Automatic adjustment method of pumping unit stroke frequency based on continuous liquid production at wellhead

Abstract

The present invention discloses a method for automatically adjusting the pumping unit stroke frequency based on the continuous liquid production at the pumping unit wellhead, comprising the following steps: obtaining a liquid production metering device to continuously collect the liquid production data of the pumping unit at each stroke; calculating the average value of the liquid production per unit time under the current well conditions; calculating the average pump efficiency under the current liquid production conditions based on the average liquid production value and the theoretical displacement of the pump; comparing the average pump efficiency value with a preset pump efficiency to obtain a comparison result, and sending a speed control instruction to a frequency converter based on the comparison result to adjust the pumping unit stroke frequency. This method achieves precise adjustment of the automatic adjustment stroke frequency of the pumping unit well, improves the system efficiency of the oil well, greatly reduces the production cost of the oil well, and improves the economic benefits of oil production in the oil field.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield automation control, and in particular to a method and system for automatically adjusting the stroke frequency of an oil pumping unit based on the continuous liquid production of the oil pumping unit wellhead. Background Art

[0002] At present, most of the pumping units used in domestic oil fields adopt frequency converter to adjust the stroke rate, and in specific applications, the stroke rate is divided into manual adjustment and automatic adjustment. Among them, automatic adjustment is rarely used, and the main reason is that there is no reliable parameter reference.

[0003] The most common indicator for measuring the optimal operating condition of a pumping unit is the oil well production rate. Currently, the most widely used technique in oil fields is "power diagram oil measurement." However, this surface power diagram yields significant discrepancies between measured well production and actual well production. To overcome this drawback, researchers have been attempting to obtain the pump's power diagram directly or indirectly. Various pump mechanics models and rapid solution algorithms have been proposed for different operating conditions and parameters, partially improving the accuracy of well production measurement. However, these methods are computationally complex, slow, and require significant technical expertise, making it difficult to online determine the optimal stroke rate for variable frequency speed control pumping units.

[0004] The application number is 201510213765.8, and the invention is titled "A Method for Optimal Stroke Frequency of Digital Pumping Units Suitable for Ultra-Low Permeability Reservoirs." It discloses a method for determining and adjusting the pumping frequency. While ensuring the liquid production, the optimal stroke frequency can be automatically found based on the liquid production of the oil well, and the stroke frequency can be adjusted to the minimum to achieve the optimal working state, thereby realizing automatic adjustment of the stroke frequency and remote manual adjustment. However, there are the following disadvantages: 1) Because it cannot be guaranteed that a power diagram can be generated for each stroke, the acquisition of the power diagram cannot be guaranteed to be continuous and real-time, and changes in the liquid supply status cannot be responded to in a timely manner; 2) The calculation method is complex and has huge errors, including theoretical errors and power diagram errors; 3) Data communication and remote calculations take up a lot of time, making it impossible to quickly determine the optimal stroke frequency.

[0005] The application number is 201810148573.7, and the name of the invention is a method for adjusting the optimal stroke rate of an oil pumping unit. It discloses that an optimal stroke rate adjustment algorithm for an oil pumping unit based on time-series global search is implanted in an existing digital oil pumping unit RTU measurement and control unit; the optimal stroke rate adjustment algorithm for an oil pumping unit based on time-series global search includes the following steps: Step 1, using the motor power limiting technology, screen and determine the frequency conversion range allowed by the frequency converter, and set the maximum frequency of the oil pumping unit as the starting frequency, and gradually reduce the frequency operation; the purpose of this step is to avoid the frequency converter from burning out the motor during the automatic adjustment of the oil pumping unit stroke rate; Step 2, collect the load and displacement data of the oil pumping unit suspension point, and calculate the actual pump efficiency based on the collected data, and use the product of the pump efficiency and the frequency as the equivalent liquid production instead of the actual liquid production for data storage; The purpose of this step is to judge the change trend of the liquid production under different strokes potential and simplify the calculation process; step three, use the time sequence global search method to quickly find the optimal reasonable stroke rate, and use the motor frequency at this time as the optimal base frequency; step four, make the pumping unit operate at the optimal base frequency and enter the frequency fine-tuning stage at the same time, that is, each time the pumping unit operates at a frequency, calculate the equivalent liquid production of the pumping unit at the current frequency, and compare it with the equivalent liquid production of the previous operating frequency, and fine-tune the current operating frequency with a frequency step according to the trend of equivalent liquid production and frequency change; step five, repeat step four, and perform fine-tuning in this cycle until the motor frequency of the pumping unit fluctuates at a certain value, which is the motor frequency of the pumping unit corresponding to the optimal reasonable stroke rate; step six, convert the pumping unit frequency obtained in step five into the optimal stroke rate of the pumping unit according to the motor speed formula; step seven, adjust the pumping unit stroke rate according to the optimal stroke rate value of the pumping unit obtained in step six. This application has the following shortcomings: 1) It cannot solve the problem of motor overheating at low frequencies, resulting in waste of electrical energy; 2) The actual pump efficiency calculated using the pumping unit suspension point load and displacement data does not take into account the elastic deformation of the light rod, so the error is large; 3) The frequency adjustment cannot adapt to real-time changes in working conditions. Summary of the Invention

