Correcting device and method for well logging after dipole sound wave casing

Abstract

The invention relates to the field of well logging signal correction, in particular to a well logging correction device and method after dipole sound wave casing. The method comprises the following steps: segmenting an original frequency dispersion curve of a sound wave signal of a cased well to obtain a plurality of frequency dispersion segmentation curves, binding corresponding matched frequency dispersion segmentation curves for known media, and determining the frequency dispersion of the sound wave signal of the cased well according to the phase difference and the amplitude difference of each frequency between the frequency ranges of the matched frequency dispersion segmentation curves of any two known media. The method comprises the following steps: acquiring a first signal distortion coefficient between any two known media according to the energy of a matched frequency dispersion subsection curve of the known media and the acoustic impedance of the known media, and acquiring a second signal distortion coefficient of an unknown medium according to the difference between the energy of the matched frequency dispersion subsection curve of the known media and the energy of an original frequency dispersion curve, and adjusting the clustering process of each data point on the original frequency dispersion curve to obtain an adjusted frequency dispersion curve. According to the method, interference components in the frequency dispersion curve of the original sound wave signal can be effectively removed, and the accuracy of signal correction in the logging process is improved.

Description

Technical Field

[0001] The present invention relates to the field of well logging signal correction, and in particular to a dipole acoustic wave sleeve post-well logging correction device and method. Background Art

[0002] Dipole acoustic post-casing logging is a core method for evaluating oil and gas reservoir characteristics. It generates flexural wave signals at the interface between casing and formation by exciting a dipole acoustic source, and inverts the shear wave velocity and mechanical parameters of the formation by combining the acoustic wave dispersion characteristics. In cased wells, the acoustic wave propagation path is affected by the coupling of multiple media such as the casing steel body, cement sheath, well fluid and formation, resulting in interference components such as mixed casing resonant waves and well fluid guided waves in the received signal.

[0003] Existing technologies usually rely on theoretical models of open hole wells to perform acoustic wave dispersion correction to eliminate the influence of interference signals. However, due to the interference of multiple media around the wellbore, and when different media are in a complex state, such as local corrosion of the casing due to long-term use, resulting in uneven changes in its thickness, cracks in the cement sheath, etc., the intensity of the acoustic wave dispersion fluctuates greatly, resulting in the inability of existing methods to effectively remove the interference components in the dispersion curve of the original acoustic wave signal, reducing the accuracy of signal correction in the logging process. Summary of the Invention

[0004] In order to solve the technical problem that the existing methods cannot effectively remove the interference components in the dispersion curve of the original acoustic signal, thereby reducing the accuracy of signal correction during the logging process, the purpose of the present invention is to provide a dipole acoustic sleeve post-logging correction device and method. The technical solutions adopted are as follows: The present invention proposes a dipole acoustic sleeve post-logging correction method, which includes: Perform frequency domain transformation on the acoustic wave signal of the cased well to obtain the phase and amplitude of each frequency, and construct the original dispersion curve of the acoustic wave signal, where the abscissa is frequency and the ordinate is phase velocity, and obtain the thickness, acoustic wave propagation velocity and acoustic impedance of each known medium in the cased well; According to the fluctuations of the original dispersion curve, the original dispersion curve is segmented to obtain multiple dispersion segment curves; according to the sound wave propagation speed and thickness of each known medium and the frequency range occupied by each dispersion segment curve, a matching dispersion segment curve for each known medium is screened from each dispersion segment curve; according to the phase difference and amplitude difference of each frequency between the frequency ranges of the matching dispersion segment curves of any two known media, and in combination with the acoustic impedance of the any two known media, a first signal distortion coefficient between any two known media is obtained; a medium interpretation degree of the original dispersion curve is obtained according to a difference between a phase velocity of each frequency in a frequency range of the matching dispersion segment curve of each known medium and a theoretical phase velocity, a difference between an amplitude of each frequency in the frequency range of the matching dispersion segment curve of each known medium and a theoretical amplitude, and an acoustic impedance of each known medium; a second signal distortion coefficient of the unknown medium is obtained according to a difference between an energy of the matching dispersion segment curve of all known media and an energy of the original dispersion curve, and the medium interpretation degree; a clustering process of each data point on the original dispersion curve is adjusted according to the first signal distortion coefficient and the second signal distortion coefficient, and an adjusted dispersion curve is obtained.

[0005] Further, the obtaining of the plurality of dispersion segment curves comprises: a second derivative value of each data point on the initial dispersion curve is obtained through a second derivative calculation on the original dispersion curve; the data point with the second derivative value greater than a preset mutation threshold is taken as a mutation data point of the original dispersion curve; the original dispersion curve is segmented by using each mutation data point, and a plurality of dispersion segment curves is obtained.

[0006] Further, the screening of the matching dispersion segment curve of each known medium from each dispersion segment curve comprises: any known medium is taken as a target known medium, a ratio of the acoustic wave propagation speed of the target known medium as a numerator and twice the thickness of the target known medium as a denominator is taken as a resonant acoustic wave frequency of the target known medium; a range formed by all frequencies between the original frequency of the acoustic wave signal of the cased well and the resonant acoustic wave frequency of the target known medium is taken as a limited acoustic wave frequency range of the target known medium; a number of frequencies contained in an intersection between the limited acoustic wave frequency range of the target known medium and a frequency range occupied by each dispersion segment curve is taken as a numerator, and a number of frequencies contained in the frequency range occupied by each dispersion segment curve is taken as a denominator, and a ratio is taken as a matching degree between each dispersion segment curve and the target known medium; a dispersion segment curve corresponding to a maximum value of the matching degree is taken as the matching dispersion segment curve of the target known medium.

