A method for calculating the liquid level depth of an oil and gas well based on sound velocity compensation correction

Abstract

The application discloses a liquid level depth calculation method based on sound velocity compensation correction, belongs to the technical field of oil and gas well acoustic logging, and adopts a measured sound velocity to identify full-well theoretical sound velocity calculation model parameters, compensates and calculates a theoretical sound velocity model without an effective joint segment, thereby obtaining full-well sound velocity, and finally, a segmented integral approximation method is adopted to calculate the liquid level depth based on the full-well sound velocity, so that the accuracy and reliability of liquid level depth measurement can be effectively improved.

Description

TECHNICAL FIELD

[0001] The application relates to an oil and gas well liquid level depth calculation method based on sound velocity compensation correction and belongs to the technical field of acoustic logging of oil and gas wells. BACKGROUND

[0002] In oil and gas well production, the liquid level depth is a core index for adaptability evaluation and optimization of oil production process flow. At present, the methods for measuring the liquid level of an oil well mainly include three methods, namely, the float method, the pressure gauge detection method and the sound velocity method. The float method measures the dynamic liquid level of an oil well by using a float immersed in oil. This method is simple in operation, but its application range is limited due to the influence of the self volume and weight of the float and human errors. The pressure gauge detection method measures the pressure value of an oil well by placing a pressure gauge above the oil, and the measurement result is relatively accurate, but the method is complex in measurement and high in cost, and is often used as one of the precise monitoring methods. The sound wave method calculates the depth by reflecting sound waves in the oil sleeve annulus. This method is simple in operation and low in cost, and can be used as an effective means for long-term depth monitoring, but the accuracy of depth calculation is greatly influenced by the sound velocity. The existing liquid level depth calculation method based on sound velocity usually takes the sound velocity at the wellhead as the average sound velocity of the whole well, and has the problem of large deviation of the calculated liquid level depth. SUMMARY

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

[0004] The application provides an oil and gas well liquid level depth calculation method based on sound velocity compensation correction, which comprises the following steps:

[0005] S1: installing a liquid level measuring device at the wellhead of an oil and gas well, obtaining acoustic logging data, including an original liquid level wave time domain signal A and a collar wave time domain signal B, performing noise reduction filtering processing on the acoustic logging signal, calculating the length N of the effective collar section through the noise-reduced collar wave time domain signal B, and calculating the reflected liquid level position L0 and the corresponding time t0 through the noise-reduced liquid level wave time domain signal A;

[0006] S2: judging whether L0 in S1 needs to be compensated and corrected by the whole well theoretical sound velocity model; when N is greater than L0, the sound velocity does not need to be compensated and corrected, the effective collar is directly used for segmented sound velocity calculation, 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, the next step is entered;

[0007] S3: compensating and correcting the whole well sound velocity, calculating the downhole pressure under different well depth conditions through a downhole pressure calculation model P H and calculating the downhole temperature under different well depth conditions through a downhole temperature calculation model TH and related technology detection means to obtain gas composition parameters X = [x1, x2, … x k ] in the oil casing annulus of the oil and gas well; a sound velocity calculation theoretical model V(H) = f(P H , T H , X) is established;

[0008] S4: using the measured sound velocity data of the effective jointed section obtained in step S2, parameters are identified for the full-well theoretical sound velocity calculation model established in step S3, and the identified parameters include the formation temperature gradient β, the relative density γ g of natural gas; the sound velocity between the end position of the effective jointed section and the reflected wave liquid surface position is calculated using the identified parameters, so as to obtain the full-well sound velocity data from the wellhead to the reflected liquid surface wave position;

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

[0010] S6: the time corresponding to the reflected liquid surface position is t0, which is calculated in seconds, and the actual liquid surface depth H r is calculated by the following segmented integral approximation of the time t0;

[0011]

[0012] In the formula, h represents the segmented depth step, Δt represents the deviation threshold of the time integral, i represents the total number of calculations, H r represents the calculated actual liquid surface depth.