[0006] In response to the defects in the existing technology, the present invention provides a method and system for automatically adjusting the stroke frequency of a pumping unit based on the continuous liquid production at the pumping unit wellhead, which realizes the precise adjustment of the automatic adjustment stroke frequency of the pumping unit well, improves the system efficiency of the oil well, greatly reduces the production cost of the oil well, and improves the economic benefits of oil production in the oil field.

[0007] In a first aspect, the present invention provides a method for automatically adjusting the stroke frequency of a pumping unit based on the continuous liquid production of the pumping unit at a wellhead, comprising the following steps:

[0008] The liquid production metering device continuously collects the liquid production data of the pumping unit at each stroke;

[0009] Find out the average value of liquid production per unit time under the current well conditions;

[0010] Calculating the average pump efficiency of the current liquid supply condition based on the average liquid production amount and the theoretical displacement of the pump;

[0011] The average pump efficiency value is compared with a preset pump efficiency value to obtain a comparison result, and a speed control instruction is sent to the frequency converter according to the comparison result to adjust the pumping unit stroke frequency.

[0012] In the second aspect, the present invention provides an automatic adjustment system for pumping unit stroke frequency based on continuous liquid production at the wellhead of the pumping unit, comprising: a liquid production metering device, a processor and a frequency converter, wherein:

[0013] The liquid production metering device is used to continuously collect the liquid production data of the pumping unit at each stroke, and transmit the liquid production data to the processor;

[0014] The processor receives the liquid production data, calculates the average value of the liquid production per unit time under the current well conditions, calculates the average pump efficiency of the current liquid supply conditions based on the average liquid production and the theoretical displacement of the pump, compares the average pump efficiency with a preset pump efficiency to obtain a comparison result, and issues a control instruction to the frequency converter based on the comparison result;

[0015] The frequency converter adjusts the rotation speed of the driving motor according to the control instruction to adjust the pumping unit stroke frequency.

[0016] Beneficial effects of the present invention:

[0017] The present invention provides a method and system for automatically adjusting the stroke frequency of a pumping unit based on the continuous liquid production at the pumping unit wellhead, which realizes the precise adjustment of the automatic stroke frequency of the pumping unit well, improves the system efficiency of the oil well, greatly reduces the production cost of the oil well, and improves the economic benefits of oil production in the oil field. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0019] Figure 1 A flow chart of a method for automatically adjusting the stroke frequency of a pumping unit based on the continuous liquid production of the pumping unit wellhead provided by the first embodiment of the present invention is shown;

[0020] Figure 2 A structural block diagram of an automatic adjustment system for pumping unit stroke frequency based on continuous liquid production at a wellhead of a pumping unit, provided by another embodiment of the present invention, is shown. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0023] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used in the specification and appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0024] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0025] As used in this specification and the appended claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0026] It should be noted that, unless otherwise specified, the technical or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0027] like Figure 1 FIG. 1 shows a flow chart of a method for automatically adjusting the number of strokes of a pumping unit based on continuous liquid production at a wellhead of a pumping unit provided by a first embodiment of the present invention. The method comprises the following steps:

[0028] The liquid production metering device continuously collects the liquid production data of the pumping unit at each stroke;

[0029] Calculate the average value of liquid production per unit time under the current well conditions;

[0030] Calculate the average pump efficiency of the current liquid supply conditions based on the average liquid production and the theoretical displacement of the pump;

[0031] The average pump efficiency value is compared with a preset pump efficiency value to obtain a comparison result, and a speed control instruction is sent to the frequency converter according to the comparison result.

[0032] The preset pump efficiency is the optimal pump efficiency determined in advance through trial operation.

