Method for eliminating array induction direct coupling signal

Abstract

The invention belongs to the technical field of petroleum well logging, and discloses a method for eliminating array induction direct coupling signals, which comprises the following steps of: calibrating the unit thickness change of an adjusting piece and the quantitative contribution of each receiving coil direct coupling signal through electromagnetic simulation modeling and an underground environment equivalent experiment; the target thickness is solved and replaced through a linear correction model, closed-loop calibration is matched to enable a direct coupling signal to approach a preset threshold value, based on array induction logging, an existing three-coil system structure is difficult to thoroughly offset the direct coupling signal due to machining errors, useful signal extraction is seriously disturbed, the method does not need to modify a core structure of an instrument, operation is easy and convenient, adaptability is high, and the method is suitable for large-scale popularization and application. Direct coupling signals are eliminated accurately and thoroughly, the measurement accuracy of the stratum conductivity is effectively improved, and reliable data support is provided for oil and gas reservoir identification and evaluation.

Description

Technical Field

[0001] This invention belongs to the field of oil well logging technology, specifically relating to a method for eliminating array inductive direct coupling signals. Background Technology

[0002] Array induction logging is a core logging method based on the principle of electromagnetic induction to measure formation conductivity, and it plays a key role in oil and gas resource exploration and development.

[0003] Its working principle is as follows: After the transmitting coil of the array induction instrument is energized with alternating current, an alternating electromagnetic field will be formed around it. Under the action of the electromagnetic field, conductive media such as the formation will induce eddy currents around the well axis. These eddy currents will generate a secondary magnetic field, which will then generate an induced electromotive force related to the conductivity of the formation in the receiving coil, i.e., a useful signal. By measuring this signal, the conductivity characteristics of the formation can be inferred, providing data support for the identification and evaluation of oil and gas reservoirs.

[0004] In the actual signal acquisition process of the receiving coil, in addition to the useful signal generated by eddy currents, the transmitting coil will also directly generate an induced electromotive force in the receiving coil. This electromotive force is unrelated to the conductivity of the formation and is called a direct-coupled signal. Since the amplitude of the direct-coupled signal is much larger than that of the useful signal, if it is not eliminated, it will seriously interfere with the extraction of the useful signal and lead to a decrease in the accuracy of formation conductivity measurement.

[0005] In existing technologies, array induction logging instruments typically employ a three-coil system structure, consisting of a transmitting coil, a main receiving coil, and a compensation coil located between the two. By designing the number of turns and spacing between the compensation coil and the main receiving coil, the direct-coupled signals generated by the two coils are made to be equal in magnitude and opposite in direction, thereby achieving cancellation of the direct-coupled signals. However, due to factors such as precision errors in the manufacturing process and deviations in coil winding tension, the direct-coupled signals of the compensation coil and the main receiving coil are difficult to match completely, resulting in the inability to completely eliminate the direct-coupled signals and the presence of residual interference, which restricts the improvement of measurement accuracy in array induction logging. Summary of the Invention

[0006] In view of the problems mentioned in the background art above, the object of the present invention is to provide a method for eliminating array inductive direct coupling signals.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A method for eliminating array-induced direct-coupled signals includes the following steps: S1. By combining electromagnetic simulation modeling with equivalent experiments of the downhole environment, the quantitative contribution of the unit thickness change of the adjustment component to the change of the direct coupling signal of each receiving coil is quantified and calibrated. S2. During the assembly stage of the array sensing instrument, a standard adjustment component with a reference thickness of 10mm is assembled in the independent spacing adjustment area between the transmitting coil and each receiving coil. S3. Start the instrument according to the preset operating parameters, including power supply frequency and current amplitude, and collect and record the initial direct coupling signal values ​​of each receiving coil. S4. Based on the quantized contribution amount in step S1 and the initial direct coupling signal value in step S3, the target adjustment component size corresponding to each receiving coil is solved by a linear correction model. S5. Replace the standard adjustment component with the target adjustment component to make the direct coupling signal value of each receiving coil approach the preset threshold, thereby achieving accurate cancellation of the direct coupling signal.

