Inversion methods, apparatus and equipment for conductivity and magnetic permeability of a single-layer tubing string in wells

Abstract

This invention discloses a method, apparatus, and equipment for inverting the conductivity and permeability of a single-layer tubing string in a downhole well, relating to the field of electromagnetic flaw detection. The method includes: constructing a forward-modeled time-domain induced voltage response model using relevant parameters of the tubing string structure model; calculating the forward-modeled time-domain induced voltage decay response using finite element or finite difference numerical simulation techniques based on the forward-modeled time-domain induced voltage decay response model; forming a simulated decay response surface database based on the forward-modeled time-domain induced voltage decay response; acquiring measured decay data of the tubing string; constructing a set of contour equations based on the measured decay data and the simulated decay response surface database; reconstructing and solving the contour equations using contour interpolation to obtain the conductivity and relative permeability of the tubing string. This invention overcomes the initial value problems in existing technologies, reduces the complexity of the inversion problem, and effectively improves the inversion speed and accuracy.

Description

Technical Field

[0001] This invention relates to the field of downhole pulsed eddy current electromagnetic flaw detection technology, specifically to a method, apparatus, and equipment for inverting the conductivity and magnetic permeability of a single-layer tubing string in a downhole well. Background Technology

[0002] The oilfield injection-production well network offers limited control over the reservoir, leading to widespread and increased casing damage in older oil and water wells. While non-destructive testing (NDT) technologies for metal pipelines are relatively mature, both time-domain and frequency-domain electromagnetic testing require inversion of the tubing conductivity and relative permeability before wall thickness calculation. Among these, time-domain electromagnetic testing based on pulsed eddy currents is currently the mainstream casing damage detection technology. It uses broadband transient pulse excitation to generate a time-varying electromagnetic field, emits a high-energy electromagnetic pulse signal from the transmitting probe, and collects the eddy current signal intensity during the attenuation process from the receiving probe. Based on the collected signal data, the tubing conductivity and relative permeability are inverted, and then the wall thickness is calculated to evaluate the pipe damage.

[0003] In existing techniques for inverting the conductivity and relative permeability of tubular components, Method 1 is based on time-domain induced voltage. It utilizes the product of conductivity and wall thickness, and relative permeability and wall thickness, to directly employ a conventional gradient descent algorithm based on a forward modeling library to solve a least-squares problem and invert the relative permeability and conductivity of the tubular component. Alternatively, it leverages the empirical fact that the sum of the partial derivatives of the received time-domain signal with respect to conductivity and relative permeability minus the partial derivative with respect to wall thickness equals zero, thus converging the solution to a unique optimal solution. Method 2 is also based on time-domain induced voltage. It uses the differential transformation formula of the zeroth derivative of the Laplace space solution, whose attenuation curve area is independent of conductivity but varies with the permeability and inner / outer radius of the tubular component. It first inverts the relative permeability of the tubular component, and then uses the differential transformation formula of the first derivative of the Laplace space solution to solve for the conductivity. The approach of the third method is based on the time-domain induced voltage. It establishes a least-squares problem between the measured value of the time-domain induced voltage signal and the theoretical calculation value to inversely determine the conductivity and relative permeability of the tested column. By gradually increasing the amplitude of the pulse excitation current, the conductivity curve is fitted, and the intersection of the curve with the vertical axis is considered to be the conductivity of the column.

[0004] However, the above processing methods have the following drawbacks: (1) Although processing method one reduces the number of inversion parameters by using coupling, the gradient descent algorithm will be severely affected by the initial value. Although the initial value problem is overcome by using the experience that the partial derivative is 0, the inversion error is large when the product of relative permeability and conductivity of the single-layer tubing is too large or too small; (2) The models used in the above processing methods are all transverse coil models, and no mention is made of how to invert the conductivity and relative permeability of the longitudinal coil model; (3) Processing method two is for specific probes and specific applications, and relies on calibration standards and well-trained technicians to interpret multivariate detection data. It is uncertain whether it is feasible for longitudinal coils; (4) The model of processing method three is a transverse coil model, and this method requires repeated changes to the excitation current amplitude. The detection method is complex and not applicable to the actual logging operation process. Summary of the Invention

[0005] In view of the above problems, the present invention is proposed to provide a method, apparatus and equipment for inverting the conductivity and magnetic permeability of a single-layer casing in wells to overcome or at least partially solve the above problems.

[0006] According to one aspect of the embodiments of this application, a method for inverting the conductivity and magnetic permeability of a single-layer downhole tubing string is provided, the method comprising:

[0007] Using the relevant parameters of the tubular structure model, a forward-modeling time-domain induced voltage response model is constructed;

[0008] Based on the forward time-domain induced voltage response model, the finite element or finite difference numerical simulation technology is used to calculate the forward time-domain induced voltage decay response, and a simulation decay response surface database is formed based on the forward time-domain induced voltage decay response.

[0009] Obtain the measured attenuation data of the tubing, and construct a set of contour equations based on the measured attenuation data and the simulated attenuation response surface database;

[0010] The conductivity and relative permeability of the tubular column are obtained by reconstructing and solving the contour equations through contour interpolation.

