Method for extracting and analyzing characteristic parameters of water attack curve after pump stopping during fracturing of deep shale

Abstract

The invention provides a method for extracting and analyzing characteristic parameters of a water attack curve after pump stopping of deep shale fracturing. The method comprises the following steps: S1, collecting fracturing construction second point data recorded in a mine field and drawing a fracturing construction pressure curve; a composite criterion is set based on the pressure and displacement change rule at the pump stopping moment, fracturing construction second point data are analyzed through the composite criterion, and a pump stopping point is automatically recognized; s2, based on the pump stopping points, extracting a pump stopping pressure change curve from the fracturing construction curve; s3, extracting a pump stop water hammer oscillation curve from the pump stop pressure change curve; and S4, analyzing the pump stop water hammer oscillation curve to obtain characteristic parameters of the pump stop water hammer oscillation curve. According to the method, deep shale fracturing process characteristics and fracturing construction curve characteristics are combined, the pressure and displacement change rule at the pump stopping moment and the water hammer oscillation characteristics after fracturing pump stopping are fully considered, the method is easy to apply to mine fields, and water hammer oscillation curve characteristic parameters after deep shale fracturing pump stopping can be rapidly and automatically extracted and analyzed.

Description

Technical Field

[0001] The present invention relates to the technical field of unconventional oil and gas production enhancement and modification, and in particular to a method for extracting and analyzing characteristic parameters of a water hammer curve after pump shutdown in deep shale fracturing. Background Art

[0002] Shale gas, an unconventional natural gas with abundant reserves in my country, is a key component in optimizing the country's energy mix. Commercial development has now begun, offering broad prospects and a crucial alternative for increasing reserves and production. The majority of my country's shale gas resources are buried at depths exceeding 3,500 meters, making deep shale gas development a hotspot in oil and gas exploration and development. Deep shale fracturing typically utilizes high fluid volumes and high displacements. When the pump is shut down after fracturing, the flow rate of the fracturing fluid in the wellbore fluctuates significantly, making it highly susceptible to water hammer oscillations. Previously, the information contained in the fracture network from this post-fracturing water hammer effect was often overlooked.

[0003] Current research indicates that the water hammer effect produced after pumping stops generates pressure pulses within the wellbore. These pulses interact with the fracture network formed during the fracturing phase before returning to the surface from the bottom of the well. The resulting pressure profile is a series of oscillations that decay over time due to friction within the wellbore and fractures. Different fracture networks generated by deep shale fracturing produce water hammer curves with distinct characteristics. These water hammer signal parameters, such as period, amplitude, and attenuation rate, vary significantly. Using these parameters, rapid analysis and evaluation of fracture network structures in deep shale gas wells can be performed.

[0004] Therefore, it is urgent to propose a method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing, so as to provide new ideas and methods for evaluating fracture networks in deep shale after fracturing. Summary of the Invention

[0005] Currently, fracturing sites analyze shale gas well pump-off pressure curves by simply extracting information such as pump-off pressure and 15-minute pump-off pressure drop, ignoring characteristic parameters such as period, amplitude, and attenuation rate in the water hammer curve. This makes it difficult to comprehensively evaluate the fracture network based on the fracturing pump-off curve, making it difficult to effectively support the rapid and accurate evaluation of the fracture network after fracturing at the shale gas fracturing site. Therefore, the present invention aims to provide a method for extracting and analyzing characteristic parameters of the water hammer curve after pump-off in deep shale fracturing, which has guiding significance for real-time optimization of fracturing processes, improving the fracturing transformation effect of deep shale gas wells, and promoting the efficient and effective development of deep shale gas.

[0006] The present invention provides a method for extracting and analyzing characteristic parameters of a water hammer curve after pump shutdown in deep shale fracturing, comprising the following steps:

[0007] S1. Collect the second-by-second data of the fracturing operation recorded at the mine site and draw a fracturing operation pressure curve; set a composite criterion based on the pressure and displacement change patterns at the time of pump stop, use the composite criterion to analyze the second-by-second data of the fracturing operation, and automatically identify the pump stop point;

[0008] S2. extracting a pump-off pressure change curve from the fracturing operation curve based on the pump-off point;

[0009] S3, extracting a pump-off water hammer oscillation curve from the pump-off pressure change curve;

[0010] S4. Analyze the pump-off water hammer oscillation curve to obtain characteristic parameters of the pump-off water hammer oscillation curve.