[0007] Further, the obtaining of the first signal distortion coefficient between any two known media comprises: an average value of the phase of all frequencies in a frequency range occupied by the matching dispersion segment curve of each known medium is taken as an overall phase value of each known medium; an average value of the amplitude of all frequencies in the frequency range occupied by the matching dispersion segment curve of each known medium is taken as an overall amplitude value of each known medium. The absolute value of the difference between the acoustic impedances of any two known media is used as the numerator, the sum of the acoustic impedances of any two known media is used as the denominator, and the ratio is used as the reflection coefficient between the any two known media; Based on the reflection coefficient between any two known media, the difference in the overall phase value and the difference in the overall amplitude value between any two known media are weighted to obtain a first signal distortion coefficient between any two known media.

[0008] Furthermore, the step of weighting the difference in the overall phase value and the difference in the overall amplitude value between the two known media based on the reflection coefficient between the two known media to obtain the first signal distortion coefficient between the two known media includes: Based on the calculation formula of the first signal distortion coefficient, the first signal distortion coefficient between any two known media is obtained. The calculation formula of the first signal distortion coefficient is: in, Indicates the Kind and A first signal distortion coefficient between two known media; Indicates the Kind and Reflection coefficients between known media; Indicates the The overall phase value of a known medium; Indicates the The overall phase value of a known medium; Indicates the The overall amplitude value of a known medium; Indicates the The overall amplitude value of a known medium.

[0009] Furthermore, obtaining the medium interpretation of the original dispersion curve includes: The phase velocity authenticity of each known medium is obtained by performing negative correlation normalization on the average of the absolute values ​​of the differences between the phase velocity at all frequencies in the frequency range of the matching dispersion segment curve of each known medium and the theoretical phase velocity; Perform negative correlation normalization on the average of the absolute values ​​of the differences between the amplitudes of all frequencies in the frequency range of the matching dispersion segment curve of each known medium and the theoretical amplitude to obtain the amplitude authenticity of each known medium; The average value of the phase velocity truth and the amplitude truth is taken as the comprehensive truth of each known medium; The medium interpretation degree of the original dispersion curve is obtained by weighting and summing the acoustic impedance of each known medium and performing normalization processing on the comprehensive reality of each known medium.

[0010] Further, the obtaining of the second signal distortion coefficient of the unknown medium comprises: The total energy value of the original dispersion curve is obtained by integral calculation on the original dispersion curve. The energy value of the matching dispersion segmented curve of each known medium is obtained by integral calculation on the matching dispersion segmented curve of each known medium, and the sum of the energy values of the matching dispersion segmented curves of all known media is taken as the reference energy value of the original dispersion curve. The residual energy value of the unknown medium is obtained based on a calculation formula of the residual energy value, and the calculation formula of the residual energy value is: wherein, Residual energy value of the unknown medium is represented by Residual energy value of the unknown medium. Medium interpretation degree of the original dispersion curve is represented by Medium interpretation degree of the original dispersion curve. Total energy value of the original dispersion curve is represented by Total energy value of the original dispersion curve. Reference energy value of the original dispersion curve is represented by Reference energy value of the original dispersion curve. The second signal distortion coefficient of the unknown medium is obtained by taking the residual energy value of the unknown medium as the numerator and the reference energy value of the original dispersion curve as the denominator.

[0011] Further, the obtaining of the adjustment dispersion curve comprises: The Euclidean distance between any two data points on the original dispersion curve is taken as the distance measurement between any two data points. The distance measurement between any two data points on the original dispersion curve is adjusted according to the first signal distortion coefficient between any two known media and the second signal distortion coefficient of the unknown medium, to obtain the adjustment distance measurement between any two data points. Based on the adjustment distance measurement between any two data points, all data points on the original dispersion curve are clustered to obtain a plurality of clustering clusters. The clustering cluster containing data points less than a preset number threshold is removed, and the data points in all remaining clustering clusters are curve-fitted, and the fitted curve is taken as the adjustment dispersion curve.

[0012] Further, the obtaining of the adjustment distance measurement between any two data points comprises: For any two data points on the original dispersion curve, if the two data points belong to different matching dispersion segment curves, the first signal distortion coefficient between the known media corresponding to the matching dispersion segment curves where the two data points are located is taken as the distance adjustment weight between the two data points; If one data point belongs to a matching dispersion segment curve and the other data point belongs to a non-matching dispersion segment curve, the average value of the first signal distortion coefficient between the known media corresponding to the matching dispersion segment curve where one data point is located and the known media corresponding to the nearest matching dispersion segment curve and the second signal distortion coefficient of the unknown medium is taken as the distance adjustment weight between the two data points; If the two data points belong to the same matching dispersion segment curve or the two data points belong to non-matching dispersion segment curves, the distance adjustment weight between the two data points is set to a value of 0; The product value of the distance adjustment weight and the distance measure between any two data points on the original dispersion curve is taken as the distance adjustment amount between the two data points; The sum value of the distance measure and the distance adjustment amount between any two data points is taken as the adjusted distance measure between the two data points.

