Intermittent pumping control method and system for oil pumping unit

Abstract

The present invention provides an intermittent pumping control method and system for an oil pumping unit, which are used to reduce the control cost of the intermittent pumping working mode of the oil pumping unit, and the method comprises: a controller receives the value of the instantaneous power of the motor sent by the frequency converter; the controller calculates the stroke power of the oil pumping unit according to the instantaneous power of the motor, and the stroke power refers to the output power of one stroke cycle of the oil pumping unit; the controller obtains the average power of multiple time periods according to the stroke power, and one time period includes at least one stroke cycle; the controller inputs the average power of multiple time periods into the intermittent pumping working mode identification model to obtain the pumping time within one working cycle; the controller determines the pumping stop time within one working cycle according to the pumping time within one working cycle.

Description

Technical Field

[0001] The invention relates to the field of petroleum, and in particular to an intermittent pumping control method and system for an oil pumping unit. Background Art

[0002] The characteristic of China's oil fields is low bottom hole pressure. After long-term exploitation, the bottom hole's fluid supply capacity has dropped significantly. The deep well pumps of the rod pumping unit will have varying degrees of "empty pumping" or even gas lock during the oil pumping process, resulting in low production, low efficiency, high energy consumption, and greatly increased production costs, which seriously affects China's strategic position in oil.

[0003] The adjustment parameters of the oil pump are stroke and stroke frequency. Long stroke is conducive to improving efficiency and reducing equipment loss, but the adjustment of stroke is limited by the structure of the oil pump itself. In order to optimize the pumping parameters, it is usually achieved by adjusting the stroke frequency. The appropriate stroke frequency can match the pumping capacity of the oil pump with the fluid supply capacity of the bottom of the well, so as to improve efficiency and reduce output costs. The conventional way to adjust the stroke frequency is to replace the motor or pulley with different speeds, but the range is limited. After the stroke frequency drops to a certain level, the efficiency of the oil pump is seriously reduced, which is counterproductive. Therefore, intermittent pumping is a better solution.

[0004] At present, many low permeability oil wells have adopted the intermittent pumping system, and there are many related studies. It is more common to measure the temperature, pressure, electrical parameters, power diagram, etc. of the oil well through sensors, analyze the liquid supply capacity of the formation, and conduct a comprehensive diagnosis of the working condition of the pumping unit. However, there are many interference factors in the power diagram detection, and sensors are required, which are expensive and need to be calibrated regularly, so it has great limitations.

[0005] How to reduce the control cost of the intermittent pumping system of the oil pump is an urgent problem to be solved. Summary of the invention

[0006] The invention provides an intermittent pumping control method and system for an oil pumping unit, which are used to reduce the control cost of the intermittent pumping working mode of the oil pumping unit.

[0007] A first aspect of an embodiment of the present application provides an intermittent pumping control method for an oil pumping unit, comprising:

[0008] The controller receives the value of the instantaneous power of the motor sent by the inverter;

[0009] The controller calculates the stroke power of the pumping unit based on the instantaneous power of the motor. The stroke power refers to the output power of one stroke cycle of the pumping unit.

[0010] The controller obtains the average power of multiple time periods according to the stroke power, and one time period includes at least one stroke cycle;

[0011] The controller inputs the average power of multiple time periods into the duty cycle identification model to obtain the pumping time within a duty cycle;

[0012] The controller determines the pumping stop time within a working cycle according to the pumping time within a working cycle.

[0013] Based on the first aspect of the embodiments of the present application, in a first implementation method of the first aspect of the embodiments of the present application, the multiple time periods are continuous time periods; the multiple time periods are time periods of equal length.

[0014] Based on the first aspect of the embodiment of the present application or the first implementation of the first aspect, in the second implementation of the first aspect of the embodiment of the present application, the multiple time periods are specifically three time periods, and the average power of the multiple time periods includes a first average power P1, a second average power P2, and a third average power P3;

[0015] The identification model of the intermittent pumping duty cycle is TR=a(yP2-xP1-zP3) / (uP1-vP2+wP3), where y=x+z, v=u+w, and TR is the pumping time in one working cycle.

