Fault diagnosis method for belt slipping of oil pumping unit

Abstract

The invention belongs to the technical field of oil pumping unit fault diagnosis, and particularly relates to an oil pumping unit belt slipping fault diagnosis method. According to the method, the current horse head displacement curve, the current horse head load curve and the current rod pumped well indicator diagram of the oil pumping unit are obtained, and whether the oil pumping unit has the belt slipping fault or not is judged according to the conditions of the curve graphs and the corresponding judgment conditions; and the problems that the ground fault detection of the oil pumping unit depends on manual inspection and the fault detection is not timely are solved.

Description

Technical Field

[0001] This invention belongs to the field of oil pumping unit fault diagnosis technology, specifically relating to a fault diagnosis method for oil pumping unit belt slippage. Background Technology

[0002] my country has over 200,000 oil pumping units of various types, with beam pumping units accounting for more than 90% of the total in operation in oil fields. During field operation, beam pumping units frequently experience vibrations, shaking, abnormal noises, and even the beam falling and damaging the wellhead due to beam head cracking. Failure to detect these issues promptly during inspections and take appropriate measures can adversely affect the stable operation of oil and gas production. Currently, inspections mainly rely on manual on-site inspections, video inspections, and drone inspections. These methods all suffer from varying degrees of problems, including high costs, low efficiency, and delayed fault detection.

[0003] Chinese invention patent application CN112884068A discloses a method, apparatus, electronic device, and storage medium for fault diagnosis. This invention acquires a two-dimensional image of the load-displacement curve, determines multiple invariant moment feature sequences based on this image, and thus determines the characteristic parameters of the indicator diagram. Fault diagnosis is then completed based on these indicator diagram characteristic parameters and a pre-constructed classification model. While this method eliminates the need for manual on-site inspections, training and testing the pre-constructed classification model requires a large amount of sample data, resulting in low efficiency and delayed fault detection. Furthermore, this method is only applicable to downhole fault detection in pumping units; monitoring surface faults (such as belt slippage) still requires on-site inspections by technicians, leading to untimely monitoring of surface faults. Summary of the Invention

[0004] The purpose of this invention is to provide a fault diagnosis method for slippage of the pumping unit belt, so as to solve the problems of low efficiency and untimely fault detection in existing fault diagnosis methods.

[0005] To solve the above-mentioned technical problems, the present invention provides a fault diagnosis method for belt slippage in oil pumping units, the method comprising:

[0006] Obtain the current donkey head displacement curve, current donkey head load curve, and current pumping unit well indicator diagram of the pumping unit; if the current donkey head displacement curve meets at least one displacement curve judgment condition, the current donkey head load curve meets at least one load curve judgment condition, and the current pumping unit well indicator diagram meets at least one indicator diagram judgment condition, then it is determined that the pumping unit has a belt slippage fault.

[0007] The displacement curve determination conditions include: the total duration of the upper and lower strokes of the current donkey head displacement curve is greater than the total duration of the upper and lower strokes of the normal donkey head displacement curve, and the degree of the difference is greater than the first set degree threshold; within the time period T1, the degree of change of the displacement value of any two points in the current donkey head displacement curve is less than the second set degree threshold.

[0008] The load curve determination conditions include: the stable load portion of both the upper and lower strokes of the current donkey head load curve shows a sawtooth curve, and the deviation of the amplitude of the sawtooth from the corresponding normal amplitude is less than the third set threshold; within the T2 time period, the change in the load value of any two points in the current donkey head load curve is less than the fourth set threshold, where the T2 time period is the time period excluding all or part of the stable load portion of the upper and lower strokes of the donkey head load curve;

[0009] The criteria for determining the dynamometer diagram include: the load stability portions of both the upper and lower strokes of the current pumping unit well dynamometer diagram show sawtooth curves, and the deviation of the amplitude of the sawtooth from the corresponding normal amplitude is less than the fifth set threshold; the duration of the upper and lower strokes of the current pumping unit well dynamometer diagram is correspondingly greater than the duration of the upper and lower strokes of the normal pumping unit well dynamometer diagram, and the degree of greaterness is greater than the sixth set threshold; the current pumping unit well dynamometer diagram is an open graph or a closed graph that is not quadrilateral.

