Induction logging skin effect correction method and device and induction logging device

Abstract

The invention provides an induction logging skin effect correction method and device and an induction logging device.A subarray is simulated in advance to detect a sample medium, apparent conductivity measured under various working frequencies and corresponding true conductivity are obtained, and the first apparent conductivity under the target frequency is determined according to the apparent conductivity and the corresponding true conductivity; calculating a first relative skin depth according to the first apparent conductivity and the source distance, calculating a ratio of the true conductivity to the first apparent conductivity under the target frequency as a conductivity ratio, and fitting each conductivity ratio with the corresponding first relative skin depth to obtain a skin depth value; obtaining a quantitative relationship among the true conductivity, the first apparent conductivity under the target frequency and the first relative skin depth; during actual well logging, second apparent conductivity and second relative skin depth under the target frequency are calculated on the basis of a method similar to that during simulation detection, and then the measured apparent conductivity is corrected by combining the quantitative relation. The scheme can improve the accuracy and reliability of the correction result.

Description

Technical Field

[0001] This application relates to the field of induction logging technology, and in particular to an induction logging skin effect correction method, device, and induction logging device. Background Technology

[0002] Utilizing the principle of electromagnetic induction to detect the properties of a medium is a common detection method. Specifically, an electromagnetic wave is emitted by a transmitting coil, and the electromagnetic wave reflected by the medium is received by a receiving coil. The received reflected electromagnetic wave signal is then processed to obtain the characteristic parameters of the medium. For example, induction logging is a logging method that uses the principle of electromagnetic induction to study the conductivity of a formation. When an alternating current is passed through the transmitting coil, eddy currents coaxial with the coil are induced in the surrounding formation by the alternating electromagnetic field. The secondary magnetic field caused by the eddy currents induces a secondary electromotive force in the receiving coil, the magnitude of which is proportional to the magnitude of the eddy currents, which in turn is proportional to the formation conductivity.

[0003] When the transmitting coil approaches a medium, the electromagnetic induction field is affected by the medium, causing a "concentration" effect of the induced current on the medium surface. This effect causes changes in the characteristic parameters of the medium surface near the transmitting coil; this is known as the skin effect. Taking induction logging as an example, when the probe (i.e., the electromagnetic induction coil) approaches the formation surface, the electromagnetic induction field is affected by the formation conductivity, causing a "concentration" effect of the induced current on the formation surface. This effect causes changes in conductivity near the wellbore, i.e., the skin effect. Due to the skin effect, the apparent conductivity of induction logging is usually less than the true conductivity of the medium surrounding the logging instrument. To ensure that the conductivity value measured by the induction logging instrument is consistent with the actual formation conductivity value, skin effect correction must be applied to the apparent conductivity measured by the induction logging instrument.

[0004] Existing skin effect correction methods include piecewise linear multiply-accumulate factor method, nonlinear function fitting method, iterative method, and multi-frequency skin effect correction method. The piecewise linear multiply-accumulate factor method and nonlinear function fitting method only have individual fitting formulas applicable within a certain conductivity range. To use them over a wider conductivity range, piecewise fitting is necessary, and the selection of conductivity segments and fitting formulas is influenced by human factors. The iterative method suffers from excessive computation and unpredictable results, making it unsuitable for some applications of induction logging data processing. The multi-frequency skin effect correction method has the problem of a large error between the correction results for high-conductivity formations and the true conductivity of the formation. Therefore, the accuracy and reliability of existing skin effect correction methods are relatively low. Summary of the Invention

[0005] This invention provides a method, apparatus, and induction logging device for correcting the skin effect in induction logging, thereby improving the accuracy and reliability of induction logging.

[0006] To address the aforementioned technical problems, the first aspect of this invention provides a method for correcting the skin effect in inductive logging, comprising performing the following operations on each subarray of a target inductive logging device: when simulating the current subarray detecting a sample medium, acquiring the apparent conductivity and the corresponding true conductivity measured by the current subarray at multiple operating frequencies; determining a first apparent conductivity at a target frequency based on the apparent conductivity corresponding to the multiple operating frequencies, and calculating a first relative skin depth based on the first apparent conductivity at the target frequency and the source distance; calculating the ratio of the true conductivity to the first apparent conductivity at the target frequency as the electrical conductivity. The conductivity ratio is fitted to a first relative skin depth. Based on the fitting result, the quantitative relationship between the true conductivity, the first apparent conductivity at the target frequency, and the first relative skin depth is determined. During actual logging, the apparent conductivity measured by the current subarray at various operating frequencies is obtained. Based on the apparent conductivity corresponding to each of the multiple operating frequencies, the second apparent conductivity at the target frequency is determined, and the second relative skin depth is calculated based on the second apparent conductivity at the target frequency and the source distance. The measured apparent conductivity is corrected based on the second apparent conductivity, the second relative skin depth, and the quantitative relationship.

[0007] In some embodiments, the measured apparent conductivity is corrected based on the second apparent conductivity, the second relative skin depth, and the quantitative relationship, including: replacing the first apparent conductivity at the target frequency with the second apparent conductivity at the target frequency, replacing the first relative skin depth with the second relative skin depth, calculating the true conductivity during actual logging based on the quantitative relationship, and using the true conductivity as the correction result.

[0008] In some embodiments, the target frequency range is (0, 1Hz).