[0013] The application further provides a dipole acoustic sleeve logging correction device, which comprises a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor implements the steps of any one of the dipole acoustic sleeve logging correction methods when executing the computer program.

[0014] The application has the following beneficial effects: The present application considers that the existing method cannot effectively remove the interference components in the original dispersion curve of the acoustic wave signal, and reduces the accuracy of signal correction in the logging process, so first, the original dispersion curve is segmented to obtain a plurality of dispersion segment curves, wherein the fluctuation characteristics of each dispersion segment curve can be considered as caused by a certain specific medium, then the matching dispersion segment curve of each known medium is selected from each dispersion segment curve, the binding of the known medium and the dispersion segment curve is realized, and the first signal distortion coefficient is obtained to reflect the degree of distortion of the acoustic wave amplitude and phase caused by reflection and transmission phenomena during the propagation of the original acoustic wave signal in different known media, considering that in addition to the interference of the known medium, there are unknown media such as casing corrosion, scale layer, reservoir thin interbed, drilling fluid invasion zone, etc., so the present application first reflects the interpretation degree of the original dispersion curve to the known medium and the possibility of the existence of unknown media around the casing well through the obtained medium interpretation degree, and reflects the degree of influence on the propagation of the acoustic wave signal in the unknown medium through the second signal distortion coefficient, and then adjusts the clustering process of each data point on the original dispersion curve to obtain an adjusted dispersion curve, effectively removes the interference components in the dispersion curve of the original acoustic wave signal, solves the signal mixing problem caused by multi-medium interference, and improves the accuracy of signal correction in the logging process. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, and the advantages thereof, below, a brief introduction will be given to the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0016] Figure 1 A flow chart of a dipole acoustic wave casing after logging correction method provided by an embodiment of the present application. DETAILED DESCRIPTION

[0017] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the specific implementation, structure, features and effects of the dipole acoustic wave casing after logging correction device and method according to the present application are described in detail as follows. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0019] The application provides a casing behind logging correction device and method for dipole acoustic wave.

[0020] Please refer to Figure 1 which shows a flow chart of a casing behind logging correction method for dipole acoustic wave provided by an embodiment of the application, and the method comprises the following steps. Step S1: performing frequency domain transformation on the acoustic wave signal of the casing well to obtain the phase and amplitude of each frequency, constructing an original dispersion curve of the acoustic wave signal, and obtaining the thickness, acoustic wave propagation speed and acoustic impedance of each known medium of the casing well, wherein the horizontal coordinate of the original dispersion curve is frequency, and the vertical coordinate is phase velocity.

[0021] The casing well cross-section structure can be roughly divided from outside to inside as follows: formation → cement sheath → guide pipe → surface casing → technical casing → oil layer casing → well center, and the dipole acoustic logging device mainly comprises a sound source emission module, a receiving module, a sensor and a processing and control module.

[0022] The sound source emission module adopts switchable monopole / dipole / quadrupole sound source, the excitation circuit uses a gated sinusoidal wave pulse design, and a wideband impedance matching technology is combined to improve the excitation efficiency of the monopole / dipole / quadrupole wave, the receiving module is equipped with a multi-directional multi-station transducer to realize full wave train acquisition, including longitudinal wave, transverse wave, cross-dipole wave and the like, the emission module is started and the dipole sound source mode is switched according to the requirement, the flexural wave is emitted to the casing, the cement sheath and the formation, the segmented linear frequency modulation signal is used to excite the dipole sound source, the signal is composed of a plurality of continuous linear frequency modulation sub-signals, the frequency range of each sub-signal covers the target detection frequency band, and there is a preset overlap degree between the frequency ranges of adjacent sub-signals, the gated timing of the excitation circuit is controlled to make the dipole sound source alternately emit the segmented linear frequency modulation signal in different directions, so that the acoustic wave energy is uniformly distributed in the target frequency band corresponding to each acoustic wave component, and then the multi-directional multi-station transducer of the receiving module starts to work to acquire the full wave train signal containing the casing, the cement sheath and the formation information, and the original acoustic wave signal is obtained.

[0023] Then, the received acoustic wave signals of the cased well are subjected to frequency domain transformation to obtain the phase and amplitude of each frequency, in an embodiment of the present application, the frequency domain transformation can be implemented by using Fourier transformation, which is not limited herein, and an original dispersion curve of the acoustic wave signals is constructed, wherein the general process of constructing the dispersion curve is as follows: for each frequency point on the frequency domain, the phase values of the frequency at different receivers are extracted, the phase velocity corresponding to the frequency is calculated by the ratio of the phase difference between adjacent receivers to the receiver spacing, and then the corresponding relationship between the frequency and the phase velocity is established to generate the original dispersion curve, which takes the frequency as the horizontal coordinate and the phase velocity as the vertical coordinate, and completely presents the propagation velocity characteristics of the acoustic wave at different frequencies at the target depth point, and the construction of the dispersion curve is a technical means well known to those skilled in the art, which will not be described herein.

