transmitting element; define the element spacing as the arc length between the centers of two adjacent transmitting elements, and define the wavelength as the electromagnetic wave wavelength of the current excitation frequency in the formation medium; Set a scanning step angle sequence that covers a circumferential range from 0 degrees to 360 degrees; for each target deflection angle, calculate the required excitation phase difference between adjacent transmitting elements using the following formula: The excitation phase difference is equal to 2π multiplied by the element spacing, then multiplied by the sine of the target deflection angle, and then divided by the wavelength. Starting from the first transmitting element, the excitation phase difference is accumulated sequentially to obtain the deflection phase of each transmitting element; The compensated excitation phase and deflection phase of each transmitting element are added together to form the scanning beam control parameters at the target deflection angle. The scanning beam control parameters are applied sequentially according to the target deflection angle, so that the main lobe direction of the synthesized beam is deflected sequentially along the circumference.

[0011] In a preferred embodiment, acquiring corresponding electromagnetic response signals under different beam patterns specifically includes the following steps: Set a preset direction, which is the circumferential azimuth angle relative to the axis of the downhole tool body; For each transmitting element, measure or calculate the distance from its geometric center to the center of the tool body, and then multiply it by the cosine of the circumferential azimuth angle to obtain the projected distance of the element in the specified direction. Divide the projected distance by the wavelength to get the projection distance multiple in wavelength units, then multiply by 2π to get the propagation phase delay of the array element due to the position difference. The focusing phase of each transmitting element is set to the opposite of the propagation phase delay, so that the electromagnetic waves emitted by each element are superimposed in phase when they propagate to the specified direction. The compensated excitation phase of each transmitting element is added to the focusing phase to form the focusing beam control parameters; The focusing beam control parameters are applied in the focusing beam mode, and the electromagnetic response waveforms of each receiving channel are synchronously acquired through a multi-channel receiving array. In scanning beam mode, electromagnetic response waveforms at each deflection angle are sequentially acquired according to the scanning beam control parameters. All waveforms acquired in these two modes are classified and recorded according to beam mode type and deflection angle, serving as electromagnetic response signals for different beam modes.

[0012] In a preferred embodiment, confirming the true target well direction from multiple candidate directions specifically includes the following steps: The response features of each candidate direction extracted under different beam modes are combined and compared. The correlation coefficient of the response amplitude with the angle between different modes is calculated. When the correlation coefficient is lower than the preset consistency threshold, it is determined that there is false enhancement interference and direction confirmation is initiated. For each candidate direction, the electromagnetic response waveforms under the left and right deflection beams of that direction are collected respectively. The deflection angles corresponding to the left peak and the right peak are extracted. The difference between the two is calculated as the peak displacement. Based on the magnitude of the peak displacement, the distance estimate of the target well is calculated according to the preset ratio. When the peak displacement is symmetrically distributed with respect to the candidate direction and the displacement amount is greater than the preset displacement threshold, it is confirmed as the true target well direction; Simultaneously, the phases of the received signals under the left and right deflection beams are extracted and compared. When the difference between the left and right phases changes from positive to negative or from negative to positive, a phase difference reversal relationship is determined. The azimuth estimate of the target well is determined based on the deflection angle corresponding to the reversal relationship, and the candidate direction is confirmed as the true target well direction. When at least one of the peak displacement relationship and the phase difference reversal relationship is satisfied, the output confirms the true target well direction, as well as the corresponding distance estimate and azimuth estimate.

[0013] In a preferred embodiment, the distance estimate and azimuth estimate corresponding to the confirmed true target well direction are output with stability weighting, specifically including: Obtain and confirm the combination of response features corresponding to the true target well direction; When the phase dispersion is greater than the preset minimum positive threshold, its reciprocal is used as the phase stability factor; when the phase dispersion is less than or equal to the minimum positive threshold, the phase stability factor is set to the preset upper limit value. Spatial gradient concentration is directly used as the gradient stability factor; the absolute value of residual convergence is used as the residual stability factor. Calculate the weighted sum of the above three factors to obtain the comprehensive stability score of the actual target well direction; The first number is set as the number of high-stability measurements, and the second number is set as the number of medium-stability measurements. The multiple distance and azimuth estimates obtained from repeated measurements of the true target well direction are sorted from high to low according to the comprehensive stability score. The first number in the sort is assigned to the high stability layer and given the first weight coefficient, and the second number is assigned to the medium stability layer and given the second weight coefficient. The first weight coefficient is greater than the second weight coefficient and both are positive. For each measurement, its distance estimate and azimuth estimate are multiplied by the corresponding weighting coefficient. The weighted values ​​in the high-stability layer are summed to obtain the first weighted sum, and the weighted values ​​in the medium-stability layer are summed to obtain the second weighted sum. The first weighted sum and the second weighted sum are added together and divided by the total number of weights of the first weighting coefficient and the second weighting coefficient to obtain the fused relative distance and relative azimuth, which are used as the final output relative distance and relative azimuth of the target well.

[0014] In a preferred embodiment, a downhole phased array composite electromagnetic ranging system includes: The excitation acquisition module is used to control multiple transmitting array elements distributed circumferentially along the downhole tool body to be excited independently in sequence according to a preset test sequence, and to acquire the independent response signal of each transmitting array element in the current downhole environment. The spectrum compensation module is used to construct the circumferential coupling imbalance spectrum of the array elements using independent response signals based on the preset array element circumferential coupling imbalance spectrum model, and calculate the required phase compensation and amplitude compensation for each transmitting array element based on the array element circumferential coupling imbalance spectrum, and generate the compensated control sequence. The beam control module is used to drive each transmitting array element to form a scanning beam that deflects circumferentially and a focused beam that focuses in a preset specified direction based on the compensated control sequence, and to acquire the corresponding electromagnetic response signals in different beam modes. The direction confirmation module is used to extract the response feature combination corresponding to each candidate direction from the electromagnetic response signal. When the consistency of response evolution between different beam modes is lower than the preset consistency threshold, the true target well direction is confirmed from multiple candidate directions based on the peak displacement relationship and phase difference reversal relationship of the deflection beams on both sides of each candidate direction. The fusion output module is used to rank the candidate directions based on the combination of response features corresponding to each candidate direction, and to perform hierarchical weighted fusion of the distance and azimuth estimates of the target well based on the stability ranking results, and output the relative distance and relative azimuth of the target well.

[0015] The technical effects and advantages of this invention are as follows: This invention controls multiple transmitting array elements distributed circumferentially along the downhole tool body to be independently excited sequentially according to a preset test sequence, collects independent response signals and constructs a circumferential coupling imbalance spectrum of the array elements, and then calculates the phase compensation and amplitude compensation required for each transmitting array element to generate a compensated control sequence. This can quantitatively identify and dynamically compensate for amplitude and phase distortions caused by asymmetric metal components in various directions in the downhole, thereby effectively suppressing the interference of near-field asymmetric coupling distortion on the ranging results and improving the anti-distortion capability of electromagnetic ranging in complex well network environments.

[0016] This invention drives each transmitting array element to form a scanning beam deflected circumferentially and a focusing beam focused in a preset direction based on a compensated control sequence. Electromagnetic response signals are acquired under different beam modes, and the response amplitude, phase dispersion, spatial gradient concentration, and residual convergence corresponding to each candidate direction are extracted. When the consistency of response evolution between different beam modes is lower than a preset consistency threshold, the true target well direction is confirmed based on the peak displacement relationship and phase difference reversal relationship of the deflected beams on both sides of each candidate direction. This can effectively distinguish the response of the true target well from the pseudo-enhanced response induced by metal components, reduce the probability of false alarms and missed alarms, and improve the accuracy of target well identification.