[0011] Furthermore, the relevant parameters of the tubular structure model include: casing parameters, probe parameters, and probe excitation parameters;

[0012] Casing parameters include: casing outer diameter and casing thickness;

[0013] The probe parameters include: coil shaft length, coil inner diameter, coil outer diameter, core size, core conductivity, core relative permeability, and coil wire diameter.

[0014] The probe excitation parameters include: excitation current, excitation rise time, excitation fall time, and excitation period.

[0015] Furthermore, the simulation attenuation response surface database includes: an attenuation surface library or a contour map library.

[0016] Furthermore, the contour equation system includes: the decay time contour equation system, the decay time channel contour equation system, or the wall thickness contour equation system.

[0017] Furthermore, the contour line equations are reconstructed and solved using contour line interpolation to obtain the conductivity and relative permeability of the tube column, which further include:

[0018] Interpolate the discrete data of the contour line equation system and reconstruct the interpolated discrete data;

[0019] The intersection points are determined based on the reconstructed discrete data.

[0020] Based on the obtained intersection points, the conductivity and relative permeability of the tubular column are determined.

[0021] Furthermore, based on the obtained intersection points, the determination of the conductivity and relative permeability of the tube column further includes:

[0022] If there are multiple intersection points, the residual between the forward-modeled time-domain induced voltage data corresponding to the multiple intersection points and the corresponding measured time-domain induced voltage data within a preset window range is calculated, and the conductivity and relative permeability corresponding to the intersection point with the smallest residual are selected as the conductivity and relative permeability of the tube column, respectively.

[0023] If there is only one intersection point, then the conductivity and relative permeability corresponding to the intersection point are taken as the conductivity and relative permeability of the tube, respectively.

[0024] According to another aspect of the embodiments of this application, an inversion device for the electrical conductivity and magnetic permeability of a single-layer casing in a well is provided, the device comprising:

[0025] The first building module is suitable for constructing a forward-modeling time-domain induced voltage response model using relevant parameters of the column structure model;

[0026] The forward modeling simulation module is suitable for calculating the forward time-domain induced voltage decay response based on the forward time-domain induced voltage response model using finite element or finite difference numerical simulation techniques, and forming a simulation decay response surface database based on the forward time-domain induced voltage decay response.

[0027] The second construction module is suitable for obtaining the measured attenuation data of the tubing and constructing a set of contour equations based on the measured attenuation data and the simulated attenuation response surface database.

[0028] The inversion module is suitable for reconstructing and solving the contour equations to obtain the conductivity and relative permeability of the tubular column.

[0029] According to another aspect of the embodiments of this application, a computing device is provided, including: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus;

[0030] The memory is used to store at least one executable instruction that causes the processor to perform the operation corresponding to the above-mentioned inversion method of conductivity and permeability of a single-layer tubing string in the well.

[0031] According to another aspect of the embodiments of this application, a computer storage medium is provided, which stores at least one executable instruction that causes a processor to perform operations corresponding to the above-described method for inverting the conductivity and permeability of a single-layer tubing string in a well.

[0032] According to another aspect of the embodiments of this application, a computer program product is provided, including at least one executable instruction, which causes a processor to perform operations corresponding to the above-described inversion method for conductivity and permeability of a single-layer tubing string in well.

[0033] According to the technical solution provided by this invention, a set of contour equations is constructed using measured attenuation data and a simulated attenuation response surface database. This effectively reduces the number of variables required for electromagnetic flaw detection, eliminating the need for other measurement information and initial values, thus overcoming the initial value problem and reducing the complexity of the inversion problem. It also overcomes the problem of large inversion errors in single-layer tubing when the product of relative permeability and conductivity is too large or too small, and overcomes the problem of existing technologies requiring repeated changes to the excitation current amplitude. This provides a favorable guarantee for accurately inverting the conductivity and relative permeability of the tubing string. Furthermore, this solution proposes a novel inversion approach, based on the downhole pulsed eddy current method for inverting conductivity and relative permeability. The proposed model is a longitudinal coil model, filling the gap in existing technologies for inverting conductivity and relative permeability of longitudinal coil models. When calculating the intersection points of contour lines, contour line interpolation and reconstruction techniques are employed to refine the discrete data of the constructed contour line equation system, improving solution accuracy. Reconstructing the interpolated discrete data ensures that the abscissa remains within a consistent range, eliminating the possibility of multiple relative permeabilities corresponding to the same conductivity, thus effectively improving the stability of the inversion results. This scheme effectively improves inversion speed and accuracy and can be applied to ranges of relative permeability and conductivity that conform to the normal and reasonable range of downhole tubing, making it of great significance for wellbore integrity detection.

[0034] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0035] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0036] Figure 1 A flowchart illustrating a method for inverting the conductivity and permeability of a single-layer tubing string in a downhole hole according to an embodiment of this application is shown.