[0009] In some embodiments, before calculating the second relative skin depth based on the second apparent conductivity and source distance at the target frequency, the method further includes: determining whether the second apparent conductivity is greater than or equal to a target threshold; if yes, performing the calculation of the second relative skin depth based on the second apparent conductivity and source distance at the target frequency; if no, determining that the corrected result is the same as the measured apparent conductivity.

[0010] In some embodiments, the target threshold is 1 S / m.

[0011] In some embodiments, the relative skin depth is calculated according to the following formula: Where Δ is the relative skin depth at the target frequency, L is the source distance, ω is the angular frequency, μ is the permeability constant of vacuum, and σ a0The apparent conductivity at the target frequency; the relative skin depth includes a first relative skin depth and a second relative skin depth.

[0012] In some embodiments, the conductivity ratio is fitted to the first relative skin depth using the following fitting formula: Where σ is the true conductivity, σ a0 Let be the first apparent conductivity at the target frequency, Δ be the first relative skin depth, and a, b, and c be the fitting coefficients.

[0013] A second aspect of the present invention provides a skin effect correction device for inductive logging, comprising: a first acquisition unit, configured to acquire, when simulating the detection of a sample medium by a current subarray, the apparent conductivity and the true conductivity corresponding to the apparent conductivity measured at various operating frequencies by the current subarray; a first calculation unit, configured to determine a first apparent conductivity at a target frequency based on the apparent conductivity corresponding to the various operating frequencies, and calculate a first relative skin depth based on the first apparent conductivity at the target frequency and the source distance; and a second calculation unit, configured to calculate the ratio of the true conductivity to the first apparent conductivity at the target frequency as a conductivity ratio, fit the conductivity ratio to the first relative skin depth, and determine the true conductivity based on the fitting result. The system comprises four parts: a first apparent conductivity at the target frequency and a second relative skin depth; a second acquisition unit for acquiring the apparent conductivity measured by the current subarray at various operating frequencies during actual logging; a third calculation unit for determining the second apparent conductivity at the target frequency based on the apparent conductivity corresponding to the multiple operating frequencies, and calculating the second relative skin depth based on the second apparent conductivity at the target frequency and the source distance; and a fourth calculation unit for replacing the first apparent conductivity at the target frequency with the second apparent conductivity at the target frequency, replacing the first relative skin depth with the second relative skin depth, calculating the true conductivity during actual logging based on the aforementioned quantitative relationship, and using the true conductivity as the correction result.

[0014] A third aspect of the present invention provides an inductive logging device, comprising: a plurality of subarrays, each subarray including an electromagnetic signal transmitting coil and an electromagnetic signal receiving coil; a controller for controlling each electromagnetic signal transmitting coil to transmit electromagnetic waves at a set frequency and controlling the electromagnetic signal receiving coil to receive electromagnetic waves; and a processor for determining the apparent conductivity based on the electromagnetic waves received by each subarray and correcting the apparent conductivity using the method described in any one of the first aspects to obtain a correction result.

[0015] In some embodiments, the inductive logging device has one electromagnetic signal transmitting coil and multiple electromagnetic signal receiving coils, and the distance between each electromagnetic signal receiving coil and the electromagnetic signal transmitting coil is not exactly the same.

[0016] In some embodiments, each electromagnetic signal receiving coil may operate at a different frequency.

[0017] A fourth aspect of the present invention provides an electronic device, comprising: a memory and a processor, wherein the processor and the memory are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to implement the skin effect correction method for inductive logging as described in any one aspect.

[0018] The fifth aspect of the present invention provides a computer storage medium storing computer program instructions, which, when executed by a processor, implement the skin effect correction method for inductive logging as described in any one of the first aspects.

[0019] The sixth aspect of the present invention provides a computer program product comprising a computer program that, when executed by a processor, implements the skin effect correction method for inductive logging as described in any of the first aspects.

[0020] The skin effect correction method, apparatus, and induction logging device provided by this invention pre-simulate the detection of a sample medium by a subarray of a target induction logging device, and obtain the apparent conductivity and the corresponding true conductivity of the subarray at multiple operating frequencies. Based on the apparent conductivity at each of the multiple frequencies, a first apparent conductivity at the target frequency is determined. Then, a first relative skin depth is calculated based on the first apparent conductivity and the source distance. The ratio of the true conductivity to the first apparent conductivity at the target frequency is calculated as the conductivity ratio. Each conductivity ratio is fitted with the corresponding first relative skin depth to obtain the quantitative relationship between the true conductivity, the first apparent conductivity at the target frequency, and the first relative skin depth. During actual logging, the apparent conductivity measured by the subarray at multiple operating frequencies is obtained, and a second apparent conductivity and a second relative skin depth at the target frequency are calculated using a method similar to that used in the simulation. The measured apparent conductivity is then corrected based on the aforementioned quantitative relationship. This method uses the ratio of apparent conductivity at the target frequency, relative skin depth, and true conductivity to apparent conductivity at the target frequency as a bridge to determine the quantitative relationship between true conductivity, the first apparent conductivity at the target frequency, and the first relative skin depth. During actual well logging, the measured apparent conductivity is then corrected based on this relationship. This method can be used over a wide conductivity range, is unaffected by human factors, has low computational complexity, high reliability, and the error between the corrected result and the true conductivity is small. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a sensing logging device.