[0010] Furthermore, if the load value variation between any two points in the donkey head load curve of the pumping unit is no greater than the seventh set threshold, then the curve with the larger load value is determined to be the load-stable part of the upstroke, and the curve with the smaller load value is determined to be the load-stable part of the downstroke.

[0011] Furthermore, if the load value variation between any two points on the pumping unit well indicator diagram of the pumping unit is no greater than the seventh set threshold, then the curve with the larger load value is determined to be the load-stable part of the upstroke, and the curve with the smaller load value is determined to be the load-stable part of the downstroke.

[0012] Furthermore, if the displacement of the donkey head during the upward stroke of the current displacement curve decreases or remains unchanged over time, an alarm will be issued.

[0013] Furthermore, if the displacement of the donkey head during the downstroke of the current displacement curve increases or remains unchanged over time, an alarm will be issued.

[0014] Furthermore, if the time taken for the crank of the pumping unit to rotate one revolution in the current stroke is greater than the time taken for the crank of the pumping unit to rotate one revolution under normal circumstances, and the degree of the excess exceeds the eighth set threshold, an alarm will be issued.

[0015] Furthermore, if, within the T3 time period, the degree of change between the load values ​​of any two points on the current donkey head load curve or the current pumping unit well dynamometer diagram is less than the ninth preset threshold, an alarm is issued; the T3 time period is greater than the total duration of the current stroke.

[0016] Furthermore, the normal donkey head displacement curve is the theoretical donkey head displacement curve of the pumping unit well or the donkey head displacement curve during normal operation of the pumping unit.

[0017] Furthermore, the normal pumping unit well dynamometer diagram is either the theoretical pumping unit well dynamometer diagram or the pumping unit well dynamometer diagram during normal operation.

[0018] Its beneficial effects are as follows: This invention is a pioneering invention. It addresses the fact that existing methods for detecting pumping unit faults all focus on downhole fault detection, while surface fault detection still relies on manual inspection. Furthermore, when belt slippage occurs, the belt does not rotate synchronously with the two pulleys, and the gearbox does not rotate according to the speed ratio, causing changes in the pumping unit's current head displacement curve, current head load curve, and current well indicator diagram. Therefore, this invention utilizes the head displacement curve, head load curve, and existing dynamometer diagrams for detecting downhole pumping unit faults to improve the detection of surface faults. Ground fault detection of the pumping unit is performed. Specifically, various curves are acquired, and the differences between each curve and the normal curve are used to determine whether the pumping unit has experienced belt slippage. Specifically, the displacement curve judgment conditions include: the total duration of the upper and lower strokes of the current pumping unit displacement curve is greater than the total duration of the upper and lower strokes of the normal pumping unit displacement curve, and the degree of this greater-than-normality exceeds a first set threshold, meaning the belt does not rotate completely synchronously with the two pulleys, and the reduction gearbox does not rotate completely according to the speed ratio following the motor, resulting in an increase in the duration of the upper and lower strokes; within the time period T1, the degree of change in the displacement value of any two points on the current pumping unit displacement curve is less than a second set threshold. The severity threshold is defined as follows: due to severe belt slippage, the displacement remains unchanged. The load curve determination criteria include: the stable load portions of both the upper and lower strokes of the current donkey head load curve exhibit sawtooth curves, and the deviation of the sawtooth amplitude from the corresponding normal amplitude is less than the third set severity threshold. In other words, when slippage is minor, the upward or downward load is in a state of intermittent, incomplete unload and load variation, resulting in a sawtooth pattern on the load curve. Within time period T2, the change in load value between any two points on the current donkey head load curve is less than the fourth set severity threshold. T2 is the time period excluding the upper and lower strokes of the donkey head load curve. The fault occurs when the upward or downward load remains unchanged for any part or all of the stable load portion of the downstroke, i.e., when slippage is severe. The dynamometer card determination criteria include: sawtooth curves appearing in the stable load portions of both the upstroke and downstroke of the current pumping unit well dynamometer card, and the deviation of the sawtooth amplitude from the corresponding normal amplitude is less than the fifth set threshold; the duration of the upstroke and downstroke of the current pumping unit well dynamometer card is correspondingly greater than the duration of the upstroke and downstroke of the normal pumping unit well dynamometer card, and the degree of this greater-than-normality exceeds the sixth set threshold; the current pumping unit well dynamometer card is an open graph or a closed graph that is not quadrilateral. If the current donkey head displacement curve meets the arbitrary displacement curve determination criteria, the current donkey head load curve meets the arbitrary load curve determination criteria, and the current pumping unit well dynamometer card meets the arbitrary dynamometer card determination criteria, then the pumping unit is determined to have experienced belt slippage.The fault diagnosis method of the present invention does not require a large amount of sample data to build a network model as in the prior art for fault diagnosis. It can determine whether the pumping unit has a belt slippage fault simply by obtaining the curves of the pumping unit and analyzing the differences between the curves. This method is more convenient and faster, and solves the problems of relying on manual inspection and untimely fault detection for ground fault detection of pumping units. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a four-bar pumping unit according to an embodiment of the present invention;

