Oil and gas well liquid level depth calculation method based on sound velocity compensation correction

Abstract

The invention discloses an oil-gas well liquid level depth calculation method based on sound velocity compensation correction, and belongs to the technical field of oil-gas well acoustic logging. Actually measured sound velocity is adopted to identify whole-well theoretical sound velocity calculation model parameters, and compensation calculation is carried out on a section without an effective joint hoop through a theoretical sound velocity model, so that the whole-well sound velocity is obtained; and finally, the accuracy and reliability of liquid level depth measurement can be effectively improved by adopting a method for calculating the liquid level depth by adopting a segmented integral approximation mode based on the whole well sound velocity.

Description

Technical Field

[0001] The invention relates to a method for calculating the liquid level depth of an oil and gas well based on sound velocity compensation correction, and belongs to the technical field of oil and gas well sonic logging. Background Art

[0002] In the production of oil and gas wells, the liquid level depth is the core indicator for evaluating and optimizing the adaptability of oil production process. At present, there are three main methods for measuring the liquid level of oil wells: the float method, the pressure gauge detection method, and the sound velocity method. The float method uses a float immersed in the oil to measure the dynamic liquid level of the oil well. Although this method is simple to operate, it is affected by the volume, weight and human error of the float itself, and its scope of use is very limited; the pressure gauge detection method is to place the pressure gauge on the oil and measure its pressure value. Its measurement result is more accurate, but the measurement is complex and the cost is high. It is often used as one of the means of precise monitoring. The acoustic wave method is to calculate the depth through the reflection of sound waves in the annulus of the casing. This method is simple to operate, low in cost, and can be used as an effective means of long-term depth monitoring, but the accuracy of the depth calculation is greatly affected by the sound velocity. The existing liquid level depth calculation method based on the sound velocity usually uses the sound velocity calculated at the wellhead as the average sound velocity of the whole well, and there is a problem of large deviation in the calculation result of the liquid level depth. Summary of the invention

[0003] In order to improve the above technical problems, the present invention provides a method for calculating the liquid level depth of an oil and gas well based on sound velocity compensation correction, which improves the accuracy of the calculation result of the liquid level depth.

[0004] The present invention provides a method for calculating the liquid level depth of an oil and gas well based on sound velocity compensation correction, comprising the following steps:

[0005] S1: Install a liquid level measurement device at the wellhead of an oil and gas well to obtain acoustic logging data, including the original liquid surface wave time domain signal A and the hoop wave time domain signal B. Perform noise reduction and filtering on the acoustic logging signal, calculate the effective hoop length N through the hoop wave time domain signal B after noise reduction, and calculate the reflected liquid surface position L through the liquid surface wave time domain signal A after noise reduction. 0 and its corresponding time t 0 ;

[0006] S2: Determine L in S1 0 Is it necessary to compensate and correct the full-well sound velocity through the full-well theoretical sound velocity model? 0 When N is less than or equal to L, there is no need to compensate for the sound velocity. The effective node is directly used to calculate the segmented sound velocity, and then the segmented integral approximation method is used to calculate the liquid level depth of the oil well. 0 When , go to the next step;

[0007] S3: Compensate and correct the full-well acoustic velocity, and calculate the downhole pressure model P under different well depth conditions H , Downhole temperature calculation model T under different well depth conditions H and related technical detection methods to obtain the gas component parameters X=[x 1 , x 2 , …x k ]; Establish a theoretical model for calculating the speed of sound V(H) = f(P H , T H , X);

[0008] S4: Using the measured sound velocity data of the effective collar section calculated in step S2, the full-well theoretical sound velocity calculation model established in step S3 is subjected to parameter identification. The identified parameters include formation temperature gradient β, natural gas relative density γ g ; Use the identified parameters to calculate the sound velocity between the end position of the effective section and the reflected wave liquid surface position, so as to obtain the data of the full-well sound velocity from the wellhead to the reflected liquid surface wave position;

[0009] S5: Perform polynomial linear fitting using the full-well acoustic velocity data obtained in step S4 to obtain a relationship between the full-well acoustic velocity and the well depth H: V = ζ(H);

[0010] S6: The time corresponding to the reflected liquid surface position is calculated by the liquid surface reflection wave as t 0 , in seconds, is approximated by the following piecewise integration 0 The actual liquid level depth H can be calculated by r ;

[0011]

[0012] In the formula, h represents the segment depth step, Δt represents the deviation threshold of time integration, i represents the total number of calculated segments, and H r Indicates the actual liquid level depth obtained by calculation.

