Casing wave relative amplitude correction method and system based on well cementation cement density

Abstract

The invention relates to a casing wave relative amplitude correction method and system based on well cementation cement density, and the method does not consider the influence of the cement density change on the casing wave amplitude during the actual well cementation quality evaluation, and simulates the full-wave waveform of sound waves received in a well through the methods of real axis integration and the like. The classic elastic wave theory and the slip interface theory are combined, and the method which is high in universality and is used for correcting the wave amplitude of the casing with the actually-measured cement density to the wave amplitude of the casing with the compared cement density is determined; according to the simulation result of the sound field in the well, the correction method has a reliable theoretical basis; the actual stratum and the rock physical model are combined, calculation is convenient and simple, universality is high, and applicability is wide.

Description

Technical Field

[0001] This disclosure belongs to the field of oil and gas exploration technology, and in particular relates to a method and system for correcting the relative amplitude of casing waves based on cement density. Background Technology

[0002] In the process of oil exploration and development, to isolate the formation and the oil, gas, and water within it, and to fix the position of the casing in the well, cement is generally used to fill the annular space between the casing and the wellbore. The casing, cement, and wellbore must be tightly bonded to achieve formation isolation and wellbore integrity. Cement is a key material for ensuring the functional integrity of oil and gas wells, playing a crucial role in supporting the casing, sealing complex underground formations, isolating underground oil, gas, and water layers, preventing cross-contamination, and protecting the producing formation. The quality of cement consolidation directly affects the safe, reliable, economical, and efficient extraction of oil and gas resources. Generally, after cementing operations are completed, the cementing quality inspection must meet the standards before proceeding to the next stage. In practice, due to well conditions and lithology, different cement densities are often used for cementing. Different cement densities have a significant impact on the relative amplitude of the casing wave; when the cement density is low, the relative amplitude of the first casing wave is significantly larger. Furthermore, during the cement solidification process, the cement density changes due to water loss, which complicates the evaluation of cement isolation in the annular space.

[0003] In production practice, acoustic logging methods are mainly used to detect and evaluate cementing quality. The main methods include non-directional cement bond logging (CBL) and variable density logging (VDL). Acoustic amplitude logging primarily relies on the casing wave amplitude measured by acoustic logging. Casing wave amplitude is affected by various factors: casing specifications, cement specifications, cement sheath thickness, formation lithology, etc. Cement bond logging (CBL) uses the amplitude of these casing waves to evaluate the quality of cement-casing bonding; however, variations in the amplitude or attenuation of a particular type of casing wave may be caused by multiple factors. Studies have found that when the bonding conditions are the same, the change in casing wave amplitude with increasing cement density is not linear. For example, when the bonding is good, the amplitude changes from 1.5 g / cm³ to... 3 Increased to 1.9 g / cm³ 3 The difference in relative amplitude was significantly greater than the difference in density from 1.9 g / cm³. 3 Increased to 2.3 g / cm³ 3 The difference in relative amplitude. Furthermore, the situation differs in soft formations compared to hard formations; for example, in well-cemented formations, the casing wave amplitude decreases with increasing cement density. Therefore, the influence of cement density needs to be comprehensively judged in conjunction with the actual situation. In the field, the industry standard for conventional cement is 1.9 g / cm³. 3 To eliminate the influence of cement density, it is necessary to correct the measured sleeve wave amplitude. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method and system for correcting the relative amplitude of casing waves based on cement density in order to solve the above-mentioned problems.

[0005] This disclosure achieves the above objectives through the following technical solutions:

[0006] A method for correcting the relative amplitude of casing waves based on cement density includes the following steps:

[0007] Within the selected depth range, acoustic waveforms at different depth points are obtained, the amplitude of the first wave of the casing wave is extracted and normalized, and the normalized well depth-acoustic amplitude curve L1 is obtained.

[0008] A physical model of the casing well was constructed, and the cementation degree-acoustic amplitude curve L2 was obtained based on the physical model of the casing well.

[0009] Based on the acoustic amplitude correspondence, the normalized well depth-acoustic amplitude curve L1 is compared with the cementing degree-acoustic amplitude curve L2 to obtain the cementing degree at different depths; the casing wave first wave amplitude at different cementing degrees is calculated by changing the cement density to obtain the casing wave first wave amplitude curve L3 under conventional cement density.