[0023] Figure 2 A schematic diagram of the skin effect correction method for induction logging provided by the present invention;

[0024] Figures 3 to 9 The figures are cross-plots of apparent conductivity and corresponding true conductivity at eight different operating frequencies obtained by the seven subarrays of the target induction logging device.

[0025] Figure 10 and Figure 11 This is a schematic diagram of the fitted curve of apparent conductivity versus frequency.

[0026] Figure 12 A cross-plot of apparent conductivity and true conductivity of multiple subarrays of an induction logging device at a target frequency;

[0027] Figure 13 This is a cross-plot showing the errors between the true conductivity value and the apparent conductivity and true conductivity.

[0028] Figure 14 This is a schematic diagram of the second fitting results for the seven subarrays of an induction logging device;

[0029] Figure 15 This is a schematic diagram showing the relative error between the corrected values ​​of apparent conductivity and true conductivity measured by each subarray of the target induction logging device during actual logging.

[0030] Figure 16 This is a cross-plot of the apparent conductivity and true conductivity measured by each subarray of the target induction logging device during actual logging.

[0031] Figure 17 A schematic diagram showing the skin effect correction results of a target induction logging device in series in a target well section from 6715.0 to 6760.0 meters.

[0032] Figure 18 A schematic diagram of the skin effect correction device for inductive logging provided by the present invention;

[0033] Figure 19 A schematic diagram of the structure of the electronic device provided by the present invention is shown. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0035] This invention provides a skin effect correction method for induction logging, which can be used for induction logging of oil, natural gas, etc. In induction logging, a logging device typically employs multiple subarrays. Each subarray includes an electromagnetic signal transmitting coil and an electromagnetic signal receiving coil, and may also include a shielding coil and a compensation coil.

[0036] like Figure 1 As shown, in some embodiments, the induction logging device may include an electromagnetic signal transmitting coil T and multiple electromagnetic signal receiving coils Rn and compensation coils Bn (shielding coils are not shown in the figure). The electromagnetic signal transmitting coil T and the corresponding supplementary coils of each electromagnetic signal receiving coil Rn and electromagnetic signal receiving coil Bn form a subarray. For example, the electromagnetic signal transmitting coil T, electromagnetic signal receiving coil R1, and compensation coil B1 form one subarray; the electromagnetic signal transmitting coil T, electromagnetic signal receiving coil R2, and compensation coil B2 form another subarray.

[0037] Each subarray's electromagnetic signal transmitting coil is energized with alternating current to emit electromagnetic waves, while the electromagnetic signal receiving coil receives electromagnetic waves reflected from the ground. The apparent conductivity is calculated based on the theoretical relationship between the electromagnetic wave signal received by the electromagnetic signal receiving coil and conductivity, which assumes the absence of the skin effect.

[0038] like Figure 2 As shown, the skin effect correction method for induction logging provided by the present invention includes performing the following operations on each subarray of the target induction logging device:

[0039] S110: When simulating the current subarray to detect the sample medium, obtain the apparent conductivity and the true conductivity corresponding to the apparent conductivity measured by the current subarray at various operating frequencies.

[0040] Alternating currents of different frequencies can be applied to the electromagnetic signal transmitting coils of the current subarray to make the current subarray operate at different operating frequencies.

[0041] In S110, the true conductivity and apparent conductivity can be obtained under experimental conditions, and the true conductivity can be preset. For example, when obtaining the true conductivity and apparent conductivity through actual physical experiments, a medium with a preset true conductivity value can be prepared in advance, and then the apparent conductivity can be obtained by measuring the medium using a target induction logging device. As another example, when obtaining the true conductivity and apparent conductivity through simulation, a simulation model of the medium can be predetermined, and the conductivity of the medium can be set to a preset value. Then, considering the skin effect, the apparent conductivity measured by the induction logging device can be determined through forward modeling.

[0042] Assume the target sensing logging device has 7 subarrays numbered 0-6. Figures 3 to 9 The diagram shows the intersection of the apparent conductivity and the corresponding true conductivity of the seven subarrays at eight operating frequencies obtained using S110.

[0043] S120: Based on multiple apparent conductivities at various operating frequencies, determine the first apparent conductivity at the target frequency, and calculate the first relative skin depth based on the first apparent conductivity at the target frequency and the source distance.

[0044] The first apparent conductivity at the target frequency can be determined by fitting the apparent conductivity corresponding to multiple operating frequencies.

[0045] In some embodiments, a coordinate system with apparent conductivity as the first coordinate and operating frequency as the second coordinate can be established. The apparent conductivity and corresponding operating frequency obtained in S110 are marked as scatter points in the coordinate system. Then, these scatter points are fitted with a curve, and the expression of the curve is determined. The expression is used as the first fitting result. Figure 10 and Figure 11 This is a schematic diagram of the fitted curve of apparent conductivity versus frequency.

[0046] In other embodiments, a network model with parameters to be adjusted can be predetermined. The apparent conductivity and corresponding operating frequency obtained in S110 are input into the network model as data. The operating frequency is used as the input to the network model. The error between the network model's output and the apparent conductivity is used to determine the target value. The network model is trained with the goal of minimizing the target value. The network model after training is used as the first fitting result.

[0047] S120 can also use other forms of fitting, such as polynomial fitting, which will not be detailed in this specification.