[0024] Meanwhile, the thickness, acoustic wave propagation velocity and acoustic impedance of each known medium of the cased well are recorded, wherein the known medium refers to various different media around the cased well, such as the formation, the cement sheath and the casing, and meanwhile, in addition to the interference of these known media on the acoustic wave signals, there can be unknown media, such as the casing corrosion and the cement sheath crack, which also interfere with the acoustic wave signals.

[0025] Step S2: segmenting the original dispersion curve according to the fluctuation of the original dispersion curve to obtain a plurality of dispersion segment curves; screening the matching dispersion segment curve of each known medium from each dispersion segment curve according to the acoustic wave propagation velocity and the thickness of each known medium and the frequency range occupied by each dispersion segment curve; and obtaining the first signal distortion coefficient between any two known media according to the phase difference and the amplitude difference of each frequency between the frequency ranges of the matching dispersion segment curves of any two known media, and combining the acoustic impedance of any two known media.

[0026] In actual production, the reservoir can have complex lithological structures such as thin interbeds, and therefore there is a problem of insufficient precision when the theoretical medium impedance is used to correct the acoustic wave error. Since the acoustic wave propagates in different media with obvious characteristic mutation points, the propagation characteristics of the acoustic wave before and after the mutation points change greatly to form obvious inflection points, which can be used as the boundary to distinguish different media, and therefore the original dispersion curve can be segmented according to the fluctuation of the original dispersion curve to obtain a plurality of dispersion segment curves, wherein the fluctuation characteristics of each dispersion segment curve can be considered as being caused by the acoustic wave in a certain specific medium, and the corresponding dispersion segment curve can be bound for each known medium to facilitate accurate analysis of the influence of the acoustic wave propagation in different known media.

[0027] Preferably, in an embodiment of the present application, the method for obtaining the plurality of dispersion segment curves specifically comprises: The second derivative value of each data point on the initial dispersion curve is obtained by performing second derivative calculation on the initial dispersion curve, the greater the absolute value of the second derivative value of a data point is, the more obvious the mutation of the initial dispersion curve at the position of the data point is, therefore, the data point with the absolute value of the second derivative value greater than a preset mutation threshold value can be taken as a mutation data point of the initial dispersion curve, and the initial dispersion curve is segmented by using each mutation data point, thereby obtaining a plurality of dispersion segment curves, wherein the preset mutation threshold value ranges from 40 to 60, in an embodiment of the present application, the preset mutation threshold value is set to 50, and the preset mutation threshold value can also be set by the implementer according to the specific implementation scene, which is not limited herein.

[0028] When the sound wave propagates in the medium layer with a limited thickness, reflection occurs at the upper and lower interfaces of the medium, forming standing wave resonance, therefore, according to the sound wave propagation speed and thickness of each known medium and the frequency range occupied by each dispersion segment curve, the matching dispersion segment curve of each known medium can be screened from each dispersion segment curve, thereby realizing the binding of the known medium and the corresponding dispersion segment curve, wherein one kind of known medium corresponds to one dispersion segment curve, that is, the matching dispersion segment curve of the kind of known medium.

[0029] Preferably, in an embodiment of the present application, the method for obtaining a plurality of dispersion segment curves specifically comprises: Since the standing wave resonance phenomenon exists in the casing well structure, the wavelength of the sound wave propagating in the medium is just about equal to twice the thickness of the medium, therefore, firstly, any kind of known medium can be taken as a target known medium, the sound wave propagation speed of the target known medium is taken as the numerator, twice the thickness of the target known medium is taken as the denominator, and the ratio is taken as the resonance sound wave frequency of the target known medium.

[0030] The range formed by all the frequencies between the initial frequency of the sound wave signal of the casing well and the resonance sound wave frequency of the target known medium is taken as the limited sound wave frequency range of the target known medium.

[0031] The number of frequencies contained in the intersection between the limited sound wave frequency range of the target known medium and the frequency range occupied by each dispersion segment curve is taken as the numerator, and the number of frequencies contained in the frequency range occupied by each dispersion segment curve is taken as the denominator, and the ratio is taken as the matching degree between each dispersion segment curve and the target known medium.

[0032] The greater the matching degree between a certain dispersion segment curve and the target known medium is, the more likely the dispersion segment curve is caused by the sound wave propagating in the target known medium, therefore, the dispersion segment curve corresponding to the maximum value of the matching degree can be taken as the matching dispersion segment curve of the target known medium.

[0033] The matching dispersion segment curve of each known medium can be obtained by the same method as above. The unselected dispersion segment curves, that is, the non-matching dispersion segment curves, can be considered to be caused by unknown media.

[0034] When sound waves propagate from one known medium to another known medium, their signal characteristics will be disturbed. For example, in the process of sound waves propagating from the casing to the cement sheath, the sound waves will be reflected and refracted simultaneously at the junction between the two, resulting in changes in the signal characteristics of the sound waves such as phase and amplitude in different known media, causing the sound wave signal to be distorted. Therefore, the phase difference and amplitude difference of each frequency between the frequency ranges of the matching dispersion segmented curves of any two known media can be used to obtain the first signal distortion coefficient between any two known media, and the acoustic impedance of any two known media can be combined. The first signal distortion coefficient reflects the degree of distortion of the sound wave amplitude and phase caused by reflection and transmission phenomena during the propagation of the original sound wave signal in different known media. Subsequently, the original dispersion curve can be adjusted based on the first signal distortion coefficient to eliminate the influence of interference components.

