Method for detecting and evaluating balance degree of downstream beam-type pumping unit in variable-frequency operation mode

Abstract

The invention relates to the technical field of oil pumping unit detection equipment, and provides a method for detecting and evaluating the balance degree of a downstream beam-type oil pumping unit in a variable-frequency operation mode. Comprising the following steps of: 1, mounting measuring equipment in a main loop and a brake loop of a pumping unit frequency converter, and acquiring input active power parameters of an upper stroke motor and a lower stroke motor of the beam-pumping unit and negative power parameters of the beam-pumping unit; 2, according to the parameters, extracting a negative power peak Prmax of the beam-pumping unit, an input active power peak Pdmax of a lower stroke motor of the beam-pumping unit and an input active power peak Pumax of an upper stroke motor of the beam-pumping unit generated in a stroke period of the beam-pumping unit; 3, determining a calculation mode according to the negative power peak Prmax of the beam-pumping unit, and calculating the balance degree of the beam-pumping unit; 4, evaluating the balance degree of the oil pumping unit according to the numerical value of the balance degree of the oil pumping unit; according to the invention, accurate calculation and evaluation of the balance degree of the oil pumping unit are realized.

Description

Technical Field

[0001] The invention relates to the technical field of oil pumping unit detection equipment and provides a method for detecting and evaluating the balance of a downstream beam-type oil pumping unit in a variable frequency operation mode. Background Art

[0002] like Figure 1 In the process of oil extraction, the oil pump is a very important equipment for producing crude oil. It can extract the underground oil and transport it to the joint station through the crude oil single well pipeline and the oil gathering station (metering station). After the complex processing process of oil, gas, water, impurities, etc., the joint station forms qualified crude oil products and exports them to chemical plants for refining.

[0003] like Figure 2 The oil production equipment used in oil field production includes pumping units, screw pumps, electric pumps, etc. Among them, the pumping unit is the main equipment in oil field production and one of the main sources of electricity consumption.

[0004] The types and specifications of pumping units vary according to the needs of oil production. They are divided into beam pumping units and beamless pumping units. The basic characteristics of beam pumping units are simple structure, easy manufacturing and convenient use. In particular, they can operate in oil fields around the clock for a long time, are reliable to use, and have a high penetration rate, with a field application rate of over 95%.

[0005] The oil production plant has a total of 2,589 oil wells. With the overall promotion of smart oil fields and the upgrading of old equipment, the oil production plant has upgraded the electrical control system of each oil pumping unit to improve the production rate and intelligent management level of the oil pumping unit and reduce the labor intensity of employees. The original ordinary industrial frequency control cabinet has been upgraded to a four-in-one frequency conversion control cabinet, that is, the control cabinet is equipped with a frequency converter and four-in-one data acquisition and control equipment, which realizes the remote frequency adjustment of the frequency converter and the adjustment (stroke) of the oil pumping unit through frequency adjustment. The extensive application of the four-in-one frequency conversion cabinet has greatly facilitated the adjustment (stroke) of the oil pumping unit and has also played a certain positive role in improving the output of the oil pumping unit.

[0006] like Figure 3 The working characteristics of the beam pump are: the beam pump operates under variable load conditions, the torque on the crankshaft changes during the entire working process, and only reaches the maximum value at a certain moment in the up and down strokes. It is found on the electric meter equipped with single-well metering that the meter has a periodic "reversal" phenomenon, and when the active power is measured with a detection instrument, it can also be found that the active power has periodic negative values, thereby judging that this negative power is caused by the motor generating electricity.

[0007] In order to overcome the large starting torque of the oil pump, a high-power motor must be selected, resulting in a big horse pulling a small cart. The motor cannot work at full load most of the time, its efficiency and power factor are not high, and the electric energy is not fully utilized. At the same time, its system efficiency is very low, generally between 20% and 30%, or even lower.

[0008] The hazards of unbalanced beam pumping units: When the beam pumping unit is operating in an ideal balanced state, the work done by the motor in the up and down processes is equal; therefore, in order for the pumping unit to operate under balanced conditions, in theory, the motor should do positive work and the values ​​should be equal in both the up and down processes; in the down stroke, the stored energy is stored in the balance block, and in the up stroke, the stored energy is used to assist the motor in doing work; however, in the actual operation of the pumping unit, an unbalanced state often occurs due to various reasons. The unbalanced working state of the beam pumping unit will lead to a series of problems such as increased power consumption during the operation of the pumping unit, increased energy consumption during operation, uneven force on various components, accelerated wear of the reduction gearbox, and reduced service life.