[0017] This invention ranks the candidate directions based on the combination of response characteristics corresponding to each candidate direction, and performs hierarchical weighted fusion of the distance and azimuth estimates of the target well based on the stability ranking results, outputting the relative distance and relative azimuth of the target well. By comprehensively weighting the phase dispersion, spatial gradient concentration, and residual convergence, high-stability and medium-stability measurements are assigned different weights and then fused, which retains the dominant role of high-stability measurements and absorbs the effective information of medium-stability measurements, making the final output relative distance and relative azimuth more reliable. Attached Figure Description

[0018] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings; Figure 1 This is a schematic diagram of a downhole phased array composite electromagnetic ranging method according to the present invention.

[0019] Figure 2 This is a schematic diagram of a downhole phased array composite electromagnetic ranging system according to the present invention. Detailed Implementation

[0020] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Reference Figure 1 - Figure 2 The following examples were obtained: Example 1: A downhole phased array composite electromagnetic ranging method, comprising the following steps: Multiple transmitting array elements distributed circumferentially along the downhole tool body are controlled to be independently excited sequentially according to a preset test sequence, and the independent response signal of each transmitting array element in the current downhole environment is collected. Based on the preset array element circumferential coupling imbalance spectrum model, the array element circumferential coupling imbalance spectrum is constructed using independent response signals. Based on the array element circumferential coupling imbalance spectrum, the required phase compensation and amplitude compensation for each transmitting array element are calculated, and the compensated control sequence is generated. Based on the compensated control sequence, each transmitting array element is driven to form a scanning beam that deflects circumferentially and a focusing beam that focuses in a preset specified direction, and the corresponding electromagnetic response signals are collected in different beam modes. The response feature combination corresponding to each candidate direction is extracted from the electromagnetic response signal, namely response amplitude, phase dispersion, spatial gradient concentration and residual convergence. When the consistency of response evolution between different beam modes is lower than the preset consistency threshold, the true target well direction is confirmed from multiple candidate directions based on the peak displacement relationship and phase difference reversal relationship of the deflection beams on both sides of each candidate direction. Based on the combination of response features corresponding to each candidate direction, the candidate directions are ranked according to their stability. Based on the stability ranking results, the distance estimate and azimuth estimate of the target well are fused in a hierarchical weighted manner to output the relative distance and relative azimuth of the target well.

[0022] The specific extraction method for response feature combination is as follows: For each candidate direction, the received signal amplitude in that direction is first directly read from the electromagnetic response waveform of the corresponding beam mode; this value is the response amplitude. During downhole drilling, for example, the scanning beam of a rescue well points to different angles sequentially. The received signal strength varies at each angle. The direction with the largest response amplitude may be the direction of the target well, but downhole metal components can also generate strong amplitudes, so other features are needed to assist in the judgment.

[0023] Next, the phase dispersion is calculated by traversing multiple measurement locations adjacent to the candidate direction, extracting the phase value of the received signal at each location, and then calculating the standard deviation of these phase values. This standard deviation is the phase dispersion. For example, when the beam is pointed towards the actual sleeve, the phase change at several adjacent measurement points is relatively gradual, and the standard deviation may only be a few degrees; when the beam is pointed towards a metal fragment, the phase between adjacent points may fluctuate, and the standard deviation will be significantly larger. Phase dispersion reflects the consistency of the phase in the vicinity of that direction.

[0024] Next, the spatial gradient concentration is calculated by performing a second-order difference operation on the response amplitudes of the candidate direction and its two adjacent directions before and after it. The reciprocal of the absolute value of the second-order difference is then taken and normalized to obtain the spatial gradient concentration. For example, the response amplitude of a real target well exhibits a sharp single peak in space, with a large absolute value of its second-order difference. After taking the reciprocal, the value becomes very small, and after normalization, it approaches zero. Conversely, a flat or highly fluctuating response curve has a small absolute value of its second-order difference, but the value becomes very large after taking the reciprocal. For ease of understanding, in practical applications, the normalized value can be subtracted by one to make the value larger for higher concentrations, but the calculation method itself still uses the reciprocal of the second-order difference for normalization. This feature describes the degree of energy concentration of the response amplitude in space.

[0025] Finally, the residual convergence is calculated. The measured response amplitude is compared with the preset theoretical amplitude to obtain the residual. For each candidate direction, three equally spaced scanning angles are taken, one for that direction and one for each of its adjacent left and right sides. The residual value at each angle is calculated separately. Then, the first-order difference between the residuals of adjacent angles is calculated: first, the residual value of the left angle is subtracted from the residual value of the middle angle, and then the residual value of the middle angle is subtracted from the residual value of the right angle. The average of these two differences is divided by the scanning angle step size to obtain the rate of change. Finally, the negative value of the rate of change is taken to obtain the residual convergence. The preset theoretical amplitude comes from an ideal dipole model, which assumes that the formation is homogeneous and the target well casing is an infinitely long cylinder. When the beam sweeps across the actual target well direction, the measured amplitude gradually approaches the theoretical value, the residual decreases rapidly, and the rate of change is negative. Taking the negative value results in a positive value, indicating convergence. When the beam sweeps across metallic interference, the residual fluctuates violently and does not have a stable decreasing trend. The rate of change may be close to zero or uncertain, and the corresponding residual convergence is close to zero or negative. For example, in a certain scan, if the step size of three adjacent angles of the candidate direction is two degrees, and the residual values ​​are 0.12, 0.08, and 0.05 respectively, then the first difference is -0.04, the second difference is -0.03, and the average difference is -0.035. Dividing by the step size of 2 degrees gives a rate of change of -0.0175. Taking the negative value, the residual convergence is 0.0175, which is positive, indicating that the direction conforms to the theoretically expected attenuation law.

[0026] The above four features describe the attributes of each candidate direction from the perspectives of signal strength, phase stability, spatial energy concentration, and theoretical consistency. For example, in a downhole experiment, the scanning beam had the largest response amplitude at an angle of 30 degrees, but the phase dispersion reached 20 degrees, the spatial gradient concentration was only 0.2, and the residual convergence was -0.1. At an angle of 42 degrees, the response amplitude was slightly smaller, but the phase dispersion was only 4 degrees, the spatial gradient concentration was 0.8, and the residual convergence was 0.5. By comprehensively comparing these four features, the true target well direction can be determined more reliably.

[0027] In existing technologies, the ideal dipole model is a widely adopted simplified electromagnetic field model. Its physical basis stems from the concept of an electric fundamental oscillator in electromagnetic field theory, which is a straight high-frequency current conductor with a length much smaller than the working wavelength and a current distribution of equal amplitude and in phase along its length. In spherical coordinates, this model can derive complete analytical expressions for the electric and magnetic field strengths through the magnetic vector potential. In practical applications of downhole adjacent well detection and electromagnetic ranging and collision avoidance while drilling, existing technologies generally equate downhole magnetic sources (such as permanent magnet short sections, solenoid assemblies, or energized solenoids) to an idealized magnetic dipole, thereby simplifying the calculation of the magnetic field distribution.

[0028] Specifically, in the step of obtaining the preset theoretical amplitude, existing technologies usually use the magnetic dipole method for analysis. First, a magnetic dipole model based on Coulomb's law is established. Then, based on this model, the expression for the magnetic field strength of the magnetic dipole in the three orthogonal directions at any point in space is derived. Based on this, the formula for calculating the magnetic field strength generated by the magnetic source at any point in space is further derived, thereby obtaining the ideal theoretical value of the magnetic induction intensity at the probe changing with distance and azimuth angle.