[0010] Calculate the ratio T of the first wave amplitude curve L3 of the casing wave under the conventional cement density to the cementation degree-sound amplitude curve L2. m Establish the first wave amplitude-correction value curve L4 of the casing wave;

[0011] Based on the casing wave first wave amplitude-correction value curve L4, the normalized well depth-acoustic amplitude curve L1 is corrected to obtain the well depth-acoustic amplitude curve L5 under conventional cement density.

[0012] As a further optimization of this disclosure, within a selected depth range, acoustic waveforms at different depth points are obtained, the amplitude of the first wave of the casing wave is extracted and normalized, and the normalized well depth-acoustic amplitude curve L1 is obtained, specifically including:

[0013] Within the selected depth range, acoustic amplitude logging is obtained through non-directional cement bonded logging and acoustic variable density logging. Based on the acoustic amplitude logging, acoustic waveforms at different depth points are obtained, and the first wave amplitude of the casing wave is extracted to obtain the well depth-acoustic amplitude curve L0.

[0014] Normalization was performed with the acoustic amplitude of the free casing section set to 1, resulting in the normalized well depth-acoustic amplitude curve L1.

[0015] As a further optimization of this disclosure, a cased well physical model is constructed, and the cementation degree-acoustic amplitude curve L2 obtained based on the cased well physical model specifically includes:

[0016] Obtain relevant data, including casing specifications, cement specifications, and formation parameters;

[0017] Based on the relevant data, the velocity-density parameters of the well fluid, casing, cement, and formation were obtained, and a physical model of the casing well was constructed.

[0018] The acoustic waveform of the casing well physical model was calculated using the real axis integral method. The amplitude of the first wave of the acoustic waveform of the casing well physical model was extracted and normalized with the free casing section as 1 to obtain the cementation degree-acoustic amplitude curve L2.

[0019] As a further optimization of this disclosure, the casing well physical model includes a free casing model, a casing well model with poor I-interface cementation represented by fluid ring thickness, a casing well model with relatively poor I-interface cementation represented by the shear coupling stiffness of the slip interface, and a well-cemented model.

[0020] As a further optimization of this disclosure, the formula for calculating the bonding degree-sound amplitude curve L2 is as follows:

[0021]

[0022] Where n represents the circumferential azimuth ordinal number, n = 0 indicates a monopole sound source; r represents the radial distance; k is the axial wavenumber; z is the axial distance; ω is the angular frequency; S(ω) is the source function; I n It is a type n-th order variant of the Bessel function; A n It is the acoustic amplitude coefficient inside the well.

[0023] As a further optimization of this disclosure, the formula for expressing the well-bonded model is as follows:

[0024]

[0025] Where fl, ca, ce, and for represent the well fluid, casing, cement, and formation, respectively; r0, r1, and r2 represent the radii of the wellbore, interface I, and interface II, respectively; T represents the coefficient matrix of the medium; Q represents the acoustic amplitude coefficients of the casing, cement, and formation; u f and σ f These represent the displacement and stress of the direct wave, respectively;

[0026] The expression formula for the casing well model with relatively poor cementation at interface I is as follows:

[0027]

[0028] Where M is a matrix relating to the coupling stiffness coefficients, expressed by the following formula:

[0029]

[0030] Where, η T η represents the shear coupling stiffness. N Indicates the normal coupling stiffness;

[0031] The formula for expressing the free sleeve model is as follows:

[0032]

[0033] The expression formula for the poorly cemented casing well model at interface I is as follows:

[0034]

[0035] Where d represents the thickness of the fluid ring.

[0036] As a further optimization of this disclosure, T is calculated. m The formula is as follows:

[0037]

[0038] Where A represents the acoustic amplitude coefficient within the well.

[0039] A casing wave relative amplitude correction system based on cement density includes:

[0040] The processing module is used to obtain the acoustic waveforms at different depth points within the selected depth range, extract the first wave amplitude of the casing wave and normalize it to obtain the normalized well depth-acoustic amplitude curve L1.

[0041] The model building module is used to build a physical model of the casing well and obtain the cementation degree-sound amplitude curve L2 based on the physical model of the casing well.