[0009] The main reasons for the imbalance of the beam pumping unit are: first, the imbalance caused by changes in the downhole working conditions; second, the imbalance caused by changes in the parameters of the surface equipment; Figure 4 , combined with the actual analysis on site, it is believed that there are mainly six influencing factors:

[0010] ① Due to the influence of geological conditions and mining factors, the fluid volume, water content, pressure, dynamic liquid level and other data of the oil pump change. When the production parameters of the oil pump do not match, the oil pump will be unbalanced. Even if the balance is achieved through mechanical balancing adjustment, it cannot be dynamically tracked and adjusted, and imbalance will still occur during operation, making the system efficiency of the oil pump too low.

[0011] ② The pumping unit is seriously waxed, which increases the resistance of the liquid flow. The friction load caused by the friction of the liquid affects the normal operation of the pumping equipment. In production, the wellhead casing is used for dosing, but due to factors such as imperfect dosing system and inadequate implementation of dosing cycle, the pumping unit is prone to waxing and scaling, which increases the load of the pumping unit.

[0012] ③Sand produced by the pumping unit causes abrasion of the ground and downhole equipment, sand jamming, and increases the operating load of the pumping unit's up and down strokes. In severe cases, the pump may even get stuck, and the workload of sand flushing, pump inspection and maintenance increases dramatically.

[0013] ④ Before and after the pump inspection, the dynamic liquid level, liquid production, pump efficiency, production parameters, etc. of the pumping well will change to a certain extent. The current of the pumping unit's up and down strokes will also change greatly. Since the original balance of the pumping unit is broken, if the difference in the up and down stroke currents is large, the pumping well may not even start when it is started after the operation.

[0014] ⑤ The pumping unit changes its working system, and the original balance of the pumping unit is destroyed. For example, if the pumping unit stroke and stroke frequency change, the work done by the motor will change, and its current will also change in the up and down strokes, and the load of the pumping unit in the up and down strokes will also change accordingly. Especially after the parameters are adjusted, the impact on the current of the motor in the up and down strokes is more obvious.

[0015] ⑥ The oil pump operates under variable load conditions. The torque on the crankshaft changes during the entire working process and only reaches the maximum value at a certain moment during the up and down strokes. In order to overcome the large starting torque of the oil pump, a high-power motor must be selected, resulting in a big horse pulling a small cart, so that the motor cannot work at full load most of the time, its efficiency and power factor are not high, and the electric energy is not fully utilized.

[0016] Although beam pumping units are equipped with balancing devices, and the balancing weight and balancing radius are reasonable, the balance of the beam pumping units may change due to changes in well fluid, the impact of fluid supply capacity, changes in supporting equipment of the beam pumping units, changes in the working conditions of the pumping units, and optimization and adjustment of machine extraction parameters. The balance of the beam pumping units may change from the original balanced state to an unbalanced state, thus affecting the normal production and operation of the beam pumping units.

[0017] Therefore, the balance state of the beam pumping unit must be constantly checked and adjusted to ensure that the beam pumping unit is always operating under reasonable balance conditions.

[0018] There are two electrical control methods for beam pumping units:

[0019] like Figure 5 One is the industrial frequency operation mode. An industrial frequency control cabinet is installed at the pumping unit operation site to provide an AC power supply with a frequency of 50Hz to the pumping unit motor.

[0020] like Figure 6 The other is the frequency conversion control method. A frequency conversion control cabinet is installed at the pumping unit operation site. A frequency converter is installed in the control cabinet. The frequency converter provides an AC power supply with a frequency of 0∽50Hz to the pumping unit motor (the frequency value is set according to production needs).

[0021] like Figure 7 The existing balance test of the pumping unit is done manually, and the working process is as follows:

[0022] The oil production plant issues a monthly balancing plan, and the inspection personnel conduct parameter testing in accordance with the enterprise standard of Sinopec Shengli Oilfield Administration Co., Ltd. (Q / SH10201911) "Pumping Unit Balance Test and Evaluation Method". After the inspection is completed, a list of rectification issues is issued for the unbalanced pumping units, requiring relevant grassroots units to make rectifications. The grassroots units accept orders and conduct on-site balancing. After the adjustment is completed, feedback is given to the inspection unit, and the inspection unit feedbacks to the oil production plant, and this work process is completed.