[0013] Further, the calculation method of the length of the effective jointed section in S1 is as follows: the jointed section data whose peak-to-peak value is greater than the adaptive threshold δ is taken as the effective jointed data, and the adaptive threshold is δ = a × δ max , δ max represents the maximum peak-to-peak value of the joint, and a represents the proportional coefficient.

[0014] Further, the formula for calculating the time corresponding to the reflected liquid surface wave position in S1 is as follows:

[0015] t0 = L0 / f

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

[0017] Further, the segmented sound velocity calculation method of the effective segment in S2 is as follows: the effective segment length N is subjected to autocorrelation calculation, the autocorrelation signal is subjected to data segmentation and interception according to a sliding window with a length of M, then the data in the sliding window is subjected to fast Fourier transform to obtain the frequency characteristics of the sliding window, and the frequency with the largest amplitude is taken as the segment frequency f of the sliding window M1 The sound velocity of the segment is represented as:

[0018]

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

[0020] The segmented sound velocity The corresponding well depth is:

[0021]

[0022] The sliding window is slid with a sliding step W, the actual sound velocity is calculated according to the above steps, the depth corresponding to the sound velocity is the depth of the last segment plus the time corresponding to the sliding step multiplied by the sound velocity of the segment, until the sliding window slides to the end of the effective segment. The depth corresponding to the kth sliding of the sliding window is calculated according to the following formula:

[0023]

[0024] In the formula, represents the depth corresponding to the k-1th sliding.

[0025] Further, S3 further includes the following steps:

[0026] S31: a theoretical model is constructed for the sound velocity under different states, and the calculation formula of the sound velocity is as follows:

[0027]

[0028] In the formula, Z represents a compression factor, c v represents the specific heat capacity, c p represents the isobaric heat capacity, R represents the ideal gas constant, T represents the temperature, and p represents the gas density, represents the first-order partial derivative of the compression coefficient Z with respect to the temperature p;

[0029] S32: a downhole temperature calculation model T H is established under different well depths, so that the temperature T H corresponding to any depth position H in the well can be obtained through the calculation of the wellhead temperature; the full-well temperature calculation model describes the relationship between the downhole temperature and the well depth by using an engineering experience model, and is specifically represented as follows:

[0030] T H = βH + T0

[0031] Where H represents the well depth; T0 represents the temperature at the wellhead; and β represents the formation temperature gradient.

[0032] S33: Establishing downhole pressure calculation models under different well depths P H The gas pressure P at any depth H in the well is obtained by calculating the casing pressure at the wellhead. H The full-well pressure calculation model uses the static pressure gas column theory, as detailed below:

[0033] P H =p C e S

[0034]

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

[0036] S34: Temperature T at different well depths H and pressure P H By incorporating the theoretical sound velocity calculation model, a full-well theoretical sound velocity calculation model can be established, enabling the calculation of theoretical sound velocities from the wellhead to any location downhole:

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

[0038] The advantages of this invention, based on the above technical solution, are as follows: For shallow wells, a more accurate liquid level depth can be calculated by the piecewise integration of measured sound velocity. For deep or ultra-deep wells, there are long data segments without effective joints in the acoustic signal. The sound velocity of the segment without effective joints is calculated using the identified whole-well theoretical sound velocity calculation model, thereby obtaining the sound velocity of the whole well. Then, the liquid level depth is calculated by the piecewise integration approximation method of the whole-well sound velocity, which effectively enhances the accuracy of the liquid level depth calculation. Attached Figure Description

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

[0040] Figure 2 Diagnostic flowchart for the method of calculating fluid level depth in oil and gas wells with online sound velocity compensation;

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

[0042] Figure 4 Figure is a schematic diagram of the calculation result of the full well sound velocity compensation correction;

[0043] Figure: 1 - pumping unit 2 - emitting sound waves 3 - sound wave generation and receiving device 4 - receiving sound waves 5 - casing 6 - joint 7 - tubing 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 application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all.