[0035] Preferably, in one embodiment of the present invention, the method for obtaining the first signal distortion coefficient between any two known media specifically includes: The average value of the phases of all frequencies in the frequency range occupied by the matching dispersion segment curve of each known medium is taken as the overall phase value of each known medium, and the average value of the amplitudes of all frequencies in the frequency range occupied by the matching dispersion segment curve of each known medium is taken as the overall amplitude value of each known medium.

[0036] The absolute value of the difference in acoustic impedance between any two known media is used as the numerator, the sum of the acoustic impedances of any two known media is used as the denominator, and the ratio is used as the reflection coefficient between any two known media. The larger the reflection coefficient, the more obvious the reflection phenomenon of the sound wave at the junction of the two known media.

[0037] Furthermore, based on the reflection coefficient between any two known media, the difference in the overall phase value and the difference in the overall amplitude value between any two known media may be weighted to obtain the first signal distortion coefficient between any two known media.

[0038] Preferably, in one embodiment of the present invention, the method for obtaining the first signal distortion coefficient between any two known media further includes: Based on the calculation formula of the first signal distortion coefficient, the first signal distortion coefficient between any two known media is obtained. The calculation formula of the first signal distortion coefficient is: in, Indicates the Kind and A first signal distortion coefficient between two known media; Indicates the Kind and Reflection coefficients between known media; Indicates the The overall phase value of a known medium; Indicates the The overall phase value of a known medium; Indicates the The overall amplitude value of a known medium; Indicates the The overall amplitude value of a known medium.

[0039] Among them, when the sound wave has a more obvious reflection phenomenon between two known media, the reflection coefficient between the two known media is If the reflection coefficient between two known media is greater than When it is smaller, the sound wave undergoes a more obvious refraction phenomenon between two known media, and the refraction characteristics of the sound wave will directly affect the phase change of the sound wave.

[0040] Step S3: Obtain the medium interpretation of the original dispersion curve based on the difference between the phase velocity and the theoretical phase velocity, the difference between the amplitude and the theoretical amplitude at each frequency in the frequency range of the matching dispersion segmented curve of each known medium, and the acoustic impedance of each known medium; obtain the second signal distortion coefficient of the unknown medium based on the difference between the energy of the matching dispersion segmented curves of all known media and the energy of the original dispersion curve, as well as the medium interpretation.

[0041] Considering that in addition to known media, there may be unknown media such as casing corrosion, scaling layer, mud cake thickening layer in the wellbore expansion area, cement annulus filling, virtual joint layer, thin reservoir interlayer, drilling fluid invasion zone, etc., and the parameters such as thickness, acoustic wave propagation velocity and acoustic impedance of the unknown medium are unknown, so it is impossible to analyze the influence of the unknown medium on acoustic wave propagation through these parameters. The existence of the unknown medium will cause energy residual in the original dispersion curve. Therefore, the embodiment of the present invention first obtains the original dispersion curve based on the difference between the phase velocity and the theoretical phase velocity, the difference between the amplitude and the theoretical amplitude at each frequency in the frequency range of the matching dispersion segment curve of each known medium, and the acoustic impedance of each known medium. The medium interpretation degree of the curve reflects the interpretation degree of the original dispersion curve for the known medium and the possibility of the existence of unknown medium around the cased well. The greater the medium interpretation degree, the better the interpretation degree of the original dispersion curve for the known medium, and the higher the possibility of the existence of known medium but no unknown medium around the cased well. Subsequently, the energy of the unknown medium represented by the original dispersion curve can be accurately calculated based on the medium interpretation degree, and the influence of the unknown medium on the propagation of the sound wave can be accurately analyzed. Among them, the theoretical phase velocity and theoretical amplitude of the sound wave in a specific known medium are both known fixed values, and the theoretical phase velocity and theoretical amplitude of different known media are different.

[0042] Preferably, in one embodiment of the present invention, the method for obtaining the medium interpretation of the original dispersion curve specifically includes: The average value of the absolute value of the difference between the phase velocity of all frequencies and the theoretical phase velocity in the frequency range of the matching dispersion segment curve of each known medium is normalized by negative correlation, and the calculation results are limited to The phase velocity authenticity of each known medium is obtained within the range. The greater the phase velocity authenticity, the higher the possibility that the known medium exists around the cased hole.

[0043] In the embodiment of the present invention, the natural constant A negative exponential function with base The function form of is used to realize the normalization processing of negative correlation, which is not limited here, and the same method can be used in subsequent steps to realize the normalization processing of negative correlation, wherein, Represents a normalization function for normalization processing. In one embodiment of the present invention, the normalization processing can be specifically, for example, maximum and minimum value normalization processing, and the normalization in subsequent steps can adopt maximum and minimum value normalization processing. In other embodiments of the present invention, other normalization methods can be selected according to the specific range of values, or activation functions and hyperbolic tangent functions can be used to implement normalization processing, which will not be repeated or limited.

[0044] The average value of the absolute value of the difference between the amplitude of all frequencies in the frequency range of the matching dispersion segment curve of each known medium and the theoretical amplitude is normalized by negative correlation, and the calculation results are limited to The amplitude truthfulness of each known medium is obtained. Similarly, the greater the amplitude truthfulness, the higher the possibility that the known medium exists around the cased hole.