[0023] It takes about 2 hours to manually check the balance of a pump on site, and it is affected by personnel, vehicles and weather, which is labor-intensive, time-consuming and labor-intensive, and has low work efficiency. The inspection center can only check the balance of 60 pumps at most per month, which accounts for less than 2.4% of the 2,589 pumps in the oil field, so it cannot meet the needs of efficient operation and management of the pumps.

[0024] At present, there are three commonly used methods for detecting the balance of oil pumps: maximum current method, peak power method, and average power method.

[0025] The most widely used method on site is the maximum current method, which is easy to operate on site and is also a method specified by enterprise standards. However, from a field perspective, this method has great limitations. Some wells may have power generation currents that cause the calculated balance to be extremely inaccurate, resulting in the defect of false balance. Practice has proved that the use of peak power method and average power method to detect the balance of the pump is relatively scientific.

[0026] Existing enterprise standards related to the balance test and evaluation of pumping units: Sinopec Shengli Petroleum Administration Bureau Co., Ltd. Enterprise Standard (Q / SH10201911) and China National Petroleum Corporation Enterprise Standard (Q / SY 1233) "Beam Pumping Unit Balance and Operation Specifications" disclose the equipment and balance detection and judgment methods involved in the balance test and evaluation of conventional pumping units, such as:

[0027] The balance determination method disclosed by the enterprise standard (Q / SH10201911) of Sinopec Shengli Petroleum Administration Bureau Co., Ltd. is as follows:

[0028] The balance of the beam pumping unit should be determined by the up and down stroke peak power method (see formula 1), and its balance is defined as:

[0029] Formula 1: εy=Pdmax / Pumax

[0030] Where: εy is the balance degree of the beam pumping unit; Pdmax is the peak active power of the downstroke of the pumping unit, kW; Pumax is the peak active power of the upstroke of the pumping unit, kW.

[0031] And the balance evaluation method:

[0032] The recommended acceptable balance range for beam pumping units is 0.7 to 1.3.

[0033] The balance calculation and judgment method disclosed in the China National Petroleum Corporation corporate standard (Q / SY1233) "Beam Pumping Unit Balance and Operation Specifications":

[0034] Calculation of average power of upstroke and downstroke: Assuming that a stroke cycle detection records N groups of data, for the crank balance method, it starts from the crank being at the "12 o'clock position", and for the walking beam balance method, it starts from the suspension point being at the bottom dead center. The average value of the first N / 2 groups of input power values ​​is the average power of the upstroke of the pump, and the average power of the last N / 2 groups of input power values ​​is the average power of the downstroke, calculated using formula (2) and formula (3).

[0035] Formula 2:

[0036] Formula 3:

[0037] In the formula: ——Average input power of the upward stroke motor, kW;

[0038] ——Average input power of the motor during the downstroke, kW;

[0039] P ei ——Instantaneous input power of the motor, kw.

[0040] Determination of balance:

[0041] Power balance is the ratio of the average power of the upstroke and downstroke of the pumping unit, calculated using formula (4).

[0042] Formula 4: or

[0043] And the balance evaluation method:

[0044] i. When one of the average powers of the upstroke and downstroke is zero or negative, the power balance is zero; ii. When the power balance is less than 0.5, it can be judged that the pump is unbalanced and the pump needs to be balanced.

[0045] The power curve of the downstream beam pumping unit in the power frequency operation mode obtained by using the equipment and methods mentioned in the above enterprise standards has the following characteristics:

[0046] In the power frequency operation mode, such as Figure 8, the negative power of the beam pump can be fed back to the power grid in each stroke cycle, and the detection instrument can detect the value of the negative power; under the power frequency operation mode, from the power curve of the pump Fig. 9 It can be seen that the detection instrument can detect the negative work power Pr of the oil pump motor.

[0047] The power curve of the downstream beam pumping unit in variable frequency operation mode has the following characteristics:

[0048] The test results of the electrical parameters of the beam pumping unit in variable frequency operation mode and power frequency operation mode are different. In variable frequency operation mode, such as Fig.10 The negative power of the beam pump cannot be fed back to the power grid in each stroke cycle (due to the working principle of the frequency converter), and the detection instrument cannot detect the value of the negative power. In the variable frequency operation mode, from the power curve of the pump Fig.11 It can be seen that the detection instrument cannot detect the negative work power Pr of the oil pump motor. This does not mean that the oil pump motor does not generate negative work. The oil pump motor also generates negative work, but the negative work is consumed by the thermal resistor in the inverter.