[0045] The terms "first", "second" and the like (if any) in the specification and claims of the present application are used to distinguish similar objects, not to describe a particular order or sequence, even if "second" is used in front of a certain technical feature to distinguish. It should be understood that in the present application, "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. It should be understood that in the present application, "multiple" means two or more. "And / or" is only a description of the relationship between the associated objects, which means that there can be three relationships, for example, X and / or Y can represent three cases: X alone, X and Y together, and Y alone. The character " / " generally represents an "or" relationship between the associated objects. "Include X, Y and Z", "include X, Y, Z" means that X, Y and Z are all included, "include X, Y or Z" means that one of X, Y and Z is included, and "include X, Y and / or Z" means that any one or any two or all of X, Y and Z is included.

[0046] As shown in the figure, the present application provides a sound velocity compensation correction based oil and gas well liquid level depth calculation method, comprising the following steps: Figures 1 to 4

[0047] S1: installing a liquid level measuring device at the wellhead of the oil and gas well, obtaining acoustic logging data, including original liquid level wave time domain signal A and joint wave time domain signal B, carrying out noise reduction filtering processing on the acoustic logging signal, calculating the length N of the effective joint section through the joint wave time domain signal B after noise reduction, and calculating the reflected liquid level position L0 and its corresponding time t0 through the liquid level wave time domain signal A after noise reduction;

[0048] ​S2: judging whether L0 in S1 needs to be compensated and corrected by a full-well theoretical sound velocity model; when N is greater than L0, the sound velocity does not need to be compensated and corrected, the effective collar is directly used for segmented sound velocity calculation, and then a 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, the next step is entered;

[0049] S3: compensating and correcting the full-well sound velocity, calculating the downhole pressure under different well depth conditions by a downhole pressure calculation model P H , calculating the downhole temperature under different well depth conditions by a downhole temperature calculation model T H , and obtaining the gas component parameters X = [x1, x2, … x k ] in the oil and gas well oil sleeve annulus by related technical detection means; a sound velocity calculation theoretical model V(H) = f(P H , T H , X) is established;

[0050] S4: using the measured sound velocity data of the effective collar segment calculated in step S2 to perform parameter identification on the full-well theoretical sound velocity calculation model established in step S3, the identified parameters include the formation temperature gradient β and the natural gas relative density γ g ; the sound velocity between the end position of the effective collar segment and the reflected wave liquid level position is calculated by using the identified parameters, so that the full-well sound velocity data from the wellhead to the reflected liquid level position is obtained;

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

[0052] S6: the time corresponding to the reflected liquid level position is t0, which is calculated by the reflected wave, and the unit is second, and the actual liquid level depth H r can be calculated by the following segmented integral approximation time t0.

[0053]

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

[0055] The present application can calculate more accurate liquid level depth results for shallow wells by the measured sound velocity segmented integral method, for deep wells or super deep wells, there is a long data segment without effective collar in the sound wave signal, the sound velocity of the segment not containing the effective collar is calculated by using the identified full-well theoretical sound velocity calculation model, so that the full-well sound velocity is obtained, and then the liquid level depth result is calculated by the full-well sound velocity segmented integral approximation method, thereby effectively enhancing the accuracy of the liquid level depth calculation.

[0056] Specifically, the calculation method of the length of the effective joint segment in S1 is: taking the joint data segment with a peak-to-peak value greater than the adaptive threshold δ as the effective joint data, and the adaptive threshold is δ = a x δ max , δ max represents the maximum peak-to-peak value of the joint, and a represents the proportion coefficient.