[0029] In practical implementation, researchers used numerical simulation methods to analyze the influence of key parameters such as the spacing between magnetic sources, the magnetic moment of the magnetic sources, the relative permeability of the casing, and the diameter of the casing on the magnetic induction intensity at the probe. Based on this, they established a calculation model for the magnetization magnetic field of the adjacent well casing based on the magnetic dipole model. Finally, they used the actual measured downhole parameters (excitation current, magnetic moment, formation equivalent conductivity, etc.) as inputs into the mathematical model to calculate the theoretical response amplitude curve and finally obtain the preset theoretical amplitude.

[0030] Collecting the independent response signal of each transmitting element in the current downhole environment specifically refers to: When acquiring the independent response signal of each transmitting element in the current downhole environment, the first step is to set up a preset test sequence that iterates through all transmitting elements. In this sequence, the excitation duration of each transmitting element is fixed to the same duration; for example, in downhole tool design, the duration is set to one or two milliseconds based on the response time of the transmitting circuit and the formation. A silence interval is left between two adjacent transmitting elements. This interval allows the eddy currents and secondary fields generated by the previous excitation to sufficiently attenuate, avoiding interference with the measurement of the next element. The interval duration is generally set to three to five times the excitation duration, for example, five to ten milliseconds. For example, if the downhole tool has eight transmitting elements evenly distributed circumferentially, the first transmitting element is activated for one millisecond, then paused for five milliseconds; then the second transmitting element is activated for one millisecond, then paused for five milliseconds, and so on, iterating through all eight elements.

[0031] During the excitation of each transmitting element, the electromagnetic response waveforms of each receiving channel are simultaneously acquired via a multi-channel receiving array. The multi-channel receiving array typically includes three or six receiving coils, distributed at different locations on the tool body. It can simultaneously record the waveforms of the signal emitted by the transmitting element after reflection and refraction through the formation and downhole metal components before reaching each receiving coil. For example, when the first transmitting element is operational, all receiving channels begin sampling simultaneously. The sampling rate can be set to 100,000 points per second, recording waveform data for one millisecond. This allows the full-field response under individual excitation of that element to be obtained.

[0032] Quadrature demodulation is performed on each acquired waveform to extract the amplitude and phase information carried by the high-frequency carrier. Quadrature demodulation yields two values: an in-phase component and a quadrature component. These components essentially decompose the received signal onto two mutually perpendicular reference axes. The amplitude of the independent response signal of the transmitting element under the current environment is calculated by taking the square root of the sum of the squares of the in-phase and quadrature components. The phase of the independent response signal is calculated by taking the arctangent of the ratio of the quadrature components. This involves dividing the quadrature component by the in-phase component and then calculating the arctangent function value, yielding the phase delay of the received signal relative to the transmitted reference signal. For example, in a measurement where the in-phase component is 0.8 and the quadrature component is 0.6, the amplitude is 1, and the phase is approximately 36.9 degrees.

[0033] Record the amplitude and phase sequences corresponding to all transmitting array elements. The amplitude sequence is formed by recording the amplitude measured by the first element as A1, the amplitude measured by the second element as A2, and so on up to the Nth element as AN. Similarly, the phase sequence is recorded sequentially for each element. The length of both the amplitude and phase sequences is equal to the total number of transmitting array elements. These two sequences together constitute an independent response signal, reflecting the actual amplitude and phase distribution of the transmitted signal in each direction after passing through the formation and surrounding metal objects in the current downhole environment. For example, in a certain well section, the amplitude sequence corresponding to eight array elements might be [0.9, 1.2, 1.5, 1.1, 0.8, 0.7, 0.9, 1.0], and the phase sequence might be [-5°, 3°, 8°, 2°, -6°, -10°, -4°, 0°]. This independent response signal provides the raw data for subsequently plotting the circumferential coupling imbalance map of the array elements.

[0034] Constructing a circumferential coupling imbalance map of array elements using independent response signals specifically refers to: First, we define an ideal amplitude for each transmitting element under ideal equilibrium conditions. This ideal amplitude is the average of the actual amplitudes of all transmitting elements. This is because it's assumed that, in the absence of asymmetric metallic interference, the transmission and reception characteristics in all circumferential directions should be consistent; therefore, the average value represents the expected amplitude under equilibrium conditions. Simultaneously, we set the ideal phase to zero degrees, indicating that under ideal equilibrium conditions, the received signals of each element have no relative phase deviation. For example, a downhole tool has eight transmitting elements, and the acquired actual amplitude sequence is [0.9, 1.2, 1.5, 1.1, 0.8, 0.7, 0.9, 1.0]. Calculating the average of these eight values ​​yields 1.0125, which is the ideal amplitude for each element.

[0035] Next, the actual amplitude of each transmitting element is compared with its ideal amplitude to obtain the amplitude imbalance coefficient for each element. For example, dividing the actual amplitude of the first element (0.9) by the ideal amplitude (1.0125) yields an amplitude imbalance coefficient of approximately 0.889, indicating attenuation distortion in that direction. Dividing the actual amplitude of the third element (1.5) by 1.0125 yields approximately 1.481, indicating gain distortion in that direction. An amplitude imbalance coefficient greater than one indicates that the downhole metal component has enhanced the magnetic field in that direction, while a coefficient less than one indicates that it has weakened the magnetic field.

[0036] The phase imbalance deviation is calculated by subtracting zero degrees from the actual phase of each transmitting element. Assuming the actual phase sequence is [-5 degrees, 3 degrees, 8 degrees, 2 degrees, -6 degrees, -10 degrees, -4 degrees, 0 degrees], then the phase imbalance deviation is these values ​​themselves. A positive value indicates that the received signal phase leads the reference, while a negative value indicates that the phase lags. Phase leadership usually implies a sudden phase change in the induced field generated by a conductor in that direction.

[0037] Finally, the amplitude imbalance coefficient and phase imbalance deviation of each transmitting element are combined in circumferential order to form a circumferentially distributed binary group sequence. For example, the first element corresponds to (0.889, -5 degrees), the second element corresponds to (1.185, 3 degrees), the third element corresponds to (1.481, 8 degrees), and so on until the eighth element. This binary group sequence is the circumferential coupling imbalance pattern of the elements.

[0038] This graph visually shows which directions in the circumferential direction have their amplitudes enhanced or attenuated, and which directions have their phases advanced or lagging. For example, during actual downhole drilling, if one side of the downhole tool is close to a metal stabilizer, the amplitude imbalance coefficient of the elements close to the stabilizer will be significantly greater than one, and the phase imbalance deviation will also show a regular change, while the coefficient of the elements far from the stabilizer is close to one, and the phase is close to zero.

[0039] Generating the compensated control sequence specifically includes the following steps: First, extract the amplitude imbalance coefficient and phase imbalance deviation of each transmitting element from the circumferential coupling imbalance map. The previously constructed map already saves these two values ​​for each element. For example, if the downhole tool has eight transmitting elements, the extracted amplitude imbalance coefficient sequence is [0.889, 1.185, 1.481, 1.087, 0.790, 0.691, 0.889, 0.988], and the phase imbalance deviation sequence is [-5 degrees, 3 degrees, 8 degrees, 2 degrees, -6 degrees, -10 degrees, -4 degrees, 0 degrees]. These coefficients reflect the coupling distortion caused by metal components in the circumferential directions in the current downhole environment.