[0049] The above-mentioned enterprise standard Sinopec Group Shengli Petroleum Administration Bureau Co., Ltd. enterprise standard (Q / SH10201911) has the following problems in the testing and evaluation methods disclosed:

[0050] 1. In variable frequency operation mode, there are problems with the detection method:

[0051] When the detection instrument cannot detect the peak negative power Prmax of the oil pump during the up and down strokes, it can only regard the peak active power Pdmax of the oil pump during the down stroke as the peak value.

[0052] 2. In variable frequency operation mode, there are problems with the evaluation method:

[0053] Since the negative power Prmax cannot be detected, the influence of negative work on the balance of the oil pump cannot be considered in the balance evaluation method, especially for seriously unbalanced oil pumps, Prmax>Pdmax may occur. Therefore, the balance of the oil pump calculated by this method (εy=Pdmax / Pumax) cannot truly reflect the balance of the oil pump, resulting in a false balance.

[0054] The detection and evaluation methods disclosed in the above-mentioned enterprise standard China National Petroleum Corporation Enterprise Standard (Q / SY 1233) "Balance and Operation Specifications for Beam Pumping Units" have the following problems:

[0055] 1. In variable frequency operation mode, there are problems with the detection method:

[0056] The detection instrument cannot detect the negative work power Pr of the oil pump when the oil pump is in the up and down strokes.

[0057] 2. In variable frequency operation mode, there are problems with the evaluation method:

[0058] Since the negative work power Pr cannot be detected, the influence of negative work on the balance of the oil pump cannot be considered in the balance evaluation method. When calculating the value of the input average power P of the up or down stroke of the oil pump, only the average value of the positive active power is calculated. The average value of the negative work power is missing, and the balance of the oil pump cannot be truly reflected, resulting in a false balance.

[0059] It can be seen that the current conventional methods for detecting and evaluating the balance of oil pumps do not take into account the detection and evaluation methods for the balance of oil pumps under variable frequency operation, and can no longer meet the requirements of the development of electrical control systems for beam pumps.

[0060] By searching a large number of literatures, it is confirmed that under variable frequency operation mode, in the balance detection and evaluation method of walking beam pumps, the negative work power generated by the pump during operation and the influence of the negative work power on the balance of the pump must be considered. Moreover, the greater the imbalance of the pump, the greater the negative work power generated by the pump, and the greater the influence on the balance of the pump. If the influence of negative work power is not considered in the balance detection of the pump, the detected balance will result in a false balance.

[0061] In addition, the applicant of the present invention also searched the following three patent documents to support the technical ideas of the present invention:

[0062] The Chinese patent application number is 201110233592.8 and the application date is 2011.08.16. It discloses a device and method for analyzing the working efficiency and balance of an oil pumping unit, and also discloses the following technical features:

[0063] The present invention provides a device and method for analyzing the working efficiency and balance of an oil pumping unit. The corresponding device includes: a speed measuring unit, which is used to detect the output speed of the oil pumping unit and output the speed detection result to a data processing unit; an electric quantity collection unit, which is used to collect the electric quantity parameters of the oil pumping unit and send the electric quantity collection result to the data processing unit; an end point detection unit, which is used to detect the start and end points of the stroke of the oil pumping unit and send the start and end detection results to the data processing unit; the data processing unit is used to perform mixed operations on the speed detection results, the electric quantity collection results and the start and end detection results, and send the operation results to the main control computer. The present invention can measure the working state of the oil pumping unit more accurately, and can simultaneously provide the measurement results of the oil pumping unit's voltage, current, active power, reactive power, apparent power, power factor, harmonic parameters, and positive and negative torque, and submit the balance data and adjustment plan of the oil pumping unit.

[0064] The above patent is essentially a research and development of an on-site electrical parameter measurement device, which can measure the working status (voltage, current, active power, reactive power, apparent power, power factor, harmonic parameters, positive and negative torque) of the oil pump on site, and transmit the data to the computer of a nearby (within 100 meters) measuring vehicle (measuring equipment) through wireless communication, providing data basis for the analysis of the working efficiency and balance of the oil pump; it does not involve specific methods for detecting and evaluating the balance.