[0016] Based on the first aspect of the embodiment of the present application, the first implementation method of the first aspect, and any one of the second implementation methods, in the third implementation method of the first aspect of the embodiment of the present application, the intermittent working mode identification model is TR=12(7P2-4.5P1-2.5P3) / (P1-2P2+P3), where 30min≤TR≤60min.

[0017] Based on the first aspect of the embodiment of the present application, and any one of the first implementation to the third implementation of the first aspect, in a fourth implementation of the first aspect of the embodiment of the present application, the controller determines the pumping stop time within a working cycle according to the pumping time within a working cycle, specifically including:

[0018] The pumping time is greater than or equal to the first preset value, and the pumping stop time is reduced;

[0019] If the pumping time is less than or equal to the second preset value, the pumping stop time is increased;

[0020] If the oil pumping time is greater than the second preset value and less than the first preset value, the pumping stop time does not change.

[0021] Based on the first aspect of the embodiment of the present application, and any one of the first to fourth implementations of the first aspect, in the fifth implementation of the first aspect of the embodiment of the present application, the minimum value of the pumping stop time TS in one working cycle is 30 minutes, and the maximum value of TS is 90 minutes;

[0022] When TR ≥ 50 min and TS > 30 min, TS is reduced by 10 min;

[0023] When TR≤40min and TS<90min, TS increases by 10min;

[0024] When 50min>TR>40min, TS does not change.

[0025] Based on the first aspect of the embodiment of the present application, and any one of the first to fifth implementations of the first aspect, in the sixth implementation of the first aspect of the embodiment of the present application, the initial value of the pumping stop time TS within a working cycle is 60 minutes.

[0026] Based on the first aspect of the embodiment of the present application and any one of the first implementation manner to the sixth implementation manner of the first aspect, in a seventh implementation manner of the first aspect of the embodiment of the present application, the method further includes:

[0027] The detection circuit of the frequency converter detects the instantaneous voltage and instantaneous current of the motor;

[0028] The inverter calculates the instantaneous power of the motor based on the instantaneous voltage and instantaneous current of the motor;

[0029] The inverter sends the value of the instantaneous power of the motor to the controller.

[0030] Based on the first aspect of the embodiment of the present application and any one of the first to seventh implementations of the first aspect, in an eighth implementation of the first aspect of the embodiment of the present application, the controller receives a value of the instantaneous power of the motor sent by the inverter, specifically including:

[0031] The controller receives the instantaneous power value of the motor sent by the inverter through 485 communication.

[0032] A second aspect of the embodiment of the present application provides an intermittent pumping control system for an oil pumping unit, comprising: a frequency converter and a controller, for executing the intermittent pumping control method for an oil pumping unit according to the first aspect;

[0033] The power supply end of the frequency converter is connected to the contactor of the main circuit, and the load end of the frequency converter is connected to the motor; the controller and the frequency converter are connected in communication; and the motor is set in the main circuit.

[0034] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0035] In the embodiment of the present application, the stroke power of the pumping unit is calculated using the instantaneous power of the motor, and the output power of the pumping unit in one stroke cycle can be accurately measured. When the stroke and stroke of the pumping unit remain unchanged, the output power of the pumping unit in one stroke cycle is positively correlated with the liquid production of the pumping unit, that is, the greater the output power, the greater the liquid production, and the smaller the output power, the smaller the liquid production. The reason for the reduction in liquid production is the insufficient liquid supply capacity at the bottom of the well. By measuring the output power to detect the downhole working conditions, there is no need to use expensive sensors downhole, saving costs. In the process of determining the intermittent pumping working system, multiple time periods are first selected, and the stroke power of each time period is multiplied by the strokes in the time period, and then divided by the length of the time period to obtain the average power. After the controller obtains the average power of each of the multiple time periods, the average power is input into the intermittent pumping working system identification model. The intermittent pumping working system identification model is a mathematical model, the input is the average power of multiple time periods, and the output is the pumping time in one working cycle. One working cycle includes pumping time and stop pumping time. The controller uses the intermittent pumping duty identification model to determine the pumping time within a cycle, and then determines the pumping stop time within a working cycle, that is, determines the duty of the pumping unit. The controller controls the operation of the pumping unit according to the duty of the pumping unit, which is simple, easy and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of the intermittent pumping control method of the oil pumping unit implemented in the present application;