[0040] The amplitude compensation for each transmitting element is set to the reciprocal of its corresponding amplitude imbalance coefficient. An element with an amplitude imbalance coefficient greater than one indicates that the signal in that direction has been amplified; taking its reciprocal yields a compensation amount less than one, used to reduce the transmit power and restore balance. An element with an amplitude imbalance coefficient less than one indicates that the signal has been attenuated; taking its reciprocal yields a compensation amount greater than one, used to increase the transmit power. For example, the amplitude imbalance coefficient of the third element is 1.481, and its reciprocal is approximately 0.675, indicating that the original transmit amplitude needs to be reduced to 0.675 times its original value. The amplitude imbalance coefficient of the first element is 0.889, and its reciprocal is approximately 1.125, indicating that the original transmit amplitude needs to be amplified to 1.125 times its original value. When the amplitude imbalance coefficient is zero, this situation will almost never occur in actual downhole operations, because zero means that no signal is received at all, which may be due to the complete damage of the array element or the receiving channel. In this case, for system safety, the amplitude compensation is set to one, that is, no amplification or reduction is made, to avoid unpredictable consequences.

[0041] The phase compensation for each transmitting element is set to the negative of its corresponding phase imbalance deviation. A positive phase imbalance deviation indicates that the received phase is ahead, requiring a negative phase offset to compensate for the lead; therefore, the compensation is negative. A negative phase imbalance deviation indicates that the received phase is lagging, and the compensation is positive. For example, the phase imbalance deviation of the third element is 8 degrees, and its negative is -8 degrees, meaning that an additional 8-degree lag is needed to compensate for the lead during transmission. The phase imbalance deviation of the sixth element is -10 degrees, and its negative is 10 degrees, meaning that an additional 10-degree lead is needed to compensate for the lag during transmission.

[0042] The amplitude and phase compensation values ​​required for each transmitting element are multiplied and added one by one against the original excitation parameters of that element. The original excitation parameters include a reference amplitude and a reference phase. The reference amplitude can be a uniform fixed value, and the reference phase can be zero degrees. The amplitude compensation value is multiplied by the reference amplitude to obtain the compensated excitation amplitude. The phase compensation value is added to the reference phase to obtain the compensated excitation phase. For example, if the reference amplitude is 1.0 and the reference phase is 0 degrees, then the compensated excitation amplitude for the third element is 1.0 multiplied by 0.675, which equals 0.675, and the compensated excitation phase is 0 degrees plus -8 degrees, which equals -8 degrees. The compensated excitation amplitude for the sixth element is 1.0 multiplied by 1.447 (the reciprocal of 0.691 is approximately 1.447), which equals 1.447, and the compensated excitation phase is 0 degrees plus 10 degrees, which equals 10 degrees.

[0043] Finally, all the compensated excitation amplitudes and phases are arranged into a sequence according to the circumferential arrangement of the transmitting array elements. This sequence is the compensated control sequence. For example, the compensated excitation amplitudes obtained by the eight array elements are [1.125, 0.844, 0.675, 0.920, 1.266, 1.447, 1.125, 1.012], and the compensated excitation phases are [5 degrees, -3 degrees, -8 degrees, -2 degrees, 6 degrees, 10 degrees, 4 degrees, 0 degrees]. This sequence is stored in the array control unit. When excitation is applied to each transmitting array element later, the amplitude and phase values ​​given by this sequence are used for driving, thereby canceling the circumferential coupling distortion caused by the asymmetric metal components downhole, so that each array element works in a balanced state.

[0044] Driving each transmitting array element to form a scanning beam deflected circumferentially includes the following steps: First, obtain the compensated excitation amplitude and phase of each transmitting element from the compensated control sequence. Define the element spacing as the arc length between the centers of two adjacent transmitting elements. For example, if eight elements are evenly arranged on a drill collar with an outer diameter of 170 mm, the element spacing is equal to the circumference of the circle divided by eight, approximately 6.7 cm. Define the wavelength as the electromagnetic wave wavelength of the current excitation frequency in the formation medium. For example, if the excitation frequency is 100 Hz and the formation resistivity is 10 ohm-meters, the estimated wavelength is approximately several hundred meters. The specific value needs to be calculated based on actual logging data.

[0045] A scanning step angle sequence is set, covering the entire circumferential range from 0 degrees to 360 degrees. The step angle can be five or ten degrees. For example, starting from 0 degrees, a target deflection angle is taken every ten degrees, up to 350 degrees, resulting in thirty-six target deflection angles. For each target deflection angle, the required excitation phase difference between adjacent transmitting elements needs to be calculated. The formula is: excitation phase difference = 2π multiplied by the element spacing, multiplied by the sine of the target deflection angle, and divided by the wavelength. For example, if the element spacing is 6.7 cm, the wavelength is 300 m, the target deflection angle is 30 degrees, and the sine is 0.5, then 2π multiplied by 0.067 m, multiplied by 0.5, and divided by 300 m, yields approximately 0.0007 radians, which is approximately 0.04 degrees. This phase difference is very small because the wavelength is much larger than the element spacing. In actual downhole detection, to improve directivity, higher frequencies (several hundred hertz) are usually used to shorten the wavelength, at which point the phase difference becomes significant.

[0046] Starting with the first transmitting element, the deflection phase of each element is obtained by sequentially accumulating the excitation phase difference. Assuming the deflection phase of the first element is zero, the deflection phase of the second element is equal to the excitation phase difference, the deflection phase of the third element is twice the excitation phase difference, and so on. When the electromagnetic waves emitted by each element are superimposed in space, the equiphase surface tilts along the deflection direction, and the main lobe of the synthesized beam points to the calculated target deflection angle.

[0047] The compensated excitation phase and deflection phase of each transmitting element are added together to form the scanning beam control parameters at the target deflection angle. For example, if the original compensated excitation phase of the first element is 5 degrees, adding a deflection phase of 0 degrees when the target deflection angle is 30 degrees will still result in 5 degrees. The original excitation phase of the second element is -3 degrees, and adding a deflection phase (e.g., 0.04 degrees) will make it -2.96 degrees. This adjusts the beam direction to the 30-degree direction.

[0048] These scanning beam control parameters are applied sequentially according to the target deflection angle, causing the main lobe direction of the synthesized beam to deflect circumferentially. For example, the parameter corresponding to zero degrees is applied first, and the beam points straight ahead; then the parameter corresponding to ten degrees is applied, and the beam deflects ten degrees to the right; this continues until 350 degrees, completing one scan. In actual downhole drilling, this scanning beam can rotate around the tool like a searchlight, detecting the presence of electromagnetic echoes from the target well in each direction, thereby obtaining a circumferential response distribution map.

[0049] Acquiring corresponding electromagnetic response signals under different beam patterns specifically includes the following steps: When acquiring corresponding electromagnetic response signals in different beam patterns, a preset direction must first be set. This direction is the circumferential azimuth angle relative to the axis of the downhole tool body. For example, in rescue well operations, if the accident well is preliminarily determined to be located at 120 degrees circumferentially around the tool body based on the results of the previous scan, this angle is set as the preset direction.

[0050] For each transmitting element, the distance from its geometric center to the center of the tool body is measured or calculated, and then multiplied by the cosine of this circumferential azimuth angle to obtain the projected distance of that element in the specified direction. For example, eight transmitting elements are evenly distributed on a circle with a radius of 85 mm, and the distance from the geometric center of each element to the center of the tool body is 85 mm. When the preset specified direction is 120 degrees, the angle of the first element may be 0 degrees, then the angle relative to 120 degrees is 120 degrees, the cosine value is -0.5, and the projected distance is 85 mm multiplied by -0.5, which equals -42.5 mm. The negative sign indicates that the element is located behind the specified direction, and its emitted wave needs to be emitted earlier to arrive at the specified direction simultaneously with the wave from the front element.

[0051] Dividing the projected distance by the wavelength yields the projection distance multiplier in wavelength units. Multiplying this by 2π gives the propagation phase delay of the array element due to its positional difference. Assuming the current excitation frequency is 200 Hz and the wavelength in the strata is approximately 250 meters, then dividing the projected distance by -42.5 millimeters by 250 meters gives approximately -0.00017 radians, which multiplied by 2π gives approximately -0.00107 radians, or approximately -0.061 degrees. This very small phase delay indicates that the distance difference between front and back array elements is negligible relative to the wavelength, but the phase delay becomes more pronounced at higher frequencies or with larger element spacing.