[0037] Figure 2 A simulation diagram of the forward time-domain induced voltage response model is shown;

[0038] Figure 3 A schematic diagram of the attenuation surface library is shown;

[0039] Figure 4 A schematic diagram of the contour map library is shown;

[0040] Figure 5 This shows a schematic diagram of the discrete data after interpolation reconstruction of the contour line equation system;

[0041] Figure 6 A schematic diagram of the inversion results before residual optimization is shown;

[0042] Figure 7 A schematic diagram of the inversion results after residual optimization is shown;

[0043] Figure 8 A schematic diagram illustrating the principle of a method for inverting the conductivity and permeability of a single-layer tubing string according to an embodiment of this application is shown.

[0044] Figure 9 A structural block diagram of a downhole single-layer tubing conductivity and magnetic permeability inversion device according to an embodiment of this application is shown;

[0045] Figure 10 A schematic diagram of the structure of a computing device according to an embodiment of this application is shown. Detailed Implementation

[0046] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0047] Figure 1A flowchart illustrating a method for inverting the conductivity and permeability of a single-layer tubing string according to an embodiment of this application is shown, as follows. Figure 1 As shown, the method includes the following steps:

[0048] Step S101: Construct a forward time-domain induced voltage response model using the relevant parameters of the column structure model.

[0049] The tubing string structure model used in this application is a single-layer tubing string; and the coil in the tubing string structure model is a longitudinal coil, that is, the model for inverting conductivity and relative permeability based on the downhole pulsed eddy current method in this application is a longitudinal coil model. In addition, the electromagnetic flaw detection tool relied upon in this application is a downhole transient electromagnetic flaw detection logging tool capable of measuring a single-layer tubing string structure model, and its detection probe consists of a coaxial and concentric excitation coil (denoted by T) and a receiving coil (denoted by R) with a magnetic core.

[0050] The relevant parameters of the tubular structure model include bushing parameters, probe parameters, and probe excitation parameters. In step S101, the bushing parameters, probe parameters, and probe excitation parameters of the tubular structure model are obtained. The bushing parameters include: bushing outer diameter and bushing thickness; the probe parameters include: coil shaft length, coil inner diameter, coil outer diameter, core size, core conductivity, core relative permeability, and coil wire diameter; the probe excitation parameters include: excitation current, excitation rise time, excitation fall time, and excitation period. After obtaining the bushing parameters, probe parameters, and probe excitation parameters, a forward-modeling time-domain induced voltage response model can be constructed based on the initialization parameters.

[0051] The expression for the forward-modeled time-domain induced voltage response model can be: Where V is the induced voltage response, f is the forward response, and od is the outer diameter of the bushing. The conductivity of the tubular column, t is the relative permeability of the tube, thk is the tube thickness, and t is the decay time.

[0052] Figure 2 A simulation diagram of the forward time-domain induced voltage response model is shown, such as... Figure 2As shown, the diagram includes an air domain, pipe, magnetic core, drive coil, and receiving coil. Different colored and typed lines represent the distribution of the primary magnetic field, induced current, and secondary magnetic field. O is the origin, z is the vertical axis, and r is the radial axis. The curves on the right side of the diagram show the changes in excitation current (shown by the purple solid line) and receiving voltage (shown by the pink solid line) over time. I(t) represents the function of excitation current over time, describing the temporal variation of the current in the excitation coil. For example, it remains constant in stage ①, providing the excitation source for subsequent magnetic field generation and electromagnetic induction, and is the initial driving factor for electromagnetic signal generation in the entire electromagnetic flaw detection process. ε(t) represents the function of receiving voltage over time, reflecting the response of the voltage received by the receiving coil under the action of the excitation current I(t), especially the dynamic process of voltage attenuation when the excitation current I(t) changes. Specifically, in stage ①, the excitation current remains constant to establish the relevant electromagnetic state; in stage ②, after the excitation current disappears, the received voltage gradually decays, reflecting the voltage response law during electromagnetic induction. This model can be used to simulate and analyze the voltage response characteristics of the tested objects such as downhole tubing under the action of pulsed eddy currents in electromagnetic flaw detection.

[0053] Step S102: Based on the forward time-domain induced voltage response model, the forward time-domain induced voltage decay response is calculated using finite element or finite difference numerical simulation technology, and a simulation decay response surface database is formed based on the forward time-domain induced voltage decay response.

[0054] Based on the forward-modeled time-domain induced voltage response model, and according to casing parameters, probe parameters, and probe excitation parameters, finite element or finite difference numerical simulation techniques are used to calculate the forward-modeled time-domain induced voltage decay response. A simulated decay response surface database is constructed for the conductivity and relative permeability ranges of the downhole exploration and development tubing string. Considering the coil size of the detection probe, a highly accurate downhole time-domain induced voltage decay response can be calculated based on a pulse excitation source. Furthermore, considering that actual downhole temperature varies with well depth, and temperature changes affect the magnetic field, leading to discrepancies between numerical simulation results and measured results, the numerical simulation results can be corrected in real-time based on the measured temperature to improve the accuracy of the numerical simulation results.

[0055] The simulated attenuation response surface database may include an attenuation surface library or a contour map library. The forward-modeled time-domain induced voltage attenuation response calculated from forward modeling can be used to form an attenuation surface library or a contour map library. Storing these libraries to form the simulated attenuation response surface database helps improve the inversion speed of the column's conductivity and relative permeability. Specifically, the contour map library can be constructed based on the attenuation time or attenuation time channel, nominal wall thickness, and coupling wall thickness at the forward-modeled time-domain induced voltage attenuation response.