[0011] Furthermore, step S1 includes the following sub-steps:

[0012] S11. Collect the second-by-second data of the fracturing operation recorded at the mine, including the second-by-second time, wellhead pressure, discharge volume, and sand concentration; and draw a fracturing operation pressure curve;

[0013] S12, extract the total number of seconds T of fracturing operation, and establish the pressure data sequence p1, p2, p3, ..., p T , displacement data sequence q1, q2, q3, ..., q T And the corresponding second time series t1, t2, t3, ..., t T , and extract the data sequence for calculation accordingly;

[0014] S13, traverse the pump stop points; set the current sequence number to i, extract the corresponding displacement q i and time t i ; Adopt the composite criterion based on the pressure and displacement change law at the time of pump shutdown to judge the displacement change at point i;

[0015] S14. If point i satisfies the composite criterion, extract the pressure p corresponding to point i i Conduct verification and determination;

[0016] S15, if the pressure corresponding to point i is p i If it meets the verification judgment, the corresponding value of point i is recorded and saved, and this point is the pump stop point; if it does not meet the verification judgment, the calculation of the next point is performed.

[0017] Furthermore, when traversing the pump stop points in step S13, the data range of the fracturing construction second point data is narrowed down in combination with the fracturing construction process characteristics.

[0018] Furthermore, the composite criterion includes:

[0019] Judgment condition 1: The displacement at the pump stop point is not lower than the preset threshold;

[0020] Judgment condition 2: The displacement after the pump stop point is less than the displacement at the pump stop point;

[0021] Judgment condition three: The displacement at the pump stop point and several subsequent data points shows a monotonically decreasing pattern.

[0022] Furthermore, the verification determination includes:

[0023] During the fracturing process, the pressure drops rapidly after the pump stop point and the pressure after the pump stop point is lower than the pressure at the pump stop point.

[0024] Furthermore, step S2 includes the following sub-steps:

[0025] S21, extracting the data of the pump stop point and subsequent points from the fracturing construction second point data, obtaining the fracturing pressure data set after the pump stop and the total number of data after the pump stop N, and drawing a pump stop pressure change curve;

[0026] S22, establish the pump stop pressure data sequence p with the pump stop time point as the starting point s1 、p s2 、p s3 ,…,p sN And the corresponding pump stop time series t s1 , t s2 , t s3 ,…,t sN , and extract the data sequence accordingly for subsequent calculation process.

[0027] Furthermore, step S3 includes the following sub-steps:

[0028] S31. Based on the time when the displacement returns to zero after the pump is stopped, select the starting and ending points of the pump-stop water hammer oscillation curve in the pump-stop pressure change curve, and extract the corresponding pump-stop water hammer oscillation pressure data from the pump-stop pressure data in sequence to draw the pump-stop water hammer oscillation curve;

[0029] S32, establish the pump stop water hammer oscillation pressure data sequence p w1 、p w2 、p w3 ,…,p wt And the corresponding pump stop water hammer oscillation second point time series t w1 , t w2 , t w3 ,…,t wt , and the subsequent calculation process is carried out accordingly.

[0030] Furthermore, step S4 includes the following sub-steps:

[0031] S41. Use numerical methods to analyze the water hammer oscillation pressure data when the pump is stopped. w3 and t wt-2Perform cyclic calculation for the starting and ending points, record the peak and trough of each water hammer oscillation curve that meets the conditions; on this basis, establish the peak data sequence p of the water hammer oscillation curve that meets the conditions. c1 、p c2 ,…,p cn and trough data series p t1 、p t2 ,…,p tn , and mark the peaks and troughs on the water hammer oscillation curve when the pump is stopped;

[0032] S42, using the pump stop water hammer oscillation curve peak data sequence p c1 、p c2 ,…,p cn And the trough data series p t1 、p t2 ,…,p tn Calculate characteristic parameters of the pump-off water hammer oscillation curve; the characteristic parameters of the pump-off water hammer oscillation curve include period, amplitude and attenuation rate.