[0008] Further specifying, in step S1, the adjusting component is an insulating, high-temperature resistant sheet structure adapted to the well logging downhole environment, specifically satisfying the following: the base width is 10mm, and the adjusting step is 0.1mm. Adjusting components with widths increasing in integer multiples of 0.1mm are named Z1, Z2, Z3..., and those decreasing are named J1, J2, J3... The core purpose of naming is to provide clear guidance for the size identification, precise matching and standardized application of the adjusting components, specifically serving the practicality and accuracy of the entire "elimination of direct coupling signal" technical solution; Its material is selected from alumina ceramic, silicon nitride ceramic or zirconium oxide ceramic. The temperature range of this material is ≥150℃, which is suitable for high temperature environment downhole. The insulation resistance is ≥10¹²Ω·cm to avoid interference with electromagnetic signals. The compressive strength is ≥200MPa to resist downhole pressure.

[0009] Further specifying, in step S1, the calibration process for quantifying the contribution is as follows: S1.1 Build an experimental platform to simulate the electromagnetic environment downhole, set the ambient temperature to 20-50℃ and the atmospheric pressure, and cover the parameters of mainstream array induction instruments with a power supply frequency of 1kHz-1MHz and a current amplitude of 0.1-1A for the transmitting coil. S1.2. Assemble adjustment components of different thicknesses in sequence. For each type of thickness, collect direct coupling signals three times and take the average value to remove abnormal data. S1.3. Establish a fitting curve between the thickness change of the regulating component and the change of the direct coupling signal through linear regression analysis, with a curve fitting degree R²≥0.995; It ensures the accuracy of quantifying contributions.

[0010] Further specifying, in step S1, the manufacturing precision of the adjusting component satisfies: thickness tolerance ≤ ±0.005mm, surface roughness Ra ≤ 0.8μm, and thickness uniformity error ≤ 0.003mm; It ensures that the impact of dimensional accuracy on the calibration effect of direct-coupled signals is controlled within ±0.05mS / m.

[0011] Further specifying, in step S2, the array sensing instrument includes one transmitting coil and at least two receiving coils, with each receiving coil evenly arranged along the axial direction of the transmitting coil; when there are six receiving coils, sequentially defined as receiving 0 to receiving 5, the quantization contribution calibrated in step S1 is as follows: for every 0.1mm increase in the thickness of the adjusting element, the direct-coupled signal of receiving 0 increases by 34.50mS / m, receiving 1 by 7.20mS / m, receiving 2 by 5.16mS / m, receiving 3 by 3.25mS / m, receiving 4 by 1.30mS / m, and receiving 5 by 0.32mS / m.

[0012] Further specifying, in step S2, the following two points must be met when assembling the standard adjustment component: ① Fix the reference distance between the transmitting coil and the receiving coil. After the adjusting piece is embedded in the distance adjustment area, the contact gap with the end face of the coil should be ≤0.01mm. ② The adjusting parts are fixed by using elastic positioning slots or threaded locking structures; It prevents the adjustment components from shifting or loosening due to downhole vibration of the instrument, and the positioning accuracy is ≤0.005mm.

[0013] Further specifying, in step S2, the spacing adjustment area is an independently isolated design, with each receiving coil corresponding to a dedicated adjustment channel; The size adjustments of each adjustment component do not interfere with each other, and the direct-coupled signal strength of different receiving coils is calibrated separately to avoid cross-interference.

[0014] Further specifying, in step S4, the general expression for the linear correction model is: Target adjustment component width = reference width - (initial direct coupling signal value / corresponding quantization contribution) × adjustment step size; Where the reference width is 10mm and the adjustment step size is 0.1mm, the specific formula is as follows when the receiving coil is in receive 0 to receive 5: Receive 0: 10mm - (Initial direct coupling signal value at Receive 0 / 34.50) × 0.1mm; Receiver 1: 10mm - (Initial direct coupling signal value of Receiver 1 / 7.20) × 0.1mm; Receiver 2: 10mm - (Initial direct coupling signal value of receiver 2 / 5.16) × 0.1mm; Receiver 3: 10mm - (Initial direct coupling signal value of receiver 3 / 3.25) × 0.1mm; Receiver 4: 10mm - (Initial direct coupling signal value of receiver 4 / 1.30) × 0.1mm; Receiver 5: 10mm - (Initial direct coupling signal value of receiver 5 / 0.32) × 0.1mm.