[0020] Figure 2 This is the theoretical pumping unit donkey head displacement curve according to an embodiment of the present invention;

[0021] Figure 3 This is the theoretical pumping unit donkey head load curve of an embodiment of the present invention;

[0022] Figure 4 This is a theoretical pumping well dynamometer diagram according to an embodiment of the present invention;

[0023] Figures 5-10 This is a graph showing the belt slippage failure of pumping units in different oil wells according to an embodiment of the present invention.

[0024] Figure 11 This is a flowchart of a method according to an embodiment of the present invention. Detailed Implementation

[0025] This invention acquires the current donkey head displacement curve, current donkey head load curve, and current pumping unit well indicator diagram of the pumping unit. Based on the conditions of each curve, it determines whether the pumping unit has experienced belt slippage. Specifically, the displacement curve determination conditions include: the total duration of the upper and lower strokes of the current donkey head displacement curve is greater than the total duration of the upper and lower strokes of the normal donkey head displacement curve, and the degree of this greater-than-normality exceeds a first set threshold; within the time period T1, the degree of change in the displacement value of any two points in the current donkey head displacement curve is less than a second set threshold. The load curve determination conditions include: the stable load portions of both the upper and lower strokes of the current donkey head load curve exhibit sawtooth curves, and the deviation of the sawtooth amplitude from the corresponding normal amplitude is less than a third set threshold. The following conditions are considered: a certain degree threshold; within time period T2, the change in load value at any two points on the current donkey head load curve is less than the fourth predetermined degree threshold, where time period T2 is the time period excluding all or part of the stable load portion of the upper and lower strokes of the donkey head load curve; the dynamometer chart determination conditions include: the stable load portion of the upper and lower strokes of the current pumping unit well dynamometer chart shows sawtooth curves, and the deviation of the sawtooth amplitude from the corresponding normal amplitude is less than the fifth predetermined degree threshold; the duration of the upper and lower strokes of the current pumping unit well dynamometer chart is correspondingly greater than the duration of the upper and lower strokes of the normal pumping unit well dynamometer chart, and the degree of greater than is greater than the sixth predetermined degree threshold; the current pumping unit well dynamometer chart is an open graph or a closed graph that is not quadrilateral. If the current donkey head displacement curve meets the arbitrary displacement curve judgment condition, the current donkey head load curve meets the arbitrary load curve judgment condition, and the current pumping unit well dynamometer card meets the arbitrary dynamometer card judgment condition, then it is determined that the pumping unit has a belt slippage fault; this solves the problem of relying on manual inspection for pumping unit ground fault detection and the problem of untimely fault detection.