[0033] Furthermore, in step S41, when determining the peaks and troughs of the pump-stop water hammer oscillation curve, the influence of abnormal data points on the identification of peaks and troughs needs to be considered. The pressure before and after the peak should show a trend of first increasing and then decreasing, and the pressure before and after the trough should show a trend of first decreasing and then increasing.

[0034] Furthermore, in step S42, the formula for calculating the water hammer oscillation curve period is as follows:

[0035]

[0036] Where T represents the period of water hammer oscillation curve, n represents the peak data sequence p of water hammer oscillation curve c1 、p c2 ,…,p cn and trough data series p t1 、p t2 ,…,p tn The number of data points.

[0037] Furthermore, in step S42, the formula for calculating the amplitude of the water hammer oscillation curve is as follows:

[0038] A=max{p c1 ,p c2 ,…,p cn}-min{p t1 ,p t2 ,…,p tn}

[0039] Where A represents the amplitude of the water hammer oscillation curve.

[0040] Furthermore, in step S42, the formula for calculating the attenuation rate of the water hammer oscillation curve is as follows:

[0041]

[0042]

[0043] Among them, α represents the attenuation rate of the water hammer oscillation curve, P w_stand To calculate the middle value.

[0044] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0045] The present invention combines the characteristics of deep shale fracturing technology and fracturing construction curves, fully considers the pressure and displacement change rules at the time of pump shutdown and the water hammer oscillation characteristics after fracturing pump shutdown, and proposes a method for extracting and analyzing the characteristic parameters of the water hammer curve after deep shale fracturing pump shutdown. This method is easy to apply in mines and can quickly and automatically extract and analyze the characteristic parameters such as the amplitude, period, and attenuation rate of the water hammer oscillation curve after deep shale fracturing pump shutdown. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings in the embodiments will be briefly introduced below. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 Flowchart of a method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing according to an embodiment of the present invention.

[0048] Figure 2 This is a fracturing construction pressure curve diagram in an embodiment of the present invention.

[0049] Figure 3 This is a schematic diagram of identifying the pump stop point during fracturing in an embodiment of the present invention.

[0050] Figure 4 This is a curve diagram of pump stop pressure change in an embodiment of the present invention.

[0051] Figure 5 This is a water hammer oscillation curve diagram when the pump is stopped in an embodiment of the present invention.

[0052] Figure 6 Schematic diagram of characteristic parameters of water hammer oscillation curve when pump is stopped.

[0053] Figure 7 Schematic diagram of extracting characteristic parameters of water hammer oscillation curve during pump stop in an embodiment of the present invention. DETAILED DESCRIPTION

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0055] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0056] Example

[0057] like Figure 1 As shown, this embodiment proposes a method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing, including the following steps:

[0058] S1. Collect the second-by-second data of the fracturing operation recorded at the mine site and draw a fracturing operation pressure curve; set a composite criterion based on the pressure and displacement change patterns at the pump stop time, use the composite criterion to analyze the second-by-second data of the fracturing operation, and automatically identify the pump stop point; specifically:

[0059] S11. Collect the second-by-second data of a certain section of a shale gas well fracturing operation recorded in the mine, including the second-by-second time, wellhead pressure, discharge volume and sand concentration; and draw the fracturing operation pressure curve, such as Figure 2 As shown;

[0060] S12, extract the total number of seconds of fracturing operation T = 10215 (seconds), and establish the pressure data sequence p1, p2, p3, ..., p T , displacement data sequence q1, q2, q3, ..., q T And the corresponding second time series t1, t2, t3, ..., t T , and extract the data sequence for calculation accordingly;