[0033] The basic optimal pump efficiency calculation method is as follows: the processor collects the fluid production data of the pumping unit at different strokes through sensors, then establishes a corresponding relationship between fluid production and the specific stroke of the pumping unit to determine the optimal fluid production number for the current well conditions. The frequency converter then uses this stroke as the benchmark stroke. Since the fluid supply of the pumping unit downhole frequently changes, the fluid production of the pumping unit well also changes. Therefore, the speed regulation of the frequency converter also changes according to the actual fluid production, and a flexible variable speed method is adopted to drive the motor during single stroke operation.

[0034] During the trial run, the pumping unit was run for 60 strokes over a wide range of strokes. The liquid production metering device collected the liquid production at each stroke and sent the corresponding liquid production for each stroke to the processor. The processor internally calculates the relationship between liquid production and stroke frequency, and based on this production data, it can calculate the optimal pump efficiency. The calculation method is as follows: First, calculate the pump efficiency based on the liquid production: η = Q 液 / Q 理 ×100%, where η is the deep well pump efficiency; Qliquid is the actual production of the oil well (liters / 60 strokes); Qtheoretical is the theoretical displacement of the pump (liters / 60 strokes). The well production volume and pump efficiency per 60 strokes have a limit value when the pumping equipment such as the pumping unit is fixed. This value is only related to the downhole fluid supply conditions and the characteristics of the pumping equipment. Therefore, for determining the liquid production volume Qper 60 strokes of the pumping equipment, 液 =Q 理 ×η=60×A×Sy×n, where A is the cross-sectional area of ​​the pump barrel; Sy is the theoretical stroke of the pump barrel; n is the average pump efficiency, Q 液 (24 hours) = 1440 × A × Sy × n. The relationship between pump efficiency and stroke rate is that, when fluid supply conditions remain unchanged and the pumping equipment is fixed, the lower the stroke rate, the higher the pump efficiency. During the trial run, the 24-hour fluid production under fixed well conditions is constant, and increasing the stroke rate will not increase production. This allows us to calculate the optimal stroke rate. This allows us to use this optimal stroke rate as a basis during actual adjustments, allowing the processor to control the inverter to ensure that the pumping well operates at the optimal stroke rate at all times.

[0035] The specific method of comparing the average pump efficiency with the preset pump efficiency to obtain a comparison result and sending a speed control instruction to the inverter according to the comparison result includes:

[0036] If the average pump efficiency is greater than the preset pump efficiency, an acceleration control instruction is sent to the frequency converter. The acceleration control instruction is used to increase the speed of the drive motor to increase the pumping unit stroke frequency.

[0037] If the average pump efficiency is less than the preset pump efficiency, a deceleration control instruction is sent to the frequency converter. The deceleration control instruction is used to reduce the speed of the drive motor to reduce the pumping unit stroke frequency.

[0038] If the average pump efficiency is equal to the preset pump efficiency, a hold control instruction is sent to the frequency converter. The hold control instruction is used to maintain the current speed of the drive motor without adjusting the pumping unit stroke frequency.

[0039] The inverter uses a constant power drive mode for speed within each stroke cycle. This means that as the output torque increases, the angular velocity decreases accordingly, achieving real-time speed regulation within the cycle. The processor records and tracks the actual elapsed time for each cycle, and fine-tunes the next stroke cycle based on the specified optimal stroke rate, keeping the stroke rate per minute within plus or minus 2 percent of the specified stroke rate, thereby ensuring the accuracy of the overall average stroke rate.

[0040] The embodiment of the present invention provides a method for automatically adjusting the number of strokes of a pumping unit based on the continuous liquid production at the wellhead of the pumping unit. The method judges the liquid supply status by continuously collecting the liquid production of each stroke, and calculates the average pump efficiency based on the average value of the liquid production. The comparison result is obtained by comparing the average pump efficiency with the preset pump efficiency. The frequency converter is controlled according to the comparison result, and the frequency converter adjusts the speed of the drive motor according to the control instruction to achieve the purpose of adjusting the number of strokes. The average value of the liquid production is used to calculate the average pump efficiency, and the data obtained is more accurate. On the basis of giving full play to the downhole liquid production capacity, the pumping unit is kept running at the best system efficiency, and the speed is adjusted in real time according to the change of load in each stroke cycle, which ensures the best production while greatly reducing the wear of the mechanical parts of the pumping unit and the energy consumption during the working process, greatly reducing the production cost of the oil well and improving the economic benefits of oil production in the oil field.