[0065] The Chinese patent application number is 201811037256.4 and the application date is September 6, 2018. It discloses a method and system for measuring the balance of a beam pumping unit and discloses the following technical features:

[0066] The present invention relates to a method and system for measuring the balance of a beam pumping unit, and belongs to the technical field of oil pumping units in petroleum engineering. The measuring method proposed by the present invention comprises the following steps: (1) collecting the inclination value information and current value information of the pumping unit cross beam; (2) judging the upstroke process and downstroke process in a complete stroke of the pumping unit according to the inclination value information; (3) comparing the sampled current values ​​in the downstroke process to find out the current maximum value I in the downstroke process; comparing the sampled current values ​​in the upstroke process to find out the current maximum value I in the upstroke process; (4) calculating the balance degree according to the maximum value I of the downstroke current and the maximum value I of the upstroke current. The present invention obtains the maximum value I of the downstroke current and the maximum value I of the upstroke current by the collection and comparison method, so that the measurement of the balance degree is more accurate and the error is smaller, further reducing the wear of the pumping unit, extending the service life of the pumping unit, and saving resources at the same time.

[0067] The method of the above invention is essentially to achieve a more accurate balance measurement by collecting the maximum current I during the up and down strokes of the oil pump and using the current method balance calculation method.

[0068] The Chinese patent with patent application number 202110443730.9 and application date 2021.04.23 discloses a balance detection method based on the electrical power diagram of the oil pump and discloses the following technical features:

[0069] The present invention discloses a balance detection method based on the electric power diagram of the oil pump. First, the working active power of the oil pump motor collected on site is obtained, and abnormal data is filtered and processed; then the active power signal period is determined by autocorrelation analysis; then, the active power sampling data of the oil pump is divided into upstroke data and downstroke data with the aid of the indicator diagram of the oil pump; finally, the maximum active power of the upstroke and downstroke of the oil pump is calculated respectively, and the balance of the oil pump is measured by the ratio of the two. The method can diagnose the counterweight balance status of the oil pump, thereby improving the operating efficiency of the oil pump equipment, reducing the energy consumption and wear of the oil pump when working, and extending the service life of the oil pump.

[0070] The method of the above invention is a balance detection method based on the electrical power diagram and indicator diagram of the oil pump. The working active power of the oil pump motor collected on-site is obtained through the electrical power diagram of the oil pump. With the help of the indicator diagram of the oil pump, the active power sampling data of the oil pump is divided into upstroke data and downstroke data; finally, the maximum active power of the upstroke and downstroke of the oil pump is calculated respectively, and the balance of the oil pump is measured by the ratio of the two.

[0071] The above three invention patents have the following deficiencies in the pumping unit balance detection and evaluation methods:

[0072] 1. The above three patents on the balance detection and evaluation methods of the oil pump are all conventional detection methods, that is, the balance detection and evaluation of the oil pump is carried out under the working frequency condition, and the influence of the balance detection and evaluation of the oil pump under the variable frequency condition is not considered.

[0073] 2. The detection location of the detection instruments is the power input side of the oil pump control cabinet. Summary of the invention

[0074] The purpose of the present invention is to address the deficiencies of the prior art and to propose a method for detecting and evaluating the balance of a downstream beam pumping unit in variable frequency operation mode, thereby solving the following technical problems:

[0075] How to detect the negative power generated during the operation of the oil pump under variable frequency operation mode; when detecting the balance of the oil pump under variable frequency operation mode, there will be problems such as incomplete detection data, inaccurate balance calculation, and false balance in balance evaluation.

[0076] In order to achieve the above object, the present invention adopts the following technical solutions:

[0077] A method for detecting and evaluating the balance of a downstream beam pumping unit in variable frequency operation mode, comprising:

[0078] Step 1: Install measuring equipment in the main circuit and brake circuit of the pumping unit inverter to obtain the input active power parameters of the upper and lower stroke motors of the beam pumping unit and the negative active power parameters of the beam pumping unit;

[0079] Step 2: According to the above parameters, extract the peak value of the negative active power of the beam pumping unit Prmax, the peak value of the active power input of the motor of the beam pumping unit in the downstroke period Pdmax and the peak value of the active power input of the motor of the beam pumping unit in the upstroke period Pumax;

[0080] Step 3, according to the peak value Prmax of the negative power of the beam pumping unit, determine the calculation method and calculate the balance degree of the pumping unit;

[0081] Step 4: Evaluate the balance of the oil pumping unit according to the balance value of the oil pumping unit.

[0082] Furthermore, the step three includes when Prmax=0, the balance calculation formula is as follows:

[0083] Formula 5: ε = Pumax / Pdmax;

[0084] Where: ε is the balance degree of the beam pumping unit, %; Pdmax is the peak value of the active power input to the motor of the beam pumping unit during the downstroke, kW; Pumax is the peak value of the active power input to the motor of the beam pumping unit during the upstroke, kW.