[0061] S13, traverse the pump stop point for the second point data; or considering that sand fracturing is the main part of fracturing construction and the water hammer effect lasts for a short time, the front and back sections of the fracturing construction second point data can be intercepted, thereby narrowing the data range of the fracturing construction second point data to Then traverse and search. Set the current sequence number to i and extract the corresponding displacement q i and time t iA composite criterion based on the pressure and displacement change patterns at the pump stop moment is used to judge the displacement change at point i. The composite criterion mainly considers the displacement change patterns at the pump stop point during the fracturing process, and appropriate criteria should be added to eliminate the impact of step-by-step displacement reduction, temporary plugging balls during the fracturing process, and other situations on the pump stop point identification, so as to improve the identification accuracy. Therefore, the composite criterion includes:

[0062] Judgment condition 1: Deep shale fracturing often uses large-volume fracturing, and the displacement at the pump stop point is not less than the preset threshold (such as 10m 3 / min);

[0063] Judgment condition 2: The displacement after the pump stop point is less than the displacement at the pump stop point, that is, Judgment condition three: The displacement at the pump stop point and several data points thereafter (usually 3 to 5) shows a monotonically decreasing law, that is, q i+j -q i+j+1 >0(j=0,1,2,…,N).

[0064] In addition, auxiliary criteria can be appropriately set according to the characteristics of deep shale fracturing technology.

[0065] S14. If point i satisfies the composite criterion, extract the pressure p corresponding to point i i Performing a verification and determination; wherein the verification and determination includes:

[0066] During the fracturing process, the pressure drops rapidly after the pump stop point and the pressure after the pump stop point is lower than the pressure at the pump stop point. And t i+j -t i+j+1 >0(j=0,1,2,…,N).

[0067] S15, if the pressure corresponding to point i is p i If it meets the verification judgment, the corresponding value of point i is recorded and saved, and this point is the pump stop point; if it does not meet the verification judgment, the calculation of the next point is performed.

[0068] Through step S1, the pump stop point is obtained as the 9041th second. Figure 3 shown.

[0069] S2, based on the pump stop point, extracting the pump stop pressure change curve from the fracturing operation curve; comprising the following sub-steps:

[0070] S21, extract the data of the pump stop point and the points thereafter from the fracturing construction second point data, obtain the pressure data set after the fracturing pump stop and the total number of data after the pump stop N, and draw the pump stop pressure change curve, such as Figure 4 As shown;

[0071] S22, establish the pump stop pressure data sequence p with the pump stop time point as the starting points1 、p s2 、p s3 ,…,p sN And the corresponding pump stop time series t s1 , t s2 , t s3 ,…,t sN , and extract the data sequence accordingly for subsequent calculation process.

[0072] S3, extracting a pump-off water hammer oscillation curve from the pump-off pressure change curve; comprising the following sub-steps:

[0073] S31. Combined with the time when the displacement returns to zero after the pump is stopped, select the starting and ending points of the pump-stop water hammer oscillation curve in the pump-stop pressure change curve (140 seconds and 280 seconds after the pump is stopped), and extract the corresponding pump-stop water hammer oscillation pressure data from the pump-stop pressure data in turn to draw the pump-stop water hammer oscillation curve, such as Figure 5 As shown;

[0074] S32, establish the pump stop water hammer oscillation pressure data sequence p w1 、p w2 、p w3 ,…,p wt And the corresponding pump stop water hammer oscillation second point time series t w1 , t w2 , t w3 ,…,t wt , and the subsequent calculation process is carried out accordingly.

[0075] S4. Analyze the pump-off water hammer oscillation curve to obtain the characteristic parameters of the pump-off water hammer oscillation curve, such as Figure 6 As shown, the characteristic parameters of the pump-off water hammer oscillation curve include the pump-off water hammer oscillation curve period, amplitude and attenuation rate; step S4 specifically includes the following sub-steps:

[0076] S41. Use numerical methods to analyze the water hammer oscillation pressure data when the pump is stopped. w3 and t wt-2 Perform cyclic calculation for the starting and ending points, record the peak and trough of each water hammer oscillation curve that meets the conditions; on this basis, establish the peak data sequence p of the water hammer oscillation curve that meets the conditions. c1 、p c2 ,…,p cn and trough data series p t1 、p t2 ,…,p tn, and mark the peaks and troughs on the pump-stop water hammer oscillation curve; when determining the peaks and troughs of the pump-stop water hammer oscillation curve, it is necessary to consider the influence of abnormal data points on the identification of peaks and troughs. The pressure before and after the peak should show a trend of first increasing and then decreasing, and the pressure before and after the trough should show a trend of first decreasing and then increasing, which can be expressed as:

[0077]

[0078] Therefore, the peaks and troughs of the recorded pump stop water hammer oscillation curve are shown in Table 1.