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0027] Method Implementation Examples:

[0028] This embodiment provides a remote diagnostic method for pumping unit belt slippage, such as... Figure 1As shown, with AB2 as the zero point of the crank angle, the pumping unit crank rotates counterclockwise at an angular velocity ω. When the crank is at B2, that is, when the pumping unit head reaches its lowest point, it indicates that the head is at the bottom dead center. Within the crank angle θ range of 0 to (π+α), the pumping unit's upward stroke is the upstroke; within the crank angle θ range of (π+α) to 2π, the pumping unit's downward stroke is the downstroke. The pumping unit motor and gearbox are driven by a V-belt. When the belt slips in the grooves of the motor pulley and the gearbox pulley, the belt does not rotate completely synchronously with the two pulleys, and the gearbox does not rotate completely according to the speed ratio, resulting in a total upstroke and downstroke time greater than the normal operating time. When the slippage is minor, the upward or downward load is in a state of intermittent, incomplete unload and load variation, resulting in a sawtooth pattern on the load curve and a deformation with a longer period on the displacement curve. Under special conditions such as rainy weather, when the slippage is severe, the upward or downward displacement of the head becomes static, and the upward or downward load remains unchanged. Therefore, this invention, based on the analysis of graphical and numerical changes in the donkey head displacement curve, donkey head load curve, and well dynamometer curve of the beam pumping unit generated using various operating parameters of the pumping unit, achieves remote diagnosis of pumping unit belt slippage faults. For example... Figure 11 As shown, it specifically includes the following:

[0029] Step 1: Collect parameters during the operation of the pumping unit, including: head displacement, head load, and walking beam inclination angle ψ.

[0030] In this embodiment, an inclination sensor is installed on the walking beam to collect the inclination angle ψ of the walking beam, and a stress sensor is used to collect stress change data. As for other implementation methods, appropriate sensors can be selected according to actual needs.

[0031] Step 2: The parameters collected in Step 1 are sent to the data receiving device. The host computer feeds back the relevant parameters received by the data receiving device to the internal digital and graphical displays to generate the donkey head displacement curve, donkey head load curve and pumping well dynamometer diagram.

[0032] ① Donkey head displacement curve.

[0033] like Figure 1 As shown, with AB2 as the zero point of the crank angle, the pumping unit crank rotates counterclockwise at an angular velocity ω. The movement of point B on the crank changes with time t and the crank angle, exhibiting a sinusoidal characteristic. Point C of the walking beam oscillates under the influence of the crank-connecting rod. Affected by the extreme position angle α and the characteristics of the four-bar linkage, the pumping unit moves upward (i.e., the upstroke) within the crank angle θ range of 0 to (π+α), and moves downward (i.e., the downstroke) within the crank angle θ range of (π+α) to 2π. The relationship between the stroke speed ratio coefficient k and the extreme position angle α is as follows:

[0034]

[0035] Under the influence of the quick-return characteristic of the stroke ratio k, the walking beam inclination angle ψ and the donkey head displacement S vary with time t and crank angle θ, approximating a non-standard sinusoidal characteristic. Crank angle θ = ωt, where ω is the crank angular velocity and t is time. Since the motion trajectory of the four-bar linkage can be determined through the constraints and geometric relationships between the links, the crank angle θ determines the corresponding walking beam inclination angle, and the walking beam inclination angle has a linear relationship with the donkey head displacement.

[0036]

[0037] Where S is the donkey head displacement, ψ is the inclination angle of the walking beam, and r is the length of the walking beam's forearm.