[0085] Further, the step three includes the following calculation formula for the balance degree when the beam pumping unit generates reverse power during the upstroke:

[0086] Formula 6: ε=[(Pumax-Prmax) / Pdmax)];

[0087] Where: ε is the balance degree of the beam pumping unit, %; Pdmax is the peak value of the active power input of the motor of the beam pumping unit in the downstroke, kW; Prmax is the peak value of the negative power input of the beam pumping unit, kW; Pumax is the peak value of the active power input of the motor of the beam pumping unit in the upstroke, kW.

[0088] Further, the step three includes the following formula for calculating the balance when the beam pumping unit generates reverse power during the downstroke:

[0089] Formula 7: ε=[(Pdmax-Prmax) / Pumax)];

[0090] Where: ε is the balance degree of the beam pumping unit, %; Pdmax is the peak value of the active power input of the motor of the beam pumping unit in the downstroke, kW; Prmax is the peak value of the negative power input of the beam pumping unit, kW; Pumax is the peak value of the active power input of the motor of the beam pumping unit in the upstroke, kW.

[0091] Furthermore, in step 4, the acceptable range of balance of the beam pumping unit is 0.6∽1.4.

[0092] Furthermore, when the balance degree of the beam pumping unit is ≤ 0, it can be directly determined to be seriously unbalanced.

[0093] Furthermore, the measuring device is a multifunctional digital meter capable of measuring voltage, current, power and electric energy.

[0094] Furthermore, the multifunctional digital meter is provided with an RS-485 communication interface, supporting the ModBus protocol.

[0095] Furthermore, a measuring device for measuring the active power parameters of the upper and lower stroke motor input of the beam pumping unit is installed at the AC power input terminal of the pumping unit inverter.

[0096] Furthermore, a measuring device for measuring the negative power parameters of the beam pumping unit is installed in the braking circuit of the frequency converter of the pumping unit.

[0097] The beneficial effects of the present invention are as follows:

[0098] Multiple monitoring points can be realized: one on the power input side of the pumping unit control cabinet, and one on the brake circuit side of the pumping unit inverter;

[0099] The accurate calculation and evaluation of the balance of the pumping unit is realized;

[0100] Automatically send out early warning signals for abnormal unbalanced conditions of the pumping unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0101] Figure 1 , crude oil extraction, gathering, transportation, refining and processing process flow chart;

[0102] Figure 2 , schematic diagram of the structure of a beam pumping unit;

[0103] Figure 3 , load characteristics and electrical parameter curves of beam pumping units;

[0104] Figure 4 , Schematic diagram of the working of beam pumping unit;

[0105] Figure 5 , electrical wiring diagram under power frequency operation mode;

[0106] Figure 6 , electrical wiring diagram under variable frequency operation mode;

[0107] Figure 7 , Workflow diagram of on-site pumping unit balance detection;

[0108] Figure 8 , schematic diagram of pumping unit power detection under power frequency operation mode;

[0109] Fig. 9 , the power curve of the oil pump under the power frequency operation mode;

[0110] Fig.10 , schematic diagram of pumping unit power detection under variable frequency operation mode;

[0111] Fig.11 , power curve of the oil pump under variable frequency operation mode;

[0112] Fig.12 , schematic diagram of detection of input active power and braking negative power of the pumping unit under variable frequency operation mode;

[0113] Fig.13 , the power curve of the pumping unit in one stroke cycle in the first calculation method;

[0114] Fig.14 , the power curve of the pumping unit in one stroke cycle in the second calculation method;

[0115] Fig.15 , the power curve of the pumping unit in one stroke cycle in the third calculation method;

[0116] Fig.16 , Working principle diagram of automatic detection and evaluation method of balance degree of pumping unit under variable frequency operation mode

[0117] Fig.17 , system diagram of automatic detection and evaluation method of pumping unit balance under variable frequency operation mode. DETAILED DESCRIPTION

[0118] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0119] Embodiment 1:

[0120] A method for detecting the balance of an oil pump under variable frequency operation:

[0121] A multifunctional digital ammeter 1 is installed in the braking resistor circuit of the oil pump inverter to detect the value of the negative work power (Pr) generated when the oil pump is running. Under the variable frequency operation mode, the negative work generated by the oil pump will not be fed back to the power supply through the inverter (determined by the working principle of the inverter), and this part of the negative work can only be directly consumed by the braking resistor installed inside the inverter. According to the law of conservation of energy, the power P detected in the inverter braking circuit is equal to the negative work power Pr of the oil pump.