[0079] Table 1, recorded peaks and troughs of the pump stop water hammer oscillation curve:

[0080]

[0081] S42, using the pump stop water hammer oscillation curve peak data sequence p c1 、p c2 ,…,p cn And the trough data series p t1 、p t2 ,…,p tn Calculate the characteristic parameters of the pump stop water hammer oscillation curve.

[0082] (1) The formula for calculating the water hammer oscillation curve period is as follows:

[0083]

[0084] Where T represents the period of water hammer oscillation curve, n represents the peak data sequence p of water hammer oscillation curve c1 、p c2 ,…,p cn and trough data series p t1 、p t2 ,…,p tn The number of data points.

[0085] (2) The formula for calculating the amplitude of the water hammer oscillation curve is as follows:

[0086] A=max{p c1 ,p c2 ,…,p cn}-min{p t1 ,p t2 ,…,p tn}

[0087] Where A represents the amplitude of the water hammer oscillation curve.

[0088] (3) The formula for calculating the attenuation rate of the water hammer oscillation curve is as follows:

[0089]

[0090]

[0091] Among them, α represents the attenuation rate of the water hammer oscillation curve, P w_stand To calculate the middle value.

[0092] The period, amplitude and attenuation rate of the pump stop water hammer oscillation curve are calculated by the above formula as follows: Figure 7 It can be seen that after the pump is stopped, obvious water hammer oscillation occurs in this shale gas well section. The characteristic parameters of the water hammer oscillation curve are: period of 14.125 seconds, amplitude of 5.525 MPa, and attenuation rate of 0.025746.

[0093] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing, characterized in that: The steps include: S1. Collect the second-by-second data of the fracturing operation recorded at the mine site and draw a fracturing operation pressure curve; set a composite criterion based on the pressure and displacement change patterns at the time of pump stop, use the composite criterion to analyze the second-by-second data of the fracturing operation, and automatically identify the pump stop point; S2. extracting a pump-off pressure change curve from the fracturing operation curve based on the pump-off point; S3, extracting a pump-off water hammer oscillation curve from the pump-off pressure change curve; S4. Analyze the pump-off water hammer oscillation curve to obtain characteristic parameters of the pump-off water hammer oscillation curve.

2. The method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing according to claim 1 is characterized in that: Step S1 includes the following sub-steps: S11. Collect the second-by-second data of the fracturing operation recorded at the mine, including the second-by-second time, wellhead pressure, discharge volume, and sand concentration; and draw a fracturing operation pressure curve; S12, extract the total number of seconds T of fracturing operation, and establish the pressure data sequence p1, p2, p3, ..., p T , displacement data sequence q1, q2, q3, ..., q T And the corresponding second time series t1, t2, t3, ..., t T , and extract the data sequence for calculation accordingly; S13, traverse the pump stop points; Set the current sequence number to i and extract the corresponding displacement q i and time t i ; Adopt the composite criterion based on the pressure and displacement change law at the time of pump shutdown to judge the displacement change at point i; S14. If point i satisfies the composite criterion, extract the pressure p corresponding to point i i Conduct verification and determination; S15, if the pressure corresponding to point i is p i If it meets the verification judgment, the corresponding value of point i is recorded and saved, and this point is the pump stop point; if it does not meet the verification judgment, the calculation of the next point is performed.

3. The method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing according to claim 2 is characterized in that: When traversing the pump stop points in step S13, the data range of the fracturing construction second point data is narrowed down in combination with the fracturing construction process characteristics.