[0037] Figure 2 It is another flow chart of the intermittent pumping control method of the oil pumping unit implemented in the present application;

[0038] Figure 3 It is a control flow chart of the intermittent pumping control system of the oil pumping unit implemented in the present application;

[0039] Figure 4 It is a structural diagram of the intermittent pumping control system of the oil pumping unit implemented in this application. DETAILED DESCRIPTION

[0040] The invention provides an intermittent pumping control method and system for an oil pumping unit, which are used to reduce the control cost of the intermittent pumping working mode of the oil pumping unit.

[0041] The embodiment of the present application provides an intermittent pumping control method for an oil pumping unit, which can be applied to a petroleum rod pumping unit and implemented by a control system composed of a pumping unit dedicated frequency converter and a controller. The controller has a built-in intelligent control algorithm, which includes an intermittent pumping duty identification model.

[0042] The detection circuit of the frequency converter in the control system detects the instantaneous voltage and instantaneous current of the motor and calculates the instantaneous power (including negative power) of the motor. The controller reads the instantaneous power through 485 communication. The controller processes the instantaneous power data to obtain the stroke power, and then detects the power of the pumping unit in multiple stroke cycles. The optimal pumping time and stop time are calculated through the intermittent pumping working system identification model, and the intermittent pumping working system is formulated to complete the self-learning of the oil well working conditions. The intermittent pumping working system identification model is a mathematical model used to identify the optimal intermittent pumping working system to maximize the liquid production. The pumping time and stop time can also be called the pumping time and stop time.

[0043] The controller controls the inverter to work according to the intermittent pumping system. During the pumping process, the control system detects the change of the stroke power in real time and performs closed-loop control on the pumping unit to achieve supply-production balance, stable production and increased efficiency.

[0044] The embodiment of the present application calculates the stroke power of the pumping unit and the average power of multiple time periods by detecting the instantaneous power of the motor, and adopts an intermittent pumping working system based on the mathematical model of the intermittent pumping working system identification model to obtain the maximum liquid production. The intelligent pumping control of the pumping unit is realized by combining digital filtering technology, mathematical modeling technology and variable frequency control technology to achieve the purpose of increasing production and efficiency and saving energy and reducing consumption.

[0045] like Figure 1 As shown, the embodiment of the present application provides an intermittent pumping control method of an oil pumping unit, comprising:

[0046] 101. The controller receives the value of the instantaneous power of the motor sent by the inverter;

[0047] 102. The controller calculates the stroke power of the pumping unit according to the instantaneous power of the motor. The stroke power refers to the output power of one stroke cycle of the pumping unit.

[0048] 103. The controller obtains the average power of multiple time periods according to the stroke power, and one time period includes at least one stroke cycle;

[0049] 104. The controller inputs the average power of multiple time periods into the pumping duty identification model to obtain the pumping time within a working cycle;

[0050] 105. The controller determines the pumping stop time within a working cycle according to the pumping time within a working cycle.

[0051] Intelligent control of the oil pump is to obtain the electrical parameters of the motor through the frequency converter and indirectly judge the downhole working conditions through the controller, determine the best intermittent pumping working system, and track the changes in the downhole working conditions to automatically adjust, so that the oil well is always operating under the best intermittent pumping working system, achieving the purpose of supply and discharge balance and maximizing liquid production.

[0052] like Figure 2 As shown, the embodiment of the present application provides an intermittent pumping control method of an oil pumping unit, comprising:

[0053] 201. The detection circuit of the frequency converter detects the instantaneous voltage and instantaneous current of the motor;

[0054] The instantaneous voltage and instantaneous current of the motor are detected by a special frequency converter, and the instantaneous power of the motor is obtained by multiplying the two.

[0055] 202. The inverter calculates the instantaneous power of the motor based on the instantaneous voltage and instantaneous current of the motor;

[0056] The controller directly reads the instantaneous power of the inverter, and the stroke power is obtained by integrating the instantaneous power within a stroke cycle.