[0015] Further specifying, after step S5, closed-loop calibration is performed, with the following steps: S6. After replacing the target adjustment component, collect the current direct coupling signal value of each receiving coil again according to the working parameters in step S3. S7. Calculate the deviation between the current direct coupling signal value and the preset threshold. If the absolute value of the deviation is > 0.1mS / m, repeat steps S4 to S7 based on the current signal value. S8. The preset threshold is ≤0.5mS / m for the absolute value of the direct coupling signal, and is adjusted to ≤0.3mS / m for high-precision logging scenarios. It can adapt to the measurement accuracy requirements of different instruments.

[0016] The beneficial effects of using the present invention are as follows: This invention combines theoretical modeling and experiments to quantify the correspondence between the size change of the regulating component and the direct coupling signal. Based on the actual acquired initial direct coupling signal value, it accurately calculates the target regulating component size of each receiving coil through a linear correction model, achieving individual targeted calibration of the direct coupling signal of each receiving coil. This overcomes the technical bottleneck of incomplete direct coupling signal cancellation caused by machining accuracy and coil tension deviation in existing three-coil systems. It enables the direct coupling signal value of each receiving coil to approach a preset threshold, fundamentally reducing the interference of the direct coupling signal on the useful signal, significantly improving the accuracy of formation conductivity measurement, and providing more reliable data support for oil and gas reservoir identification and evaluation.

[0017] This invention clarifies the complete process from quantitative calibration of adjustment components, standard component assembly, signal acquisition, size calculation to replacement calibration. The adjustment components adopt a standardized design and naming rule of "reference size + fixed step size", which allows operators to quickly match the corresponding adjustment components according to the calculation results without complicated conversion or additional measurement. At the same time, the independent spacing adjustment channel design avoids cross-interference between the calibration of each receiving coil, and the closed-loop calibration steps further ensure the stability of the calibration effect. The entire method is clear and the steps are well-defined, which not only reduces the difficulty of instrument assembly and calibration, but also facilitates mass production, inventory management and maintenance and replacement after downhole operations, and is suitable for large-scale application scenarios of different models of array induction logging tools.

[0018] This invention does not require significant modifications to the core structure of existing array sensing instruments. Direct coupling signal elimination can be achieved simply by adding a standardized adjustment component between the transmitting and receiving coils. It has strong compatibility with existing instrument structures. Furthermore, the method itself is not limited to a specific number of receiving coils or wellbore conditions. The preset threshold can be adjusted according to the instrument's measurement accuracy requirements, leaving room for subsequent technical optimization and adaptation to different logging scenarios. This further enhances the practical value and application life of the technical solution. Attached Figure Description

[0019] The present invention can be further illustrated by the non-limiting embodiments given in the accompanying drawings; Figure 1 This is a smooth schematic block diagram of an embodiment of a method for eliminating array-induced direct coupling signals according to the present invention; Figure 2 This is a schematic diagram illustrating the use of the adjustment standard component in an embodiment of the method for eliminating array inductive direct coupling signals according to the present invention. Detailed Implementation To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0020] like Figure 1 , Figure 2 As shown, a method for eliminating array-induced direct coupling signals according to the present invention includes the following steps: S1. By combining electromagnetic simulation modeling with equivalent experiments of the downhole environment, the quantitative contribution of the unit thickness change of the adjustment component to the change of the direct coupling signal of each receiving coil is quantified and calibrated. S2. During the assembly stage of the array sensing instrument, a standard adjustment component with a reference thickness of 10mm is assembled in the independent spacing adjustment area between the transmitting coil and each receiving coil. S3. Start the instrument according to the preset operating parameters, including power supply frequency and current amplitude, and collect and record the initial direct coupling signal values ​​of each receiving coil. S4. Based on the quantized contribution amount in step S1 and the initial direct coupling signal value in step S3, the target adjustment component size corresponding to each receiving coil is solved by a linear correction model. S5. Replace the standard adjustment component with the target adjustment component to make the direct coupling signal value of each receiving coil approach the preset threshold, thereby achieving accurate cancellation of the direct coupling signal.

