Fault diagnosis method for high return pressure of oil pumping unit

Abstract

The invention belongs to the technical field of oil pumping unit fault diagnosis, and particularly relates to a fault diagnosis method for high return pressure of an oil pumping unit. According to the method, the current horse head load curve and the current rod pumped well indicator diagram of the oil pumping unit are obtained; and judging whether the pumping unit has a fault of high return pressure or not according to the corresponding difference between the graph presented by the current horsehead load curve and the current pumping unit well indicator diagram and the graph presented by the normal horsehead load curve and the normal pumping unit well indicator diagram. The problems that ground fault detection of the oil pumping unit depends on manual inspection and fault detection is not timely are solved.

Description

Technical Field

[0001] This invention belongs to the field of oil pumping unit fault diagnosis technology, and specifically relates to a fault diagnosis method for high back pressure in oil pumping units. 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 oilfields. During field operation, beam pumping units frequently experience malfunctions such as reduced oil and gas production, tubing blockage, wellhead leakage, and environmental pollution due to high back pressure. Failure to detect these issues promptly during inspections and implement appropriate measures can negatively impact 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 CN101285463A discloses a method and system for controlling the pumping of a rod pump. This method generates a surface dynamometer diagram by collecting data on the suspension point load and displacement of the pumping unit, calculates the underground pump dynamometer diagram using wave equations, and determines whether the pumping unit has malfunctioned based on the graphical characteristics of the pump dynamometer diagram. While this method eliminates the need for manual inspection, it can only identify downhole malfunctions and cannot determine or identify surface malfunctions. Surface malfunctions still rely on manual inspection, resulting in delayed detection and low efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a fault diagnosis method for high back pressure in oil pumping units, in order to solve the problems of relying on manual inspection and untimely fault detection for ground fault detection of oil pumping units.

[0005] To solve the above-mentioned technical problems, the present invention provides a fault diagnosis method for high back pressure in an oil pumping unit, the method comprising:

[0006] Obtain the current donkey head load curve and the current pumping unit well indicator diagram; if the current donkey head load curve meets any three of the donkey head load judgment conditions and the current pumping unit well indicator diagram meets any three of the indicator diagram judgment conditions, then it is determined that the pumping unit has a high back pressure fault.

[0007] The donkey head load determination conditions include: the duration of the stable load portion of the upper and lower strokes of the current donkey head load curve is correspondingly shorter than the duration of the stable load portion of the upper and lower strokes of the normal donkey head load curve, and the degree of less is greater than the corresponding first set threshold; the rate of change of the loading and unloading portion of the current donkey head load curve is correspondingly shorter than the rate of change of the loading and unloading portion of the normal donkey head load curve, and the degree of less is greater than the corresponding second set threshold; the duration of the loading and unloading portion of the current donkey head load curve is correspondingly longer than the duration of the loading and unloading portion of the normal donkey head load curve, and the degree of greater is greater than the third set threshold; the load of the stable load portion of the upper stroke of the current donkey head load curve is greater than the load of the stable load portion of the upper stroke of the normal donkey head load curve, and the degree of greater is greater than the fourth set threshold; and the load of the stable load portion of the lower stroke of the current donkey head load curve is less than the load of the stable load portion of the lower stroke of the normal donkey head load curve, and the degree of less is greater than the fourth set threshold.

[0008] The dynamometer chart determination conditions include: the duration of the stable load portion of the upper and lower strokes of the current pumping unit well dynamometer chart is correspondingly less than the duration of the stable load portion of the upper and lower strokes of the normal pumping unit well dynamometer chart, and the degree of less is greater than the corresponding first set threshold; the rate of change of the loading and unloading portion of the current pumping unit well dynamometer chart is correspondingly less than the rate of change of the loading and unloading portion of the normal pumping unit well dynamometer chart, and the degree of less is greater than the corresponding second set threshold; the duration of the loading and unloading portion of the current pumping unit well dynamometer chart is correspondingly greater than the duration of the loading and unloading portion of the normal pumping unit well dynamometer chart, and the degree of greater is greater than the third set threshold; the load of the stable load portion of the upper stroke of the current pumping unit well dynamometer chart is greater than the load of the stable load portion of the upper stroke of the normal pumping unit well dynamometer chart, and the degree of greater is greater than the fourth set threshold; and the load of the stable load portion of the lower stroke of the current pumping unit well dynamometer chart is less than the load of the stable load portion of the lower stroke of the normal pumping unit well dynamometer chart, and the degree of less is greater than the fourth set threshold.