[0052] The focusing phase of each transmitting element is set to the inverse of the propagation phase delay, so that the electromagnetic waves emitted by each element are in phase and superimposed when they propagate to the specified direction. For example, if the phase delay calculated above is -0.061 degrees, the inverse is +0.061 degrees, which means that the transmission phase of this element needs to be advanced by 0.061 degrees to compensate for the lag caused by its later position.

[0053] The compensated excitation phase of each transmitting element is added to the focusing phase to form the focusing beam control parameters. The compensated excitation phase of each element has already been obtained from the compensated control sequence. For example, the first element's excitation phase is 5 degrees, which becomes 5.061 degrees after adding the focusing phase (0.061 degrees). The second element's excitation phase is -3 degrees plus its own focusing phase, and so on. In this way, the synthesized beam energy will be concentrated around 120 degrees in a preset, designated direction.

[0054] In focused beam mode, these focused beam control parameters are applied, and the electromagnetic response waveforms of each receiving channel are synchronously acquired through a multi-channel receiving array. For example, in focused beam mode, each transmitting element transmits simultaneously according to the focused phase, and the receiving array records the waveform data of all channels. These data reflect the target well echo intensity in the specified direction.

[0055] In scanning beam mode, the electromagnetic response waveforms at each deflection angle are acquired sequentially according to the scanning beam control parameters. The scanning beam control parameters have been calculated in advance, for example, a set of parameters every ten degrees from zero to 360 degrees. Each set of parameters drives the beam to point to a specific angle, and the response waveforms at the corresponding angles are acquired sequentially.

[0056] Finally, all waveforms acquired under these two modes are categorized and recorded according to beam mode type and deflection angle, serving as electromagnetic response signals for different beam modes. For example, a focus mode directory and a scan mode directory are created within the folder. The focus mode stores waveform files for a preset direction of 120 degrees, while the scan mode stores waveform files for various angles such as 0 degrees, 10 degrees, and 20 degrees. These signals will subsequently be used to extract features such as response amplitude, phase dispersion, spatial gradient concentration, and residual convergence to determine the true target well direction.

[0057] The process of identifying the true target well direction from multiple candidate directions includes the following steps: First, the response characteristics of each extracted candidate direction under different beam patterns are combined and compared to calculate the correlation coefficient of the response amplitude as a function of angle between different modes. This correlation coefficient is used to measure whether the curves of the response amplitude as a function of angle measured under scanning beam pattern and focused beam pattern are consistent. The closer the correlation coefficient is to one, the more consistent the response trends of the two modes are in the same direction, and the higher the credibility of the real target well. A correlation coefficient close to zero or negative indicates that the information given by the two modes is contradictory, and there is likely to be spurious enhancement interference. When the correlation coefficient is lower than the preset consistency threshold, spurious enhancement interference is determined to exist and direction confirmation is initiated. The consistency threshold is generally preset based on field test or simulation results. For example, in test wells with known target wells, the correlation coefficient of the real target well is usually higher than 0.9, while the correlation coefficient of the interference source is often lower than 0.6. Therefore, the consistency threshold can be set between 0.7 and 0.8. For example, in a certain detection, the peak response amplitude in the scanning beam mode appears at 120 degrees, and the peak value in the focused beam mode appears at 115 degrees. The correlation coefficient of the two curves is calculated to be only 0.5, which is lower than the preset threshold of 0.7. The system determines that the current measurement is affected by interference from metal supports or sleeve joints, and the direction confirmation step needs to be initiated.

[0058] For each candidate direction, electromagnetic response waveforms under the left and right deflection beams of that direction are acquired separately. The left deflection beam refers to pointing the main lobe of the scanning beam to the left of the candidate direction at a fixed small angle (e.g., a deflection of five or ten degrees), and the right deflection beam points to the right of the candidate direction at the same angle. The deflection angles corresponding to the left peak and the right peak are extracted, and the difference between the two is calculated as the peak displacement. This peak displacement reflects the degree of asymmetry in the target well's response to beam deflection. Based on the magnitude of this peak displacement, the distance estimate of the target well is calculated according to a preset proportional relationship. The preset proportional relationship can be obtained through downhole calibration tests, for example, by measuring the peak displacement at distances of two meters, five meters, and ten meters from the target well, and establishing a mapping table or fitting formula between displacement and distance. Generally, the closer the distance, the larger the peak displacement; the farther the distance, the smaller the peak displacement. In actual measurements, the peak displacement ranges from 0.5 degrees to 15 degrees, and the corresponding distance estimates range from tens of meters to one or two meters.

[0059] When the peak displacement is symmetrically distributed relative to the candidate direction and the displacement is greater than a preset displacement threshold, it is confirmed as the true target well direction. Symmetrical distribution means that the left and right peak deflection angles are approximately equal relative to the candidate direction. For example, if the candidate direction is 120 degrees, and the left beam shows a peak at 115 degrees and the right beam shows a peak at 125 degrees, with both left and right offsets of 5 degrees, then the symmetry condition is met. The displacement threshold is usually set to two to three degrees. Peak displacements smaller than this threshold may be caused by noise or slight interference and are not considered true targets. For example, in a certain detection, if the peak displacement at 90 degrees of the candidate direction is six degrees and symmetrical, exceeding the three-degree threshold, then it is confirmed as the true target well direction.

[0060] The phases of the received signals from the left and right deflected beams are compared. When the phase difference between the left and right beams changes from positive to negative or vice versa, a phase reversal is identified. This reversal point corresponds precisely to the target well's location. The physical reason is that the target well casing, as a good conductor, produces opposite phase changes in electromagnetic waves passing through it. For example, as the scanning beam gradually deflects from 80 degrees to 100 degrees, the received phase of the left deflected beam (pointing to 80 degrees) is 10 degrees larger than the phase of the right deflected beam (pointing to 100 degrees) (left minus right is positive). When the beam center points to 90 degrees, the phase difference between the left and right beams approaches zero. Continuing to deflect to the right, the left phase becomes smaller than the right phase (the difference becomes negative). The angle at which this positive-to-negative reversal occurs is the true direction of the target well. Based on the deflection angle corresponding to this reversal, the estimated azimuth of the target well is directly determined without further calculations, and the candidate direction is confirmed as the true target well direction.

[0061] When at least one of the peak displacement relationship and the phase difference reversal relationship is satisfied, the true target well direction is output, along with the corresponding distance and azimuth estimates. The two relationships can corroborate each other or exist independently. For example, in environments with strong interference, the peak displacement may be submerged, but the phase difference reversal relationship remains clear and usable; conversely, if the target well is far away, the phase difference reversal relationship may not be obvious, but the peak displacement relationship may still provide a reliable judgment. The two relationships are independent yet mutually reinforcing, improving the robustness of direction confirmation.

[0062] It should be specifically noted that the preset proportional relationship is derived from downhole calibration tests. Measurements were taken at multiple accurate distance points from the target well, and the peak displacement value corresponding to each distance point was recorded. For example, at a distance of two meters from the target well, the peak displacement is usually relatively large, and the measured data may show between twelve and fifteen degrees. At a distance of five meters from the target well, the peak displacement decreases significantly, generally falling within the range of four to six degrees. At a distance of ten meters from the target well, the peak displacement further shrinks to between one and a half and two and a half degrees. Plotting these discrete measurement point data on a coordinate system with distance as the horizontal axis and peak displacement as the vertical axis, a monotonically decreasing curve can be observed, and this curve exhibits obvious nonlinear characteristics. Specifically, in the close-range section (two to five meters), the rate of decrease in peak displacement is faster for every meter increase in distance, decreasing by approximately two to three degrees; while in the far-range section (five to ten meters), the rate of decrease in peak displacement is slower for every meter increase in distance, decreasing by approximately only 0.5 to one degree. This variation pattern conforms to the attenuation characteristics of electromagnetic fields in conductive media, that is, the magnetic field strength is inversely proportional to the cube of the distance. Therefore, the peak displacement and the distance are not a simple linear relationship, but follow an attenuation law in the form of a power function.

