Working condition diagnosis method for suspension system of oil pumping unit

Abstract

The invention relates to an oil pumping unit suspension system working condition diagnosis method, and belongs to the technical field of petroleum engineering. And processing the obtained indicator diagram data of the oil pumping unit to obtain displacement and load data. And determining a displacement interval in which the load is suddenly changed according to the minimum displacement point, finding all displacement points and all corresponding load values in the displacement interval in which the load is suddenly changed, fitting according to the displacement points and the corresponding load values to obtain a slope K of a fitting straight line, and determining a minimum load value Fmin in the displacement interval in which the load is suddenly changed. The average load value Favg in the effective descending stroke range of the pumping unit is calculated, the difference value between the Favg and the Fmin is used as delta F, delta f is calculated according to the difference value between the average load value Favg in the effective descending stroke range of the pumping unit and the minimum load value fmin in the effective descending stroke, and whether the abnormal working condition occurs currently or not is judged according to the size relation among the slope K, the delta F and the delta f. The problems that the data processing time is long, and the working condition diagnosis speed of the oil pumping unit is low are effectively solved.

Description

Technical Field

[0001] The present invention relates to a method for diagnosing the working condition of a pumping unit suspension system, belonging to the technical field of petroleum engineering. Background Art

[0002] The beam pumping unit oil production system accounts for a large proportion in the process of oil production. The schematic diagram of the existing pumping unit suspension system is as Figure 1 shown. The suspension system includes a wire rope hanger 1, a walking beam pin 2, a wire rope (pigtail) 3, and a polished rod hanger 4.

[0003] During the exploitation process, the pumping unit suspension system is vulnerable to various factors such as equipment aging, component damage, and environmental factors, which may lead to frequent failures of the pumping unit suspension system. The specific failure manifestations include cracks in the walking beam steel plate due to fatigue and gradual deterioration, broken wires in the wire rope due to fatigue or corrosion, and periodic rapid unloading caused by the square clamp hitting the wellhead.

[0004] The failure of the pumping unit suspension system may also lead to a decrease in the well opening rate, an increase in production costs, an increase in safety risks, and damage to the oil well. Therefore, it is very important to diagnose and timely maintain the working condition of the pumping unit suspension system. It is also necessary to carry out research on the working condition of the pumping unit suspension system. By using technical means to monitor the complex working condition in real time, potential faults can be detected in advance, reminding the management to make timely decision-making rectifications to ensure the normal operation and efficient production of the pumping unit.

[0005] The dynamometer card of an oil well reflects the change of the polished rod load of the pumping unit with displacement. By analyzing the geometric shape of the dynamometer card, the operating condition of the pumping unit can be judged. Traditional dynamometer card analysis is to manually identify the dynamometer card collected on site to judge the downhole working condition, and then the on-site engineer puts forward production measures according to the results. At present, most oilfields have installed fixed dynamometers for each pumping unit to realize the online collection of dynamometer cards, and the dynamometer card data can be obtained in real time. The change analysis of the dynamometer card provides a data basis for diagnosing and predicting the equipment working condition.

[0006] The Chinese patent application document with the application publication number of CN114810037A discloses a data-driven fault discrimination method for pumping unit wells. This fault discrimination method compares the maximum load and minimum load of the dynamometer card of the pumping unit well in the most recent 1 hour of operation with the normal dynamometer card to judge the current working condition of the pumping unit well. However, the data range selected by this fault discrimination method is relatively wide, resulting in a long data processing time. In fact, the area where the pumping unit fault occurs is small, which leads to a slow diagnosis speed of the pumping unit working condition. Summary of the Invention

[0007] The object of the present invention is to provide a method for diagnosing the working conditions of a pumping unit suspension system, which is used to solve the problems of long data processing time and slow diagnosis speed of the working conditions of the pumping unit in the prior art.