[0048] from Figures 3 to 9As can be seen, the higher the operating frequency of the subarray, the more pronounced the skin effect. Theoretically, the lower the operating frequency, the smaller the skin effect, and the smaller the error in apparent conductivity. At an operating frequency of 0, the apparent conductivity equals the true conductivity. However, at 0, the electromagnetic signal transmitting coil is either energized with direct current or not energized at all. In this case, the subarray cannot measure the apparent conductivity based on the principle of electromagnetic induction. Therefore, this design aims for a near-zero frequency.

[0049] In some cases, the target frequency can be in the range of (0, 1Hz). This range is merely a range of optimal values ​​for the target frequency and does not mean that values ​​outside this range cannot achieve the correction method described in this solution and achieve the required correction effect. For example, a target frequency of 2Hz or 3Hz is acceptable.

[0050] Figure 12 This is a cross-plot of the apparent conductivity and true conductivity of multiple subarrays of an induction logging device at a target frequency of 1 kHz. Figure 12 It can be seen that at the target frequency, when the apparent conductivity or true conductivity is less than 1 S / m, the error between the apparent conductivity and the true conductivity is very small. When the apparent conductivity or true conductivity is greater than 1 S / m, the larger the value of the apparent conductivity or true conductivity, the greater the error between the apparent conductivity and the true conductivity. Figure 13 This is a cross-plot showing the errors between the true conductivity value and the apparent conductivity and true conductivity.

[0051] It is important to note that the apparent conductivity and relative skin depth at the target frequency will differ depending on the medium measured by the subarray of the induction logging device. In this manual, the calculation methods for "first apparent conductivity" and "second apparent conductivity" are consistent, differing only in the values ​​used; similarly, the calculation methods for "first relative skin depth" and "second relative skin depth" are consistent, differing only in the values ​​used.

[0052] Source distance refers to the distance between the electromagnetic signal receiving coil and the electromagnetic signal transmitting coil in the subarray. Theoretically, the closer the electromagnetic signal transmitting coil is to the electromagnetic signal transmitting coil, the more pronounced the skin effect becomes. Therefore, the source distance of the subarray will affect the error of the apparent conductivity, and thus also affect the correction range of the apparent conductivity.

[0053] The concept of "skin depth" exists in existing technology. Skin depth refers to the distance an electromagnetic wave travels after entering a conductor and its amplitude drops to 1 / e of the surface amplitude. In electromagnetism, skin depth is commonly used to describe the degree of the skin effect.

[0054] It is important to note that the "relative skin depth" in this scheme differs from the "skin depth" commonly referred to in existing technologies. The "relative skin depth" in this scheme is calculated based on the source distance of the subarray. It is related not only to the skin effect of electromagnetic waves propagating in a conductor but also to the structure of the induction logging device (i.e., the source distance). The "skin depth" in existing technologies only describes the skin effect of electromagnetic waves propagating in a conductor and does not consider the influence of the structure of the induction logging device.

[0055] In some embodiments, the first relative skin depth can be calculated according to the following formula:

[0056]

[0057] Where Δ is the first relative skin depth, L is the source distance, ω is the angular frequency, μ is the permeability constant of vacuum, and σ a0 This represents the first apparent conductivity at the target frequency. The angular frequency ω can take the value 2π.

[0058] The above formula for calculating relative skin depth is merely an example. In some embodiments, other formulas or variations of the above formula can also be used to calculate relative skin depth. Accordingly, the quantitative relationship between the true conductivity determined by the first relative skin depth, the first apparent conductivity at the target frequency, and the first relative skin depth will also change.

[0059] Since multiple "apparent conductivity - true conductivity" data pairs are acquired in S110, multiple relative skin depths can be calculated for each subarray; and due to the influence of source distance, the same "apparent conductivity - true conductivity" data pair can correspond to multiple relative skin depths.

[0060] S130: Calculate the ratio of the true conductivity to the first apparent conductivity at the target frequency as the conductivity ratio, fit the conductivity ratio to the first relative skin depth, and determine the quantitative relationship between the true conductivity, the first apparent conductivity at the target frequency, and the first relative skin depth based on the fitting result.

[0061] Specifically, the ratio of true conductivity to apparent conductivity at the target frequency is... In other words, S130 is... Fitting is performed with the relative skin depth. The specific fitting method can be found in the fitting method described in S120 above, and will not be detailed in this specification.

[0062] In some embodiments, S130 may employ a polynomial fitting method, such as a quadratic polynomial. Specifically, S130 may use the following formula for fitting:

[0063]

[0064] Where σ is the true conductivity, σ a0 Let be the first apparent conductivity at the target frequency, Δ be the first relative skin depth, and a, b, and c be the fitting coefficients. Both true conductivity and apparent conductivity were obtained using S110.

[0065] Figure 14 This is a schematic diagram of the second fitting result for seven subarrays of an induction logging device. Each coil represents a subarray, the correction formula is the second fitting result, and coefficients a, b, and c refer to the values ​​of the corresponding coefficients in the correction formula on the left.

[0066] It is important to note that each subarray corresponds to one of the aforementioned quantitative relationships, meaning that these relationships are related to the source distance of the subarray but are not affected by the medium. Based on this understanding, the quantitative relationships between the true conductivity, the first apparent conductivity at the target frequency, and the first relative skin depth determined by simulating the current subarray's detection of the sample medium can be applied to actual well logging.