[0057] 203. The inverter sends the value of the instantaneous power of the motor to the controller.

[0058] In one implementation, the inverter and the controller are connected via 485 communication. The inverter sends the value of the instantaneous power of the motor to the controller via 485 communication.

[0059] 204. The controller receives the value of the instantaneous power of the motor sent by the frequency converter;

[0060] In one implementation, the controller receives the value of the instantaneous power of the motor sent by the inverter through 485 communication.

[0061] 205. The controller calculates the stroke power of the pumping unit according to the instantaneous power of the motor. The stroke power refers to the output power of one stroke cycle of the pumping unit.

[0062] The unit of stroke power is kilowatt (kW). One stroke cycle refers to one round of reciprocating motion of the pump.

[0063] 206. The controller obtains the average power of multiple time periods according to the stroke power, and one time period includes at least one stroke cycle;

[0064] The average power of a period is the stroke power multiplied by the number of strokes in the period, divided by the length of the period.

[0065] 207. The controller inputs the average power of multiple time periods into the pumping duty identification model to obtain the pumping time within a working cycle;

[0066] The controller controls the dedicated inverter of the oil pump to operate at a fixed stroke frequency.

[0067] In one implementation, the controller measures the average power of three consecutive equal time intervals T: the first average power P1, the second average power P2 and the third average power P3, and the pumping time can be obtained by the intermittent pumping duty identification model.

[0068] The identification model of the intermittent pumping duty cycle is TR=a(yP2-xP1-zP3) / (uP1-vP2+wP3), where y=x+z, v=u+w, and TR is the pumping time in one working cycle.

[0069] In one implementation, the intermittent working system identification model is:

[0070] TR=12(7P2-4.5P1-2.5P3) / (P1-2P2+P3), the lower limit of TR value is 30min, and the upper limit is 60min.

[0071] 208. The controller determines the pumping stop time within a working cycle according to the pumping time within a working cycle.

[0072] In one implementation, the pumping time is greater than or equal to a first preset value, and the pumping stop time is reduced;

[0073] If the pumping time is less than or equal to the second preset value, the pumping stop time is increased;

[0074] If the oil pumping time is greater than the second preset value and less than the first preset value, the pumping stop time does not change.

[0075] In one implementation, the initial value of the stop pumping time TS is 60 minutes, the minimum value is 30 minutes, and the maximum value is 90 minutes, which is adjusted according to the following rules:

[0076] When TR≥50min and TS>30min, the current TS is the previous TS-10, that is, TS is reduced by 10min;

[0077] When TR≤40min and TS<90min, the current TS is the previous TS+10, that is, TS increases by 10min;

[0078] When 40min<TR<50min, TS does not change and the last pumping stop time is maintained.

[0079] The initial execution of steps 204 to 208 may be referred to as a self-learning phase, and the subsequent cyclic execution of steps 204 to 208 may be referred to as a closed-loop control phase.

[0080] In the self-learning stage, the controller measures the data of the pumping unit's stroke power changing with time through the frequency converter and draws a mathematical model of the stroke power changing with time. Based on the mathematical model of the stroke power changing with time and the intermittent pumping duty identification model, the optimal intermittent pumping duty corresponding to the maximum liquid production is determined;

[0081] In the closed-loop control stage, the pumping time and stop time in the calculated optimal intermittent pumping system are used as the given values ​​of the benchmark system. Combined with the changes in the downhole fluid supply capacity, the closed-loop control of the system is carried out to achieve stable production and increased production.

[0082] like Figure 3 to Figure 4 As shown, an embodiment of the present application provides an intermittent pumping control system for an oil pump, comprising: a frequency converter and a controller for executing an intermittent pumping control method for an oil pump; the power supply end of the frequency converter is connected to a contactor of a main circuit, and the load end of the frequency converter is connected to a motor; the controller and the frequency converter are communicatively connected; and the motor is arranged in the main circuit.