[0009] 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 fifth 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.

[0010] Furthermore, if the degree of change between the load values ​​of any two points on two curves in the pumping unit well dynamometer diagram is no greater than the fifth 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 dynamometer 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 dynamometer diagram.

[0011] Furthermore, the rate of change of the loading and unloading portion of the current donkey head load curve is less than the rate of change of the loading and unloading portion of the normal donkey head load curve, and the degree of less than is greater than the corresponding second set threshold means that the absolute value of the slope of the loading and unloading portion of the current donkey head load curve is less than the absolute value of the slope of the loading and unloading portion of the normal donkey head load curve, and the degree of less than is greater than the corresponding second set threshold.

[0012] Furthermore, the statement that the rate of change of the loading and unloading portion of the current pumping unit well dynamometer diagram is correspondingly less than the rate of change of the loading and unloading portion of the normal pumping unit well dynamometer diagram, and the degree of less is greater than the corresponding second set threshold, means that the absolute value of the slope of the loading and unloading portion of the current pumping unit well dynamometer diagram is correspondingly less than the absolute value of the slope of the loading and unloading portion of the normal pumping unit well dynamometer diagram, and the degree of less is greater than the second set threshold.

[0013] Furthermore, if the current pumping unit well dynamometer card meets any three of the aforementioned dynamometer card determination conditions compared to a normal pumping unit well dynamometer card within the previous T1 hour period, then the back pressure pipeline is determined to have a freezing or wax blockage fault; if the current pumping unit well dynamometer card meets any three of the aforementioned dynamometer card determination conditions compared to a normal pumping unit well dynamometer card within the previous X1 strokes, then the back pressure pipeline is determined to have a mechanical fault due to reversed flow.

[0014] Furthermore, 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.

[0015] 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.

[0016] Furthermore, within the adjacent X2 strokes of the pumping unit operation, if the maximum value of the current donkey head load curve is greater than the maximum value of a certain donkey head load curve within the previous X2 strokes and the degree of the difference is greater than the sixth set threshold, and the minimum value of the current donkey head load curve is less than the minimum value of a certain donkey head load curve within the previous X2 strokes and the degree of the difference is greater than the sixth set threshold, then an alarm is triggered.

[0017] Furthermore, within the adjacent T2 time period of the pumping unit's operation, if the maximum value of the current donkey head load curve is greater than the maximum value of a certain donkey head load curve in the previous T2 time period and the degree of the difference is greater than the seventh set threshold, and the minimum value of the current donkey head load curve is less than the minimum value of a certain donkey head load curve in the previous T2 time period and the degree of the difference is greater than the seventh set threshold, then an alarm is triggered.