[0122] The multifunctional digital ammeter 2 installed in the frequency conversion cabinet of the oil pump can detect the value of the active power (Pu, Pd) input to the oil pump motor, and substitute it together with the value of the negative active power (Pr) generated when the oil pump is running into the balance calculation formula (Formula 5, 6, 7), so as to accurately calculate the balance of the oil pump.

[0123] The present invention can make the balance detection and evaluation method of the beam pumping unit in the variable frequency operation mode more scientific, more reasonable and more accurate, and provide an optimal solution.

[0124] Embodiment 2

[0125] A calculation formula for the balance degree of the pumping unit under variable frequency operation mode:

[0126] Under variable frequency operation, three methods have been developed to calculate the balance degree of the beam pumping unit based on the negative power generated in one stroke cycle. They are introduced as follows:

[0127] The first calculation method:

[0128] In variable frequency operation mode, when there is no reverse power generation in the up and down strokes of the beam pump, that is, Prmax = 0, the balance calculation formula is 5:

[0129] Formula 5: ε = Pumax / Pdmax

[0130] Where: ε is the balance degree of the beam pumping unit, %; Pdmax is the peak value of the active power input to the motor of the beam pumping unit during the downstroke, kW; Pumax is the peak value of the active power input to the motor of the beam pumping unit during the upstroke, kW.

[0131] The second calculation method:

[0132] In variable frequency operation mode, when the beam pumping unit generates electricity in reverse during the upstroke (balance calculation formula 6):

[0133] Formula 6: ε=[(Pumax-Prmax) / Pdmax)]

[0134] Where: ε is the balance degree of the beam pumping unit, %; Pdmax is the peak value of the active power input of the motor of the beam pumping unit in the downstroke, kW; Prmax is the peak value of the negative power input of the beam pumping unit, kW; Pumax is the peak value of the active power input of the motor of the beam pumping unit in the upstroke, kW.

[0135] The third calculation method:

[0136] In variable frequency operation mode, the balance calculation formula when the beam pumping unit generates reverse power during the downstroke is 7:

[0137] Formula 7: ε=[(Pdmax-Prmax) / Pumax)]

[0138] Where: ε is the balance degree of the beam pumping unit, %; Pdmax is the peak value of the active power input of the motor of the beam pumping unit in the downstroke, kW; Prmax is the peak value of the negative power input of the beam pumping unit, kW; Pumax is the peak value of the active power input of the motor of the beam pumping unit in the upstroke, kW.

[0139] Embodiment three:

[0140] A method for evaluating the balance of an oil pumping unit under variable frequency operation:

[0141] According to the calculation results of balance calculation formulas 5, 6, and 7, the balance of the beam pumping unit is evaluated:

[0142] 1. The recommended acceptable balance range for beam pumping units is 0.6∽1.4.

[0143] 2. When the balance degree of the beam pump is ≤0, it can be directly determined to be severely unbalanced.

[0144] Embodiment 4:

[0145] The invention discloses an automatic detection and evaluation method for the balance degree of a downstream beam-type oil pumping unit in a variable frequency operation mode, which consists of two parts: a negative work detection unit and a data acquisition and monitoring unit.

[0146] Negative power detection unit: beam pumping unit frequency conversion cabinet 1, frequency converter 2, frequency converter braking resistor circuit 3, multi-function DC energy meter 4, oil well multi-function digital energy meter 13.

[0147] The unit function is to collect and upload the electrical parameters (voltage U, current I, power Pr, electric energy Wr) of the braking circuit through the multifunctional DC electric energy meter 4 installed in the inverter braking circuit; the multifunctional digital electric meter 13 in the oil well field control cabinet is responsible for collecting and uploading the input active power and other electrical parameters of the pumping unit motor, all of which are uploaded to the data acquisition module 5 of the data acquisition and monitoring unit through the RS-485 communication interface (supporting Modbus protocol).

[0148] Data acquisition and monitoring unit: beam pumping unit data acquisition module 5, pumping unit multi-function digital meter 6, modem 7, PDM2000-SCADA system 8, brake resistor circuit fault alarm 9, pumping unit imbalance warning 10, monitoring workstation 11, engineer workstation 12.

[0149] Unit function: the beam pumping unit data acquisition module 5 uploads the collected data to the PDM2000-SCADA system 8 via the modem 7, and provides the data to the monitoring workstation 11 and the engineer workstation 12 after data processing.