[0067] like Figure 2 As shown, the skin effect correction method for induction logging provided by the present invention further includes the following steps:

[0068] S140: In actual logging, obtain the apparent conductivity of the current subarray measured at various operating frequencies.

[0069] S140 is used by induction logging devices to obtain actual apparent conductivity during actual induction logging. Actual apparent conductivity is a conductivity value calculated by the induction logging device based on the theoretical relationship between the electromagnetic wave signal received by the electromagnetic signal receiving coil and conductivity. This theoretical relationship is based on the premise that there is no skin effect.

[0070] S150: Based on multiple apparent conductivities at various operating frequencies, determine the second apparent conductivity at the target frequency, and calculate the second relative skin depth based on the second apparent conductivity at the target frequency and the source distance.

[0071] The description of S150 can be referenced from S120. The difference lies in the data being processed, but the data processing method is the same.

[0072] In some embodiments, S150 can fit the apparent conductivity to the operating frequency using a polynomial fitting method, determine the coefficients of the fitting polynomial, and then determine the second apparent conductivity at the target frequency based on the fitting polynomial with the determined coefficients.

[0073] The formula used in S150 to calculate the second relative skin depth is the same as the formula used in S120 to calculate the first relative skin depth.

[0074] S160: The measured visual conductivity is corrected based on the second visual conductivity, the second relative skin depth, and the quantitative relationship.

[0075] Specifically, S160 can replace the first apparent conductivity at the target frequency with the second apparent conductivity at the target frequency, replace the first relative skin depth with the second relative skin depth, and calculate the true conductivity during actual logging based on the quantitative relationship, and use the true conductivity as the correction result.

[0076] Taking the following fitting formula to fit the conductivity ratio to the first relative skin depth as an example: At this point, a, b, and c are constant values ​​in the formula, relative to the skin depth Δ and the apparent conductivity σ at the target frequency. a0 It has been calculated that only the true conductivity σ is unknown, and therefore the true conductivity σ can be calculated. This true conductivity σ is the apparent conductivity σ measured during actual well logging. a0 The result of the correction.

[0077] In some embodiments, each apparent conductivity measured during actual logging can be corrected using a predetermined quantitative relationship between true conductivity, first apparent conductivity at target frequency, and first relative skin depth.

[0078] In other embodiments, before calculating the relative skin depth based on the source distance of the current subarray and the target apparent conductivity of the current subarray at the target frequency, it can be determined whether the second apparent conductivity is greater than or equal to the target threshold. If yes, the calculation of the second relative skin depth based on the second apparent conductivity at the target frequency and the source distance is performed, and the corrected result is further determined based on the second apparent conductivity and the second relative skin depth. If no, the corrected result can be directly determined to be the same as the measured apparent conductivity.

[0079] from Figure 13 As can be seen, when the apparent conductivity or true conductivity at the target frequency is less than 1, the error between the true conductivity and the apparent conductivity is almost zero. Therefore, when the second apparent conductivity at the target frequency is less than 1, it can be directly determined that the corrected result is the same as the measured apparent conductivity. This setting allows for a good correction effect without complex calculations when the second apparent conductivity at the target frequency is less than 1. It reduces the amount of calculation and avoids introducing larger errors by correcting the apparent conductivity based on a pre-determined quantitative relationship between the true conductivity, the first apparent conductivity at the target frequency, and the first relative skin depth. This improves the accuracy of the correction scheme provided by this invention across the entire range.

[0080] Based on the above analysis, it can be seen that in some embodiments, the target threshold can be 1 S / m.

[0081] Figure 15 This diagram illustrates the relative error between the corrected apparent conductivity values ​​and the true conductivity measured by each subarray of the target induction logging device during actual logging operations. The horizontal axis represents the true conductivity of the formation, and the vertical axis represents the relative error between the apparent conductivity measured by the seven subarrays of the target induction logging device after correction using the skin effect correction method provided in this invention and the true conductivity of the formation. Figure 15 It can be seen that for formations with conductivity ranging from 0.001 to 1000 S / m, the skin effect correction method applied in series shows that the apparent conductivity after skin effect correction is not significantly different from the true conductivity. The relative errors between the apparent conductivity after skin effect correction and the true conductivity of coils 0 to 5 are all less than 1%. The apparent conductivity after skin effect correction of coil 6 has a slightly larger error, but the relative error with the true conductivity is still less than 2%.

[0082] Figure 16 This is a cross-plot of the apparent conductivity and true conductivity measured by each subarray of the target induction logging device during actual logging.

[0083] The horizontal axis represents the true conductivity of the formation, and the vertical axis represents the result of the skin effect correction method for induction logging provided in this invention, which is used to correct the seven subarrays of the target induction logging device.