[0042] The comparison module is used to compare the normalized well depth-sound amplitude curve L1 with the cementation degree-sound amplitude curve L2 based on the sound amplitude correspondence to obtain the cementation degree at different depths; and to calculate the first wave amplitude of the casing wave at different cementation degrees by changing the cement density to obtain the first wave amplitude curve of the casing wave under conventional cement density L3.

[0043] The calculation module is used to calculate the ratio T of the first wave amplitude curve L3 of the casing wave under the conventional cement density to the cementation degree-sound amplitude curve L2. m Establish the first wave amplitude-correction value curve L4 of the casing wave;

[0044] The correction module is used to correct the normalized well depth-sound amplitude curve L1 based on the casing wave first wave amplitude-correction value curve L4, so as to obtain the well depth-sound amplitude curve L5 under conventional cement density.

[0045] An electronic device includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus;

[0046] Memory, used to store computer programs;

[0047] The processor, when executing a program stored in memory, implements a method for correcting the relative amplitude of casing waves based on cement density.

[0048] A computer-readable storage medium storing a computer program that, when executed by a processor, implements a method for correcting the relative amplitude of casing waves based on cement density.

[0049] The beneficial effects of this disclosure are as follows:

[0050] This disclosure does not consider the impact of changes in cement density on the casing wave amplitude when evaluating actual cementing quality. It simulates the full waveform of the acoustic waves received in the well using methods such as real-axis integration. Combining classical elastic wave theory and slip interface theory, it determines a universal method for correcting the casing wave amplitude of the measured cement density to that of the comparative cement density. The simulation results of the acoustic field in the well demonstrate that this correction method has a reliable theoretical basis. This disclosure combines actual formation and rock physics models, making the calculation convenient and simple, highly universal, and widely applicable. Attached Figure Description

[0051] Figure 1 This is a flowchart of the method disclosed herein;

[0052] Figure 2 This is a schematic diagram of a scale model wellbore established in the laboratory according to an embodiment of this disclosure;

[0053] Figure 3 This is a graph showing the relationship between fluid ring thickness and acoustic amplitude normalization under different cement densities in the embodiments of this disclosure.

[0054] Figure 4 This is a graph showing the relationship between different cementing shear coupling stiffness and acoustic amplitude normalization in the embodiments of this disclosure.

[0055] Figure 5 This is a sound amplitude-sound amplitude correction curve diagram for different cement densities in the embodiments of this disclosure;

[0056] Figure 6 This is a diagram showing the results of the calibration well processing in an embodiment of this disclosure;

[0057] Figure 7 This is a system structure block diagram in an embodiment of this disclosure;

[0058] Figure 8 This is a block diagram of the device structure in an embodiment of this disclosure. Detailed Implementation

[0059] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0060] like Figure 1 As shown, a method for correcting the relative amplitude of casing waves based on cement density includes the following steps:

[0061] Step 1: Within the selected depth range, obtain the acoustic waveforms at different depth points, extract the amplitude of the first wave of the casing wave and normalize it to obtain the normalized well depth-acoustic amplitude curve L1.

[0062] Specifically, within the selected depth range, acoustic amplitude logging is obtained through non-directional cement bonded logging and acoustic variable density logging. Based on the acoustic waveforms obtained at different depth points from the acoustic amplitude logging, the amplitude of the first wave of the casing wave is extracted to obtain the depth-acoustic amplitude curve L0. The acoustic amplitude of the free casing section is normalized to 1 (100%) to obtain the normalized depth-acoustic amplitude curve L1.

[0063] Step 2: Construct a physical model of the casing well and obtain the cementation degree-sound amplitude curve L2 based on the physical model of the casing well;

[0064] Specifically, based on the velocity-density parameters of the well fluid, casing, cement, and formation obtained from data such as casing specifications, cement specifications, and formation parameters, a physical model of the casing well is constructed; the acoustic waveform of the casing well model is calculated using the real axis integral method, the amplitude of the first wave of the casing wave is extracted, and normalization is performed with the free casing section as 1 (100%) to obtain the cementation degree-acoustic amplitude curve L2;

[0065] The established physical models of casing wells include a free casing model, a casing well model with poor I-interface cementation (represented by fluid ring thickness), a casing well model with relatively poor I-interface cementation (represented by shear coupling stiffness of the slip interface), and a well-cemented model.