[0056] When selecting the decay time, try to avoid the response time range of direct coupling between the excitation coil and the receiving coil, and choose a later time. The decay time channel can be obtained by integrating the decay time into multiple uniform or non-uniform time segments, allowing for overlapping time. The rules for selecting the decay time channel are the same as those for selecting the decay time.

[0057] Figure 3 and Figure 4 Schematic diagrams of the attenuation surface library and the contour map library are shown respectively. The conductivity of the tubular column, Let be the relative permeability of the tubular column. Relative permeability is a dimensionless quantity, denoted by 1, and its unit is dimensionless. For example... Figure 3 As shown, the conductivity of column 1 is 5.6 MS / m and the relative permeability is 60; the conductivity of column 2 is 4.6 MS / m and the relative permeability is 160; and the conductivity of column 3 is 3.6 MS / m and the relative permeability is 80.

[0058] Step S103: Obtain the measured attenuation data of the tubing, and construct a set of contour equations based on the measured attenuation data and the simulated attenuation response surface database.

[0059] Obtain measured attenuation data of the tubing string. Measured attenuation data refers to measured downhole time-domain electromagnetic flaw detection logging data. Specifically, measured attenuation data may include measured attenuation curves. The constructed contour equation set may also be called the inversion equation set model. The contour equation set may specifically include: attenuation time contour equation set, attenuation time channel contour equation set, or wall thickness contour equation set.

[0060] The method for constructing the isoline equation system of decay time and the isoline equation system of decay time channel is as follows: the measured decay curve and the simulated decay curve of the simulated decay response surface database have the same conductivity and relative permeability at two different decay times (or decay time channels) at the same location. The values ​​of the measured decay curve at the nominal wall thickness and the coupling wall thickness can be used to construct the isoline two-variable linear functional equation system based on the decay surface library or isoline map library in the simulated decay response surface database.

[0061] Record the measured attenuation curve at the i-th attenuation time for the nominal wall thickness. The decay response at is At the (i+k)th decay time The decay response at is In the i-th decay time channel The decay response is In the (i+k)th decay time channel The decay response is When the coupling wall thickness is specified, at the i-th decay time... The decay response at is At the (i+k)th decay time The decay response at is In the i-th decay time channel The decay response is In the (i+k)th decay time channel The decay response is Then, based on the attenuation surface library or contour map library in the simulation attenuation response surface database, a system of two-variable linear functional equations for contour lines is constructed. The constructed system of equations is as follows:

[0062] Equation (1); or Equation (2); or Equation (3); or Equation (4).

[0063] Where f is the forward response, Let be the relative permeability of the tube. Let nthk be the conductivity of the tubing, nthk be the nominal wall thickness of the tubing, and cthk be the coupling wall thickness of the tubing. The attenuation time contour equations include equation (1) or equation (2); the attenuation time channel contour equations include equation (3) or equation (4). By performing contour interpolation reconstruction and solving the attenuation time contour equations or the attenuation time channel contour equations, the conductivity and relative permeability of the tubing can be calculated.

[0064] The method for constructing the wall thickness contour equation system is as follows: The measured attenuation curve and the simulated attenuation curve of the simulated attenuation response surface database have the same conductivity and relative permeability at the nominal wall thickness and coupling wall thickness at the same attenuation time (or attenuation time channel). The values ​​of the measured attenuation curve at attenuation time one and attenuation time two (or attenuation time channel one and attenuation time channel two) can be used to construct the contour two-variable linear functional equation system based on the attenuation surface library or contour map library in the simulated attenuation response surface database.

[0065] Record the measured decay curve at the i-th decay time. At that time, the attenuation response at the nominal wall thickness is The attenuation response at the thickest part of the coupling wall is ; in the i-th decay time channel At that time, the attenuation response at the nominal wall thickness is The attenuation response at the thickest part of the coupling wall is Then, based on the attenuation surface library or contour map library in the simulation attenuation response surface database, a system of two-variable linear functional equations for contour lines is constructed. The constructed system of equations is as follows:

[0066] Equation (5); or Equation (6).

[0067] Where f is the forward response, Let be the relative permeability of the tube. Let nthk be the electrical conductivity of the tubing, nthk be the nominal wall thickness of the tubing, and cthk be the coupling wall thickness of the tubing. In other words, the wall thickness contour equations include equation (5) or equation (6). By reconstructing and solving the wall thickness contour equations through contour interpolation, the electrical conductivity and relative permeability of the tubing can be calculated.

[0068] This application constructs a system of isoline-based linear functional equations based on the measured attenuation curves and the simulated attenuation curves from the simulated attenuation response surface database, which exhibit the same conductivity and relative permeability at two different attenuation times (or attenuation time channels) at the same attenuation time (or the same attenuation time channel) at both the nominal wall thickness and the coupling wall thickness. This effectively reduces the number of variables requiring inversion. The equations are directly constructed from time-domain measured data and forward modeling data to invert the conductivity and relative permeability of the tubing. It does not limit fixed theoretical model data, does not require separate testing tools, requires no other measurement information, and does not require initial values. This overcomes the initial value problem, solves the multiple solution problem, reduces the complexity of the inversion problem, and overcomes the problem of large inversion errors when the product of relative permeability and conductivity is too large or too small for single-layer tubing. This application is not targeted at any specific probe or application; it can be applied to any range of relative magnetic permeability and electrical conductivity that falls within the normal and reasonable range of downhole tubing.