[0038] In actual operation, tilt sensors are installed on the walking beam. Each rotation of the crank causes the walking beam to move up and down once, and the tilt sensors collect N sets of tilt angle change data simultaneously, calculating and generating a real-time walking beam displacement curve; for example... Figure 2 As shown, the relationship between the inclination angle of the walking beam and the displacement of the donkey head changes with time, exhibiting a sinusoidal characteristic. The displacement is plotted as the vertical axis, and time and crank angle are plotted as the horizontal axis.

[0039] ② Donkey head load curve.

[0040] When the pumping unit moves upward, the load on the piston head mainly includes the weight of the rod and the weight of the liquid above the piston; when the pumping unit moves downward, the load on the piston head mainly includes the weight of the rod in the liquid column. During normal operation, the upward and downward piston head load curves are two parallel lines. Based on the upward and downward piston head loads, the change in the rod elastic load is superimposed, resulting in two inclined lines connecting the upward and downward piston head load curves for the transitions from upward to downward and from downward to upward. The slope of these inclined lines is related to the rod elongation δ, the crank angular velocity ω, and time t. Therefore, during normal operation, the stress sensor measures the load values ​​at 256 piston head suspension points simultaneously in each stroke. Figure 3 As shown, the donkey head load curve is a trapezoidal wave with load as the ordinate and time and crank angle as the abscissa. In this embodiment, 256 load points are measured at the donkey head suspension points. In other implementations, the number can be set according to actual needs.

[0041] The formula for calculating the elongation δ of the rod is:

[0042]

[0043] Where F represents the tensile force on the sucker rod string, in Newtons (N); L represents the length of the sucker rod string, in meters (m); E represents the elastic modulus of the sucker rod string, in Pascals (Pa); and A represents the cross-sectional area of ​​the sucker rod string, in square meters (m²). 2 ); δ is the elastic deformation that the donkey's head must overcome before it undergoes displacement, and its unit is meters (m).

[0044] ③Diagram of pumping unit well.

[0045] like Figure 4 As shown, the dynamometer diagram in this embodiment only considers the static load borne by the donkey head suspension point, i.e., the elastic deformation of the tubing caused by the static load. The load changes with displacement in the form of a parallelogram. In actual operation, the shape of the dynamometer diagram varies from well to well, but during normal operation of a four-bar pumping unit, the dynamometer diagram is usually unchanged between adjacent strokes.

[0046] Step 3: Based on the generated current donkey head displacement curve, current donkey head load curve, and current pumping unit well indicator diagram, respectively, compare them with the corresponding displacement curve judgment condition, load curve judgment condition, and indicator diagram judgment condition. Determine whether the pumping unit has experienced belt slippage based on the judgment results. If the current donkey head displacement curve meets at least one displacement curve judgment condition, the current donkey head load curve meets at least one load curve judgment condition, and the current pumping unit well indicator diagram meets at least one indicator diagram judgment condition, then the pumping unit is determined to have experienced belt slippage. Specific judgment methods include:

[0047] (1) Displacement curve determination conditions: The total duration of the upper and lower strokes of the current donkey head displacement curve is increased by more than 10% (i.e., the first set degree threshold) compared to the total duration of the upper and lower strokes of the normal donkey head displacement curve; within the T1 time period, the degree of change between the displacement values ​​of any two points in the current donkey head displacement curve is less than the second set degree threshold.

[0048] The pumping unit motor and gearbox are driven by a V-belt. When the belt slips in the grooves of the motor pulley and the gearbox pulley, the belt does not rotate completely synchronously with the two pulleys, and the gearbox does not rotate completely according to the speed ratio. The total time for the up and down strokes is greater than the normal operating time. When the slippage is minor, the donkey head displacement curve shows a deformation with a longer period due to the increase in the total stroke time. Under the influence of special conditions such as rain, when the slippage is severe, the upward or downward displacement of the donkey head becomes static, that is, the donkey head displacement curve approaches a straight line.