[0066] Based on array acoustic logging, density logging, and caliper logging data within the depth range, actual data such as formation velocity, density, and caliper diameter are obtained. Based on this data, acoustic waveforms for different cementation conditions are simulated and calculated using the following formula:

[0067]

[0068] Where n represents the circumferential azimuth ordinal number, n = 0 indicates a monopole sound source; r represents the radial distance; k is the axial wavenumber; z is the axial distance; ω is the angular frequency; S(ω) is the source function; I n It is a type n-th order variant of the Bessel function; A n It is the acoustic amplitude coefficient inside the well, and the calculation method for the acoustic amplitude coefficient varies depending on the type of cementation.

[0069] a) Well bonded:

[0070]

[0071] Where "fl, ca, ce, for" represent the well fluid, casing, cement, and formation, respectively; "r0, r1, r2" represent the radii of the wellbore, interface I, and interface II; "T" represents the coefficient matrix of the medium (for the specific algorithm, see reference: Tang Xiaoming, Zheng Chuanhan. 2004. Quantitative Logging Acoustics. Beijing: Petroleum Industry Press, 20-50.); "Q" represents the acoustic amplitude coefficients of the casing, cement, and formation; u f and σ f This represents the displacement and stress of the direct wave.

[0072] b) Sliding interface:

[0073]

[0074] Where "M" is a matrix relating to the coupling stiffness coefficients:

[0075]

[0076] Depending on the stress, coupling stiffness can be divided into shear coupling stiffness η. T and normal coupling stiffness η N Normal coupling stiffness η N Taking infinity, the shear coupling stiffness η T The magnitude of η can indicate the degree of bonding, and the shear coupling stiffness is... T The larger the size, the better the bonding.

[0077] c) I interface does not bond:

[0078]

[0079] Wherein, "d" represents the thickness of the fluid ring.

[0080] d) Free sleeve:

[0081]

[0082] Step 3: Based on the acoustic amplitude correspondence, compare the normalized well depth-acoustic amplitude curve L1 with the cementing degree-acoustic amplitude curve L2 to obtain the cementing degree at different depths; change the cementing density to calculate the first wave amplitude of the casing wave at different cementing degrees to obtain the first wave amplitude curve of the casing wave under conventional cement density L3.

[0083] Specifically, based on the acoustic amplitude correspondence, the normalized well depth-acoustic amplitude curve L1 is compared with the cementation degree-acoustic amplitude curve L2 to obtain the cementation degree at different depths; different well sections are divided according to the cementation degree (preliminarily divided into fluid annular sections and coupling stiffness sections), and numbered from top to bottom (represented by m);

[0084] Without changing other parameters of the casing well physical model, only the cement density is changed (the cement density is set to the conventional cement density of 1.9 g / cm³). 3 (The same applies below), calculate the first wave amplitude of the casing wave under different degrees of cementation, and obtain the first wave amplitude curve L3 of the casing wave under conventional cement density;

[0085] Based on the normalized depth-amplitude curve L1 extracted from the acoustic amplitude logging waveform and the normalized amplitude of different cementation types calculated by simulation, the cementation status of this well section is determined and sorted from top to bottom. The cementation status determined in this way is more accurate and more in line with reality.

[0086] The other conditions of the casing well model remain unchanged, except that the measured cement density is changed to the conventional cement density. This casing well model is the model compared in this invention.

[0087] Step 4: Calculate the ratio T of the first wave amplitude curve L3 of the casing wave under conventional cement density to the cementation degree-sound amplitude curve L2. m Establish the first wave amplitude-correction value curve L4 of the casing wave;

[0088] Specifically, calculate the ratio T of the first wave amplitude curve L3 of the casing wave under conventional cement density to the cementation degree-sound amplitude curve L2. m Establish the first wave amplitude-correction value curve L4 of the casing wave;

[0089] Correction value T m It is the ratio of the initial wave amplitude of the casing wave at conventional cement density, calculated theoretically under the same cementing conditions, to the initial wave amplitude of the casing wave at actual cement density. The calculation formula is:

[0090]

[0091] Step 5: Correct the normalized well depth-acoustic amplitude curve L1 based on the casing wave first wave amplitude-correction value curve L4 to obtain the well depth-acoustic amplitude curve L5 under conventional cement density.