[0057] Wherein, the peak-to-peak value is the difference between the adjacent maximum value and the minimum value of the joint length data;

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

[0059] t0 = L0 / f

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

[0061] Specifically, the calculation method of the segmented sound speed of the effective joint segment in S2 is: performing autocorrelation calculation on the effective joint segment length N, performing data segmentation and interception on the autocorrelation signal according to the length of the sliding window M, then performing fast Fourier transform on the data in the sliding window to obtain the frequency characteristics of the sliding window, and taking the frequency with the largest amplitude as the joint frequency f M1 of the sliding window, then the sound speed of the segment is:

[0062]

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

[0064] The segmented sound speed The corresponding well depth is:

[0065]

[0066] With a sliding step W, the sliding window is slid, and the actual sound speed is calculated according to the above steps, and the depth corresponding to the sound speed is the depth of the last segment plus the time corresponding to the sliding step multiplied by the sound speed of the segment, until the sliding window slides to the end of the effective joint data segment. The depth corresponding to the kth sliding of the sliding window is calculated according to the following formula:

[0067]

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

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

[0070] S31: constructing a theoretical model for the sound speed under different states, and the calculation formula of the sound speed is as follows:

[0071]

[0072] wherein Z is a compressibility factor, c v represents the isochoric heat capacity, c p represents the isobaric heat capacity, R represents the ideal gas constant, T represents the temperature, and p represents the gas density, represents the first order partial derivative of the compressibility factor Z with respect to the temperature p;

[0073] S32: Establishing a downhole temperature calculation model T H , the temperature T corresponding to any depth position H in the well can be obtained by calculating the wellhead temperature H ; the full-well temperature calculation model describes the relationship between the downhole temperature and the well depth using an engineering empirical model, and is specifically expressed as follows:

[0074] T H = βH + T0

[0075] wherein H represents the well depth; T0 represents the temperature of the wellhead, and β represents the formation temperature gradient;

[0076] S33: Establishing a downhole pressure calculation model P H , the gas pressure P corresponding to any depth position H in the well can be obtained by calculating the wellhead casing pressure H ; the full-well pressure calculation model is calculated using the static pressure gas column theory, and is specifically expressed as follows:

[0077] P H = p C e S

[0078]

[0079] wherein p c represents the wellhead pressure; γ g represents the relative density of natural gas; represents the average absolute temperature of the gas; represents the average deviation coefficient of the gas, and e represents the base number of the natural logarithm:

[0080] S34: Bringing the temperature T H and the pressure P H at different well depths into the theoretical sound velocity calculation model can establish a full-well theoretical sound velocity calculation model, so as to realize the calculation of the theoretical sound velocity at any position from the wellhead to the downhole:

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

[0082] The specific principle and process are as follows: the schematic diagram of the double-channel liquid level testing device system is as Figure 1As shown, a double-channel liquid level testing device is installed at the wellhead casing interface, and the sound wave generation and receiving device 3 in the device includes a sound wave generator, a microphone, and a hardware filtering sampling circuit component. The sound wave generator generates sound waves, and the microphone receives the 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 analysis, infrared spectroscopy, or photoacoustic spectroscopy.

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

[0084] (1) The obtained original liquid level wave time domain signal A and collar wave time domain signal B are subjected to noise reduction filtering processing, as shown in Figure 3 As shown, the proportional coefficient a can be set to 0.3. The effective collar segment data length is calculated to be 3036 by using the effective collar segment data length calculation method for the noise-reduced collar wave time domain signal. The sampling point L0 corresponding to the reflected liquid level wave position is 6281, and the corresponding time t0 is 12.56 seconds. Since the reflected liquid level wave position is greater than the effective collar data length, the full-well theoretical sound velocity calculation model is used for calculation and compensation for the data not containing the effective collar segment.

[0085] (2) The effective collar segment data is subjected to segmented sound velocity calculation. For the effective collar segment data with a length of 3036, the self-correlation calculation is first performed, the sliding window length is selected to be 256, and the tubing length Len is selected to be 9.8 meters. The data in the sliding window is subjected to fast Fourier transform, and the frequency with the largest amplitude is taken as the sliding window collar frequency f M1 The sound velocity of this segment is: The actual measured sound velocity The corresponding well depth is: The sliding step is taken to be 128, the sliding window is slid to the right of the data, a new sliding window with a length of 256 is formed, and the actual sound velocity is calculated in the same way as the above steps. The depth corresponding to the sound velocity is the depth of the last segment plus the time corresponding to the sliding step multiplied by the sound velocity of this segment. The depth corresponding to the kth sliding of the sliding window is The depth corresponding to the k-1th sliding is represented by the above method. 22 groups of actual measured sound velocities and their corresponding depth data are calculated.