[0069] Step S104: Reconstruct and solve the contour equations by contour interpolation to obtain the conductivity and relative permeability of the tubular column.

[0070] The process involves interpolating the discrete data of the contour line equations and reconstructing the interpolated data. Intersection points are then calculated based on the reconstructed data. Based on these intersection points, the conductivity and relative permeability of the tubing are determined. Contour line interpolation and reconstruction techniques are employed when calculating the intersection points. Specifically, fine interpolation of the constructed contour line equations improves the solution accuracy. Reconstructing the interpolated data places the equiaxial range data into two contour lines, ensuring the abscissa is within a consistent range. This eliminates the possibility of multiple relative permeabilities corresponding to the same conductivity, effectively improving the stability of the inversion results. The intersection points are then calculated based on the reconstructed discrete data, i.e., the intersection point coordinates are determined. Figure 5 The diagram shows a schematic representation of the discrete data reconstructed from the contour line equations. Methods for finding intersection points include, but are not limited to, the bisection method, iterative method, and equation-solving method. It is necessary to record the coordinates of all existing intersection points and the coordinates of the position with the minimum contour line spacing when no intersection points exist.

[0071] Taking the equation-solving method as an example, let the discrete data be d, and the sign of the discrete data be calculated as... two adjacent points and The absolute value of the sign difference is Where diff is the difference; if the value of d2 is 2, then at two adjacent points ( , If there are intersection points within the interval, establish the curve equation using these two adjacent points. k1 and b1 are the slope and intercept corresponding to the curve equation; two discrete data points can be used to establish two curve equations, such as the other curve equation being... Let k2 and b2 be the slope and intercept corresponding to the curve equation, then the system of equations is: Solving for the intersection point yields the inverted conductivity and relative permeability of the tube. If there is no intersection point, the shortest distance between the two curves can be calculated, which represents the inverted conductivity and relative permeability of the tube.

[0072] If there are multiple intersection points, the residuals between the forward-modeled time-domain induced voltage data corresponding to the multiple intersection points and the corresponding measured time-domain induced voltage data within a preset window range are calculated, and the conductivity and relative permeability corresponding to the intersection point with the smallest residual are selected as the conductivity and relative permeability of the tube, respectively. If there is only one intersection point, the conductivity and relative permeability corresponding to the intersection point are used as the conductivity and relative permeability of the tube, respectively.

[0073] Considering that there may be multiple intersection points obtained, a residual optimization technique is introduced to select the conductivity and relative permeability corresponding to the intersection point with the smallest residual as the conductivity and relative permeability of the tube, respectively. For example, the results of inversion for multiple decay times (or multiple decay time channels) may have multiple intersection points, such as... Figure 6 As shown, where *channeli* refers to the identifier of the decay time channel, and *true point* refers to a point in the measured decay data. Based on the forward-modeled time-domain induced voltage data corresponding to multiple intersection points (i.e., multiple inversion results), the residual between the original and the corresponding measured time-domain induced voltage data (i.e., the data corresponding to the intersection points in the measured decay data) is calculated within a preset window range. The preset window range can be the full window range or a custom window range; no specific limitation is made here. Then, the conductivity and relative permeability corresponding to the intersection point with the smallest residual are selected as the conductivity and relative permeability of the tube, respectively. In other words, the final inversion result is determined, as shown below. Figure 7 As shown, the inversion point refers to the intersection point with the smallest residual determined from the multiple intersection points obtained from the solution.

[0074] This application reconstructs the equivalent data by interpolating the projection lines on the nominal wall thickness and coupling wall thickness surfaces at two different decay times (or decay time channels) or at the same decay time (or decay time channel) based on measured decay data. Then, it solves for the intersection points based on the discrete data of the reconstructed isolines to obtain the inverted conductivity and relative permeability of the tubing.

[0075] Figure 8 A schematic diagram illustrating the principle of a method for inverting the conductivity and permeability of a single-layer tubing string according to an embodiment of this application is shown, as follows. Figure 8 As shown, the input of the tubing structure model refers to the input of relevant parameters of the tubing structure model, including bushing parameters, probe parameters, and probe excitation parameters. Using these parameters, a forward-modeled time-domain induced voltage response model is constructed. Based on this model, and according to the decay time or decay time channel, forward simulation is performed using finite element or finite difference numerical simulation techniques. The forward-modeled time-domain induced voltage decay response calculated can be used to form a decay surface library or a contour map library. Storing these libraries creates a simulation decay response surface database (i.e.,...). Figure 8 (Database in the database); obtain the measured attenuation data of the tubing (i.e., Figure 8 The measured data in the database are used to construct a set of contour equations based on the measured attenuation data and the simulated attenuation response surface database. Contour data interpolation and reconstruction refers to performing contour interpolation and reconstruction on the constructed set of contour equations. All intersection points are calculated, and the forward-modeled time-domain induced voltage data corresponding to the intersection points are obtained (i.e., Figure 8If there are multiple intersection points, the residuals between the forward modeling data corresponding to the multiple intersection points and the corresponding measured data within a preset window range are calculated, and the conductivity and relative permeability of the intersection point with the smallest residual are output as the conductivity and relative permeability of the tube column, respectively.