[0092] Specifically, the correction value T for different well sections is obtained segment by segment based on the casing wave initial amplitude-correction value curve L4 and the normalized well depth-acoustic amplitude curve L1. m This yields the well depth-sonic amplitude curve L5, which corrects the cement density from the actual casing wave amplitude to the standard cement density.

[0093] The following detailed description of specific embodiments of this invention supports the technical problem to be solved by the present invention.

[0094] Figure 2 This is a schematic diagram of the wellbore of the calibration model well established in the laboratory. The reason for selecting this well is that the wellbore contains cement rings with four different cement densities and free casing sections, and the formation lithology is sandstone, which can clearly demonstrate the correctness of the calibration method.

[0095] Figure 2 The density of the cement used for cementing the well, from top to bottom, is 1.0 g / cm³. 3 (Water), 1.2gcm 3 1.5gcm 3 1.89gcm 3 2.25gcm 3 The uppermost layer is a free casing section, with each section being 2m long. Since this wellbore is a calibrated well, parameters such as formation velocity, density, well diameter, and the cementation status of the wellbore are known. Therefore, this invention uses cement with a density of 1.2 g / cm³. 3 1.5gcm 3 2.25gcm 3 The well section was used as a correction section, with a cement density of 1.89 g / cm³. 3 The well section in question is the comparison well section;

[0096] Figure 3 and Figure 4 The graph shows the relationship between fluid ring thickness, shear coupling stiffness, and normalized acoustic amplitude under different cement densities, calculated using the real axis integral method. A larger fluid ring thickness or a smaller shear coupling stiffness indicates poorer cementation quality. The graph also shows that as cement density decreases, the normalized amplitude of the casing wave's initial wave increases; this variation is independent of the cementation condition.

[0097] Figure 5 The density of cementing cement under different bonding conditions is 1.2 g / cm³. 3 1.5gcm 3 and 2.25gcm 3 The normalized amplitude of the casing wave and the cement density are 1.89 g / cm³. 3By comparing the normalized amplitude of the casing wave, the amplitude-sound amplitude correction curve under different cement densities is obtained, and the calibration well is corrected according to the curve.

[0098] Figure 6 The two curves in the first passage are the CBL curve (CBL) and the CBL amplitude correction curve (CBL_corr). Comparing the two curves, it can be found that at 1.2 gcm 3 1.5gcm 3 The CBL curves for the two segments are larger than the CBL_corr curve. Before correction, the minimum values ​​for the two segments were 7.1% and 2.86%, respectively, while after correction, the minimum values ​​were 1.023% and 0.96%. At 2.25 g / cm³... 3 The CBL curve for the layer is smaller than the CBL_corr curve; the minimum value before correction is 0.4%, and the minimum value after correction is 1.1%; the cement density is 1.89 g / cm³. 3 The minimum value of the segment is 0.85%, which shows that the CBL curves of different cement densities, after correction, are close to the CBL values ​​of conventional cement densities. This demonstrates the correctness and strong adaptability of the correction method of the invention.

[0099] like Figure 7 As shown, embodiments of this disclosure provide a casing wave relative amplitude correction system based on cement density, comprising:

[0100] The processing module is used to obtain the acoustic waveforms at different depth points within the selected depth range, extract the first wave amplitude of the casing wave and normalize it to obtain the normalized well depth-acoustic amplitude curve L1.

[0101] The model building module is used to build a physical model of the casing well and obtain the cementation degree-sound amplitude curve L2 based on the physical model of the casing well.

[0102] The comparison module is used to compare the normalized well depth-sound amplitude curve L1 with the cementation degree-sound amplitude curve L2 based on the sound amplitude correspondence to obtain the cementation degree at different depths; and to calculate the first wave amplitude of the casing wave at different cementation degrees by changing the cement density to obtain the first wave amplitude curve of the casing wave under conventional cement density L3.

[0103] The calculation module is used to calculate the ratio T of the first wave amplitude curve L3 of the casing wave under the conventional cement density to the cementation degree-sound amplitude curve L2. m Establish the first wave amplitude-correction value curve L4 of the casing wave;

[0104] The correction module is used to correct the normalized well depth-sound amplitude curve L1 based on the casing wave first wave amplitude-correction value curve L4, so as to obtain the well depth-sound amplitude curve L5 under conventional cement density.

[0105] The implementation process of the functions and roles of each module in the above system is detailed in the implementation process of the corresponding steps in the above method, and will not be repeated here.