4. The method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing according to claim 2 is characterized in that: The composite criteria include: Judgment condition 1: The displacement at the pump stop point is not lower than the preset threshold; Judgment condition 2: The displacement after the pump stop point is less than the displacement at the pump stop point; Judgment condition three: The displacement at the pump stop point and several subsequent data points shows a monotonically decreasing pattern.

5. The method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing according to claim 2 is characterized in that: The verification determination includes: During the fracturing process, the pressure drops rapidly after the pump stop point and the pressure after the pump stop point is lower than the pressure at the pump stop point.

6. The method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing according to claim 1 is characterized in that: Step S2 includes the following sub-steps: S21, extracting the data of the pump stop point and subsequent points from the fracturing construction second point data, obtaining the fracturing pressure data set after the pump stop and the total number of data after the pump stop N, and drawing a pump stop pressure change curve; S22, establish the pump stop pressure data sequence p with the pump stop time point as the starting point s1 、p s2 、p s3 ,…,p sN And the corresponding pump stop time series t s1 , t s2 , t s3 ,…,t sN , and extract the data sequence accordingly for subsequent calculation process.

7. The method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing according to claim 6, characterized in that: Step S3 includes the following sub-steps: S31. Based on the time when the displacement returns to zero after the pump is stopped, select the starting and ending points of the pump-stop water hammer oscillation curve in the pump-stop pressure change curve, and extract the corresponding pump-stop water hammer oscillation pressure data from the pump-stop pressure data in sequence to draw the pump-stop water hammer oscillation curve; S32, establish the pump stop water hammer oscillation pressure data sequence p w1 、p w2 、p w3 ,…,p wt And the corresponding pump stop water hammer oscillation second point time series t w1 , t w2 , t w3 ,…,t wt , and the subsequent calculation process is carried out accordingly.

8. The method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing according to claim 7 is characterized in that: Step S4 includes the following sub-steps: S41. Use numerical methods to analyze the water hammer oscillation pressure data when the pump is stopped. w3 and t wt-2 Perform cyclic calculation for the starting and ending points, record the peak and trough of each water hammer oscillation curve that meets the conditions; on this basis, establish the peak data sequence p of the water hammer oscillation curve that meets the conditions. c1 、p c2 ,…,p cn and trough data series p t1 、p t2 ,…,p tn , and mark the peaks and troughs on the water hammer oscillation curve when the pump is stopped; S42, using the pump stop water hammer oscillation curve peak data sequence p c1 、p c2 ,…,p cn And the trough data series p t1 、p t2 ,…,p tn Calculate characteristic parameters of the pump-off water hammer oscillation curve; the characteristic parameters of the pump-off water hammer oscillation curve include period, amplitude and attenuation rate.

9. The method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing according to claim 8, characterized in that: In step S41, when determining the peaks and troughs of the pump-stop water hammer oscillation curve, the influence of abnormal data points on the identification of peaks and troughs needs to be considered. The pressure before and after the peak should show a trend of first increasing and then decreasing, and the pressure before and after the trough should show a trend of first decreasing and then increasing.

10. The method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing according to claim 8, characterized in that: In step S42, the formula for calculating the water hammer oscillation curve period is as follows: Where T represents the period of water hammer oscillation curve, n represents the peak data sequence p of water hammer oscillation curve c1 、p c2 ,…,p cn and trough data series p t1 、p t2 ,…,p tn The number of data points.

11. The method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing according to claim 8, characterized in that: In step S42, the formula for calculating the amplitude of the water hammer oscillation curve is as follows: A=max{p c1 ,p c2 ,…,p cn }-min{p t1 ,p t2 ,…,p tn } Where A represents the amplitude of the water hammer oscillation curve.

12. The method for extracting and analyzing characteristic parameters of water hammer curves after pump shutdown in deep shale fracturing according to claim 8, characterized in that: In step S42, the formula for calculating the attenuation rate of the water hammer oscillation curve is as follows: Among them, α represents the attenuation rate of the water hammer oscillation curve, P w_stand To calculate the middle value.

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