[0086] (3) The wellhead pressure and temperature corresponding to the test data are 6MPa and 25℃, respectively. By querying the gas detection record 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 aforementioned downhole gas composition, wellhead casing pressure and temperature, and measured sound velocity data as input parameters, the parameters of the whole-well theoretical sound velocity model established in step S3 are identified. The identified parameters are: formation temperature gradient β = 0.032, natural gas relative density γ. g =0.83. Substituting the identified model parameters into the whole-well theoretical sound velocity model, the relationship between sound velocity and well depth in the downhole section without effective joints is obtained. Combined with the measured sound velocity calculated from the effective joint section, a polynomial fitting method is used to obtain the expression for the relationship between the whole-well sound velocity and well depth. Using this relationship, a piecewise integral approximation method is then used to calculate the fluid level depth. The calculation results are as follows: Figure 4 As shown, the test data corresponds to a liquid surface wave reflection time of 12.56 s. The liquid surface depth calculated using the wellhead sound velocity as the average sound velocity of the entire well is 2675.9 meters. The liquid surface depth obtained by approximating the result using a piecewise integral of the fitted whole-well sound velocity is 2917 meters, where the piecewise depth step size h is 10 meters and the time integration deviation threshold Δt is 0.01 s. The two calculation results differ by approximately 241.1 meters, which is a significant deviation. This method fully integrates the advantages of both the joint measurement method and the theoretical modeling method, enhancing the reliability and accuracy of the sound velocity calculation process.

[0091] To further verify this invention, five actual test data from two other wells were used for verification. The comparison between the fluid level depth calculation results based on this invention and the calculation results of the traditional fluid level calculation method, as well as the actual fluid level depth, is shown in Table 2 below. The actual fluid level position was estimated by the oilfield based on pressure gauge test results. Table 2 shows that using the sound velocity obtained through wellhead clamp calculation as the average sound velocity for the entire well for fluid level depth calculation generally resulted in a calculated depth that was smaller than the actual fluid level position. After sound velocity compensation correction using this invention, the calculated depth is closer to the actual fluid level position, and the relative error was reduced from the original maximum error of 5.8% to 1.7%.

[0092]

[0093] Table 2. Comparison of Calculated Liquid Surface Depth with Actual Liquid Surface Depth

[0094] In summary, the application adopts the measured sound velocity to identify the full well theoretical sound velocity calculation model parameters, compensates and calculates the theoretical sound velocity model without effective joint segment, so as to obtain the full well sound velocity, and finally adopts the segmented integral approximation method to calculate the liquid level depth based on the full well sound velocity, which can effectively improve the accuracy and reliability of the liquid level depth measurement.

[0095] In addition to the preferred embodiments described above, the application also has other embodiments. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor belong to the scope of the application.