[0106] For the system embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The system embodiments described above are merely illustrative. The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this disclosure according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0107] In the above embodiments, any number of modules can be combined into one module, or any one module can be split into multiple modules. Alternatively, at least some functionality of one or more modules can be combined with at least some functionality of other modules and implemented in one module. At least one of the modules can be at least partially implemented as hardware circuitry, such as a Field Programmable Gate Array (FPGA), a Programmable Logic Array (PLA), a System-on-Chip, a System-on-Substrate, a System-on-Package, an Application-Specific Integrated Circuit (ASIC), or any other reasonable method of integrating or packaging circuitry, or implemented in software, hardware, or firmware, or in any suitable combination of any of these three methods. Alternatively, at least one of the modules can be at least partially implemented as a computer program module that, when run, performs a corresponding function.

[0108] See Figure 8 The electronic device provided in the embodiments of this disclosure includes a processor 1110, a communication interface 1120, a memory 1130 and a communication bus 1140, wherein the processor 1110, the communication interface 1120 and the memory 1130 communicate with each other through the communication bus 1140.

[0109] Memory 1130 is used to store computer programs;

[0110] When the processor 1110 executes the program stored in the memory 1130, it implements the following method for correcting the relative amplitude of casing waves based on cement density.

[0111] The aforementioned communication bus 1140 can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. This communication bus 1140 can be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, it is represented by only one thick line in the figure, but this does not indicate that there is only one bus or one type of bus.

[0112] The communication interface 1120 is used for communication between the above-mentioned electronic device and other devices.

[0113] The memory 1130 may include random access memory (RAM) or non-volatile memory, such as at least one disk storage device. Optionally, the memory 1130 may also be at least one storage device located remotely from the aforementioned processor 1110.

[0114] The processor 1110 mentioned above can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0115] Embodiments of this disclosure also provide a computer-readable storage medium. The computer-readable storage medium stores a computer program that, when executed by a processor, implements the casing wave relative amplitude correction method based on cement density as described above.

[0116] The computer-readable storage medium may be included in the device / apparatus described in the above embodiments; or it may exist independently and not assembled into the device / apparatus. The computer-readable storage medium carries one or more programs that, when executed, implement the casing wave relative amplitude correction method based on cement density according to embodiments of this disclosure.

[0117] According to embodiments of this disclosure, the computer-readable storage medium can be a non-volatile computer-readable storage medium, such as including, but not limited to: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this disclosure, the computer-readable storage medium can be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0118] The embodiments described above are merely examples of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these modifications and improvements all fall within the protection scope of this disclosure.

Claims

1. A method for correcting the relative amplitude of casing waves based on cement density, characterized in that, Includes the following steps: Within the selected depth range, acoustic waveforms at different depth points are obtained, the amplitude of the first wave of the casing wave is extracted and normalized, and the normalized well depth-acoustic amplitude curve L1 is obtained. A physical model of the casing well was constructed, and the cementation degree-acoustic amplitude curve L2 was obtained based on the physical model of the casing well. Based on the acoustic amplitude correspondence, the normalized well depth-acoustic amplitude curve L1 is compared with the cementing degree-acoustic amplitude curve L2 to obtain the cementing degree at different depths; the casing wave first wave amplitude at different cementing degrees is calculated by changing the cement density to obtain the casing wave first wave amplitude curve L3 under conventional cement density. Calculate the ratio T of the first wave amplitude curve L3 of the casing wave under the conventional cement density to the cementation degree-sound amplitude curve L2. m Establish the first wave amplitude-correction value curve L4 of the casing wave; Based on the casing wave first wave amplitude-correction value curve L4, the normalized well depth-acoustic amplitude curve L1 is corrected to obtain the well depth-acoustic amplitude curve L5 under conventional cement density.

2. The method for correcting the relative amplitude of casing waves based on cement density according to claim 1, characterized in that, Within the selected depth range, acoustic waveforms at different depth points are obtained. The amplitude of the first wave of the casing wave is extracted and normalized to obtain the normalized well depth-acoustic amplitude curve L1, which specifically includes: Within the selected depth range, acoustic amplitude logging is obtained through non-directional cement bonded logging and acoustic variable density logging. Based on the acoustic amplitude logging, acoustic waveforms at different depth points are obtained, and the first wave amplitude of the casing wave is extracted to obtain the well depth-acoustic amplitude curve L0. Normalization was performed with the acoustic amplitude of the free casing section set to 1, resulting in the normalized well depth-acoustic amplitude curve L1.