[0008] To achieve the above object, the technical solution provided by the present invention is:

[0009] The present invention provides a method for diagnosing the working conditions of a pumping unit suspension system. The diagnosis method includes the following steps:

[0010] 1) Process the obtained dynamometer card data of the pumping unit to obtain displacement and load data;

[0011] 2) Determine the displacement interval where the load suddenly changes according to the minimum displacement point, find all displacement points and corresponding load values within the displacement interval where the load suddenly changes, fit the slope K of the fitting line according to the displacement points and corresponding load values, and determine the minimum load value Fmin within the displacement interval where the load suddenly changes;

[0012] 3) Calculate the average load value Favg within the effective downstroke range of the pumping unit, take the difference between Favg and Fmin as ΔF, calculate Δf according to the difference between the average load value Favg within the effective downstroke range of the pumping unit and the minimum load value fmin within the effective downstroke range, and judge whether an abnormal working condition occurs currently according to the magnitude relationship among the slope K, ΔF, and Δf.

[0013] Further, when ΔF is greater than or equal to Δf and K is greater than the set first threshold, it is considered that an abnormal working condition occurs currently.

[0014] Further, if an abnormal working condition occurs currently, based on the time point when the abnormal working condition occurs, judge the development trend of the abnormal working condition according to the magnitude relationship between ΔF and Δf in each dynamometer card collected within the set time afterwards.

[0015] Further, when ΔF is greater than or equal to Δf and a is greater than the set second threshold, it indicates that the working condition of the pumping unit equipment is gradually deteriorating; when ΔF is greater than or equal to Δf and a is equal to the set second threshold, it indicates that the working condition of the pumping unit equipment remains stable; when ΔF is less than Δf and a is less than the set second threshold, it indicates that the working condition of the pumping unit equipment returns to normal, where a is the slope of the fitting line obtained by fitting the time points of each dynamometer card collected within the set time and the abnormal values, and the abnormal value refers to the difference between ΔF and Δf.

[0016] Further, when deterioration occurs, an alarm is given.

[0017] Further, the set second threshold is 0.

[0018] Further, when calculating the average load value Favg within the effective downward stroke range of the pumping unit, the load data corresponding to the displacement intervals where the load undergoes sudden changes is removed.

[0019] Further, if the minimum displacement points are repeated, the displacement interval where the load undergoes sudden changes is determined based on the position where the first minimum displacement point appears.

[0020] Beneficial effects: The method for diagnosing the working conditions of the suspension system of the pumping unit proposed by the present invention, compared with the existing methods for diagnosing the working conditions of the suspension system of the pumping unit, takes into account the load data and displacement data, and the considered features are relatively comprehensive. Moreover, the present invention determines the displacement interval where the load undergoes sudden changes based on the minimum displacement point, narrowing the area where pumping unit failures occur, thereby reducing the data processing time and effectively solving the problems of long data processing time and slow diagnosis speed of the working conditions of the pumping unit in the prior art. Description of the Drawings

[0021] Figure 1 is a schematic diagram of the existing suspension system of the pumping unit;

[0022] Figure 2 is a flow chart of the method for diagnosing the working conditions of the suspension system of the pumping unit of the present invention;

[0023] Figure 3 is a dynamometer card of the normal working condition of the pumping unit of the present invention;

[0024] Figure 4 is a dynamometer card of the working conditions of the suspension system of the pumping unit of the present invention;

[0025] Figure 5 is a marked diagram for determining the displacement range of load mutation of the present invention;

[0026] Figure 6 is a marked diagram of the minimum load value and the average load value of the present invention;

[0027] Figure 7 is a marked diagram of the minimum load value within the effective downward stroke of the present invention;

[0028] In the figures: 1. wire rope hanger; 2. walking beam pin; 3. wire rope (pigtail); 4. suspension clamp. Detailed Embodiments

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the drawings and embodiments.

[0030] The working condition diagnosis method for the pumping unit suspension system proposed by the present invention calculates the average load value within the effective downstroke range of the pumping unit, the minimum load value within the displacement interval where the load undergoes a sudden change, and the minimum load value within the effective downstroke based on the displacement data and load data of the dynamometer card. The method of fitting a straight line to data points is adopted, and the working condition of the suspension system of the pumping unit is diagnosed according to the relationship between the slope of the straight line and the average load value, the minimum load value within the displacement interval where the load undergoes a sudden change, and the minimum load value within the effective downstroke. Compared with the prior art, the present invention effectively solves the problems of long data processing time and slow diagnosis speed of the working conditions of the pumping unit in the prior art.