[0021] In this implementation case, the correlation logic between the size of the regulating component and the direct coupling signal is constructed through theoretical modeling. Combined with equivalent experimental verification and data correction, the quantitative calibration of the correspondence between the change in the size of the regulating component and the change in the direct coupling signal of each receiving coil is completed, and the quantitative contribution is clarified. During the assembly of the array sensing instrument, a standard regulating component with a reference width of 10mm is precisely assembled in the independent spacing adjustment area between the transmitting coil and each receiving coil. After the instrument is assembled, the equipment is started according to the preset power supply frequency and current amplitude, and the initial direct coupling signal value of each receiving coil is collected and recorded in real time. Based on the calibrated quantitative contribution, the collected initial direct coupling signal value is substituted into the model, and the target regulating component size required for each receiving coil is calculated one by one through the linear correction model. Then, all the standard regulating components on the instrument are replaced with the calculated target regulating components, so that the direct coupling signal value of each receiving coil gradually approaches the preset threshold, and finally the precise cancellation of the direct coupling signal is achieved. The core is to establish a clear and quantifiable correspondence between the size of the adjustment component and the direct-coupled signal, breaking the limitations of traditional technology that relies on coil turns ratio and fixed spacing compensation. Through a closed-loop process of "quantization calibration - signal acquisition - precise calculation - replacement calibration", the direct-coupled signal strength of each receiving coil is individually adapted, blocking the interference path of the direct-coupled signal to the useful signal from the source. It does not require disruptive modifications to the core electromagnetic structure of existing array sensing instruments. The technology can be implemented simply by adding standardized adjustment components. The process steps are clear and easy to understand. Operators can master it after simple training. At the same time, the direct-coupled signal elimination is more targeted and accurate, effectively improving the reliability of formation conductivity measurement data and providing solid data support for the accurate identification, evaluation and development decision of oil and gas reservoirs.

[0022] In preferred step S1, the adjusting component is an insulating, high-temperature resistant sheet structure adapted to the well logging downhole environment. Specifically, it meets the following requirements: the base width is 10mm, and the adjusting step is 0.1mm. The adjusting components with widths increasing in multiples of 0.1mm are named Z1, Z2, Z3..., and the decreasing ones are named J1, J2, J3...; its material is selected from alumina ceramic, silicon nitride ceramic or zirconium oxide ceramic.

[0023] In this implementation case, the adjusting component in step S1 adopts a sheet-like structure design, which is specially adapted to the complex working conditions of well logging. It has insulation and high temperature resistance characteristics. Its base width is set to 10mm, and the adjusting step is fixed in 0.1mm increments. The adjusting components with widths increasing in multiples of 0.1mm are named Z1, Z2, Z3..., and the adjusting components with widths decreasing in multiples of 0.1mm are named J1, J2, J3..., respectively. The material is selected from alumina ceramic, silicon nitride ceramic, or zirconium oxide ceramic. The selected material must meet the technical specifications of temperature resistance ≥150℃, insulation resistance ≥10¹²Ω・cm, and compressive strength ≥200MPa. The naming rules are directly linked to the size change logic of the regulating components, allowing for quick identification of size parameters without additional labeling. The material selection fully considers the environmental characteristics of high temperature, high pressure, and strong electromagnetic interference in the well, achieving dual optimization of "standardized identification" and "operating condition adaptability" of the regulating components. Operators can quickly match the required size based solely on the name of the adjustment component, significantly shortening assembly and replacement time and avoiding operational errors caused by size confusion. The insulating material effectively prevents the adjustment component from interfering with the coil's electromagnetic signal, and its high temperature and high pressure resistance ensures that the adjustment component maintains structural stability and reliable performance in harsh downhole environments, providing a fundamental guarantee for the continuous and effective implementation of the direct coupling signal elimination scheme.

[0024] In the preferred step S1, the calibration process for quantifying the contribution is specifically as follows: S1.1 Build an experimental platform to simulate the electromagnetic environment downhole, set the ambient temperature to 20-50℃ and the atmospheric pressure, and cover the parameters of mainstream array induction instruments with a power supply frequency of 1kHz-1MHz and a current amplitude of 0.1-1A for the transmitting coil. S1.2. Assemble adjustment components of different thicknesses in sequence. For each type of thickness, collect direct coupling signals three times and take the average value to remove abnormal data. S1.3. Establish a fitting curve between the thickness change of the regulating component and the change of the direct coupling signal through linear regression analysis, with a curve fitting degree R²≥0.995.