[0076] The inversion method for conductivity and permeability of a single-layer tubing string provided in this application utilizes measured attenuation data and a simulated attenuation response surface database to construct a set of contour equations. This effectively reduces the number of variables required for electromagnetic flaw detection, eliminates the need for other measurement information and initial values, overcomes the initial value problem, reduces the complexity of the inversion problem, and overcomes the problem of large inversion errors when the product of relative permeability and conductivity is too large or too small for a single-layer tubing string. It also overcomes the problem of requiring repeated changes to the excitation current amplitude in existing technologies, providing a favorable guarantee for accurate inversion of the conductivity and relative permeability of the tubing string. Furthermore, this scheme proposes a novel inversion approach based on the downhole pulsed eddy current method. The conductivity and relative permeability model is a longitudinal coil model, filling the gap in existing technologies for conductivity and relative permeability inversion methods using longitudinal coil models. When calculating the intersection points of contour lines, contour line interpolation and reconstruction techniques are employed to refine the discrete data of the constructed contour line equation system, improving solution accuracy. Reconstructing the interpolated discrete data ensures that the abscissa is within a consistent range, eliminating the possibility of multiple relative permeabilities corresponding to the same conductivity, thus effectively improving the stability of the inversion results. This scheme effectively improves inversion speed and accuracy and can be applied to ranges of relative permeability and conductivity that conform to the normal and reasonable range of downhole tubing, which is of great significance for wellbore integrity detection.

[0077] Figure 9 A structural block diagram of a downhole single-layer tubing conductivity and magnetic permeability inversion device according to an embodiment of this application is shown, as follows: Figure 9 As shown, the device includes: a first construction module 910, a forward simulation module 920, a second construction module 930, and an inversion module 940.

[0078] The first building module 910 is suitable for: constructing a forward time-domain induced voltage response model using relevant parameters of the column structure model.

[0079] The forward modeling simulation module 920 is suitable for: calculating the forward time-domain induced voltage decay response based on the forward time-domain induced voltage response model, using finite element or finite difference numerical simulation technology, and forming a simulation decay response surface database based on the forward time-domain induced voltage decay response.

[0080] The second construction module 930 is suitable for: acquiring measured attenuation data of the tubing, and constructing a set of contour equations based on the measured attenuation data and the simulated attenuation response surface database.

[0081] The inversion module 940 is suitable for: performing contour interpolation reconstruction and solving the contour equation system to obtain the conductivity and relative permeability of the tubular column.

[0082] Optionally, the relevant parameters of the tubular structure model include: sleeve parameters, probe parameters, and probe excitation parameters; the sleeve parameters include: sleeve outer diameter and sleeve thickness; the probe parameters include: coil shaft length, coil inner diameter, coil outer diameter, core size, core conductivity, core relative permeability, and coil wire diameter; the probe excitation parameters include: excitation current, excitation rise time, excitation fall time, and excitation period.

[0083] Optionally, the simulation attenuation response surface database includes: an attenuation surface library or a contour map library.

[0084] Optionally, the contour equation set includes: a decay time contour equation set, a decay time channel contour equation set, or a wall thickness contour equation set.

[0085] Optionally, the inversion module 940 is further adapted to: interpolate the discrete data of the contour equation system and reconstruct the interpolated discrete data; solve for the intersection points based on the reconstructed discrete data; and determine the conductivity and relative permeability of the tube based on the solved intersection points.

[0086] Optionally, the inversion module 940 is further adapted to: if there are multiple intersection points, calculate the residual between the forward-modeled time-domain induced voltage data corresponding to the multiple intersection points and the corresponding measured time-domain induced voltage data within a preset window range, and select the conductivity and relative permeability corresponding to the intersection point with the smallest residual as the conductivity and relative permeability of the tube, respectively; if there is only one intersection point, use the conductivity and relative permeability corresponding to the intersection point as the conductivity and relative permeability of the tube, respectively.

[0087] The inversion device for conductivity and permeability of a single-layer tubing string provided in this application utilizes measured attenuation data and a simulated attenuation response surface database to construct a set of contour equations. This effectively reduces the number of variables required for electromagnetic flaw detection, eliminating the need for other measurement information and initial values, thus overcoming the initial value problem and reducing the complexity of the inversion problem. It also overcomes the problem of large inversion errors when the product of relative permeability and conductivity is too large or too small for a single-layer tubing string, and overcomes the problem of requiring repeated changes to the excitation current amplitude in existing technologies. This provides a favorable guarantee for accurately inverting the conductivity and relative permeability of the tubing string. Furthermore, this scheme proposes a novel inversion approach based on the downhole pulsed eddy current method. The conductivity and relative permeability model is a longitudinal coil model, filling the gap in existing technologies for conductivity and relative permeability inversion methods using longitudinal coil models. When calculating the intersection points of contour lines, contour line interpolation and reconstruction techniques are employed to refine the discrete data of the constructed contour line equation system, improving solution accuracy. Reconstructing the interpolated discrete data ensures that the abscissa is within a consistent range, eliminating the possibility of multiple relative permeabilities corresponding to the same conductivity, thus effectively improving the stability of the inversion results. This scheme effectively improves inversion speed and accuracy and can be applied to ranges of relative permeability and conductivity that conform to the normal and reasonable range of downhole tubing, which is of great significance for wellbore integrity detection.