[0018] Its beneficial effects are as follows: This invention is a pioneering invention. It considers 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 a pumping unit experiences high back pressure, the compression and release of oil and gas can cause abnormal increases or decreases in load during the up and down strokes, and the loading and unloading times also change abnormally. This leads to abnormal changes in the pumping unit's head load curve and dynamometer diagram. Therefore, this invention uses the head load curve and existing dynamometer diagrams for detecting downhole pumping unit faults to detect surface faults. By combining the changes in the current head load curve and the current dynamometer diagram, this invention determines whether a high back pressure fault has occurred in the pumping unit, aiming to improve the accuracy of pumping unit fault diagnosis. This invention discovers that when a pumping unit experiences a high back pressure fault, due to progressive freezing or wax blockage in the back pressure pipeline, the flow-through inner diameter of the back pressure pipeline gradually decreases. This blockage leads to increasingly obstructed oil and gas flow from the well, causing the pumping unit's head load curve to exhibit a trapezoidal wave with a higher and narrower top, a lower and narrower bottom, and two increasingly gentle, longer, and higher slopes. Based on this, a judgment condition is established based on changes in the current head load curve and the current pumping unit well dynamometer diagram to diagnose pumping unit faults.The donkey head load determination conditions include: the duration of the stable load portion of the upper and lower strokes of the current donkey head load curve is correspondingly shorter than the duration of the stable load portion of the upper and lower strokes of the normal donkey head load curve, and the degree of less is greater than the corresponding first set threshold, i.e., the top and bottom of the donkey head load curve become narrower; the rate of change of the loading and unloading portions of the current donkey head load curve is correspondingly shorter than the rate of change of the loading and unloading portions of the normal donkey head load curve, and the degree of less is greater than the corresponding second set threshold, i.e., the two slopes of the donkey head load curve become gentler; the duration of the loading and unloading portions of the current donkey head load curve is correspondingly longer than the duration of the loading and unloading portions of the normal donkey head load curve, and the degree of greater is greater than the third set threshold, i.e., the two slopes of the donkey head load curve become longer; the load of the stable load portion of the upper stroke of the current donkey head load curve is greater than the load of the stable load portion of the upper stroke of the normal donkey head load curve, and the degree of greater is greater than the fourth set threshold, and the load of the stable load portion of the lower stroke of the current donkey head load curve is less than the load of the stable load portion of the lower stroke of the normal donkey head load curve, and the degree of less is greater than the fourth set threshold. The load curve is higher than the fourth preset threshold, meaning the two slopes of the donkey head load curve become higher. The dynamometer card determination conditions include: the duration of the stable load portion of the upper and lower strokes of the current pumping unit well dynamometer card is correspondingly shorter than the duration of the stable load portion of the upper and lower strokes of the normal pumping unit well dynamometer card, and the degree of this shorterness exceeds the corresponding first preset threshold; the rate of change of the loading and unloading portions of the current pumping unit well dynamometer card is correspondingly shorter than the rate of change of the loading and unloading portions of the normal pumping unit well dynamometer card, and the degree of this shorterness exceeds the corresponding second preset threshold; the current pumping unit well... The duration of the loading and unloading portions of the dynamometer card is correspondingly greater than the duration of the loading and unloading portions of the normal pumping unit well dynamometer card, and the degree of this greater duration exceeds the third set threshold. The load of the stable portion of the upstroke load of the current pumping unit well dynamometer card is greater than the load of the stable portion of the upstroke load of the normal pumping unit well dynamometer card, and the degree of this greater duration exceeds the fourth set threshold. Furthermore, the load of the stable portion of the downstroke load of the current pumping unit well dynamometer card is less than the load of the stable portion of the downstroke load of the normal pumping unit well dynamometer card, and the degree of this lessness exceeds the fourth set threshold. If the current donkey head load curve meets any three of the donkey head load judgment conditions and the current pumping unit well dynamometer card meets any three of the dynamometer card judgment conditions, then the pumping unit is determined to have a high back pressure fault, thus solving the problem of relying on manual inspection for pumping unit surface fault detection and the untimely fault detection. 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 donkey head load curve of the four-bar pumping unit according to an embodiment of the present invention;

[0021] Figure 3 This is a theoretical pumping well dynamometer diagram of the four-bar pumping unit according to an embodiment of the present invention;

[0022] Figure 4 This is a graph showing the normal operation of the four-bar pumping unit according to an embodiment of the present invention;

[0023] Figure 5 This is a graph showing the high back pressure fault of the four-bar pumping unit according to an embodiment of the present invention.

[0024] Figure 6 This is a dynamometer diagram of a pumping unit well during normal operation of a four-bar linkage pumping unit according to an embodiment of the present invention.

[0025] Figure 7 This is a dynamometer diagram of a pumping unit well when a high back pressure fault occurs in a four-bar pumping unit according to an embodiment of the present invention.