[0013] Furthermore, the length of the effective knot hoop segment in S1 is calculated as follows: the knot hoop data segment whose peak-to-peak value is greater than the adaptive threshold δ is taken as the effective knot hoop data, and the adaptive threshold is δ=a×δ max , δ max represents the maximum peak-to-peak value of the node hoop, and a represents the proportional coefficient.

[0014] Furthermore, the calculation formula for the time from the position of the reflected liquid surface wave in S1 to the corresponding time is:

[0015] t 0 =L 0 / f

[0016] Wherein, f is the sampling rate of the liquid surface wave time domain signal and the hoop wave time domain signal.

[0017] Furthermore, the segmented sound velocity calculation method of the effective node hoop segment in S2 is: perform autocorrelation calculation on the effective node hoop segment length N, segment the data of the autocorrelation signal according to the sliding window of length M, and then perform fast Fourier transform on the data in the sliding window to obtain the frequency characteristics of the sliding window, and take the frequency with the largest amplitude as the node hoop frequency f of the sliding window M1 , then the sound speed of this section is expressed as:

[0018]

[0019] Where, Len represents the length of the oil pipe;

[0020] The segment speed The corresponding well depth is:

[0021]

[0022] The sliding window is slid with a sliding step length W, and the actual sound velocity is calculated according to the above steps. The depth corresponding to the sound velocity is the depth of the previous section plus the time corresponding to the sliding step length multiplied by the sound velocity of this section, until the sliding window slides to the end of the valid node hoop data section. The depth calculation formula corresponding to the k-th sliding of the sliding window is as follows:

[0023]

[0024] In the formula, Indicates the depth corresponding to the k-1th time.

[0025] Furthermore, S3 also includes the following steps:

[0026] S31: A theoretical model is constructed for the speed of sound under different conditions. The calculation formula for the speed of sound is as follows:

[0027]

[0028] Among them, Z is the compression factor, c v represents isovolumetric heat capacity, c p represents isobaric heat capacity, R represents the ideal gas constant, T represents temperature, ρ represents gas density, represents the first-order partial differential of the compressibility coefficient Z with respect to temperature ρ;

[0029] S32: Establishing the downhole temperature calculation model T under different well depth conditions H , the temperature T corresponding to any depth H in the well can be obtained by calculating the wellhead temperature H The full-well temperature calculation model uses an engineering experience model to describe the relationship between downhole temperature and well depth, which is specifically expressed as follows:

[0030] T H =βH+T 0

[0031] Where H represents the well depth; T 0 represents the temperature at the wellhead, and β represents the formation temperature gradient;

[0032] S33: Establish downhole pressure calculation model P under different well depth conditions H , the gas pressure P corresponding to any depth H in the well can be obtained by calculating the casing pressure at the wellhead H The full well pressure calculation model adopts the static pressure gas column theory, which is specifically expressed as follows:

[0033] P H =p C e S

[0034]

[0035] Among them, p c represents the wellhead pressure; γ g —Relative density of natural gas; —mean absolute temperature of the gas; —Gas average deviation coefficient, e represents the base of the natural logarithm:

[0036] S34: The temperature T at different well depths H and pressure P H By bringing in the theoretical sound velocity calculation model, a full-well theoretical sound velocity calculation model can be established to realize the theoretical sound velocity calculation from the wellhead to any position underground:

[0037] V(H)=f(P H , T H ,X).