[0088] The present invention also provides a non-volatile computer storage medium storing at least one executable instruction that can execute the inversion method for the conductivity and magnetic permeability of a single-layer tubing in any of the above method embodiments.

[0089] This invention provides a computer program product comprising at least one executable instruction or computer program that enables a processor to perform operations corresponding to the downhole single-layer tubing conductivity and magnetic permeability inversion methods described in any of the above method embodiments.

[0090] Figure 10 The diagram shows a structural schematic of a computing device according to one embodiment of the present application. The specific embodiments of the present application do not limit the specific implementation of the computing device.

[0091] like Figure 10 As shown, the computing device may include: a processor 1002, a communication interface 1004, a memory 1006, and a communication bus 1008.

[0092] The processor 1002, communication interface 1004, and memory 1006 communicate with each other via communication bus 1008. Communication interface 1004 is used to communicate with other network elements, such as clients or other servers. Processor 1002 executes program 1010, specifically performing the relevant steps in the above-described embodiment of the method for inverting the conductivity and permeability of a single-layer tubing string in a well for calculating equipment.

[0093] Specifically, program 1010 may include program code that includes computer operation instructions.

[0094] The processor 1002 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application. The computing device includes one or more processors, which may be processors of the same type, such as one or more CPUs; or processors of different types, such as one or more CPUs and one or more ASICs.

[0095] Memory 1006 is used to store program 1010. Memory 1006 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device.

[0096] Specifically, program 1010 can be used to cause processor 1002 to execute the inversion method for the conductivity and permeability of a single-layer tubing in the above-described method embodiments. The specific implementation of each step in program 1010 can be found in the corresponding steps and units described in the above-described inversion embodiments for the conductivity and permeability of a single-layer tubing, and will not be repeated here. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the described equipment and modules can be referred to the corresponding process descriptions in the foregoing method embodiments, and will not be repeated here.

[0097] The algorithms and displays provided herein are not inherently related to any particular computer, virtual system, or other device. Various general-purpose systems can also be used in conjunction with the teachings herein. The required structure for constructing such systems is apparent from the above description. Furthermore, this invention is not directed to any particular programming language. It should be understood that the contents of the invention described herein can be implemented using various programming languages, and the above description of specific languages ​​is for the purpose of disclosing the best mode of implementation of the invention.

[0098] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0099] Similarly, it should be understood that, in order to streamline this disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0100] Those skilled in the art will understand that modules in the device of the embodiments can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiments can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components. Except where at least some of such features and / or processes or units are mutually exclusive, any combination can be used to combine all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or units of any method or device so disclosed. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose.

[0101] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0102] The various component embodiments of the present invention can be implemented in hardware, or as software modules running on one or more processors, or a combination thereof. Those skilled in the art will understand that microprocessors or digital signal processors (DSPs) can be used in practice to implement some or all of the functions of some or all of the components according to the embodiments of the present invention. The present invention can also be implemented as a device or apparatus program (e.g., a computer program and computer program product) for performing part or all of the methods described herein. Such programs implementing the present invention can be stored on a computer-readable medium, or can be in the form of one or more signals. Such signals can be downloaded from an Internet website, provided on a carrier signal, or provided in any other form.

[0103] It should be noted that the above embodiments are illustrative of the invention and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