Claims

1. An oil and gas well fluid level depth calculation method based on sound velocity compensation correction, characterized in that: The method comprises the following steps: S1: install a liquid level measuring device at the wellhead position of the oil and gas well, obtain acoustic logging data, including original liquid level wave time domain signal A and clamp wave time domain signal B, perform noise reduction filtering processing on the acoustic logging signal, calculate the length N of the effective clamp section through the noise-reduced clamp wave time domain signal B, and calculate the reflected liquid level position through the noise-reduced liquid level wave time domain signal A and its corresponding time ; S2: Determine the value in S1 Does the well's sound velocity need to be compensated and corrected using a full-well theoretical sound velocity model? When N is greater than... When there is no need to compensate for the sound velocity, the effective joint is used to calculate the segmented sound velocity directly, and then the segmented integral approximation method is used to calculate the liquid level depth of the oil well; when N is less than or equal to Then proceed to the next step; S3: compensating and correcting the full well sound velocity, calculating the downhole pressure model under different well depth conditions , calculating the downhole temperature model under different well depth conditions , and obtaining the gas component parameters in the oil and gas well oil casing annulus by related technical detection means ; establishing a sound velocity calculation theoretical model ; S4: using the measured sound velocity data of the effective segment of the joint obtained in step S2, performing parameter identification on the full-well theoretical sound velocity calculation model established in step S3, the identified parameters including the formation temperature gradient , the relative density of natural gas ; using the identified parameters to calculate the sound velocity between the end position of the effective joint segment and the reflection wave liquid surface position, thereby obtaining the full-well sound velocity data from the wellhead to the reflection liquid surface position; S5: Perform polynomial linear fitting on the full-hole sound velocity data obtained in step S4 to obtain a relationship between the full-hole sound velocity and the well depth H ; S6: the time corresponding to the reflected liquid surface position is calculated by liquid surface reflection wave , unit: second, the actual liquid surface depth can be calculated by the following piecewise integral approximation method ; ， wherein denotes the segment depth step size, denotes the time integrated deviation threshold, denotes the total number of segments calculated, denotes the actual liquid level depth calculated.

2. The method of claim 1, wherein: The calculation method for the length of the effective hoop segment in S1 is as follows: the peak-to-peak value of the hoop segment data is greater than the adaptive threshold. The hoop data segment is the valid hoop data, and the adaptive threshold is... , This indicates the maximum peak value of the hoop. This represents the proportionality coefficient.

3. The method of claim 1, wherein: The calculation formula of the position of the reflected liquid surface wave to the corresponding time in S1 is: ， wherein, is the sampling rate of the surface wave time domain signal and the knuckle wave time domain signal.

4. The method of claim 1, wherein: The calculation method of the segmented sound velocity of the effective segment of the S2 is: the effective segment length N is autocorrelated, the autocorrelation signal is segmented and intercepted according to the length of the sliding window M, then the data in the sliding window is subjected to fast Fourier transform to obtain the frequency characteristics of the sliding window, and the frequency with the maximum amplitude is taken as the segment frequency of the sliding window The sound velocity of the segment is represented as ， wherein represents the length of the tubing; The segmented sound velocity The corresponding well depth is: ； The sliding window is slid with a sliding step W, and the actual sound velocity is calculated according to the above steps, and the depth corresponding to the sound velocity is the depth in the last section plus the time corresponding to the sliding step multiplied by the sound velocity in the section until the sliding window slides to the end point of the effective section of the data; the depth calculation formula corresponding to the kth sliding of the sliding window is as follows: ， In the formula, represents the depth corresponding to the k-1th.

5. The method of claim 1, wherein: S3 further comprises the following steps: S31: constructing a theoretical model for the sound velocity under different states, and the calculation formula of the sound velocity is as follows: ， where Ztable is a compressibility factor, represents the isochoric heat capacity, represents the isobaric heat capacity, R represents the ideal gas constant, and T represents the temperature, represents the gas density, represents the first partial derivative of the compressibility factor Z with respect to temperature ; S32: Establish a downhole temperature calculation model under different well depth conditions That is, the downhole temperature at any depth can be calculated from the wellhead temperature The corresponding temperature The full-well temperature calculation model describes the relationship between downhole temperature and well depth using an engineering experience model, which is specifically represented as follows: ， wherein, wherein denotes the depth of the well; denotes the temperature at the well head, denotes the formation temperature gradient; S33: Establishing a downhole pressure calculation model under different well depth conditions , through wellhead casing pressure calculation to obtain the downhole position at any depth corresponding to the gas pressure ; the full well pressure calculation model uses static pressure gas column theory calculation, which is specifically represented as follows: ； ， wherein, P = represents the wellhead pressure; — natural gas relative density; — gas average absolute temperature; — gas average deviation factor, ln = represents the base of the natural logarithm: S34: Temperature at different well depths and pressure By incorporating the theoretical sound velocity calculation model, a full-well theoretical sound velocity calculation model can be established, enabling the calculation of theoretical sound velocities from the wellhead to any location downhole: 。

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