[0038] By adopting the above technical scheme, the advantages of the present invention are: for shallow wells, a more accurate liquid level depth result can be calculated by means of piecewise integration of the measured sound velocity; for deep wells or ultra-deep wells, there are relatively long data segments without effective node collars in the acoustic wave signal, and the sound velocity of the whole well without effective node collar segments is calculated by using the identified full-well theoretical sound velocity calculation model, thereby obtaining the sound velocity of the whole well, and then calculating the liquid level depth result by means of piecewise integration approximation of the whole-well sound velocity, thereby effectively enhancing the accuracy of the liquid level depth calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the acoustic logging system structure;

[0040] Figure 2 Diagnostic flow chart of the calculation method of the liquid level depth of oil and gas wells with online compensation of sonic velocity;

[0041] Figure 3 It is a schematic diagram of full-well sound velocity calculation based on sound velocity compensation correction;

[0042] Figure 4 It is a schematic diagram of the calculation results based on the full-well acoustic velocity compensation correction;

[0043] In the figure: 1 - pumping unit 2 - transmitting sound wave 3 - sound wave generating and receiving device 4 - receiving sound wave 5 - casing 6 - joint collar 7 - oil pipe 8 - liquid level 9 - pressure and temperature transmitter. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0045] The terms "first", "second", etc. (if any) in the specification and claims of the present invention are used to distinguish similar objects, rather than to describe a specific order or sequence. Even if "second" is used to distinguish before a certain technical feature, it does not necessarily indicate that "first" is present. It should be understood that in the present invention, "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. It should be understood that in the present invention, "multiple" refers to two or more. "And / or" is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, X and / or Y can represent: X exists alone, X and Y exist at the same time, and Y exists alone. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "Containing X, Y and Z", "Containing X, Y, Z" means that X, Y, and Z are all included, "Containing X, Y or Z" means that one of X, Y, and Z is included, and "Containing X, Y and / or Z" means that any one, any two, or three of X, Y, and Z are included.

[0046] like Figures 1 to 4 As shown, the present invention provides a method for calculating the liquid level depth of an oil and gas well based on sound velocity compensation correction, comprising the following steps:

[0047] S1: Install a liquid level measurement device at the wellhead of an oil and gas well to obtain acoustic logging data, including the original liquid surface wave time domain signal A and the hoop wave time domain signal B. Perform noise reduction and filtering on the acoustic logging signal, calculate the effective hoop length N through the hoop wave time domain signal B after noise reduction, and calculate the reflected liquid surface position L through the liquid surface wave time domain signal A after noise reduction. 0 and its corresponding time t 0 ;

[0048] S2: Determine L in S1 0 Is it necessary to compensate and correct the full-well sound velocity through the full-well theoretical sound velocity model? 0 When N is less than or equal to L, there is no need to compensate for the sound velocity. The effective node is directly used to calculate the segmented sound velocity, and then the segmented integral approximation method is used to calculate the liquid level depth of the oil well. 0 When , go to the next step;

[0049] S3: Compensate and correct the full-well acoustic velocity, and calculate the downhole pressure model P under different well depth conditions H , Downhole temperature calculation model T under different well depth conditions H and related technical detection methods to obtain the gas component parameters X=[x 1 , x 2 , …x k ]; Establish a theoretical model for calculating the speed of sound V(H) = f(P H , T H , X);

[0050] S4: Using the measured sound velocity data of the effective collar section calculated in step S2, the full-well theoretical sound velocity calculation model established in step S3 is subjected to parameter identification. The identified parameters include formation temperature gradient β, natural gas relative density γ g ; Use the identified parameters to calculate the sound velocity between the end position of the effective section and the reflected wave liquid surface position, so as to obtain the data of the full-well sound velocity from the wellhead to the reflected liquid surface wave position;

[0051] S5: Perform polynomial linear fitting using the full-well acoustic velocity data obtained in step S4 to obtain a relationship between the full-well acoustic velocity and the well depth H: V = ζ(H);

[0052] S6: The time corresponding to the reflected liquid surface position is calculated by the liquid surface reflection wave as t 0 , in seconds, is approximated by the following piecewise integration 0 The actual liquid level depth H can be calculated by r ;

[0053]

[0054] In the formula, h represents the segment depth step, Δt represents the deviation threshold of time integration, i represents the total number of calculated segments, and H r Indicates the actual liquid level depth obtained by calculation.