[0084] Figure 17This diagram illustrates the skin effect correction results for a target induction logging system in a target well section between 6715.0 and 6760.0 meters. Specifically, SGMAS0 represents the apparent conductivity curve after skin effect correction for subarray 0; SGMA01re represents the apparent conductivity measured at 10 kHz for subarray 0; SGMA02re represents the apparent conductivity measured at 30 kHz for subarray 0; SGMA03re represents the apparent conductivity measured at 50 kHz for subarray 0; SGMA04re represents the apparent conductivity measured at 70 kHz for subarray 0; SGMA05re represents the apparent conductivity measured at 90 kHz for subarray 0; and SGMA06re represents the apparent conductivity measured at 110 kHz for subarray 0. The apparent conductivity measurements are as follows: SGMA07re is the apparent conductivity measured at 130kHz for subarray 0, and SGMA08re is the apparent conductivity measured at 150kHz for subarray 0. SGGMAS1 is the apparent conductivity curve after skin effect correction for subarray 1; SGMA11re is the apparent conductivity measured at 10kHz for subarray 1, SGMA12re is the apparent conductivity measured at 30kHz for subarray 1, SGMA13re is the apparent conductivity measured at 50kHz for subarray 1, and SGMA14re is the apparent conductivity measured at 7kHz for subarray 1. The apparent conductivity is measured at 0 kHz. SGMA15re represents the apparent conductivity of subarray 1 at 90 kHz, SGMA16re at 110 kHz, SGMA17re at 130 kHz, and SGMA18re at 150 kHz. SGMA2S2 shows the apparent conductivity curve of subarray 2 after skin effect correction. SGMA21re represents the apparent conductivity of subarray 2 at 10 kHz. SGMA22re... SGMA23re represents the apparent conductivity measured at 30kHz for subarray 2; SGMA24re represents the apparent conductivity measured at 70kHz for subarray 2; SGMA25re represents the apparent conductivity measured at 90kHz for subarray 2; SGMA26re represents the apparent conductivity measured at 110kHz for subarray 2; SGMA27re represents the apparent conductivity measured at 130kHz for subarray 2; and SGMA28re represents the apparent conductivity measured at 150kHz for subarray 2.SGMAS3 is the apparent conductivity curve of subarray 3 after skin effect correction; SGMA31re is the apparent conductivity of subarray 3 measured at 10kHz; SGMA32re is the apparent conductivity of subarray 3 measured at 30kHz; SGMA33re is the apparent conductivity of subarray 3 measured at 50kHz; SGMA34re is the apparent conductivity of subarray 3 measured at 70kHz; SGMA35re is the apparent conductivity of subarray 3 measured at 90kHz; and SGMA36re is the apparent conductivity of subarray 3 measured at 110kHz. The apparent conductivity of subarray 3 is shown in SGMA37re, measured at 130 kHz; SGMA38re, measured at 150 kHz; and SGMA4re, measured after skin effect correction for subarray 4, shows the apparent conductivity curves after skin effect correction for subarray 4. SGMA41re, measured at 10 kHz; SGMA42re, measured at 30 kHz; SGMA43re, measured at 50 kHz; and SGMA44re, measured at 70 kHz. The apparent conductivity measured at Hz is shown in SGMA45re at 90kHz, SGMA46re at 110kHz, SGMA47re at 130kHz, and SGMA48re at 150kHz. SGMAS5 shows the apparent conductivity curves of subarray 5 after skin effect correction. SGMA51re shows the apparent conductivity of subarray 5 at 10kHz. SGMA52re shows... The apparent conductivity of subarray 5 is measured at 30 kHz. SGMA53re is measured at 50 kHz. SGMA54re is measured at 70 kHz. SGMA55re is measured at 90 kHz. SGMA56re is measured at 110 kHz. SGMA57re is measured at 130 kHz. SGMA58re is measured at 150 kHz.SGMAS6 represents the apparent conductivity curve of subarray 6 after skin effect correction. SGMA61re represents the apparent conductivity of subarray 6 measured at 10 kHz, SGMA62re at 30 kHz, SGMA63re at 50 kHz, SGMA64re at 70 kHz, SGMA65re at 90 kHz, SGMA66re at 110 kHz, SGMA67re at 130 kHz, and SGMA68re at 150 kHz.

[0085] The skin effect correction method for induction logging provided by this invention pre-simulates the detection of a sample medium by a subarray of a target induction logging device, and obtains the apparent conductivity and the corresponding true conductivity of the subarray at various operating frequencies. Based on the apparent conductivity at each of the multiple frequencies, a first apparent conductivity at the target frequency is determined. Then, a first relative skin depth is calculated based on the first apparent conductivity and the source distance. The ratio of the true conductivity to the first apparent conductivity at the target frequency is calculated as a conductivity ratio. Each conductivity ratio is fitted with the corresponding first relative skin depth to obtain the quantitative relationship between the true conductivity, the first apparent conductivity at the target frequency, and the first relative skin depth. During actual logging, the apparent conductivity measured by the subarray at various operating frequencies is obtained, and a second apparent conductivity and a second relative skin depth at the target frequency are calculated using a method similar to that used in the simulation. The measured apparent conductivity is then corrected based on the aforementioned quantitative relationship. This method uses the ratio of apparent conductivity at the target frequency, relative skin depth, and true conductivity to apparent conductivity at the target frequency as a bridge to determine the quantitative relationship between true conductivity, the first apparent conductivity at the target frequency, and the first relative skin depth. During actual well logging, the measured apparent conductivity is then corrected based on this relationship. This method can be used over a wide conductivity range, is unaffected by human factors, has low computational complexity, high reliability, and the error between the corrected result and the true conductivity is small.