[0045] Then the average value of phase velocity truth and amplitude truth is taken as the comprehensive truth of each known medium. The comprehensive truth of each known medium is used to perform weighted summation of the acoustic impedance of each known medium and normalize it. The calculation result is limited to range, thereby obtaining the medium interpretation of the original dispersion curve.

[0046] As an example, in one embodiment of the present invention, the expression of the medium interpretation of the original dispersion curve can be specifically, for example, as follows: in, Indicates the medium interpretation of the original dispersion curve; Indicates the The comprehensive authenticity of the known media; Indicates the The acoustic impedance of a known medium; Indicates the number of known media types; Represents the hyperbolic tangent function, which is used for normalization.

[0047] The unknown medium surrounding the cased well will show residual energy on the original dispersion curve. Therefore, the second signal distortion coefficient of the unknown medium can be obtained based on the difference between the energy of the dispersion segment curves corresponding to all known media and the energy of the original dispersion curve, combined with the medium interpretation degree of the original dispersion curve. The second signal distortion coefficient reflects the degree of influence on the propagation process of the acoustic wave signal in the unknown medium. Subsequently, the first signal distortion coefficient between the known media and the second signal distortion coefficient of the unknown medium can be combined to effectively adjust the original dispersion curve and remove the interference components in the original dispersion curve.

[0048] Preferably, in one embodiment of the present invention, the method for obtaining the second signal distortion coefficient of the unknown medium specifically includes: The original dispersion curve is integrated to obtain the total energy value of the original dispersion curve, and then the matching dispersion segmented curve of each known medium is integrated to obtain the energy value of the matching dispersion segmented curve of each known medium. The sum of the energy values ​​of the matching dispersion segmented curves of all known media is used as the reference energy value of the original dispersion curve. The reference energy value can be considered as the energy size of the known medium on the original dispersion curve.

[0049] Then, based on the calculation formula of the residual energy value, the residual energy value of the unknown medium is obtained. The calculation formula of the residual energy value is: in, Represents the residual energy value of the unknown medium; Indicates the medium interpretation of the original dispersion curve; Represents the total energy value of the original dispersion curve; Indicates the reference energy value of the original dispersion curve.

[0050] The residual energy value of the unknown medium is used as the numerator, the reference energy value of the original dispersion curve is used as the denominator, and the ratio is used as the second signal distortion coefficient of the unknown medium.

[0051] As an example, in one embodiment of the present invention, the expression of the second signal distortion coefficient of the unknown medium may be specifically, for example, as follows: in, A second signal distortion coefficient representing the unknown medium; Represents the residual energy value of the unknown medium; Indicates the reference energy value of the original dispersion curve.

[0052] At this point, the impact of unknown media on acoustic signals has been accurately analyzed.

[0053] Step S4: adjusting the clustering process of each data point on the original dispersion curve according to the first signal distortion coefficient and the second signal distortion coefficient to obtain an adjusted dispersion curve.

[0054] Since the acoustic wave signal will be interfered with when it propagates in different known media and unknown media, the original dispersion curve of the acoustic wave signal will contain more interference components and undergo certain distortion, making the original dispersion curve unable to accurately reflect the reservoir characteristics of the cased well. Therefore, the clustering process of each data point on the original dispersion curve can be adjusted according to the first signal distortion coefficient and the second signal distortion coefficient to obtain an adjusted dispersion curve.

[0055] Preferably, in one embodiment of the present invention, the method for adjusting the acquisition of the dispersion curve specifically includes: First, the Euclidean distance between any two data points on the original dispersion curve is used as the distance measure between any two data points.

[0056] According to the first signal distortion coefficient between any two known media and the second signal distortion coefficient of the unknown medium, the distance metric between any two data points on the original dispersion curve is adjusted to obtain an adjusted distance metric between the two data points.

[0057] Preferably, in an embodiment of the present application, the method for obtaining the adjusted distance metric between any two data points specifically comprises: For any two data points on the original dispersion curve, if the two data points belong to different matching dispersion segment curves, it indicates that the two data points are formed by sound waves in two different known media, and thus the first signal distortion coefficient between the known media corresponding to the matching dispersion segment curves where the two data points are located can be taken as the distance adjustment weight between the two data points. The greater the distance adjustment weight, the greater the degree of adjustment of the distance metric between the two data points.

[0058] If one data point belongs to a matching dispersion segment curve and the other data point belongs to a non-matching dispersion segment curve, it indicates that the two data points are formed by sound waves in a certain known medium and an unknown medium respectively, and thus the average of the first signal distortion coefficient between the known media corresponding to the matching dispersion segment curve where one data point is located and the known media corresponding to the nearest matching dispersion segment curve, and the second signal distortion coefficient of the unknown medium, can be taken as the distance adjustment weight between the two data points.

[0059] If the two data points belong to the same matching dispersion segment curve or the two data points belong to non-matching dispersion segment curves, it indicates that the two data points are formed by sound waves in the same known medium or unknown medium, and at this time the sound waves have not been disturbed, and thus the distance adjustment weight between the two data points can be set to a value of 0, i.e. no adjustment is needed for the distance metric between the two data points.