[0055] The present invention can calculate a more accurate liquid level depth result for shallow wells by means of piecewise integration of the measured sound velocity. For deep wells or ultra-deep wells, there is a relatively long data segment without effective node collars in the acoustic wave signal. The sound velocity of the segment not containing the effective node collar is calculated by using the identified full-well theoretical sound velocity calculation model, thereby obtaining the sound velocity of the full well. The liquid level depth result is then calculated by means of piecewise integration approximation of the full-well sound velocity, thereby effectively enhancing the accuracy of the liquid level depth calculation.

[0056] Specifically, the length of the effective knot segment in S1 is calculated as follows: the knot data segment whose peak-to-peak value of the knot data is greater than the adaptive threshold δ is taken as the effective knot data, and the adaptive threshold is δ=a×δ max , δ max represents the maximum peak-to-peak value of the node hoop, and a represents the proportional coefficient.

[0057] The peak-to-peak value is the difference between the maximum and minimum values ​​of the section hoop length data;

[0058] Among them, the calculation formula from the position of the reflected liquid surface wave in S1 to the corresponding time is:

[0059] t 0 =L 0 / f

[0060] Wherein, f is the sampling rate of the liquid surface wave time domain signal and the hoop wave time domain signal.

[0061] Specifically, the segmented sound velocity calculation method of the effective node hoop segment in S2 is: perform autocorrelation calculation on the effective node hoop segment length N, perform data segmentation interception on the autocorrelation signal according to a sliding window of length M, and then perform fast Fourier transform on the data in the sliding window to obtain the frequency characteristics of the sliding window, and take the frequency with the largest amplitude as the node hoop frequency f of the sliding window M1 , then the sound speed of this section is expressed as:

[0062]

[0063] Where, Len represents the length of the oil pipe;

[0064] The segment speed The corresponding well depth is:

[0065]

[0066] The sliding window is slid with a sliding step length W, and the actual sound velocity is calculated according to the above steps. The depth corresponding to the sound velocity is the depth of the previous section plus the time corresponding to the sliding step length multiplied by the sound velocity of this section, until the sliding window slides to the end of the valid node hoop data section. The depth calculation formula corresponding to the k-th sliding of the sliding window is as follows:

[0067]

[0068] In the formula, Indicates the depth corresponding to the k-1th time.

[0069] Specifically, S3 also includes the following steps:

[0070] S31: A theoretical model is constructed for the speed of sound under different conditions. The calculation formula for the speed of sound is as follows:

[0071]

[0072] Among them, Z is the compression factor, c v represents isovolumetric heat capacity, c p represents isobaric heat capacity, R represents the ideal gas constant, T represents temperature, ρ represents gas density, represents the first-order partial differential of the compressibility coefficient Z with respect to temperature ρ;

[0073] S32: Establishing the downhole temperature calculation model T under different well depth conditions H , the temperature T corresponding to any depth H in the well can be obtained by calculating the wellhead temperature H The full-well temperature calculation model uses an engineering experience model to describe the relationship between downhole temperature and well depth, which is specifically expressed as follows:

[0074] T H =βH+T 0

[0075] Where H represents the well depth; T 0 represents the temperature at the wellhead, and β represents the formation temperature gradient;

[0076] S33: Establish downhole pressure calculation model P under different well depth conditions H , the gas pressure P corresponding to any depth H in the well can be obtained by calculating the casing pressure at the wellhead H The full well pressure calculation model adopts the static pressure gas column theory, which is specifically expressed as follows:

[0077] P H =p C e S

[0078]

[0079] Among them, p c represents the wellhead pressure; γ g —Relative density of natural gas; —mean absolute temperature of the gas; —Gas average deviation coefficient, e represents the base of the natural logarithm:

[0080] S34: The temperature T at different well depthsH and pressure P H By bringing in the theoretical sound velocity calculation model, a full-well theoretical sound velocity calculation model can be established to realize the theoretical sound velocity calculation from the wellhead to any position underground:

[0081] V(H)=f(P H , T H ,X).