[0086] This invention also provides an inductive logging skin effect correction device, which can be used to implement the above-mentioned inductive logging skin effect correction method. For example... Figure 18 As shown, the device includes a first acquisition unit 10, a first calculation unit 20, a second calculation unit 30, a second acquisition unit 40, a third calculation unit 50, and a fourth calculation unit 60.

[0087] The first acquisition unit 10 is used to acquire the apparent conductivity and the true conductivity corresponding to the apparent conductivity when simulating the detection of the sample medium by the current subarray at various operating frequencies.

[0088] The first calculation unit 20 is used to determine the first apparent conductivity at the target frequency based on the apparent conductivity corresponding to multiple operating frequencies, and to calculate the first relative skin depth based on the first apparent conductivity at the target frequency and the source distance.

[0089] The second calculation unit 30 is used to calculate the ratio of the true conductivity to the first apparent conductivity at the target frequency as the conductivity ratio, fit the conductivity ratio to the first relative skin depth, and determine the quantitative relationship between the true conductivity, the first apparent conductivity at the target frequency, and the first relative skin depth based on the fitting result.

[0090] The second acquisition unit 40 is used to acquire the apparent conductivity of the current subarray at various operating frequencies during actual logging.

[0091] The third calculation unit 50 is used to determine the second apparent conductivity at the target frequency based on the apparent conductivity corresponding to multiple operating frequencies, and to calculate the second relative skin depth based on the second apparent conductivity at the target frequency and the source distance.

[0092] The fourth calculation unit 60 is used to replace the first apparent conductivity at the target frequency with the second apparent conductivity at the target frequency, replace the first relative skin depth with the second relative skin depth, calculate the true conductivity during actual logging based on the quantitative relationship, and use the true conductivity as the correction result.

[0093] The description and function of the above-mentioned device can be understood by referring to the section on skin effect correction methods in induction logging, and will not be repeated here.

[0094] The present invention also provides an inductive logging device, comprising multiple subarrays, a controller, and a processor.

[0095] Each subarray includes an electromagnetic signal transmitting coil and an electromagnetic signal receiving coil.

[0096] The controller is used to control each electromagnetic signal transmitting coil to transmit electromagnetic waves at a set frequency, and to control the electromagnetic signal receiving coil to receive electromagnetic waves.

[0097] The processor determines the apparent conductivity based on the electromagnetic waves received by each subarray, and corrects the apparent conductivity using the skin effect correction method described above for inductive logging, thus obtaining the correction result.

[0098] This invention also provides an electronic device, such as... Figure 19As shown, the electronic device may include a processor 1901 and a memory 1902, wherein the processor 1901 and the memory 1902 may be connected via a bus or other means. Figure 19 Taking the example of a connection between China and Israel via a bus.

[0099] Processor 1901 can be a Central Processing Unit (CPU). Processor 1901 can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or combinations of the above types of chips.

[0100] Memory 1902, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer-executable programs, and modules, such as the program instructions / modules corresponding to the skin effect correction method for inductive logging in this embodiment of the invention (e.g., Figure 18 The first acquisition unit 10, the first calculation unit 20, the second calculation unit 30, the second acquisition unit 40, the third calculation unit 50, and the fourth calculation unit 60 are shown. The processor 1901 executes various functional applications and data processing by running non-transitory software programs, instructions, and modules stored in the memory 1902, thereby realizing the skin effect correction method for induction logging in the above method embodiment.

[0101] The memory 1902 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created by the processor 1901, etc. Furthermore, the memory 1902 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory 1902 may optionally include memory remotely located relative to the processor 1901, and these remote memories may be connected to the processor 1901 via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0102] The one or more modules are stored in the memory 1902, and when executed by the processor 1901, they perform the following: Figure 1 The skin effect correction method for induction logging in the illustrated embodiment.

[0103] The specific details of the above-mentioned electronic device can be understood by referring to the relevant descriptions and effects in the method embodiments, and will not be repeated here.

[0104] The present invention also provides a computer storage medium storing computer program instructions, which, when executed, implement the steps of the above-described induction logging skin effect correction method.

[0105] The present invention also provides a computer program product comprising a computer program that, when executed by a processor, implements the steps of the above-described inductive logging skin effect correction method.

[0106] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk drive (HDD), or solid-state drive (SSD), etc.; the storage medium can also include combinations of the above types of memory.

[0107] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. The focus of each embodiment is to describe the differences from other embodiments.

[0108] The systems, devices, modules, or units described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions.

[0109] For ease of description, the above devices are described separately by function as various units. Of course, in implementing this application, the functions of each unit can be implemented in one or more software and / or hardware.

[0110] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute certain parts of the methods of various embodiments of this application.

[0111] This application can be used in a wide variety of general-purpose or special-purpose computer system environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics devices, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, etc.

[0112] This application can be described in the general context of computer-executable instructions, such as program modules, that are executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform a specific task or implement a specific abstract data type. This application can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0113] Although this application has been described through embodiments, those skilled in the art will know that this application has many modifications and variations without departing from the spirit of this application, and it is intended that the appended claims cover such modifications and variations without departing from the spirit of this application.