[0060] Further, the product of the distance adjustment weight and the distance metric between any two data points on the original dispersion curve is taken as the distance adjustment amount between the two data points, and the sum of the distance metric and the distance adjustment amount between any two data points is taken as the adjusted distance metric between the two data points.

[0061] Then, based on the adjusted distance metric between any two data points, all data points on the original dispersion curve are clustered to obtain a plurality of clustering clusters. In an embodiment of the present application, the clustering operation can be implemented by using an existing DBSCAN clustering algorithm or other clustering algorithms, which are not limited or described herein.

[0062] The smaller the number of data points contained in a certain cluster is, the more the data points in the cluster belong to interference noise points formed by sound wave propagation in different known media and unknown media, so the cluster containing data points less than a preset number threshold can be removed, and the data points in all the remaining clusters are curve fitted, so that the fitted curve is taken as the adjusted dispersion curve, wherein the preset number threshold is in the range of 10-20, in an embodiment of the present application, the preset number threshold is set to 10, and the preset number threshold can also be set by the implementer according to the specific implementation scene, which is not limited here, and in the embodiment of the present application, the existing least square method or other fitting methods can be selected to realize curve fitting, which is not limited here.

[0063] After obtaining the adjusted dispersion curve, the geological features such as thin interbeds and formation interfaces around the casing well can be accurately analyzed by using the adjusted dispersion curve, which provides accurate acoustic data support for oil and gas reservoir evaluation, wellbore stability analysis and development plan formulation.

[0064] An embodiment of the present application provides a dipole acoustic wave casing after logging correction device, which comprises a memory, a processor and a computer program, wherein the memory is used for storing the corresponding computer program, the processor is used for running the corresponding computer program, and the computer program can realize the method described in steps S1-S4 when running in the processor.

[0065] It should be noted that: the above-mentioned embodiment sequence of the present application is only for description, not representing the advantages and disadvantages of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-task processing and parallel processing are also possible or can be advantageous.

[0066] Each embodiment in the specification is described in a progressive manner, and the same and similar parts between each embodiment can be referred to each other, and each embodiment mainly describes the difference from other embodiments.

Claims

1. A dipole acoustic sleeve post-logging correction method, characterized in that: The method comprises: Perform frequency domain transformation on the acoustic wave signal of the cased well to obtain the phase and amplitude of each frequency, and construct the original dispersion curve of the acoustic wave signal, where the abscissa is frequency and the ordinate is phase velocity, and obtain the thickness, acoustic wave propagation velocity and acoustic impedance of each known medium in the cased well; According to the fluctuations of the original dispersion curve, the original dispersion curve is segmented to obtain multiple dispersion segment curves; according to the sound wave propagation speed and thickness of each known medium and the frequency range occupied by each dispersion segment curve, a matching dispersion segment curve for each known medium is screened from each dispersion segment curve; according to the phase difference and amplitude difference of each frequency between the frequency ranges of the matching dispersion segment curves of any two known media, and in combination with the acoustic impedance of the any two known media, a first signal distortion coefficient between any two known media is obtained; Obtaining the medium interpretation of the original dispersion curve based on the difference between the phase velocity and the theoretical phase velocity at each frequency in the frequency range of the matched dispersion segment curve of each known medium, the difference between the amplitude and the theoretical amplitude, and the acoustic impedance of each known medium; obtaining the second signal distortion coefficient of the unknown medium based on the difference between the energy of the matched dispersion segment curves of all known media and the energy of the original dispersion curve, and the medium interpretation; According to the first signal distortion coefficient and the second signal distortion coefficient, the clustering process of each data point on the original dispersion curve is adjusted to obtain an adjusted dispersion curve.

2. A dipole acoustic sleeve post-logging correction method according to claim 1, characterized in that: The obtaining of a plurality of dispersion segment curves comprises: Calculate the second-order derivative of the original dispersion curve to obtain the second-order derivative value of each data point on the original dispersion curve; The data point whose second-order derivative value is greater than a preset mutation threshold is used as the mutation data point of the original dispersion curve; The original dispersion curve is segmented using each mutation data point to obtain multiple dispersion segmented curves.

3. A dipole acoustic sleeve post-logging correction method according to claim 1, characterized in that: The step of selecting a matching dispersion segment curve for each known medium from each dispersion segment curve comprises: Taking any known medium as a target known medium, taking the acoustic wave propagation velocity of the target known medium as the numerator, taking twice the thickness of the target known medium as the denominator, and taking the ratio as the resonant acoustic wave frequency of the target known medium; The range formed by all frequencies between the original frequency of the acoustic wave signal of the cased well and the resonant acoustic wave frequency of the target known medium is used as the finite acoustic wave frequency range of the target known medium; The number of frequencies included in the intersection between the finite acoustic wave frequency range of the target known medium and the frequency range occupied by each dispersion segment curve is used as the numerator, the number of frequencies included in the frequency range occupied by each dispersion segment curve is used as the denominator, and the ratio is used as the matching degree between each dispersion segment curve and the target known medium; The dispersion segment curve corresponding to the maximum value of the matching degree is used as the matching dispersion segment curve of the target known medium.