[0041] The technical effects of the method for automatically adjusting the pumping unit stroke frequency based on the continuous liquid production at the wellhead of the pumping unit provided by the embodiment of the present invention are as follows:

[0042] 1) Using highly accurate wellhead continuous liquid production data instead of equivalent liquid production data with large errors in "power chart oil measurement", the error is greatly reduced;

[0043] 2) Ensure optimal output while achieving real-time speed regulation within each stroke cycle, effectively reducing mechanical losses;

[0044] 3) The amount of data required is greatly reduced, the calculation process is simplified, and a large amount of calculation and memory space are saved;

[0045] 4) Completely avoids the possibility of motor overheating or even burning during the stroke adjustment process;

[0046] 5) The range of automatic adjustment of stroke frequency is large and the operation process is stable, which can be achieved from 0.5 times / min to 12 times / min;

[0047] 6) Rapid adjustment speed, the ideal stroke frequency can be achieved within 3 to 5 strokes after startup, and then real-time dynamic adjustment is carried out;

[0048] 7) Wide range of adaptability, including permanent magnet synchronous motor, high-speed synchronous motor and ordinary asynchronous motor;

[0049] 8) Perfectly solve the problem of "a big horse pulling a small cart", greatly improve the efficiency of the motor, so that a lower power motor can be used to drive the pumping unit;

[0050] 9) Save electricity, basically no reverse power generation, and protect the quality of the power grid.

[0051] like Figure 2 The figure shows a schematic structural diagram of a pumping unit stroke automatic adjustment system based on the continuous liquid production at the wellhead of the pumping unit, according to another embodiment of the present invention. The system includes: a liquid production metering device, a processor, and a frequency converter. The liquid production metering device is used to continuously collect liquid production data of the pumping unit at each stroke and transmit the liquid production data to the processor. The processor receives the liquid production data and calculates the average liquid production per unit time under the current well conditions. Based on the average liquid production per unit time and the theoretical displacement of the pump, the average pump efficiency for the current liquid production conditions is calculated. The average pump efficiency is compared with a preset pump efficiency to obtain a comparison result. Based on the comparison result, a control instruction is issued to the frequency converter. The frequency converter adjusts the speed of the drive motor according to the control instruction to adjust the pumping unit stroke frequency. In this embodiment, the processor is a single-chip microcomputer.

[0052] The processor includes an analysis module, which is used to compare the average pump efficiency with the preset pump efficiency to obtain a comparison result, and issue a control instruction to the inverter according to the comparison result, specifically including:

[0053] If the average pump efficiency is greater than the preset pump efficiency, an acceleration control instruction is sent to the frequency converter. The acceleration control instruction is used to increase the speed of the drive motor to increase the pumping unit stroke frequency.

[0054] If the average pump efficiency is less than the preset pump efficiency, a deceleration control instruction is sent to the frequency converter. The deceleration control instruction is used to reduce the speed of the drive motor to reduce the pumping unit stroke frequency.

[0055] If the average pump efficiency is equal to the preset pump efficiency, a hold control instruction is sent to the frequency converter. The hold control instruction is used to maintain the current speed of the drive motor without adjusting the pumping unit stroke frequency.

[0056] The inverter uses a constant power drive mode for speed within each stroke cycle. This means that as the output torque increases, the angular velocity decreases accordingly, achieving real-time speed regulation within the cycle. The processor records and tracks the actual elapsed time for each cycle, and fine-tunes the next stroke cycle based on the specified optimal stroke rate, keeping the stroke rate per minute within plus or minus 2 percent of the specified stroke rate, thereby ensuring the accuracy of the overall average stroke rate.

[0057] An embodiment of the present invention provides an automatic pumping unit stroke adjustment system based on the continuous liquid production at the wellhead of the pumping unit. The system continuously collects the liquid production of each stroke through a liquid production metering sensor and transmits the liquid production data to a processor. The processor calculates the average liquid production per unit time under the current well conditions, calculates the average pump efficiency based on the average liquid production, compares the average pump efficiency with a preset pump efficiency to obtain a comparison result, and controls a frequency converter based on the comparison result. The frequency converter adjusts the speed of the drive motor according to the control instruction to achieve the purpose of adjusting the pumping unit stroke. If the average pump efficiency is greater than the preset pump efficiency, an acceleration control instruction is sent to the frequency converter, which is used to increase the speed of the drive motor to increase the pumping unit stroke rate. If the average pump efficiency is less than the preset pump efficiency, a deceleration control instruction is sent to the frequency converter, which is used to reduce the speed of the pumping unit drive motor to reduce the stroke rate. If the average pump efficiency is equal to the preset pump efficiency, a hold control instruction is sent to the frequency converter, which is used to maintain the current speed of the drive motor without adjusting the pumping unit stroke rate. On the basis of giving full play to the downhole liquid production capacity, the pumping unit is kept running at the best system efficiency, and the speed is adjusted in real time according to the change of load in each stroke cycle, ensuring the best production while greatly reducing the wear of the mechanical parts and energy consumption of the pumping unit during the working process, greatly reducing the production cost of the oil well and improving the economic benefits of oil production in the oil field.