[0082] The specific principles and processes are as follows: The schematic diagram of the dual-channel liquid level test device system is as follows: Figure 1 As shown, a dual-channel liquid level test device is installed at the wellhead casing interface. The sound wave generating and receiving device 3 in the device includes a sound wave generator, a microphone, and a hardware filter sampling circuit component. The sound wave generator generates sound waves, and the microphone receives sound waves and converts them into electrical signals. The pressure and temperature sensor 9 can collect and obtain the wellhead casing pressure and temperature values ​​as one of the input parameters of the full-well sound velocity theoretical calculation model. The gas component parameters in the oil and gas well need to be obtained through relevant technical analysis methods, such as gas chromatography, infrared spectroscopy or photoacoustic spectroscopy.

[0083] The original signals of the liquid surface wave time domain signal A and the hoop wave time domain signal B obtained by field testing, the signal hardware sampling frequency is 500Hz, and the single test liquid surface wave time domain signal A and the hoop wave time domain signal B are the data collected continuously for 20s by the liquid surface testing device. After obtaining the test data, the liquid surface depth value can be calculated by using the method for calculating the liquid surface depth of oil and gas wells based on sound velocity compensation correction described in the present invention. The calculation process is as follows: Figure 2 As shown, the specific steps are as follows:

[0084] (1) The original liquid surface wave time domain signal A and the hoop wave time domain signal B are subjected to noise reduction and filtering processing on the acoustic logging signal, such as Figure 3 As shown in the figure, the proportional coefficient a can be set to 0.3. The effective length of the effective segment data is calculated by the effective segment data length calculation method for the noise-reduced segment wave time domain signal, which is 3036. The sampling point L corresponding to the position of the reflected liquid surface wave is 0 is 6281, and the corresponding time is t 0 , the unit is 12.56 seconds; because the position of the reflected liquid surface wave is greater than the effective collar data length, the full well theoretical sound velocity calculation model is used to calculate and compensate for the section that does not contain the effective collar;

[0085] (2) The effective node segment data is segmented and the sound velocity is calculated. For the effective node segment number with a data length of 3036, the autocorrelation calculation is first performed. The sliding window length is selected as 256, and the tubing length Len is taken as 9.8 meters. The data in the sliding window is fast Fourier transformed, and the frequency with the largest amplitude is taken as the node frequency f of the sliding window. M1 , then the speed of sound in this section is: The measured sound speed The corresponding well depth is: Take the sliding step length as 128, slide the sliding window to the right of the data, and form a new sliding window with a length of 256. The actual sound speed is calculated in the same way as above. The depth corresponding to the sound speed is the depth of the previous section plus the time corresponding to the sliding step length multiplied by the sound speed of this section. The depth corresponding to the sliding window sliding kth time is represents the depth corresponding to the k-1th time, and 22 sets of measured sound speed and its corresponding depth data are calculated by the above method;

[0086] (3) The wellhead pressure and temperature corresponding to the test data are 6 MPa and 25°C, respectively. By querying the gas detection records of the well, the gas composition parameters in the test well are shown in Table 1.