[0026] Figure 8 This is a flowchart of a method according to an embodiment of the present invention. Detailed Implementation

[0027] This invention obtains the current donkey head load curve and the current pumping unit well indicator diagram of the pumping unit. If the current donkey head load curve meets any three of the donkey head load determination conditions and the current pumping unit well indicator diagram meets any three of the indicator diagram determination conditions, then the pumping unit is determined to have a high back pressure fault. The donkey head load determination conditions include: the duration of the stable load portion of the upper and lower strokes of the current donkey head load curve is correspondingly shorter than the duration of the stable load portion of the upper and lower strokes of the normal donkey head load curve, and the degree of less is greater than a corresponding first set threshold; the loading of the current donkey head load curve, The rate of change of the unloading portion is correspondingly less than the rate of change of the loading and unloading portions of the normal donkey head load curve, and the degree of less is greater than the corresponding second set threshold; the duration of the loading and unloading portions of the current donkey head load curve is correspondingly greater than the duration of the loading and unloading portions of the normal donkey head load curve, and the degree of greater is greater than the third set threshold; the load of the stable portion of the load during the upstroke of the current donkey head load curve is greater than the load of the stable portion of the load during the upstroke of the normal donkey head load curve, and the degree of greater is greater than the fourth set threshold; and the load of the stable portion of the load during the downstroke of the current donkey head load curve... The load of the current pumping unit well is less than the load of the stable portion of the downstroke of the normal pumping unit well load curve, and the degree of less is greater than the fourth set threshold. The dynamometer card determination conditions include: the duration of the stable portion of the load of the upstroke and downstroke of the current pumping unit well dynamometer card is correspondingly less than the duration of the stable portion of the load of the upstroke and downstroke of the normal pumping unit well dynamometer card, and the degree of less is greater than the corresponding first set threshold; the rate of change of the loading and unloading portions of the current pumping unit well dynamometer card is correspondingly less than the rate of change of the loading and unloading portions of the normal pumping unit well dynamometer card, and the degree of less is greater than the corresponding second set threshold. Thresholds: The duration of the loading and unloading portions of the current pumping unit well dynamometer diagram is greater than the duration of the loading and unloading portions of the normal pumping unit well dynamometer diagram, and the degree of the difference is greater than the third set threshold; The load of the stable portion of the load during the upstroke of the current pumping unit well dynamometer diagram is greater than the load of the stable portion of the load during the upstroke of the normal pumping unit well dynamometer diagram, and the degree of the difference is greater than the fourth set threshold; and the load of the stable portion of the load during the downstroke of the current pumping unit well dynamometer diagram is less than the load of the stable portion of the load during the downstroke of the normal pumping unit well dynamometer diagram, and the degree of the difference is greater than the fourth set threshold.

[0028] 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.

[0029] Method Implementation Examples:

[0030] This embodiment presents a fault diagnosis method for high back pressure in a pumping unit. When the back pressure pipeline experiences progressive freezing or wax blockage, the flow-through inner diameter gradually decreases. This blockage leads to obstructed oil and gas flow from the well, resulting in excessive pressure on the oil well's main pipeline, ultimately causing a high back pressure fault in the pumping unit. Based on this, by analyzing the changes in the current beam pumping unit's load curve and the current pumping unit well dynamometer curve, remote diagnosis of the high back pressure fault is achieved. Figure 8 As shown, it specifically includes the following:

[0031] Step 1: Collect parameters during the operation of the pumping unit, including: head displacement, head load, and walking beam inclination angle ψ.

[0032] 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.

[0033] Step 2: The parameters collected in Step 1 are sent to the data receiving device. The host computer then feeds back the relevant parameters received by the data receiving device to the internal digital and graphical displays to generate the current donkey head load curve and the current pumping unit well dynamometer diagram.

[0034] ① Donkey head load curve:

[0035] 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. When the crank is at B2, that is, when the pumping unit head is at its lowest point, it indicates that the head is at the bottom dead center. Among them, in the range of crank angle θ from 0 to (π+α), the pumping unit's upward stroke is the upstroke, and the head load mainly includes the weight of the rod and the weight of the liquid above the piston. In the range of crank angle θ from (π+α) to 2π, the pumping unit's downward stroke is the downstroke, and the head load mainly consists of the weight of the rod in the liquid column. During normal operation of the pumping unit, the upward and downward load curves of the lifting rod are two parallel lines. Based on the lifting and downward lifting rod loads, the change in rod elastic load is superimposed. The lifting rod load curves transitioning from upward to downward and from downward to upward are two inclined lines connecting the upward and downward load curves. The slope of these lines is related to the rod elongation δ, the crank angular velocity ω, and time t. Therefore, during normal operation of the pumping unit, the stress sensor measures the load values ​​at 256 lifting rod points simultaneously within each stroke. Figure 2 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.