[0063] For rapid calculations in engineering applications, piecewise linear interpolation can be used to approximate the true proportional relationship. Specifically, the distance points obtained from calibration tests are divided into several intervals, for example, two meters to five meters in one interval, and five meters to ten meters in another. Within each interval, it is assumed that the peak displacement changes linearly with distance, and the slope and intercept of the line are calculated using the coordinates of the interval's endpoints. When a peak displacement value is actually measured, it is first determined which interval the value falls into, and then the distance estimate is calculated using the corresponding linear formula. For example, in the two-meter to five-meter interval, two meters corresponds to 15 degrees, and five meters corresponds to 5 degrees. Therefore, for every meter increase in distance within this interval, the peak displacement decreases by approximately 3.3 degrees. The linear formula is: distance equals initial distance plus displacement difference divided by slope. Although this method has an approximation, it is sufficient to meet the accuracy requirements in actual downhole directional drilling operations because the distance between the rescue well and the accident well often changes continuously, and the distance value at the previous moment can provide a good initial estimate for the current moment.

[0064] Another more accurate fitting method is to use a nonlinear power function: the relationship between peak displacement and distance is expressed as peak displacement equal to a coefficient multiplied by the distance to the power of negative cube, or more generally: peak displacement equals a coefficient multiplied by the distance to the power of negative n, where n is three under ideal conditions, but may vary between 2.5 and 3.5 in actual strata. Multiple discrete points collected in the calibration test can be used to determine the undetermined coefficients and exponents in the function using the least squares method, minimizing the total error between the fitted curve and all measured points. For example, if the fitted function obtained in a calibration is peak displacement equal to 120 divided by the distance to the power of cube, then when the measured peak displacement is 3.75 degrees, the calculated distance is 120 divided by the cube root of 3.75, which is approximately 5.7 meters. This nonlinear fitting method provides continuous distance output across the entire measurement range, avoiding the jump problems that may occur at interval boundaries in piecewise linear interpolation. The choice between the two methods depends on the complexity of the downhole environment and computational resources. Nonlinear fitting is preferred in drilling tools with powerful processors, while piecewise linear interpolation can achieve usable results in older tools with limited resources. Regardless of the method used, the core principle is to establish a one-to-one correspondence between peak displacement and distance through prior calibration tests, thereby accurately converting the measured peak displacement into a distance estimate for the target well.

[0065] The distance and azimuth estimates corresponding to the confirmed true target well direction are output with stability weighting, specifically including: First, obtain the response feature combination corresponding to the confirmed true target well direction. This feature combination includes three values: phase dispersion, spatial gradient concentration, and residual convergence in that direction. For example, if the true target well direction has been confirmed to be 120 degrees in downhole exploration, the corresponding phase dispersion is 2.3 degrees, the spatial gradient concentration is 0.85, and the residual convergence is 0.92.

[0066] The phase dispersion is handled according to the actual situation: When the phase dispersion is greater than a preset minimum positive threshold, its reciprocal is used as the phase stability factor. The preset minimum positive threshold is generally set between one-tenth and half a degree, for example, 0.2 degrees. The basis for setting this threshold is that when the phase dispersion is less than 0.2 degrees, the jitter in the measured phase is already very small, and further increasing the accuracy does not contribute much to the stability improvement. On the contrary, it will produce excessive numerical interference in the weighted result due to taking the reciprocal. When the phase dispersion is less than or equal to 0.2 degrees, the phase stability factor is set to a preset upper limit value. The upper limit value can be ten or twenty, because the reciprocal of 0.2 degrees is five, and the reciprocal of 0.1 degrees is ten. An upper limit value between ten and twenty can avoid the occurrence of infinity. For example, if the phase dispersion is 2.3 degrees, which is greater than 0.2 degrees, taking the reciprocal gives about 0.435, which is the phase stability factor. If the phase dispersion is only 0.1 degrees, then taking the reciprocal directly will give ten. In this case, the phase stability factor is set to the upper limit value of ten as set.

[0067] The spatial gradient concentration can be directly used as the gradient stability factor. The spatial gradient concentration itself is between zero and one; a larger value indicates more concentrated energy and better stability, without the need for additional transformation. For example, 0.85 can be directly used as the gradient stability factor.

[0068] Simultaneously, the absolute value of the residual convergence is used as the residual stability factor. The residual convergence can be positive or negative; taking the absolute value yields a non-negative number. The larger the absolute value, the more obvious the convergence trend and the better the stability. For example, if the residual convergence is 0.92, the absolute value is also 0.92.

[0069] When calculating the weighted sum of the three factors, each factor needs to be assigned a weight coefficient, and the sum of the three weight coefficients is normalized to one. The weight coefficients are set based on the different contributions of each factor to stability. The gradient stability factor is directly derived from the spatial gradient concentration, which best reflects the energy concentration characteristics along the actual target well direction. Downhole tests have shown that it has the best stability and repeatability, therefore it is assigned the highest weight, with a value between 0.35 and 0.5, for example, 0.4. The phase stability factor has the next highest reliability because phase dispersion is slightly more affected by near-field metal interference than spatial gradient concentration; therefore, it is assigned a middle weight, with a value between 0.25 and 0.35, for example, 0.3. The residual stability factor has the highest volatility because it depends on the accuracy of the preset theoretical amplitude, which has certain deviations under different formation conditions; therefore, it is assigned the lowest weight, with a value between 0.2 and 0.3, for example, 0.3.

[0070] Substituting the three weights mentioned above into the calculation, the overall stability score is equal to 0.4 times the gradient stability factor plus 0.3 times the phase stability factor plus 0.3 times the residual stability factor. Substituting the values ​​from the previous example (gradient stability factor 0.85, phase stability factor 0.435, residual stability factor 0.92) yields approximately 0.746. This score can be used for comparisons between different measurement times.

[0071] The first number is set as the number of highly stable measurements, and the second number is set as the number of moderately stable measurements. The first number is typically three to five, and the second number is two to three. For example, if ten valid measurements are obtained in multiple consecutive measurements, the first number could be three, and the second number two. This way, the highly stable layer selects the three highest-scoring measurements, the moderately stable layer selects the two next highest-scoring measurements, and the remaining five lower-scoring measurements are not included in the fusion, as these data may be subject to severe interference or have large measurement errors.

[0072] The multiple distance and azimuth estimates obtained from repeated measurements of the true target well direction are sorted from highest to lowest according to the comprehensive stability score. For example, in ten measurements, the first measurement has a distance estimate of 12.5 meters and an azimuth estimate of 118 degrees, with a comprehensive stability score of 0.746; the second measurement has a distance estimate of 12.8 meters and an azimuth estimate of 122 degrees, with a score of 0.712; the third measurement has a distance estimate of 12.3 meters and an azimuth estimate of 119 degrees, with a score of 0.768; and so on, all measurement values ​​are sorted from highest to lowest score.

[0073] The first three measurements in the sorting are assigned to the high-stability layer and given a first weight coefficient, which can be 0.7 or 0.8. The next two measurements are assigned to the medium-stability layer and given a second weight coefficient, which can be 0.3 or 0.2. The first weight coefficient is greater than the second weight coefficient and both are positive, ensuring that the measurements in the high-stability layer dominate the fusion process.