[0049] like Figure 5 , Figure 6 , Figure 7 , Figure 8 It is evident that the donkey head displacement curves in each figure exhibit deformation and longer periods; for example... Figure 9 , Figure 10 It is evident that the donkey head displacement curves in each figure are severely distorted and straightened into a single line. In particular, this embodiment... Figures 5-10The graphs represent the belt slippage faults of pumping units in different oil wells according to embodiments of the present invention. The gray curves in each graph are the donkey head load curves, with time on the horizontal axis and load magnitude on the vertical axis. The green curves in each graph are the donkey head displacement curves, with time on the horizontal axis and displacement magnitude on the vertical axis. The red curves in each graph are the pumping unit well dynamometer diagrams, with displacement magnitude on the horizontal axis and load magnitude on the vertical axis. Note that, due to the reverse installation direction of the sensors during the actual measurement, the donkey head displacement curves and dynamometer diagrams in each graph show the opposite time strokes relative to the donkey head load curves.

[0050] (2) Load curve determination conditions: The load stability part of the upper and lower strokes of the current donkey head load curve both show sawtooth curves, and the deviation of the amplitude of the sawtooth from the corresponding normal amplitude is less than 5% (i.e., the third set degree threshold); within the T2 time period, the change in the load value of any two points in the current donkey head load curve is less than the fourth set degree threshold, where the T2 time period is not entirely the load stability part of the upper and lower strokes of the donkey head load curve, that is, the T2 time period is the time period other than all or part of the load stability part of the upper and lower strokes of the donkey head load curve.

[0051] The pumping unit motor and gearbox are driven by a V-belt. When the belt slips in the grooves of the motor pulley and the gearbox pulley, the belt does not rotate completely synchronously with the two pulleys, and the gearbox does not rotate completely according to the speed ratio. When the slippage is slight, the upward or downward load is in a state of intermittent and incomplete unload and load change, and a sawtooth pattern appears on the load curve. When the slippage is severe under special conditions such as rain, the upward or downward load remains unchanged on the load curve outside the stable part of the load, for example, the upward and downward loads are equal.

[0052] like Figure 5 , Figure 7 , Figure 8 As shown, it is evident that the stable load portions (i.e., the top and bottom of the trapezoidal wave) of the donkey-head load curves in each figure are densely covered with sawtooth patterns; for example... Figure 6 , Figure 9 , Figure 10 It is clear that the donkey head load curves in each figure are straightened into a single line.

[0053] (3) Dynamometer Diagram Judgment Criteria: The load stability portion of both the upper and lower strokes of the current pumping unit well dynamometer diagram shows sawtooth curves, and the deviation of the amplitude of the sawtooth from the corresponding normal amplitude is less than 5% (i.e., the fifth set threshold); the duration of the upper and lower strokes of the current pumping unit well dynamometer diagram is increased by more than 10% compared with the duration of the upper and lower strokes of the normal pumping unit well dynamometer diagram (i.e., the sixth set threshold); the current pumping unit well dynamometer diagram is an open graph; the current pumping unit well dynamometer diagram is a closed graph but not a quadrilateral graph.

[0054] The horizontal axis of the dynamometer chart represents displacement, and the vertical axis represents load. When the pumping unit belt slips, the changes in displacement and load cause corresponding changes in the dynamometer chart. Currently, dynamometer charts for pumping unit wells exhibit densely jagged upward and downward lines, severe distortion, and even incomplete or non-quadrilateral shapes. For example... Figure 5 , Figure 7 As shown, it is evident that the downward and downward lines of the pumping unit well indicator diagrams in each figure are densely covered with serrated edges; such as Figure 6 , Figure 8 It is evident that the dynamometer diagrams of the pumping units in each figure are severely distorted; for example... Figure 7 , Figure 9 , Figure 10 As shown, it is clear that the dynamometer diagram of the pumping unit well in this figure is not closed; as Figure 8 It is evident that the pumping unit well dynamometer diagrams in each figure are not quadrilaterals.