[0036] The formula for calculating the elongation δ of the rod is:

[0037]

[0038] 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 can move, and the unit is meters (m).

[0039] ② Pumping unit well indicator diagram:

[0040] like Figure 3 As shown, the dynamometer diagram only considers the static load borne by the donkey head suspension point, and the load changes with displacement in a parallelogram shape. 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.

[0041] Step 3: Compare the generated current donkey head load curve and current pumping unit well dynamometer diagram with the normal donkey head load curve and normal pumping unit well dynamometer diagram, respectively, and determine whether the pumping unit has a high back pressure fault based on the comparison results.

[0042] Specific discrimination methods include:

[0043] (1) The conditions for determining the load of the donkey head include: the duration of the load stabilization portion of the upper and lower strokes of the current donkey head load curve is reduced by more than 5% compared to the duration of the load stabilization portion of the upper and lower strokes of the normal donkey head load curve (i.e., the first set threshold); the absolute value of the slope of the loading and unloading portion of the current donkey head load curve is reduced by more than 5% compared to the absolute value of the slope of the loading and unloading portion of the normal donkey head load curve (i.e., the second set threshold); the duration of the loading and unloading portion of the current donkey head load curve is extended by more than 5% compared to the duration of the loading and unloading portion of the normal donkey head load curve (i.e., the third set threshold); the load of the load stabilization portion of the upper stroke of the current donkey head load curve is increased by more than 10% compared to the load stabilization portion of the upper stroke of the normal donkey head load curve (i.e., the fourth set threshold), and the load of the load stabilization portion of the lower stroke of the current donkey head load curve is reduced by more than 10% compared to the load stabilization portion of the lower stroke of the normal donkey head load curve (i.e., the fourth set threshold).

[0044] When a pumping unit experiences high back pressure, due to progressive freezing or wax blockage in the back pressure pipeline, during the upward movement of the pump head, the oil and gas above the moving valve of the deep well pump in the wellbore cannot flow through the blockage point in time. The reaction force of this compressed oil and gas acts on the pump head, increasing the upward load, reducing the upward time, and lengthening the loading time. During the downward movement, the elastic energy of the compressed oil and gas is released, resulting in a decrease in the downward load, a decrease in the downward time, and a lengthening of the unloading time. When mechanical failures such as reverse flow occur in the back pressure pipeline, the oil and gas produced from the well cannot pass through the back pressure pipeline. Within a few strokes, the compression and release of the oil and gas will lead to a sharp increase in the upward load and a sharp decrease in the downward load, with both the upward loading time and the downward unloading time becoming longer. Based on this, the pump head load curve presents as a trapezoidal wave with narrower tops and bottoms, and the two sloping lines become gentler, longer, and higher. In addition, since changes in each data point will cause changes in related data, for example, within a stroke time, when the two slopes of the donkey head load curve become gentler, longer and higher, the top and bottom will become narrower. Therefore, if any three of the above judgment conditions are met, the judgment conditions of the donkey head load curve are determined to be met.

[0045] like Figure 4 This is a graph showing the operating conditions of the pumping unit in this embodiment. Figure 5 This is a graph showing the back pressure failure of the pumping unit in this embodiment. Figure 4 , Figure 5 A comparison shows that if the pumping unit experiences a high back pressure fault, the top of the trapezoidal wave of the current donkey head load curve becomes higher and narrower, while the bottom becomes lower and narrower, and the two sloping lines become gentler, longer, and higher; in this embodiment... Figure 4 , Figure 5 The gray curves in the figures represent the donkey head load curves, with time on the x-axis and load magnitude on the y-axis. The green curves in each figure represent the donkey head displacement curves, with time on the x-axis and displacement magnitude on the y-axis. The red curves in each figure represent the pumping unit well dynamometer diagrams, with displacement magnitude on the x-axis and load magnitude on the y-axis. Note that due to the sensor being installed in the wrong direction during the actual measurement, the donkey head displacement curves and dynamometer diagrams in each figure show the opposite time stroke relative to the donkey head load curve.