[0087]

[0088]

[0089] Table 1. Gas composition table

[0090] Using the above-mentioned downhole gas composition, wellhead casing pressure and temperature, and measured sound velocity data as input parameters, the full-well theoretical sound velocity model established in step S3 is subjected to parameter identification, and the formation temperature gradient β = 0.032, the natural gas relative density γ g =0.83, the identified model parameters are brought into the theoretical sound velocity model of the whole well to obtain the relationship data between the sound velocity and the well depth of the section without effective collar, and then combined with the measured sound velocity calculated by the effective collar section, the expression of the relationship between the sound velocity and the well depth of the whole well is obtained by polynomial fitting. Based on this relationship, the calculation method of piecewise integral approximation is used to obtain the liquid surface depth. The calculation results are shown in Figure 4 As shown in the figure, the time corresponding to the reflection of the liquid surface wave in the test data is 12.56s. The liquid surface depth is calculated to be 2675.9 meters by using the wellhead sound velocity as the average sound velocity of the whole well. The liquid surface depth obtained by the fitted full-well sound velocity segmented integral approximation is 2917 meters. Among them, the segmented depth step h is 10 meters, and the time integral deviation threshold Δt is 0.01s. The difference between the two calculation results is about 241.1 meters, which is a large deviation. This method fully integrates the advantages of the joint hoop measurement method and the theoretical modeling method to enhance the reliability and accuracy of the sound velocity calculation process.

[0091] In order to further verify the present invention, five actual test data of two other wells were verified. The comparison between the calculation results of the liquid level depth based on the present invention and the calculation results of the traditional liquid level calculation method and the actual liquid level depth is shown in Table 2 below, where the actual liquid level position is obtained by the oil field according to the pressure gauge test results. As can be seen from Table 2, the sound velocity obtained by the wellhead collar calculation is used as the average sound velocity of the whole well for the liquid level depth calculation, resulting in the calculation result being generally smaller than the actual liquid level position. After the sound velocity compensation correction is performed by the present invention, the calculated depth is closer to the actual liquid level position, and the relative error is reduced from the original maximum error of 5.8% to 1.7%.

[0092]

[0093] Table 2. Comparison between calculated liquid level depth and actual liquid level depth

[0094] In summary, the present invention uses the measured sound velocity to identify the parameters of the full-well theoretical sound velocity calculation model, performs compensation calculation on the section without effective nodes through the theoretical sound velocity model, thereby obtaining the full-well sound velocity, and finally calculates the liquid level depth by piecewise integral approximation based on the full-well sound velocity. This method can effectively improve the accuracy and reliability of the liquid level depth measurement.

[0095] In addition to the above-mentioned preferred embodiments, the present invention also has other implementation modes. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection requested by the present invention.

Claims

1. A method for calculating the liquid level depth of an oil and gas well based on sound velocity compensation correction, characterized in that: The following steps are involved: S1: Install a liquid level measurement device at the wellhead of an oil and gas well to obtain acoustic logging data, including the original liquid surface wave time domain signal A and the hoop wave time domain signal B, perform noise reduction and filtering on the acoustic logging signal, calculate the length N of the effective hoop segment through the hoop wave time domain signal B after noise reduction, and calculate the reflected liquid surface position L0 and its corresponding time t0 through the liquid surface wave time domain signal A after noise reduction; S2: Determine whether L0 in S1 needs to be compensated and corrected for the full-well sound velocity through the full-well theoretical sound velocity model; when N is greater than L0, there is no need to compensate and correct the sound velocity, and the effective node collar is directly used to calculate the segmented sound velocity, and then the segmented integral approximation method is used to calculate the liquid level depth result of the oil well; when N is less than or equal to L0, go to the next step; S3: Compensate and correct the full-well acoustic velocity, and calculate the downhole pressure model P under different well depth conditions H , Downhole temperature calculation model T under different well depth conditions H And related technical detection means to obtain the gas component parameters X=[x1,x2,…x k ]; Establish a theoretical model for calculating the speed of sound V(H) = f(P H , T H , X); S4: Using the measured sound velocity data of the effective collar section calculated in step S2, the full-well theoretical sound velocity calculation model established in step S3 is subjected to parameter identification. The identified parameters include formation temperature gradient β, natural gas relative density γ g ; Use the identified parameters to calculate the sound velocity between the end position of the effective section and the reflected wave liquid surface position, so as to obtain the data of the full-well sound velocity from the wellhead to the reflected liquid surface wave position; S5: Perform polynomial linear fitting using the full-well acoustic velocity data obtained in step S4 to obtain a relationship between the full-well acoustic velocity and the well depth H: V = ζ(H); S6: The time corresponding to the reflected liquid surface position is calculated by the liquid surface reflection wave as t0, in seconds. The actual liquid surface depth H can be calculated by the following segmented integral approximation method to time t0: r ; In the formula, h represents the segment depth step, Δt represents the deviation threshold of time integration, i represents the total number of calculated segments, and H r Indicates the actual liquid level depth obtained by calculation.