[0025] In this implementation case, the calibration of the quantitative contribution in step S1 is performed according to a fixed procedure: First, an experimental platform simulating the downhole electromagnetic environment is built, and the platform environmental parameters are set to a temperature of 20-50℃ and normal pressure. The power supply frequency of the transmitting coil is adjusted to the range of 1kHz-1MHz, and the current amplitude is set to 0.1-1A, fully covering the working parameter range of mainstream array induction instruments. Then, adjustment components of different thicknesses are assembled on the platform in sequence. For each type of adjustment component thickness, the direct coupling signal is repeatedly collected 3 times. The average value of the 3 collected data is taken and abnormal data is removed. Finally, a fitting curve of the change in adjustment component thickness and the change in direct coupling signal is established through linear regression analysis. The curve fitting degree R² ≥ 0.995 is required to complete the calibration of the quantitative contribution. By combining the design of simulating actual downhole working conditions parameters, averaging multiple data acquisitions, eliminating abnormal data, and performing high-fit linear regression analysis, a calibration system of "working condition equivalence - data noise reduction - accurate fitting" was constructed, which made up for the error defects caused by environmental parameter distortion and data randomness in traditional calibration. The quantified contribution obtained from calibration can truly and accurately reflect the correlation between the size of the regulating component and the direct-coupled signal, effectively avoiding calculation errors in the size of the target regulating component due to calibration deviations. This provides core data support for the accurate calibration of each receiving coil in the future, ensuring the stability and consistency of the direct-coupled signal elimination effect.

[0026] In preferred step S1, the manufacturing precision of the adjustment component meets the following requirements: thickness tolerance ≤ ±0.005mm, surface roughness Ra ≤ 0.8μm, and thickness uniformity error ≤ 0.003mm.

[0027] In this implementation case, the adjustment component in step S1 needs to meet specific precision requirements during the manufacturing stage: the thickness tolerance is controlled within ±0.005mm, the surface roughness Ra≤0.8μm, and the thickness uniformity error≤0.003mm. The above precision indicators are achieved through strict production process control. Incorporate the manufacturing precision of the adjusting components into the technical solution's limitations, control the dimensional deviation of the adjusting components themselves from the production source, and avoid the problem of inconsistency between the "calculated dimensions" and the "actual functional dimensions" due to insufficient precision of the adjusting components; It can effectively control the influence of the adjustment component size accuracy on the calibration effect of direct coupling signal within ±0.05mS / m, ensuring that the target adjustment component can accurately perform the calibration function after replacement, avoiding the direct coupling signal residue caused by the adjustment component's own error, and further improving the accuracy and reliability of direct coupling signal elimination.

[0028] In preferred step S2, the array sensing instrument includes one transmitting coil and at least two receiving coils, with each receiving coil evenly arranged along the axial direction of the transmitting coil. When there are six receiving coils, sequentially defined as receiver 0 to receiver 5, the quantization contribution calibrated in step S1 is as follows: for every 0.1 mm increase in the thickness of the adjusting element, the direct-coupled signal of receiver 0 increases by 34.50 ms / m, receiver 1 by 7.20 ms / m, receiver 2 by 5.16 ms / m, receiver 3 by 3.25 ms / m, receiver 4 by 1.30 ms / m, and receiver 5 by 0.32 ms / m.

[0029] In this implementation example, step S2 specifies the coil configuration standard of the array sensing instrument: it includes one transmitting coil and at least two receiving coils, with each receiving coil evenly arranged along the axial direction of the transmitting coil; when the number of receiving coils is 6, they are defined as receiving 0 to receiving 5 in sequence. At this time, the quantization contribution amount calibrated in step S1 is specifically as follows: for every 0.1mm increase in the thickness of the adjusting component, the direct coupling signal of receiving 0 increases by 34.50mS / m, receiving 1 by 7.20mS / m, receiving 2 by 5.16mS / m, receiving 3 by 3.25mS / m, receiving 4 by 1.30mS / m, and receiving 5 by 0.32mS / m. Subarray For every 0.1mm increase in the thickness of the plug gauge, the direct coupling signal increases by mS / m. Receive 0 34.50 Receive 1 7.20 Receive 2 5.16 Receive 3 3.25 Receive 4 1.30 Receive 5 0.32 The basic configuration requirements of the instrument coils are clearly defined, and specific quantitative contribution data are given for six receiving coil scenarios. This not only adapts to the general scenario of multiple receiving coils, but also provides directly usable calibration data for the mainstream 6-coil configuration, thus expanding the applicability of the technical solution. Users do not need to conduct complex quantitative calibration experiments themselves; they can directly apply the established data to calculate the size of the target adjustment component, which greatly reduces the difficulty of operation and time cost. The uniformly arranged coil structure combined with the precise quantitative contribution ensures that the calibration of each receiving coil can be specifically adapted to the design scheme of mainstream array sensing instruments, thereby improving the versatility and operability of the technical solution.