[0046] (2) The criteria for determining the dynamometer diagram include: the duration of the load-stable portion of the upper and lower strokes of the current pumping unit well dynamometer diagram is reduced by more than 5% compared to the duration of the load-stable portion of the upper and lower strokes of the normal pumping unit well dynamometer diagram (i.e., the first set threshold); the absolute value of the slope of the loading and unloading portion of the current pumping unit well dynamometer diagram is reduced by more than 5% compared to the absolute value of the slope of the loading and unloading portion of the normal pumping unit well dynamometer diagram (i.e., the second set threshold); the duration of the loading and unloading portion of the current pumping unit well dynamometer diagram... The time is extended by more than 5% compared to the duration of the loading and unloading sections of the normal pumping unit well dynamometer diagram (i.e., the third set threshold); the load of the stable load section of the current pumping unit well dynamometer diagram during the upstroke is increased by more than 10% compared to the stable load section of the current pumping unit well dynamometer diagram during the upstroke (i.e., the fourth set threshold), and the load of the stable load section of the current pumping unit well dynamometer diagram during the downstroke is decreased by more than 10% compared to the stable load section of the current pumping unit well dynamometer diagram during the downstroke (i.e., the fourth set threshold).

[0047] Since the horizontal axis of the dynamometer chart of a pumping unit well represents displacement and the vertical axis represents load, when a high back pressure fault occurs in the pumping unit, the displacement of the pumping unit will not change abnormally. However, the load in the upper stroke is greater than normal, and the duration of the stable load portion in the upper stroke is shorter. Similarly, the load in the lower stroke is less than normal, and the duration of the stable load portion in the lower stroke is shorter. The loading and unloading times are both longer. As a result, the dynamometer chart of the pumping unit well appears as a taller and narrower curve, that is, the stable load portion of the dynamometer chart becomes narrower, and the loading and unloading curves become flatter, longer, and taller. If any three of the dynamometer chart criteria are met, it is determined that the dynamometer chart criteria are met.

[0048] like Figure 6 This is a dynamometer diagram of the pumping unit well during normal operation in this embodiment. Figure 7 This is a comparison of the pumping unit well indicator diagram when a high back pressure fault occurs in the pumping unit of this embodiment. Figure 6 , Figure 7It is known that if a pumping unit experiences a high back pressure fault, the pumping unit well indicator diagram will gradually rise and narrow, indicating potential faults such as freezing or wax blockage in the back pressure pipeline. Specifically, the current pumping unit well indicator diagram must satisfy any three of the indicator diagram criteria compared to a normal pumping unit well indicator diagram within the previous T1 hours. In this embodiment, T1 = 24, meaning it is compared to the pumping unit indicator diagram during normal operation within the previous 24 hours of the current stroke. In other implementations, this can be customized, for example, setting T1 to 12 hours. If the pumping unit well indicator diagram experiences a sudden rise and narrowing, indicating potential mechanical faults such as reversed flow in the back pressure pipeline, then a high back pressure fault is determined to have occurred. This means the current pumping unit well indicator diagram must satisfy any three of the indicator diagram criteria compared to a normal pumping unit well indicator diagram within the previous X1 strokes. If the stroke being compared is one of the X1 strokes adjacent to the current stroke within T1 hours, it is preferentially determined to be sudden. Only if the suddenness determination condition is not met is it determined to be gradual.

[0049] Within a stroke, when the load value between any two points on the current donkey head load curve of the pumping unit increases or decreases by no more than 3% (i.e., the fifth 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.

[0050] Within a stroke, when the load value between any two points on the pumping unit well indicator diagram does not exceed 3% (i.e., the fifth set threshold), it indicates that the unit is at the top or bottom. The curve with the larger load value is the stable load part of the upper stroke, and the curve with the smaller load value is the stable load part of the lower stroke.

[0051] Step 4: If a high back pressure fault is determined to have occurred in the pumping unit well, an alarm will be triggered by calculation and comparison.