2. The method for calculating the liquid level depth of an oil and gas well based on sound velocity compensation correction according to claim 1, characterized in that: The length of the effective hoop segment in S1 is calculated as follows: the hoop data segment whose peak-to-peak value is greater than the adaptive threshold δ is taken as the effective hoop data, and the adaptive threshold is δ = a × δ max , δ max represents the maximum peak-to-peak value of the node hoop, and a represents the proportional coefficient.

3. The method for calculating the liquid level depth of an oil and gas well based on sound velocity compensation correction according to claim 1, characterized in that: The calculation formula for the time from the position of the reflected liquid surface wave in S1 to the corresponding time is: t0=L0 / f Wherein, f is the sampling rate of the liquid surface wave time domain signal and the hoop wave time domain signal.

4. The method for calculating the liquid level depth of an oil and gas well based on sound velocity compensation correction according to claim 1, characterized in that: The calculation method of the segmented sound velocity of the effective node hoop segment in S2 is as follows: perform autocorrelation calculation on the effective node hoop segment length N, segment the data of the autocorrelation signal according to the sliding window of length M, and then perform fast Fourier transform on the data in the sliding window to obtain the frequency characteristics of the sliding window, and take the frequency with the largest amplitude as the node hoop frequency f of the sliding window M1 , then the sound speed of this section is expressed as: Where, Len represents the length of the oil pipe; The segment speed The corresponding well depth is: The sliding window is slid with a sliding step length W, and the actual sound velocity is calculated according to the above steps. The depth corresponding to the sound velocity is the depth of the previous section plus the time corresponding to the sliding step length multiplied by the sound velocity of this section, until the sliding window slides to the end of the valid node hoop data section. The depth calculation formula corresponding to the k-th sliding of the sliding window is as follows: In the formula, Indicates the depth corresponding to the k-1th time.

5. The method for calculating the liquid level depth of an oil and gas well based on sound velocity compensation correction according to claim 1, characterized in that: S3 also includes the following steps: S31: A theoretical model is constructed for the speed of sound under different conditions. The calculation formula for the speed of sound is as follows: Among them, Z is the compression factor, c v represents isovolumetric heat capacity, c p represents isobaric heat capacity, R represents the ideal gas constant, T represents temperature, ρ represents gas density, represents the first-order partial differential of the compressibility coefficient Z with respect to temperature ρ; S32: Establishing the downhole temperature calculation model T under different well depth conditions H , the temperature T corresponding to any depth H in the well can be obtained by calculating the wellhead temperature H The full-well temperature calculation model uses an engineering experience model to describe the relationship between downhole temperature and well depth, which is specifically expressed as follows: T H =βH+T0 Where H represents the well depth; T0 represents the temperature at the wellhead, and β represents the formation temperature gradient; S33: Establish downhole pressure calculation model P under different well depth conditions H , the gas pressure P corresponding to any depth H in the well can be obtained by calculating the casing pressure at the wellhead H The full well pressure calculation model adopts the static pressure gas column theory, which is specifically expressed as follows: P H =p C e S Among them, p c represents the wellhead pressure; γ g —Relative density of natural gas; —mean absolute temperature of the gas; —Gas average deviation coefficient, e represents the base of the natural logarithm: S34: The temperature T at different well depths H and pressure P H By bringing in the theoretical sound velocity calculation model, a full-well theoretical sound velocity calculation model can be established to realize the theoretical sound velocity calculation from the wellhead to any position underground: V(H)=f(P H ,T H ,X)。

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