[0031] Embodiment of the working condition diagnosis method for the pumping unit suspension system:

[0032] The flow of the working condition diagnosis method for the pumping unit suspension system of the present invention is as Figure 2 shown, and the technical solution of the present invention is described as follows:

[0033] 1. Process the obtained dynamometer card data of the pumping unit to obtain displacement and load data

[0034] First, obtain the dynamometer card data of the pumping unit. The dynamometer card of the normal working condition of the pumping unit of the present invention is as Figure 3 shown, and the dynamometer card of the working condition of the suspension system of the pumping unit of the present invention is as Figure 4 shown. At the moment when the downstroke ends and the upstroke starts, the load does not show a gradually increasing trend with the increase of displacement, but shows a trend of instantaneously decreasing, then rapidly rising and returning to the normal value within a very short time with the increase of displacement. This phenomenon is caused by cracks in the pumping unit donkey head steel plate. The dynamometer card data is generally a long text string stored in a database, which includes two sets of data, displacement and load, separated by a ";" sign, and each displacement data and load data are separated by a "," sign. The format is: [x1,x2,...,x 256 ; [y1,y2,...,y 256 .

[0035] Then process the dynamometer card data to obtain the required displacement data (x) and load data (y). The split() function is used to split the string into two types of data according to displacement and load, obtaining a discrete displacement array [x1,x2,...,x 256 and a corresponding load array [y1,y2,...,y 256 .

[0036] 2. Determine the displacement interval where the load mutation occurs according to the minimum displacement point, find all displacement points and their corresponding load values within the displacement interval where the load mutation occurs, fit the slope K of the fitting line based on the displacement points and the corresponding load values, and determine the minimum load value Fmin within the displacement interval where the load mutation occurs

[0037] Traverse the displacement values of the indicator diagram, find the minimum displacement point, and mark it as S1. If the minimum displacement point is repeated, starting from the position where the first minimum displacement point appears, take 9 more displacement values backward in sequence. The 10 displacement values are S1, S2, S3, S4, S5, S6, S7, S8, S9, S 10 , then the determined displacement interval where the load mutation occurs is S1~S 10 , as Figure 5 shown. In this embodiment, S1, S2, S3, S4, S5, S6, S7, S8, S9, S 10 are 0.00, 0.01, 0.02, 0.03, 0.04, 0.06, 0.07, 0.09, 0.11, 0.13 respectively.

[0038] Find all displacement points [X1, X2, …, X n and their corresponding all load values [Y1, Y2, …, Y n within the displacement range of 0 to 0.13 meters. Fit a straight line based on the displacement points and the corresponding load values, and calculate the slope K of the straight line. In this embodiment, the slope K≈28.6.

[0039] 3. Calculate the average load value Favg within the effective downstroke range of the pumping unit, use the difference between Favg and Fmin as ΔF, calculate Δf according to the difference between the average load value Favg and the minimum load value fmin within the effective downstroke, and judge whether an abnormal working condition occurs currently according to the magnitude relationship among the slope K, ΔF, and Δf

[0040] There are four values a, b, c, d after the end “$” symbol in the load data of the indicator diagram, which represent the bottom dead center, the loading completion point, the top dead center, and the unloading completion point respectively. The positions in the displacement array [x1, x2,..., x 256 are x a , x b , x c , x d . In this embodiment, the four values after the load data “$” symbol are 230, 5, 105, 143 respectively. Then the position of the unloading completion point is x 143= 3.88. Therefore, the load values within the effective downward stroke range (0.13 - 3.88 m) of the pumping unit are selected for calculation, and the average load value Favg on the polished rod during the downward movement of the pump piston is calculated. The calculated average load value does not include the load values corresponding to the displacement range of 0 - 0.13 m. In this embodiment, Favg = 59.75 KN. At the same time, the minimum load value Fmin within the displacement interval where the load changes suddenly is screened out from the load array. As Figure 6 shown, in this embodiment, Fmin is 20 KN.

[0041] Due to factors such as the vibration of the polished rod during the downward movement of the pump piston, the load value in the initial section of the effective downward stroke will fluctuate. To rule out the possibility that Fmin is caused by this reason, the minimum load value within the effective downward stroke is denoted as fmin. As Figure 7 shown, in this embodiment, fmin = 54.93 KN. The threshold value Δf = Favg - fmin = 59.75 - 54.93 = 4.82 KN, and ΔF = Favg - Fmin = 59.75 - 20 = 39.75 KN. It can be judged that when ΔF ≥ 4.82 KN and K is greater than the set first threshold value. In this embodiment, the set first threshold value is tan85° ≈ 11.43, which indicates that an abnormal working condition has occurred currently. The setting of the first threshold value is to reflect the rapid downward trend of the load line, and the fitting straight line obtained by fitting the displacement point and the corresponding load value approaches the y-axis, and the angle between the fitting straight line and the x-axis is close to 90°. Meeting the above conditions can be set as the first threshold value.