[0074] For each measurement, its distance estimate and azimuth estimate are multiplied by the corresponding weighting coefficient. For example, in the high-stability layer, the highest-scoring measurement has a distance of 12.3 meters multiplied by 0.7 to get 8.61, and an azimuth of 119 degrees multiplied by 0.7 to get 83.3 degrees; the second measurement has a distance of 12.5 meters multiplied by 0.7 to get 8.75, and an azimuth of 118 degrees multiplied by 0.7 to get 82.6 degrees; the third measurement has a distance of 12.1 meters multiplied by 0.7 to get 8.47, and an azimuth of 120 degrees multiplied by 0.7 to get 84 degrees. The weighted values ​​within the high-stability layer are summed to obtain the first weighted sum, i.e., 8.61 + 8.75 + 8.47 equals 25.83 for distance, and 83.3 + 82.6 + 84 equals 249.9 degrees for azimuth. Similarly, the two measurements within the medium-stability layer are weighted by 0.3 and summed to obtain the second weighted sum.

[0075] The first weighted sum is added to the second weighted sum, and then divided by the sum of the weighted numbers of the first and second weighting coefficients. The first weighting coefficient is multiplied by the number of measurements in the high-stability layer to obtain the total weight of the upper layer, and the second weighting coefficient is multiplied by the number of measurements in the middle-stability layer to obtain the total weight of the middle layer. These two are added together to obtain the denominator. For example, the total weight of the three measurements in the upper layer is 0.7 multiplied by 3 equals 2.1, and the total weight of the two measurements in the middle layer is 0.3 multiplied by 2 equals 0.6, with a denominator of 2.7. The first weighted sum of the distances is added to the second weighted sum, and then divided by 2.7 to obtain the fused relative distance. The azimuth value is processed similarly to obtain the fused relative azimuth. These two values ​​serve as the final output relative distance and relative azimuth of the target well. This layered fusion method retains the main contribution of the high-stability measurements while appropriately incorporating the effective information from the middle-stability measurements, avoiding the excessive influence of random errors from single measurements on the final result.

[0076] Example 2: A downhole phased array composite electromagnetic ranging system, comprising: The excitation acquisition module is used to control multiple transmitting array elements distributed circumferentially along the downhole tool body to be excited independently in sequence according to a preset test sequence, and to acquire the independent response signal of each transmitting array element in the current downhole environment. The spectrum compensation module is used to construct the circumferential coupling imbalance spectrum of the array elements using independent response signals based on the preset array element circumferential coupling imbalance spectrum model, and calculate the required phase compensation and amplitude compensation for each transmitting array element based on the array element circumferential coupling imbalance spectrum, and generate the compensated control sequence. The beam control module is used to drive each transmitting array element to form a scanning beam that deflects circumferentially and a focused beam that focuses in a preset specified direction based on the compensated control sequence, and to acquire the corresponding electromagnetic response signals in different beam modes. The direction confirmation module is used to extract the response feature combination corresponding to each candidate direction from the electromagnetic response signal. When the consistency of response evolution between different beam modes is lower than the preset consistency threshold, the true target well direction is confirmed from multiple candidate directions based on the peak displacement relationship and phase difference reversal relationship of the deflection beams on both sides of each candidate direction. The fusion output module is used to rank the candidate directions based on the combination of response features corresponding to each candidate direction, and to perform hierarchical weighted fusion of the distance and azimuth estimates of the target well based on the stability ranking results, and output the relative distance and relative azimuth of the target well.

[0077] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0078] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0079] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0080] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0081] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A downhole phased array composite electromagnetic ranging method, characterized in that, Includes the following steps: Multiple transmitting array elements distributed circumferentially along the downhole tool body are controlled to be independently excited sequentially according to a preset test sequence, and the independent response signal of each transmitting array element in the current downhole environment is collected. Based on the preset array element circumferential coupling imbalance spectrum model, the array element circumferential coupling imbalance spectrum is constructed using independent response signals. Based on the array element circumferential coupling imbalance spectrum, the required phase compensation and amplitude compensation for each transmitting array element are calculated, and the compensated control sequence is generated. Based on the compensated control sequence, each transmitting array element is driven to form a scanning beam that deflects circumferentially and a focusing beam that focuses in a preset specified direction, and the corresponding electromagnetic response signals are collected in different beam modes. The response feature combination corresponding to each candidate direction is extracted from the electromagnetic response signal, namely response amplitude, phase dispersion, spatial gradient concentration and residual convergence. When the consistency of response evolution between different beam modes is lower than the preset consistency threshold, the true target well direction is confirmed from multiple candidate directions based on the peak displacement relationship and phase difference reversal relationship of the deflection beams on both sides of each candidate direction. Based on the combination of response features corresponding to each candidate direction, the candidate directions are ranked according to their stability. Based on the stability ranking results, the distance estimate and azimuth estimate of the target well are fused in a hierarchical weighted manner to output the relative distance and relative azimuth of the target well.

2. The downhole phased array composite electromagnetic ranging method according to claim 1, characterized in that, The specific extraction method for response feature combination is as follows: For each candidate direction, the received signal amplitude in that direction is extracted from the electromagnetic response waveform of the corresponding beam mode as the response amplitude; The phase dispersion is calculated as follows: traverse multiple measurement positions adjacent to the candidate direction, extract the received signal phase at each position, and calculate the standard deviation of these phases. This standard deviation is the phase dispersion. The spatial gradient concentration is calculated as follows: perform a second-order difference operation on the response amplitude of the candidate direction and its two adjacent directions before and after, take the reciprocal of the absolute value of the second-order difference and normalize it to obtain the spatial gradient concentration. The residual convergence is calculated as follows: the measured response amplitude is calculated by subtracting the preset theoretical amplitude to obtain the residual, and the negative value of the rate of change of the residual at multiple continuous scanning angles is taken as the residual convergence.

3. The downhole phased array composite electromagnetic ranging method according to claim 2, characterized in that, Collecting the independent response signal of each transmitting element in the current downhole environment specifically refers to: Set a preset test sequence that iterates through all transmitting elements, where the excitation duration of each transmitting element is a fixed duration and a silent interval is set between adjacent excitations; During the excitation of each transmitting element, the electromagnetic response waveforms of each receiving channel are synchronously acquired through a multi-channel receiving array; For each set of acquired waveforms, perform quadrature demodulation to obtain in-phase and quadrature components. Calculate the amplitude of the independent response signal of the transmitting array element under the current environment by taking the square root of the sum of squares, and calculate the phase of the independent response signal by taking the arctangent of the ratio of the quadrature components. Record the amplitude sequence and phase sequence corresponding to all transmitting array elements, where the length of both the amplitude sequence and the phase sequence is equal to the total number of transmitting array elements. The amplitude sequence and the phase sequence together constitute an independent response signal.

4. The downhole phased array composite electromagnetic ranging method according to claim 3, characterized in that, Constructing a circumferential coupling imbalance map of array elements using independent response signals specifically refers to: Under an ideal equilibrium state, the ideal amplitude of each transmitting element is the average of the actual amplitudes of all transmitting elements, and the ideal phase is zero degrees. The amplitude imbalance coefficient of each transmitting element is obtained by comparing the actual amplitude with the ideal amplitude. The phase imbalance deviation of each transmitting element is obtained by calculating the difference between the actual phase and the ideal phase. The amplitude imbalance coefficient and phase imbalance deviation of each transmitting element are combined in circumferential order to form a circumferentially distributed two-element group sequence, which is the circumferential coupling imbalance map of the array elements.