[0055] In this embodiment, the normal donkey head displacement curve is the theoretical donkey head displacement curve of the pumping unit well or the donkey head displacement curve during normal operation of the pumping unit; the normal donkey head load curve is the theoretical donkey head load curve of the pumping unit or the donkey head load curve during normal operation of the pumping unit; and the normal pumping unit well dynamometer diagram is the theoretical pumping unit well dynamometer diagram of the pumping unit or the pumping unit well dynamometer diagram during normal operation of the pumping unit.

[0056] Within a stroke, when the load value of any two points in the current donkey head load curve of the pumping unit does not exceed 3% (i.e., the seventh set threshold), it represents the top or bottom. The curve with the larger load value is the stable load part of the upstroke, and the curve with the smaller load value is the stable load part of the downstroke.

[0057] Within a stroke, when the load value variation between any two points in the current pumping unit well indicator diagram does not exceed 3% (i.e., the seventh set threshold) in both curves, it indicates that it is at the top or bottom. The curve with the larger load value is the stable load part of the upstroke, and the curve with the smaller load value is the stable load part of the downstroke.

[0058] Step 4: If it is determined that the pumping unit well has a belt slippage fault, an alarm will be triggered by calculation and comparison.

[0059] If the analysis reveals any abnormalities in the current displacement curve, current load curve, or current pumping unit well indicator diagram of the pumping unit, an alarm will also be triggered.

[0060] In addition, an automatic alarm will be triggered if any of the following phenomena appear in the acquired curves:

[0061] Within the range of crank angle θ from 0 to (π+α), the displacement curve of the pumping unit increases monotonically with time. When the current displacement curve of the current stroke is detected to decrease monotonically or remain unchanged with time within this range, an automatic alarm is triggered.

[0062] Within the range of crank angle θ (π+α) to 2π, the displacement curve of the pumping unit decreases monotonically with time. When it is detected that the current displacement curve of the current stroke is monotonically increasing or unchanged with time when the crank angle is within this range, an automatic alarm is triggered.

[0063] Within one stroke, the time it takes for the crank to rotate one revolution is 10% longer than the time it takes for the crank to rotate one revolution during normal operation (i.e., the eighth set threshold).

[0064] Within a stroke, the load value at a certain point fluctuates by less than 5% compared to the load value at adjacent points (i.e., the ninth set threshold) and the duration exceeds the total stroke duration.

[0065] It should be noted that the various threshold values ​​set in this invention were obtained by those skilled in the art through repeated experiments and verifications. For example, the first threshold value set in this embodiment is 10% of the degree when the total duration of the upper and lower strokes in the current donkey head displacement curve is increased by more than 10% compared to the total duration of the upper and lower strokes in the normal donkey head displacement curve. This value is obtained by comparing the total duration of the upper and lower strokes of the donkey head displacement curves when multiple pumping units experience belt slippage failures with the total duration of the upper and lower strokes of the donkey head displacement curve under normal conditions, and then taking the average value.

[0066] Therefore, the remote diagnostic method for pumping unit belt slippage of the present invention combines the donkey head displacement curve, the donkey head load curve, and the pumping unit well dynamometer diagram to determine and identify whether the pumping unit has malfunctioned and whether the malfunction is belt slippage. This detection method is simpler and more efficient, and can detect pumping unit belt slippage in real time, avoiding serious accidents such as belt burnout and well shutdown due to untimely fault identification, or even well collapse and fire.