[0030] In the preferred step S2, the following two points are satisfied when assembling the standard adjustment component: ① Fix the reference distance between the transmitting coil and the receiving coil. After the adjusting piece is embedded in the distance adjustment area, the contact gap with the end face of the coil should be ≤0.01mm. ② The adjusting parts are fixed by using elastic positioning slots or threaded locking structures.

[0031] In this implementation case, two requirements must be strictly followed when assembling the standard adjustment component in step S2: First, fix the reference distance between the transmitting coil and the receiving coil. After embedding the standard adjustment component into the distance adjustment area, ensure that the contact gap between the adjustment component and the coil end face is ≤0.01mm using a special tooling. Second, use an elastic positioning slot or threaded locking structure to fix the adjustment component to ensure that the positioning accuracy of the adjustment component is ≤0.005mm. The assembly process is standardized from two aspects: "fitting gap" and "fixed structure". In response to the problem that vibration of downhole instruments can easily cause displacement of the adjustment components, the stability of the fixed structure is strengthened. At the same time, the fitting gap is strictly controlled to ensure the accurate effective working distance between the adjustment components and the coil. It avoids dimensional deviations caused by loose or insecure fit of the adjustment components, prevents displacement or loosening of the adjustment components during instrument vibration downhole, ensures that the adjustment components are always in the preset working position, guarantees the stability of the direct coupling signal calibration effect, and avoids measurement errors caused by assembly problems during downhole operations.

[0032] In preferred step S2, the spacing adjustment area is designed to be independently isolated, with each receiving coil corresponding to a dedicated adjustment channel.

[0033] In this implementation case, the spacing adjustment area in step S2 adopts an independent isolation design. Each receiving coil corresponds to a dedicated adjustment channel, and the adjustment channels are separated by an insulating isolation structure to ensure that each channel does not affect the others. Breaking through the limitations of traditional integrated adjustment area design, the independent isolation design enables "dedicated" adjustment of each receiving coil, avoiding indirect impact of the size adjustment of a single adjustment component on the spacing of other receiving coils; The size adjustments of each adjustment component do not interfere with each other, and calibration operations can be carried out separately for the direct coupling signal strength of different receiving coils, effectively avoiding cross interference, making the calibration of each receiving coil more independent and targeted, and further improving the accuracy of direct coupling signal elimination.

[0034] In the preferred step S4, the general expression for the linear correction model is: Target adjustment component width = reference width - (initial direct coupling signal value / corresponding quantization contribution) × adjustment step size; Where the reference width is 10mm and the adjustment step size is 0.1mm, the specific formula is as follows when the receiving coil is in receive 0 to receive 5: Receive 0: 10mm - (Initial direct coupling signal value at Receive 0 / 34.50) × 0.1mm; Receiver 1: 10mm - (Initial direct coupling signal value of Receiver 1 / 7.20) × 0.1mm; Receiver 2: 10mm - (Initial direct coupling signal value of receiver 2 / 5.16) × 0.1mm; Receiver 3: 10mm - (Initial direct coupling signal value of receiver 3 / 3.25) × 0.1mm; Receiver 4: 10mm - (Initial direct coupling signal value of receiver 4 / 1.30) × 0.1mm; Receiver 5: 10mm - (Initial direct coupling signal value of receiver 5 / 0.32) × 0.1mm.