4. A dipole acoustic sleeve post-logging correction method according to claim 1, characterized in that: Obtaining a first signal distortion coefficient between any two known media includes: Taking the average value of the phases of all frequencies in the frequency range occupied by the matching dispersion segment curve of each known medium as the overall phase value of each known medium; The average value of the amplitudes of all frequencies in the frequency range occupied by the matching dispersion segment curve of each known medium is taken as the overall amplitude value of each known medium; The absolute value of the difference between the acoustic impedances of any two known media is used as the numerator, the sum of the acoustic impedances of any two known media is used as the denominator, and the ratio is used as the reflection coefficient between the any two known media; Based on the reflection coefficient between any two known media, the difference in the overall phase value and the difference in the overall amplitude value between any two known media are weighted to obtain a first signal distortion coefficient between any two known media.

5. A dipole acoustic sleeve post-logging correction method according to claim 4, characterized in that: The step of weighting the difference in the overall phase value and the difference in the overall amplitude value between the two known media based on the reflection coefficient between the two known media to obtain a first signal distortion coefficient between the two known media includes: Based on the calculation formula of the first signal distortion coefficient, the first signal distortion coefficient between any two known media is obtained. The calculation formula of the first signal distortion coefficient is: ； in, Indicates the Species and A first signal distortion coefficient between two known media; Indicates the Species and Reflection coefficients between known media; Indicates the The overall phase value of a known medium; Indicates the The overall phase value of a known medium; Indicates the The overall amplitude value of a known medium; Indicates the The overall amplitude value of a known medium.

6. A dipole acoustic sleeve post-logging correction method according to claim 1, characterized in that: The medium interpretation of the original dispersion curve is obtained by: The phase velocity authenticity of each known medium is obtained by performing negative correlation normalization on the average of the absolute values ​​of the differences between the phase velocity at all frequencies in the frequency range of the matching dispersion segment curve of each known medium and the theoretical phase velocity; Perform negative correlation normalization on the average of the absolute values ​​of the differences between the amplitudes of all frequencies in the frequency range of the matching dispersion segment curve of each known medium and the theoretical amplitude to obtain the amplitude authenticity of each known medium; The average value of the phase velocity truth and the amplitude truth is taken as the comprehensive truth of each known medium; By utilizing the comprehensive truthfulness of each known medium, the acoustic impedance of each known medium is weightedly summed and normalized to obtain the medium interpretation degree of the original dispersion curve.

7. A dipole acoustic sleeve post-logging correction method according to claim 1, characterized in that: Obtaining the second signal distortion coefficient of the unknown medium includes: Integrate the original dispersion curve to obtain the total energy value of the original dispersion curve; Performing an integral calculation on the matching dispersion segment curve of each known medium to obtain an energy value of the matching dispersion segment curve of each known medium, and taking the sum of the energy values ​​of the matching dispersion segment curves of all known media as a reference energy value of the original dispersion curve; Based on the calculation formula of the residual energy value, the residual energy value of the unknown medium is obtained. The calculation formula of the residual energy value is: ； in, Represents the residual energy value of the unknown medium; Indicates the medium interpretation of the original dispersion curve; Represents the total energy value of the original dispersion curve; Indicates the reference energy value of the original dispersion curve; The residual energy value of the unknown medium is used as a numerator, the reference energy value of the original dispersion curve is used as a denominator, and the ratio is used as the second signal distortion coefficient of the unknown medium.

8. The dipole acoustic sleeve post-logging correction method according to claim 1, characterized in that: The obtaining and adjusting the dispersion curve comprises: The Euclidean distance between any two data points on the original dispersion curve is used as the distance measure between any two data points; adjusting a distance metric between any two data points on an original dispersion curve according to the first signal distortion coefficient between any two known media and the second signal distortion coefficient of an unknown medium to obtain an adjusted distance metric between the any two data points; Based on the adjusted distance metric between any two data points, all data points on the original dispersion curve are clustered to obtain multiple clusters; The clusters containing data points whose number is less than a preset threshold are eliminated, and the data points in all the remaining clusters are subjected to curve fitting, and the fitted curve is used as the adjusted dispersion curve.

9. A dipole acoustic sleeve post-logging correction method according to claim 8, characterized in that: Obtaining the adjusted distance metric between any two data points includes: For any two data points on the original dispersion curve, if the two data points belong to different matching dispersion segment curves, the first signal distortion coefficient between the known media corresponding to the matching dispersion segment curves where the two data points are located is used as the distance adjustment weight between the two data points; If one of the data points belongs to a matching dispersion piecewise curve and the other data point belongs to a non-matching dispersion piecewise curve, then the average of the first signal distortion coefficient between the known medium corresponding to the matching dispersion piecewise curve where one of the data points is located and the known medium corresponding to the nearest matching dispersion piecewise curve and the second signal distortion coefficient of the unknown medium is used as the distance adjustment weight between the two data points; If two data points belong to the same matching dispersion segment curve or the two data points belong to non-matching dispersion segment curves, the distance adjustment weight between the two data points is set to a value of 0; Using the product value of the distance adjustment weight and the distance metric between any two data points on the original dispersion curve as the distance adjustment amount between any two data points; The sum of the distance metric and the distance adjustment amount between any two data points is used as the adjusted distance metric between any two data points.

10. A dipole acoustic sleeve post-logging correction device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 9 are implemented.

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