3. The method for correcting the relative amplitude of casing waves based on cement density according to claim 1, characterized in that, Constructing a physical model of the casing well, and obtaining the cementation degree-acoustic amplitude curve L2 based on the physical model, specifically includes: Obtain relevant data, including casing specifications, cement specifications, and formation parameters; Based on the relevant data, the velocity-density parameters of the well fluid, casing, cement, and formation were obtained, and a physical model of the casing well was constructed. The acoustic waveform of the casing well physical model was calculated using the real axis integral method. The amplitude of the first wave of the acoustic waveform of the casing well physical model was extracted and normalized with the free casing section as 1 to obtain the cementation degree-acoustic amplitude curve L2.

4. The method for correcting the relative amplitude of casing waves based on cement density according to claim 3, characterized in that, The physical model of the casing well includes a free casing model, a casing well model with poor I-interface cementation represented by fluid ring thickness, a casing well model with relatively poor I-interface cementation represented by shear coupling stiffness of the slip interface, and a well-cemented model.

5. The method for correcting the relative amplitude of casing waves based on cement density according to claim 4, characterized in that, The formula for calculating the bonding degree-sound amplitude curve L2 is as follows: Where n represents the circumferential azimuth ordinal number, n = 0 indicates a monopole sound source; r represents the radial distance; k is the axial wavenumber; z is the axial distance; ω is the angular frequency; S(ω) is the source function; I n It is a type n-th order variant of the Bessel function; A n It is the acoustic amplitude coefficient inside the well.

6. The method for correcting the relative amplitude of casing waves based on cement density according to claim 5, characterized in that, The formula for expressing the well-bonded model is as follows: Where fl, ca, ce, and for represent the well fluid, casing, cement, and formation, respectively; r0, r1, and r2 represent the radii of the wellbore, interface I, and interface II, respectively; T represents the coefficient matrix of the medium; Q represents the acoustic amplitude coefficients of the casing, cement, and formation; u f and σ f These represent the displacement and stress of the direct wave, respectively; The expression formula for the casing well model with relatively poor cementation at interface I is as follows: Where M is a matrix relating to the coupling stiffness coefficients, expressed by the following formula: Where, η T η represents the shear coupling stiffness. N Indicates the normal coupling stiffness; The formula for expressing the free sleeve model is as follows: The expression formula for the poorly cemented casing well model at interface I is as follows: Where d represents the thickness of the fluid ring.

7. The method for correcting the relative amplitude of casing waves based on cement density according to claim 6, characterized in that, Calculate T m The formula is as follows: Where A represents the acoustic amplitude coefficient within the well.

8. A casing wave relative amplitude correction system based on cement density, characterized in that, include: The processing module is used to obtain the acoustic waveforms at different depth points within the selected depth range, extract the first wave amplitude of the casing wave and normalize it to obtain the normalized well depth-acoustic amplitude curve L1. The model building module is used to build a physical model of the casing well and obtain the cementation degree-sound amplitude curve L2 based on the physical model of the casing well. The comparison module is used to compare the normalized well depth-sound amplitude curve L1 with the cementation degree-sound amplitude curve L2 based on the sound amplitude correspondence to obtain the cementation degree at different depths; and to calculate the first wave amplitude of the casing wave at different cementation degrees by changing the cement density to obtain the first wave amplitude curve of the casing wave under conventional cement density L3. The calculation module is used to calculate the ratio T of the first wave amplitude curve L3 of the casing wave under the conventional cement density to the cementation degree-sound amplitude curve L2. m Establish the first wave amplitude-correction value curve L4 of the casing wave; The correction module is used to correct the normalized well depth-sound amplitude curve L1 based on the casing wave first wave amplitude-correction value curve L4, so as to obtain the well depth-sound amplitude curve L5 under conventional cement density.

9. An electronic device, characterized in that, It includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; A processor, when executing a program stored in a memory, implements the casing wave relative amplitude correction method based on cement density as described in any one of claims 1-7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the casing wave relative amplitude correction method based on cement density as described in any one of claims 1-7.

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