[0035] In this implementation case, step S4 clarifies that the general expression of the linear correction model is: target adjustment width = reference width - (initial direct coupling signal value / corresponding quantization contribution) × adjustment step size, where the reference width is fixed at 10mm and the adjustment step size is fixed at 0.1mm; when the receiving coils are receiver 0 to receiver 5, the specific calculation formulas are as follows: receiver 0: 10mm - (initial direct coupling signal value of receiver 0 / 34.50) × 0.1mm, receiver 1: 10mm - (initial direct coupling signal value of receiver 1 / 7.20) × 0.1mm, receiver 2: 10mm - (initial direct coupling signal value of receiver 2 / 5.16) × 0.1mm, receiver 3: 10mm - (initial direct coupling signal value of receiver 3 / 3.25) × 0.1mm, receiver 4: 10mm - (initial direct coupling signal value of receiver 4 / 1.30) × 0.1mm, receiver 5: 10mm - (initial direct coupling signal value of receiver 5 / 0.32) × 0.1mm; It provides a clear general calculation model and precise formulas for specific scenarios, transforming the abstract "linear correction" into directly applicable calculation steps, thus avoiding errors caused by ambiguity in calculation logic. Operators can directly substitute the acquired initial direct-coupled signal value for calculation without complex logical deduction or parameter conversion, which greatly reduces the calculation difficulty and error probability, ensuring the accuracy and consistency of the target adjustment component size calculation, and providing a computational guarantee for the accurate cancellation of direct-coupled signals.

[0036] Preferably, after step S5, closed-loop calibration is performed, as follows: S6. After replacing the target adjustment component, collect the current direct coupling signal value of each receiving coil again according to the working parameters in step S3. S7. Calculate the deviation between the current direct coupling signal value and the preset threshold. If the absolute value of the deviation is > 0.1mS / m, repeat steps S4 to S7 based on the current signal value. S8. The preset threshold is ≤0.5mS / m for the absolute value of the direct-coupled signal, and is adjusted to ≤0.3mS / m for high-precision logging scenarios.

[0037] In this implementation case, after replacing the target adjustment component in step S5, the closed-loop calibration process is initiated: the current direct coupling signal value of each receiving coil is collected again according to the working parameters set in step S3; the deviation between the current direct coupling signal value and the preset threshold is calculated; if the absolute value of the deviation is >0.1mS / m, steps S4 to S7 are re-executed based on the currently collected direct coupling signal value until the deviation meets the requirements; the preset threshold standard is the absolute value of the direct coupling signal ≤0.5mS / m, and for high-precision logging scenarios, the threshold can be adjusted to ≤0.3mS / m; After "replacement calibration", a closed-loop verification and secondary correction process is added. At the same time, a threshold standard that can be adapted to different scenarios is designed to make up for the residual error that may exist in a single calibration and expand the adaptability of the technical solution to different accuracy requirements. Multiple cyclic calibrations ensure that the direct-coupled signal value stabilizes and approaches the preset threshold, effectively eliminating the random error of a single calibration and making the direct-coupled signal elimination more thorough. The threshold differentiation design for conventional and high-precision scenarios can meet the accuracy requirements of different logging tasks, improve the flexibility and applicability of the technical solution, and ensure the extraction accuracy of useful signals in various logging scenarios.

[0038] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for eliminating array-induced direct-coupled signals, characterized in that, Includes the following steps: S1. By combining electromagnetic simulation modeling with equivalent experiments of the downhole environment, the quantitative contribution of the unit thickness change of the adjustment component to the change of the direct coupling signal of each receiving coil is quantified and calibrated. S2. During the assembly stage of the array sensing instrument, a standard adjustment component with a reference thickness of 10mm is assembled in the independent spacing adjustment area between the transmitting coil and each receiving coil. S3. Start the instrument according to the preset operating parameters, including power supply frequency and current amplitude, and collect and record the initial direct coupling signal values ​​of each receiving coil. S4. Based on the quantized contribution amount in step S1 and the initial direct coupling signal value in step S3, the target adjustment component size corresponding to each receiving coil is solved by a linear correction model. S5. Replace the standard adjustment component with the target adjustment component to make the direct coupling signal value of each receiving coil approach the preset threshold, thereby achieving accurate cancellation of the direct coupling signal.

2. The method for eliminating array-induced direct coupling signals according to claim 1, characterized in that: In step S1, the adjusting component is an insulating, high-temperature resistant sheet structure adapted to the well logging downhole environment. Specifically, it meets the following requirements: the base width is 10mm, and the adjusting step is 0.1mm. The adjusting components with widths increasing in integer multiples of 0.1mm are named Z1, Z2, Z3..., and the decreasing ones are named J1, J2, J3...; its material is selected from alumina ceramic, silicon nitride ceramic or zirconium oxide ceramic.