[0052] It should be noted that an alarm will also be triggered if the current donkey head load curve or the current pumping unit well indicator diagram shows any abnormalities. Specifically, this includes:

[0053] The current donkey head load curve satisfies at least one of the donkey head load determination criteria;

[0054] The current pumping unit well dynamometer diagram meets at least one of the dynamometer diagram judgment criteria;

[0055] If, compared to the donkey head load curve of any stroke in the previous X2 strokes, the maximum value of the current donkey head load curve increases by more than 10% (i.e., the sixth preset threshold), and the load of the stable portion of the downstroke load of the current donkey head load curve decreases by more than 10% compared to the stable portion of the downstroke load of the normal donkey head load curve (i.e., the sixth preset threshold), an automatic alarm will be triggered. If, compared to the donkey head load curve within the previous T2 time period, the maximum value of the current donkey head load curve increases by more than 10% (the seventh preset threshold), and the load of the stable portion of the downstroke load of the current pumping unit well dynamometer chart decreases by more than 10% compared to the stable portion of the downstroke load of the normal pumping unit well dynamometer chart (the seventh preset threshold), an automatic alarm will be triggered.

[0056] It should be noted that the threshold values ​​set in this invention were obtained by those skilled in the art through repeated experiments and verifications. For example, in the donkey head load determination condition of this invention, the duration of the stable load portion of the upper and lower strokes of the current donkey head load curve is reduced by more than 5% compared to the duration of the stable load portion of the upper and lower strokes of the normal donkey head load curve. This 5% is the first threshold value, which is obtained by comparing the duration of the stable load portion of the upper and lower strokes of the donkey head load curves when multiple pumping units experience high back pressure faults with the duration of the stable load portion of the upper and lower strokes of the donkey head load curve under normal conditions, and then taking the average value.

[0057] This invention provides a fault diagnosis method for high back pressure in pumping units. By combining the changes in the current pumping unit's head load curve and the current pumping unit well indicator diagram, it determines whether a high back pressure fault has occurred in the pumping unit. It enables remote online real-time alarms, which facilitates a more scientific and reasonable arrangement of the frequency of on-site inspections and video inspections, reduces reliance on on-site inspections, increases the number of wells per person, thereby reducing labor costs and traffic risks, and improving the economic efficiency of pumping unit wells.

Claims

1. A fault diagnosis method for high back pressure in an oil pumping unit, characterized in that, The method includes: Obtain the current donkey head load curve and the current pumping unit well indicator diagram; if the current donkey head load curve meets any three of the donkey head load judgment conditions and the current pumping unit well indicator diagram meets any three of the indicator diagram judgment conditions, then it is determined that the pumping unit has a high back pressure fault. The donkey head load determination conditions include: the duration of the stable load portion of the upper and lower strokes of the current donkey head load curve is correspondingly shorter than the duration of the stable load portion of the upper and lower strokes of the normal donkey head load curve, and the degree of less is greater than the corresponding first set threshold; the rate of change of the loading and unloading portion of the current donkey head load curve is correspondingly shorter than the rate of change of the loading and unloading portion of the normal donkey head load curve, and the degree of less is greater than the corresponding second set threshold; the duration of the loading and unloading portion of the current donkey head load curve is correspondingly longer than the duration of the loading and unloading portion of the normal donkey head load curve, and the degree of greater is greater than the third set threshold; the load of the stable load portion of the upper stroke of the current donkey head load curve is greater than the load of the stable load portion of the upper stroke of the normal donkey head load curve, and the degree of greater is greater than the fourth set threshold; and the load of the stable load portion of the lower stroke of the current donkey head load curve is less than the load of the stable load portion of the lower stroke of the normal donkey head load curve, and the degree of less is greater than the fourth set threshold. The dynamometer chart determination conditions include: the duration of the stable load portion of the upper and lower strokes of the current pumping unit well dynamometer chart is correspondingly less than the duration of the stable load portion of the upper and lower strokes of the normal pumping unit well dynamometer chart, and the degree of less is greater than the corresponding first set threshold; the rate of change of the loading and unloading portion of the current pumping unit well dynamometer chart is correspondingly less than the rate of change of the loading and unloading portion of the normal pumping unit well dynamometer chart, and the degree of less is greater than the corresponding second set threshold; the duration of the loading and unloading portion of the current pumping unit well dynamometer chart is correspondingly greater than the duration of the loading and unloading portion of the normal pumping unit well dynamometer chart, and the degree of greater is greater than the third set threshold; the load of the stable load portion of the upper stroke of the current pumping unit well dynamometer chart is greater than the load of the stable load portion of the upper stroke of the normal pumping unit well dynamometer chart, and the degree of greater is greater than the fourth set threshold; and the load of the stable load portion of the lower stroke of the current pumping unit well dynamometer chart is less than the load of the stable load portion of the lower stroke of the normal pumping unit well dynamometer chart, and the degree of less is greater than the fourth set threshold.