[0042] Mark the abnormal values that meet the condition of ΔF ≥ 4.82 KN and mark them as F. Based on the time point when this special working condition appears, take several adjacent time points backward. In this embodiment, take three adjacent time points backward. The reason for taking three adjacent time points is that currently, most oil fields push the online dynamometer card on average every 10 minutes. Within 30 minutes, the small faults characterized by the three dynamometer cards may develop into accidents. Therefore, the specific number of points cannot be too many. For the corresponding abnormal value F that meets the conditions, with the time point as the x-axis and the abnormal value F as the y-axis, fit a straight line according to two points and calculate the slope a of the straight line.

[0043] Judge the magnitude relationship among the slope a, ΔF, and Δf. When ΔF ≥ Δf and a is greater than the set second threshold value, it indicates that the working condition of the pumping unit equipment is gradually deteriorating, and a warning message is sent at this time; when ΔF ≥ Δf and a is equal to the set second threshold value, it indicates that the working condition of the pumping unit equipment remains stable, usually the square clamp touches the wellhead; when ΔF

Claims

1. A method for diagnosing the working condition of a pumping unit suspension system, characterized in that, The diagnostic method includes the following steps: 1) Process the obtained dynamometer card data of the pumping unit to obtain displacement and load data; 2) Determine the displacement interval where the load mutation occurs according to the minimum displacement point, find all displacement points and corresponding load values within the displacement interval where the load mutation occurs, fit the slope K of the fitting line according to the displacement points and corresponding load values, and determine the minimum load value Fmin within the displacement interval where the load mutation occurs; 3) Calculate the average load value Favg within the effective downstroke range of the pumping unit, take the difference between Favg and Fmin as ΔF, calculate Δf according to the difference between the average load value Favg within the effective downstroke range of the pumping unit and the minimum load value fmin within the effective downstroke, and judge whether an abnormal working condition occurs currently according to the magnitude relationship among the slope K, ΔF, and Δf.

2. The working condition diagnosis method of the pumping unit suspension system according to claim 1, wherein, When ΔF is greater than or equal to Δf and K is greater than the set first threshold, it is considered that an abnormal working condition occurs currently.

3. The working condition diagnosis method of the pumping unit suspension system according to claim 2, characterized in that, If an abnormal working condition occurs currently, based on the time point when the abnormal working condition occurs, judge the development trend of the abnormal working condition by judging the magnitude relationship between ΔF and Δf in each dynamometer card collected within the set time later.

4. The working condition diagnosis method of the pumping unit suspension system according to claim 3, characterized in that, When ΔF is greater than or equal to Δf and a is greater than the set second threshold, it indicates that the working condition of the pumping unit equipment deteriorates gradually; when ΔF is greater than or equal to Δf and a is equal to the set second threshold, it indicates that the working condition of the pumping unit equipment remains stable; when ΔF is less than Δf and a is less than the set second threshold, it indicates that the working condition of the pumping unit equipment returns to normal, where a is the slope of the fitting line obtained by fitting the time points and abnormal values of each dynamometer card collected within the set time, and the abnormal value refers to the difference between ΔF and Δf.

5. The working condition diagnosis method of the pumping unit suspension system according to claim 4, characterized in that When deterioration occurs, an alarm is given.

6. The working condition diagnosis method of the pumping unit suspension system according to claim 4, characterized in that, The set second threshold is 0.

7. The working condition diagnosis method of the pumping unit suspension system according to claim 1, characterized in that The average load value Favg within the effective downstroke range of the pumping unit excludes the load data corresponding to the displacement interval where the load mutation occurs during calculation.

8. The working condition diagnosis method of the pumping unit suspension system according to claim 1, characterized in that, If the minimum displacement point repeats, the displacement interval where the load mutation occurs is determined based on the position where the first minimum displacement point appears.

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