3. The method for eliminating array-induced direct coupling signals according to claim 1, characterized in that: In step S1, the calibration process for quantifying the contribution is as follows: S1.1 Build an experimental platform to simulate the electromagnetic environment downhole, set the ambient temperature to 20-50℃ and the atmospheric pressure, and cover the parameters of mainstream array induction instruments with a power supply frequency of 1kHz-1MHz and a current amplitude of 0.1-1A for the transmitting coil. S1.

2. Assemble adjustment components of different thicknesses in sequence. For each type of thickness, collect direct coupling signals three times and take the average value to remove abnormal data. S1.

3. Establish a fitting curve between the thickness change of the regulating component and the change of the direct coupling signal through linear regression analysis, with a curve fitting degree R²≥0.

995.

4. The method for eliminating array-induced direct coupling signals according to claim 1, characterized in that: In step S1, the manufacturing precision of the adjustment component meets the following requirements: thickness tolerance ≤ ±0.005mm, surface roughness Ra ≤ 0.8μm, and thickness uniformity error ≤ 0.003mm.

5. The method for eliminating array-induced direct coupling signals according to claim 1, characterized in that: In step S2, the array sensing instrument includes one transmitting coil and at least two receiving coils, with each receiving coil evenly arranged along the axial direction of the transmitting coil. When there are six receiving coils, sequentially defined as receiving coils 0 to 5, the quantization contribution calibrated in step S1 is as follows: for every 0.1 mm increase in the thickness of the adjusting element, the direct-coupled signal of receiving coil 0 increases by 34.50 ms / m, receiving coil 1 by 7.20 ms / m, receiving coil 2 by 5.16 ms / m, receiving coil 3 by 3.25 ms / m, receiving coil 4 by 1.30 ms / m, and receiving coil 5 by 0.32 ms / m.

6. The method for eliminating array-induced direct coupling signals according to claim 1, characterized in that: In step S2, the following two points must be met when assembling the standard adjustment parts: ① Fix the reference distance between the transmitting coil and the receiving coil. After the adjusting piece is embedded in the distance adjustment area, the contact gap with the end face of the coil should be ≤0.01mm. ② The adjusting parts are fixed by using elastic positioning slots or threaded locking structures.

7. The method for eliminating array-induced direct coupling signals according to claim 1, characterized in that: In step S2, the spacing adjustment area is designed to be independently isolated, with each receiving coil corresponding to a dedicated adjustment channel.

8. The method for eliminating array-induced direct coupling signals according to claim 1, characterized in that: In step S4, the general expression for the linear correction model is: Target adjustment component width = reference width - (initial direct coupling signal value / corresponding quantization contribution) × adjustment step size; Where the reference width is 10mm and the adjustment step size is 0.1mm, the specific formula is as follows when the receiving coil is in receive 0 to receive 5: Receive 0: 10mm - (Initial direct coupling signal value at Receive 0 / 34.50) × 0.1mm; Receiver 1: 10mm - (Initial direct coupling signal value of Receiver 1 / 7.20) × 0.1mm; Receiver 2: 10mm - (Initial direct coupling signal value of receiver 2 / 5.16) × 0.1mm; Receiver 3: 10mm - (Initial direct coupling signal value of receiver 3 / 3.25) × 0.1mm; Receiver 4: 10mm - (Initial direct coupling signal value of receiver 4 / 1.30) × 0.1mm; Receiver 5: 10mm - (Initial direct coupling signal value of receiver 5 / 0.32) × 0.1mm.

9. The method for eliminating array-induced direct coupling signals according to claim 1, characterized in that: After step S5, closed-loop calibration is performed, as follows: S6. After replacing the target adjustment component, collect the current direct coupling signal value of each receiving coil again according to the working parameters in step S3. S7. Calculate the deviation between the current direct coupling signal value and the preset threshold. If the absolute value of the deviation is > 0.1mS / m, repeat steps S4 to S7 based on the current signal value. S8. The preset threshold is ≤0.5mS / m for the absolute value of the direct-coupled signal, and is adjusted to ≤0.3mS / m for high-precision logging scenarios.

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