Claims

1. A method for correcting the skin effect in induction logging, characterized in that, This includes performing the following operations on each subarray of the target induction logging device: When simulating the detection of the sample medium by the current subarray, the apparent conductivity and the true conductivity corresponding to the apparent conductivity are obtained by measuring the current subarray at various operating frequencies. Based on the apparent conductivity corresponding to multiple operating frequencies, the first apparent conductivity at the target frequency is determined, and the first relative skin depth is calculated based on the first apparent conductivity at the target frequency and the source distance. The ratio of true conductivity to the first apparent conductivity at the target frequency is calculated as the conductivity ratio. The conductivity ratio is then fitted with the first relative skin depth. Based on the fitting results, the quantitative relationship between true conductivity, the first apparent conductivity at the target frequency, and the first relative skin depth is determined. In actual logging, the apparent conductivity of the current subarray is obtained at various operating frequencies. Based on the apparent conductivity corresponding to multiple operating frequencies, the second apparent conductivity at the target frequency is determined, and the second relative skin depth is calculated based on the second apparent conductivity at the target frequency and the source distance. The measured visual conductivity is corrected based on the second visual conductivity, the second relative skin depth, and the quantitative relationship.

2. The method according to claim 1, characterized in that, The measured visual conductivity is corrected based on the second visual conductivity, the second relative skin depth, and the aforementioned quantitative relationship, including: The first apparent conductivity at the target frequency is replaced by the second apparent conductivity at the target frequency, the first relative skin depth is replaced by the second relative skin depth, and the true conductivity during actual logging is calculated based on the quantitative relationship. The true conductivity is then used as the correction result.

3. The method according to claim 1, characterized in that, The target frequency range is (0, 1Hz).

4. The method according to claim 1, characterized in that, Before calculating the second relative skin depth based on the second apparent conductivity and source distance at the target frequency, the following steps are also included: Determine whether the second apparent conductivity is greater than or equal to the target threshold; In this case, the second relative skin depth is calculated based on the second apparent conductivity and source distance at the target frequency; If not, ensure that the corrected result is the same as the measured apparent conductivity.

5. The method according to claim 4, characterized in that, The target threshold is 1 S / m.

6. The method according to claim 1, characterized in that, The relative skin depth is calculated using the following formula: Where Δ is the relative skin depth at the target frequency, L is the source distance, ω is the angular frequency, μ is the permeability constant of vacuum, and σ a0 The apparent conductivity at the target frequency; the relative skin depth includes a first relative skin depth and a second relative skin depth.

7. The method according to claim 1, characterized in that, The conductivity ratio is fitted to the first relative skin depth using the following formula: Where σ is the true conductivity, σ a0 Let be the first apparent conductivity at the target frequency, Δ be the first relative skin depth, and a, b, and c be the fitting coefficients.

8. A skin effect correction device for inductive logging, characterized in that, include: The first acquisition unit is used to acquire the apparent conductivity and the true conductivity corresponding to the apparent conductivity when the current subarray detects the sample medium at various operating frequencies. The first calculation unit is used to determine the first apparent conductivity at the target frequency based on the apparent conductivity corresponding to multiple operating frequencies, and to calculate the first relative skin depth based on the first apparent conductivity at the target frequency and the source distance. The second calculation unit is used to calculate the ratio of the true conductivity to the first apparent conductivity at the target frequency as the conductivity ratio, fit the conductivity ratio to the first relative skin depth, and determine the quantitative relationship between the true conductivity, the first apparent conductivity at the target frequency, and the first relative skin depth based on the fitting result. The second acquisition unit is used to acquire the apparent conductivity of the current subarray at various operating frequencies during actual logging. The third calculation unit is used to determine the second apparent conductivity at the target frequency based on the apparent conductivity corresponding to multiple operating frequencies, and to calculate the second relative skin depth based on the second apparent conductivity at the target frequency and the source distance. The fourth calculation unit is used to replace the first apparent conductivity at the target frequency with the second apparent conductivity at the target frequency, replace the first relative skin depth with the second relative skin depth, calculate the true conductivity during actual logging based on the quantitative relationship, and use the true conductivity as the correction result.

9. An inductive logging device, characterized in that, include: Multiple subarrays, each subarray including an electromagnetic signal transmitting coil and an electromagnetic signal receiving coil; The controller is used to control each electromagnetic signal transmitting coil to transmit electromagnetic waves at a set frequency, and to control the electromagnetic signal receiving coil to receive electromagnetic waves. The processor determines the apparent conductivity based on the electromagnetic waves received by each subarray, and corrects the apparent conductivity using the method described in any one of claims 1-7 to obtain the correction result.

10. The inductive logging device according to claim 9, characterized in that, The inductive logging device has one electromagnetic signal transmitting coil and multiple electromagnetic signal receiving coils, and the distance between each electromagnetic signal receiving coil and the electromagnetic signal transmitting coil is not exactly the same.

11. The inductive logging device according to claim 10, characterized in that, Each electromagnetic signal receiving coil can operate at different frequencies.

12. An electronic device, characterized in that, include: The system includes a memory and a processor, which are interconnected. The memory stores computer instructions, and the processor executes the computer instructions to implement the skin effect correction method for induction logging as described in any one of claims 1 to 7.

13. A computer storage medium, characterized in that, The computer storage medium stores computer program instructions, which, when executed by a processor, implement the skin effect correction method for induction logging as described in any one of claims 1 to 7.

14. A computer program product, characterized in that, It includes a computer program that, when executed by a processor, implements the skin effect correction method for induction logging as described in any one of claims 1 to 7.

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