[0150] The present invention realizes 24-hour automatic detection of the balance of the beam pumping unit. The management personnel in the control room of the oil production plant can view the relevant data of the balance of 2589 pumping units in the plant (active power of upper and lower strokes, negative power of upper and lower strokes, balance of the pumping unit). At the same time, the system can automatically send out early warning signals for the imbalance of the pumping unit, reminding the management personnel to adjust the balance in time, ensuring that the beam pumping unit is in an efficient operation state. Compared with the previous manual on-site detection (regardless of which balance detection method is used for the detection of the balance of the beam pumping unit), the work efficiency is doubled, and the error of on-site manual reading is eliminated, greatly improving the accuracy of the detection.

[0151] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for detecting and evaluating the balance of a downstream beam pumping unit in variable frequency operation mode, comprising: Step 1: Install measuring equipment in the main circuit and brake circuit of the pumping unit inverter to obtain the input active power parameters of the upper and lower stroke motors of the beam pumping unit and the negative active power parameters of the beam pumping unit; Step 2: According to the above parameters, extract the peak value of the negative active power of the beam pumping unit Prmax, the peak value of the active power input of the motor of the beam pumping unit in the downstroke period Pdmax and the peak value of the active power input of the motor of the beam pumping unit in the upstroke period Pumax; Step 3, according to the peak value Prmax of the negative power of the beam pumping unit, determine the calculation method and calculate the balance degree of the pumping unit; Step 4: Evaluate the balance of the oil pumping unit according to the balance value of the oil pumping unit.

2. The method for detecting and evaluating the balance of a downstream beam pumping unit in variable frequency operation mode according to claim 1 is characterized in that: The step three includes when Prmax=0, the balance calculation formula is as follows: Formula 5: ε = Pumax / Pdmax; Where: ε is the balance degree of the beam pumping unit, %; Pdmax is the peak value of the active power input to the motor of the beam pumping unit during the downstroke, kW; Pumax is the peak value of the active power input to the motor of the beam pumping unit during the upstroke, kW.

3. The method for detecting and evaluating the balance of downstream beam pumping units in variable frequency operation mode according to claim 1 is characterized in that: The step three includes the following calculation formula for the balance degree when the beam pumping unit generates reverse power during the upstroke: Formula 6: ε=[(Pumax-Prmax) / Pdmax)]; Where: ε is the balance degree of the beam pumping unit, %; Pdmax is the peak value of the active power input of the motor of the beam pumping unit in the downstroke, kW; Prmax is the peak value of the negative power input of the beam pumping unit, kW; Pumax is the peak value of the active power input of the motor of the beam pumping unit in the upstroke, kW.

4. The method for detecting and evaluating the balance of downstream beam pumping units in variable frequency operation mode according to claim 1 is characterized in that: The step three includes the following calculation formula for the balance degree when the beam pumping unit generates reverse power during the downstroke: Formula 7: ε=[(Pdmax-Prmax) / Pumax)]; Where: ε is the balance degree of the beam pumping unit, %; Pdmax is the peak value of the active power input of the motor of the beam pumping unit in the downstroke, kW; Prmax is the peak value of the negative power input of the beam pumping unit, kW; Pumax is the peak value of the active power input of the motor of the beam pumping unit in the upstroke, kW.

5. A method for detecting and evaluating the balance of a downstream beam pumping unit in variable frequency operation mode according to any one of claims 1 to 4, characterized in that: In the step 4, the acceptable range of balance of the beam pumping unit is 0.6∽1.

4.

6. The method for detecting and evaluating the balance of a downstream beam pumping unit in variable frequency operation mode according to claim 5, characterized in that: When the balance degree of the beam pump is ≤0, it can be directly determined to be severely unbalanced.

7. A method for detecting and evaluating the balance of a downstream beam pumping unit in variable frequency operation mode according to any one of claims 1 to 4 and 6, characterized in that: The measuring device is a multifunctional digital ammeter capable of measuring voltage, current, power and electric energy.

8. The method for detecting and evaluating the balance of a downstream beam pumping unit in variable frequency operation mode according to claim 7, characterized in that: The multifunctional digital electric meter is provided with an RS-485 communication interface and supports the ModBus protocol.

9. A method for detecting and evaluating the balance of a downstream beam pumping unit in variable frequency operation mode according to claim 8, characterized in that: The measuring device used to measure the active power parameters of the upper and lower stroke motor input of the beam pumping unit is installed at the AC power input terminal of the pumping unit inverter.

10. The method for detecting and evaluating the balance of a downstream beam pumping unit in variable frequency operation mode according to claim 8, characterized in that: The measuring device for measuring the negative power parameters of the beam pumping unit is installed in the braking circuit of the pumping unit frequency converter.

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