[0058] The embodiment of the present invention provides a method and system for automatically adjusting the stroke frequency of a pumping unit based on the continuous liquid production at the pumping unit wellhead, which realizes the precise adjustment of the automatic adjustment stroke frequency of the pumping unit well, improves the system efficiency of the oil well, greatly reduces the production cost of the oil well, and improves the economic benefits of oil production in the oil field.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for automatically adjusting the pumping frequency based on the continuous liquid production of the pumping unit at the wellhead, characterized in that: The following steps are involved: The liquid production metering device continuously collects the liquid production data of the pumping unit at each stroke; Calculate the average value of liquid production per unit time under the current well conditions; Calculating the average pump efficiency of the current liquid production status based on the average liquid production amount and the theoretical displacement of the pump; Comparing the average pump efficiency with a preset pump efficiency to obtain a comparison result, and sending a speed control instruction to the frequency converter according to the comparison result to adjust the pumping unit stroke frequency; The specific method of comparing the average pump efficiency with the preset pump efficiency to obtain a comparison result, and sending a speed control instruction to the frequency converter according to the comparison result includes: If the average pump efficiency is greater than the preset pump efficiency, an acceleration control instruction is sent to the frequency converter. The acceleration control instruction is used to increase the speed of the drive motor to increase the pumping unit stroke frequency. If the average pump efficiency is less than the preset pump efficiency, a deceleration control instruction is sent to the frequency converter. The deceleration control instruction is used to reduce the speed of the drive motor to reduce the pumping unit stroke frequency. If the average pump efficiency is equal to the preset pump efficiency, a hold control instruction is sent to the frequency converter. The hold control instruction is used to maintain the current speed of the drive motor without adjusting the pumping unit stroke frequency.

2. The method according to claim 1, wherein The calculation formula of the pump efficiency is: η=Q 液 / Q 理 ×100%, where η is the pump efficiency, Q 液 is the actual production of the oil well, Q 理 is the theoretical displacement of the pump.

3. The method according to claim 2, wherein The frequency converter drives the motor in a constant power manner.

4. An automatic adjustment system for pumping unit stroke frequency based on continuous liquid production at the wellhead of the pumping unit, characterized in that: include: Liquid metering device, processor and frequency converter, among which, The liquid production metering device is used to continuously collect the liquid production data of the pumping unit at each stroke, and transmit the liquid production data to the processor; The processor receives the liquid production data, calculates the average value of the liquid production per unit time under the current well conditions, calculates the average pump efficiency of the current liquid production conditions based on the average liquid production and the theoretical displacement of the pump, compares the average pump efficiency with a preset pump efficiency to obtain a comparison result, and issues a control instruction to the frequency converter based on the comparison result; The frequency converter adjusts the speed of the driving motor according to the control instruction to adjust the pumping unit stroke frequency; The processor includes an analysis module, which is used to compare the average pump efficiency with a preset pump efficiency to obtain a comparison result, and issue a control instruction to the frequency converter according to the comparison result, specifically including: If the average pump efficiency is greater than the preset pump efficiency, an acceleration control instruction is sent to the frequency converter. The acceleration control instruction is used to increase the speed of the drive motor to increase the pumping unit stroke frequency. If the average pump efficiency is less than the preset pump efficiency, a deceleration control instruction is sent to the frequency converter. The deceleration control instruction is used to reduce the speed of the drive motor to reduce the pumping unit stroke frequency. If the average pump efficiency is equal to the preset pump efficiency, a hold control instruction is sent to the frequency converter. The hold control instruction is used to maintain the current speed of the drive motor without adjusting the pumping unit stroke frequency.

5. The system according to claim 4, wherein: The calculation formula of the pump efficiency is: η=Q 液 / Q 理 ×100%, where η is the pump efficiency, Q 液 is the actual production of the oil well, Q 理 is the theoretical displacement of the pump.

6. The system according to claim 4, wherein: The frequency converter drives the motor in a constant power manner.

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