Claims

1. A method for diagnosing belt slippage in an oil pumping unit, characterized in that, The method includes: Obtain the current donkey head displacement curve, current donkey head load curve, and current pumping unit well indicator diagram of the pumping unit; if the current donkey head displacement curve meets at least one displacement curve judgment condition, the current donkey head load curve meets at least one load curve judgment condition, and the current pumping unit well indicator diagram meets at least one indicator diagram judgment condition, then it is determined that the pumping unit has a belt slippage fault. The displacement curve determination conditions include: the total duration of the upper and lower strokes of the current donkey head displacement curve is greater than the total duration of the upper and lower strokes of the normal donkey head displacement curve, and the degree of the difference is greater than the first set degree threshold; within the time period T1, the degree of change of the displacement value of any two points in the current donkey head displacement curve is less than the second set degree threshold. The load curve determination conditions include: the stable load portion of both the upper and lower strokes of the current donkey head load curve shows a sawtooth curve, and the deviation of the amplitude of the sawtooth from the corresponding normal amplitude is less than the third set threshold; within the T2 time period, the change in the load value of any two points in the current donkey head load curve is less than the fourth set threshold, where the T2 time period is the time period excluding all or part of the stable load portion of the upper and lower strokes of the donkey head load curve; The criteria for determining the dynamometer diagram include: the load stability portions of both the upper and lower strokes of the current pumping unit well dynamometer diagram show sawtooth curves, and the deviation of the amplitude of the sawtooth from the corresponding normal amplitude is less than the fifth set threshold; the duration of the upper and lower strokes of the current pumping unit well dynamometer diagram is correspondingly greater than the duration of the upper and lower strokes of the normal pumping unit well dynamometer diagram, and the degree of greaterness is greater than the sixth set threshold; the current pumping unit well dynamometer diagram is an open graph or a closed graph that is not quadrilateral.

2. The fault diagnosis method for pumping unit belt slippage according to claim 1, characterized in that, If the load value variation between any two points in the donkey head load curve of the pumping unit is no greater than the seventh set threshold, then the curve with the larger load value is determined to be the load-stable part of the upstroke of the donkey head load curve, and the curve with the smaller load value is determined to be the load-stable part of the downstroke of the donkey head load curve.

3. The fault diagnosis method for pumping unit belt slippage according to claim 1, characterized in that, If the load value variation between any two points on the pumping unit well indicator diagram is no greater than the seventh set threshold, then the curve with the larger load value is determined to be the load-stable part of the upstroke of the pumping unit well indicator diagram, and the curve with the smaller load value is determined to be the load-stable part of the downstroke of the pumping unit well indicator diagram.

4. The method for diagnosing belt slippage in an oil pumping unit according to any one of claims 1 to 3, characterized in that, If the displacement of the donkey head during the upward stroke of the current displacement curve decreases or remains unchanged over time, an alarm will be issued.

5. The method for diagnosing belt slippage in an oil pumping unit according to any one of claims 1 to 3, characterized in that, If the displacement of the donkey head during the downstroke of the current displacement curve increases or remains unchanged over time, an alarm will be issued.

6. The method for diagnosing belt slippage in an oil pumping unit according to any one of claims 1 to 3, characterized in that, If the time taken for the crank of the pumping unit to rotate once during the current stroke is longer than the normal time taken for the crank of the pumping unit to rotate once, and the degree of excess exceeds the eighth preset threshold, an alarm will be issued.

7. The fault diagnosis method for pumping unit belt slippage according to claim 1, characterized in that, If, within the T3 time period, the degree of change between the load values ​​of any two points on the current donkey head load curve or the current pumping unit well dynamometer diagram is less than the ninth preset threshold, an alarm will be issued; the T3 time period is longer than the total duration of the current stroke.

8. The fault diagnosis method for pumping unit belt slippage according to claim 1, characterized in that, The normal donkey head displacement curve is the theoretical donkey head displacement curve of the pumping unit well or the donkey head displacement curve during normal operation of the pumping unit.

9. The fault diagnosis method for pumping unit belt slippage according to claim 1, characterized in that, The normal pumping unit well dynamometer diagram refers to either the theoretical pumping unit well dynamometer diagram or the pumping unit well dynamometer diagram during normal operation.

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