Claims

1. A method for inverting the conductivity and permeability of a single-layer downhole tubing string, characterized in that, The method includes: Using the relevant parameters of the tubular structure model, a forward-modeling time-domain induced voltage response model is constructed; Based on the forward time-domain induced voltage response model, the forward time-domain induced voltage decay response is calculated using finite element or finite difference numerical simulation techniques, and a simulation decay response surface database is formed based on the forward time-domain induced voltage decay response. Obtain the measured attenuation data of the tubing, and construct a set of contour equations based on the measured attenuation data and the simulated attenuation response surface database; The contour line equations are reconstructed by contour line interpolation and solved to obtain the electrical conductivity and relative magnetic permeability of the tubular column. The contour equation set includes: a decay time contour equation set, a decay time channel contour equation set, or a wall thickness contour equation set. The step of constructing a set of contour equations based on the measured attenuation data and the simulated attenuation response surface database further includes: Based on the measured attenuation curve and the simulated attenuation curve in the simulated attenuation response surface database, two different attenuation times or attenuation time channels at the same location have the same conductivity and relative permeability. Using the measured attenuation curve at the nominal wall thickness and the coupling wall thickness, and based on the simulated attenuation response surface database, a set of attenuation time contour equations and a set of attenuation time channel contour equations are constructed. Based on the measured attenuation curve and the simulated attenuation curve in the simulated attenuation response surface database, which have the same conductivity and relative permeability at the nominal wall thickness and coupling wall thickness at the same attenuation time or attenuation time channel, the wall thickness contour equations are constructed using the measured values ​​of the attenuation curve at attenuation time one and attenuation time two, or attenuation time channel one and attenuation time channel two, according to the simulated attenuation response surface database. The step of reconstructing and solving the contour equations to obtain the conductivity and relative permeability of the tubular column further includes: Interpolate the discrete data of the contour line equation system, and reconstruct the interpolated discrete data; The intersection points are determined based on the reconstructed discrete data; the coordinates of the intersection points include electrical conductivity and relative magnetic permeability. If there are multiple intersection points, then based on the forward time-domain induced voltage data corresponding to the multiple intersection points, calculate the residual between the original and the corresponding measured time-domain induced voltage data within a preset window range, and select the conductivity and relative permeability corresponding to the intersection point with the smallest residual as the conductivity and relative permeability of the column, respectively. If there is only one intersection point, then the conductivity and relative permeability corresponding to the intersection point are taken as the conductivity and relative permeability of the tube column, respectively.

2. The method for inverting the conductivity and permeability of a single-layer downhole tubing string according to claim 1, characterized in that, The relevant parameters of the tubular structure model include: sleeve parameters, probe parameters, and probe excitation parameters; The casing parameters include: casing outer diameter and casing thickness; The probe parameters include: coil shaft length, coil inner diameter, coil outer diameter, core size, core conductivity, core relative permeability, and coil wire diameter. The probe excitation parameters include: excitation current, excitation rise time, excitation fall time, and excitation period.

3. The method for inverting the conductivity and permeability of a single-layer downhole tubing string according to claim 1, characterized in that, The simulation attenuation response surface database includes: an attenuation surface library or a contour map library.

4. A device for inverting the conductivity and magnetic permeability of a single-layer downhole tubing string, characterized in that, The device includes: The first building module is suitable for constructing a forward-modeling time-domain induced voltage response model using relevant parameters of the column structure model; The forward modeling simulation module is suitable for calculating the forward time-domain induced voltage decay response based on the forward time-domain induced voltage response model using finite element or finite difference numerical simulation techniques, and forming a simulation decay response surface database based on the forward time-domain induced voltage decay response. The second construction module is adapted to acquire the measured attenuation data of the tubing and construct a set of contour equations based on the measured attenuation data and the simulated attenuation response surface database. The inversion module is suitable for performing contour interpolation reconstruction and solving the contour equation system to obtain the conductivity and relative permeability of the tubular column; The contour equation set includes: a decay time contour equation set, a decay time channel contour equation set, or a wall thickness contour equation set. The second building module is further adapted to: Based on the measured attenuation curve and the simulated attenuation curve in the simulated attenuation response surface database, two different attenuation times or attenuation time channels at the same location have the same conductivity and relative permeability. Using the measured attenuation curve at the nominal wall thickness and the coupling wall thickness, and based on the simulated attenuation response surface database, a set of attenuation time contour equations and a set of attenuation time channel contour equations are constructed. Based on the measured attenuation curve and the simulated attenuation curve in the simulated attenuation response surface database, which have the same conductivity and relative permeability at the nominal wall thickness and coupling wall thickness at the same attenuation time or attenuation time channel, the wall thickness contour equations are constructed using the measured values ​​of the attenuation curve at attenuation time one and attenuation time two, or attenuation time channel one and attenuation time channel two, according to the simulated attenuation response surface database. The inversion module is further adapted to: Interpolate the discrete data of the contour line equation system, and reconstruct the interpolated discrete data; The intersection points are determined based on the reconstructed discrete data; the coordinates of the intersection points include electrical conductivity and relative magnetic permeability. If there are multiple intersection points, then based on the forward time-domain induced voltage data corresponding to the multiple intersection points, calculate the residual between the original and the corresponding measured time-domain induced voltage data within a preset window range, and select the conductivity and relative permeability corresponding to the intersection point with the smallest residual as the conductivity and relative permeability of the column, respectively. If there is only one intersection point, then the conductivity and relative permeability corresponding to the intersection point are taken as the conductivity and relative permeability of the tube column, respectively.

5. A computing device, characterized in that, include: The processor, memory, communication interface, and communication bus are provided, wherein the processor, memory, and communication interface communicate with each other via the communication bus. The memory is used to store at least one executable instruction that causes the processor to perform the operation corresponding to the inversion method of conductivity and permeability of a single-layer tubing string as described in any one of claims 1-3.

6. A computer storage medium, characterized in that, The computer storage medium stores at least one executable instruction that causes the processor to perform the operation corresponding to the inversion method of conductivity and permeability of a single-layer tubing string as described in any one of claims 1-3.

7. A computer program product, characterized in that, It includes at least one executable instruction that causes the processor to perform the operation corresponding to the inversion method of conductivity and permeability of a single-layer tubing string as described in any one of claims 1-3.

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