2. The fault diagnosis method for high back pressure in an oil pumping unit 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 fifth 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 high back pressure in an oil pumping unit according to claim 1, characterized in that, If the load value variation between any two points on two curves in the pumping unit well dynamometer diagram does not exceed the fifth preset 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 dynamometer 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 dynamometer diagram.

4. The fault diagnosis method for high back pressure in an oil pumping unit according to claim 1, characterized in that, The rate of change of the loading and unloading portion of the current donkey head load curve is less than the rate of change of the loading and unloading portion of the normal donkey head load curve, and the degree of less is greater than the corresponding second set threshold. This means that the absolute value of the slope of the loading and unloading portion of the current donkey head load curve is less than the absolute value of the slope of the loading and unloading portion of the normal donkey head load curve, and the degree of less is greater than the corresponding second set threshold.

5. The fault diagnosis method for high back pressure in an oil pumping unit according to claim 1, characterized in that, The phrase "the rate of change of the loading and unloading portion of the current pumping unit well dynamometer diagram is correspondingly less than the rate of change of the loading and unloading portion of the normal pumping unit well dynamometer diagram, and the degree of less than is greater than the corresponding second set threshold" means that the absolute value of the slope of the loading and unloading portion of the current pumping unit well dynamometer diagram is correspondingly less than the absolute value of the slope of the loading and unloading portion of the normal pumping unit well dynamometer diagram, and the degree of less than is greater than the second set threshold.

6. The fault diagnosis method for high back pressure in an oil pumping unit according to claim 1, characterized in that, If the current pumping unit well dynamometer card meets any three of the dynamometer card determination conditions compared to a normal pumping unit well dynamometer card within the previous T1 hour period, then the back pressure pipeline is determined to have a freezing or wax blockage fault; if the current pumping unit well dynamometer card meets any three of the dynamometer card determination conditions compared to a normal pumping unit well dynamometer card within the previous X1 strokes, then the back pressure pipeline is determined to have a mechanical fault of reversed flow.

7. The fault diagnosis method for high back pressure in an oil pumping unit according to any one of claims 1 to 6, characterized in that, The normal donkey head load curve is the theoretical donkey head load curve of the pumping unit or the donkey head load curve when the pumping unit is operating normally.

8. The fault diagnosis method for high back pressure in an oil pumping unit according to any one of claims 1 to 6, 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.

9. The fault diagnosis method for high back pressure in an oil pumping unit according to claim 1, characterized in that, If, within the adjacent X2 strokes of the pumping unit, the maximum value of the current donkey head load curve is greater than the maximum value of a certain donkey head load curve within the previous X2 strokes and the degree of the difference is greater than the sixth set threshold, and the minimum value of the current donkey head load curve is less than the minimum value of a certain donkey head load curve within the previous X2 strokes and the degree of the difference is greater than the sixth set threshold, then an alarm is triggered.

10. The fault diagnosis method for high back pressure in an oil pumping unit according to claim 1, characterized in that, If, during the T2 time period adjacent to the operation of the pumping unit, the maximum value of the current donkey head load curve is greater than the maximum value of a certain donkey head load curve in the previous T2 time period and the degree of the difference is greater than the seventh set threshold, and the minimum value of the current donkey head load curve is less than the minimum value of a certain donkey head load curve in the previous T2 time period and the degree of the difference is greater than the seventh set threshold, then an alarm will be triggered.

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