5. The downhole phased array composite electromagnetic ranging method according to claim 4, characterized in that, Generating the compensated control sequence specifically includes the following steps: Extract the amplitude imbalance coefficient and phase imbalance deviation of each transmitting element from the circumferential coupling imbalance map of the array elements; The amplitude compensation amount of each transmitting array element is set to the reciprocal of its corresponding amplitude imbalance coefficient, wherein when the amplitude imbalance coefficient is zero, the amplitude compensation amount of the transmitting array element is set to one. The phase compensation amount of each transmitting element is set to the negative of its corresponding phase imbalance deviation; The amplitude compensation and phase compensation required for each transmitting element are multiplied and added one by one according to the original excitation parameters of the corresponding transmitting element to obtain the compensated excitation amplitude and excitation phase. All compensated excitation amplitudes and excitation phases are arranged into a compensated control sequence according to the circumferential arrangement of the transmitting array elements.

6. The downhole phased array composite electromagnetic ranging method according to claim 5, characterized in that, Driving each transmitting array element to form a scanning beam deflected circumferentially includes the following steps: From the compensated control sequence, obtain the compensated excitation amplitude and excitation phase of each transmitting element; define the element spacing as the arc length between the centers of two adjacent transmitting elements, and define the wavelength as the electromagnetic wave wavelength of the current excitation frequency in the formation medium; Set a scanning step angle sequence that covers a circumferential range from 0 degrees to 360 degrees; for each target deflection angle, calculate the required excitation phase difference between adjacent transmitting elements using the following formula: The excitation phase difference is equal to 2π multiplied by the element spacing, then multiplied by the sine of the target deflection angle, and then divided by the wavelength. Starting from the first transmitting element, the excitation phase difference is accumulated sequentially to obtain the deflection phase of each transmitting element; The compensated excitation phase and deflection phase of each transmitting element are added together to form the scanning beam control parameters at the target deflection angle. The scanning beam control parameters are applied sequentially according to the target deflection angle, so that the main lobe direction of the synthesized beam is deflected sequentially along the circumference.

7. The downhole phased array composite electromagnetic ranging method according to claim 6, characterized in that, Acquiring corresponding electromagnetic response signals under different beam patterns specifically includes the following steps: Set a preset direction, which is the circumferential azimuth angle relative to the axis of the downhole tool body; For each transmitting element, measure or calculate the distance from its geometric center to the center of the tool body, and then multiply it by the cosine of the circumferential azimuth angle to obtain the projected distance of the element in the specified direction. Divide the projected distance by the wavelength to get the projection distance multiple in wavelength units, then multiply by 2π to get the propagation phase delay of the array element due to the position difference. The focusing phase of each transmitting element is set to the opposite of the propagation phase delay, so that the electromagnetic waves emitted by each element are superimposed in phase when they propagate to the specified direction. The compensated excitation phase of each transmitting element is added to the focusing phase to form the focusing beam control parameters; The focusing beam control parameters are applied in the focusing beam mode, and the electromagnetic response waveforms of each receiving channel are synchronously acquired through a multi-channel receiving array. In scanning beam mode, electromagnetic response waveforms at each deflection angle are sequentially acquired according to the scanning beam control parameters. All waveforms acquired in these two modes are classified and recorded according to beam mode type and deflection angle, serving as electromagnetic response signals for different beam modes.

8. The downhole phased array composite electromagnetic ranging method according to claim 7, characterized in that, The process of identifying the true target well direction from multiple candidate directions includes the following steps: The response features of each candidate direction extracted under different beam modes are combined and compared. The correlation coefficient of the response amplitude with the angle between different modes is calculated. When the correlation coefficient is lower than the preset consistency threshold, it is determined that there is false enhancement interference and direction confirmation is initiated. For each candidate direction, the electromagnetic response waveforms under the left and right deflection beams of that direction are collected respectively. The deflection angles corresponding to the left peak and the right peak are extracted. The difference between the two is calculated as the peak displacement. Based on the magnitude of the peak displacement, the distance estimate of the target well is calculated according to the preset ratio. When the peak displacement is symmetrically distributed with respect to the candidate direction and the displacement amount is greater than the preset displacement threshold, it is confirmed as the true target well direction; Simultaneously, the phases of the received signals under the left and right deflection beams are extracted and compared. When the difference between the left and right phases changes from positive to negative or from negative to positive, a phase difference reversal relationship is determined. The azimuth estimate of the target well is determined based on the deflection angle corresponding to the reversal relationship, and the candidate direction is confirmed as the true target well direction. When at least one of the peak displacement relationship and the phase difference reversal relationship is satisfied, the output confirms the true target well direction, as well as the corresponding distance estimate and azimuth estimate.

9. The downhole phased array composite electromagnetic ranging method according to claim 8, characterized in that, The distance and azimuth estimates corresponding to the confirmed true target well direction are output with stability weighting, specifically including: Obtain and confirm the combination of response features corresponding to the true target well direction; When the phase dispersion is greater than the preset minimum positive threshold, its reciprocal is used as the phase stability factor; when the phase dispersion is less than or equal to the minimum positive threshold, the phase stability factor is set to the preset upper limit value. Spatial gradient concentration is directly used as the gradient stability factor; the absolute value of residual convergence is used as the residual stability factor. Calculate the weighted sum of the above three factors to obtain the comprehensive stability score of the actual target well direction; The first number is set as the number of high-stability measurements, and the second number is set as the number of medium-stability measurements. The multiple distance and azimuth estimates obtained from repeated measurements of the true target well direction are sorted from high to low according to the comprehensive stability score. The first number in the sort is assigned to the high stability layer and given the first weight coefficient, and the second number is assigned to the medium stability layer and given the second weight coefficient. The first weight coefficient is greater than the second weight coefficient and both are positive. For each measurement, its distance estimate and azimuth estimate are multiplied by the corresponding weighting coefficient. The weighted values ​​in the high-stability layer are summed to obtain the first weighted sum, and the weighted values ​​in the medium-stability layer are summed to obtain the second weighted sum. The first weighted sum and the second weighted sum are added together and divided by the total number of weights of the first weighting coefficient and the second weighting coefficient to obtain the fused relative distance and relative azimuth, which are used as the final output relative distance and relative azimuth of the target well.

10. A downhole phased array composite electromagnetic ranging system, used to implement the downhole phased array composite electromagnetic ranging method as described in any one of claims 1-9, characterized in that, include: The excitation acquisition module is used to control multiple transmitting array elements distributed circumferentially along the downhole tool body to be excited independently in sequence according to a preset test sequence, and to acquire the independent response signal of each transmitting array element in the current downhole environment. The spectrum compensation module is used to construct the circumferential coupling imbalance spectrum of the array elements using independent response signals based on the preset array element circumferential coupling imbalance spectrum model, and calculate the required phase compensation and amplitude compensation for each transmitting array element based on the array element circumferential coupling imbalance spectrum, and generate the compensated control sequence. The beam control module is used to drive each transmitting array element to form a scanning beam that deflects circumferentially and a focused beam that focuses in a preset specified direction based on the compensated control sequence, and to acquire the corresponding electromagnetic response signals in different beam modes. The direction confirmation module is used to extract the response feature combination corresponding to each candidate direction from the electromagnetic response signal. When the consistency of response evolution between different beam modes is lower than the preset consistency threshold, the true target well direction is confirmed from multiple candidate directions based on the peak displacement relationship and phase difference reversal relationship of the deflection beams on both sides of each candidate direction. The fusion output module is used to rank the candidate directions based on the combination of response features corresponding to each candidate direction, and to perform hierarchical weighted fusion of the distance and azimuth estimates of the target well based on the stability ranking results, and output the relative distance and relative azimuth of the target well.

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