[0083] The control system is based on a dedicated inverter for oil pumping units and an intelligent controller, which is used to identify the optimal intermittent pumping mode for oil pumping units. The power supply end of the dedicated inverter for oil pumping units in the control system is connected to the contactor of the main circuit, and the load end is connected to the motor. The control system also includes a controller with a built-in intelligent control algorithm, and the controller is a dedicated controller for oil pumping units, which exchanges data with the inverter through communication.

[0084] like Figure 3 As shown, the input end of the inverter obtains the DC bus voltage and the set frequency. The DC bus voltage is input into the DC overvoltage regulator to obtain the additional output frequency, and the set frequency is input into the acceleration and deceleration ramp integrator to obtain the basic output frequency. The basic output frequency and the additional output frequency signals intersect, and the positive feedback gain is performed to obtain the output frequency. The output frequency is input into the SPWM control unit, and the V / F curve and the closed-loop control operation signal sent by the controller are also input into the SPWM control unit. The output end of the SPWM control unit is the output end of the inverter, and the output end of the inverter is connected to the motor. The inverter collects the voltage and current at the output end and calculates the instantaneous power of the motor. The obtained instantaneous power of the motor is input into the controller.

[0085] The controller's stroke power consumption calculation unit receives the instantaneous power of the motor sent by the frequency converter and inputs it into the controller. The stroke power consumption calculation unit outputs the stroke power consumption to the self-learning model and the well condition dynamic tracking model. The self-learning model obtains the pumping time based on the stroke power consumption, and further obtains the pumping stop time to determine the intermittent pumping working system. The intermittent pumping working system is input into the well condition dynamic tracking model. The well condition dynamic tracking model outputs a closed-loop control operation signal to the SPWM control unit of the frequency converter.

[0086] like Figure 4As shown, the U port, V port, W port and PE port of the inverter are respectively connected to the U1 port, V1 port, W1 port and ground port of the motor; the R port, S port and T port are respectively connected to the output port of the contactor to power the inverter; the K1 port, K2 port and COM port are respectively connected to the normally open contacts of KA1 and KA2 of the relay to control the operation and stop of the inverter; the 1 port and 2 port are connected to the DC reactor; the A+ port and B- port are connected to the 485 bus to communicate with the controller.

[0087] It should be understood that, although the steps in the flowcharts involved in the above embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0088] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0089] The terms "first", "second", "third", "fourth", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than that shown or described herein.

[0090] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0091] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0092] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0093] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the various embodiments of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, read-only memory), random access memory (RAM, random access memory), disk or optical disk, etc., which can store program code.

Claims

1. A method for controlling intermittent pumping of an oil pumping unit, characterized in that: include: The controller receives the value of the instantaneous power of the motor sent by the inverter; The controller calculates the stroke power of the pumping unit based on the instantaneous power of the motor. The stroke power refers to the output power of one stroke cycle of the pumping unit. The controller obtains the average power of multiple time periods according to the stroke power, wherein one time period includes at least one stroke cycle; The controller inputs the average power of multiple time periods into the duty cycle identification model to obtain the pumping time within a duty cycle; The controller determines the pumping stop time within a working cycle according to the pumping time within a working cycle; The multiple time periods are specifically three time periods, and the average powers of the multiple time periods include a first average power P1, a second average power P2, and a third average power P3; TR is the pumping time in one working cycle. Specifically, the identification model of the intermittent pumping working system is TR=12(7P2-4.5P1-2.5P3) / (P1-2P2+P3), where 30min≤TR≤60min; The controller determines the pumping stop time in a working cycle according to the pumping time in a working cycle, specifically including: The pumping time is greater than or equal to the first preset value, and the pumping stop time is reduced; If the pumping time is less than or equal to the second preset value, the pumping stop time is increased; If the oil pumping time is greater than the second preset value and less than the first preset value, the pumping stop time does not change.

2. The intermittent pumping control method of the oil pumping unit according to claim 1, characterized in that: Multiple time periods are continuous time periods; multiple time periods are time periods of equal length.

3. The intermittent pumping control method of a pumping unit according to claim 1, characterized in that: The minimum TS of the pumping stop time in a working cycle is 30 minutes, and the maximum TS is 90 minutes; When TR ≥ 50 min and TS > 30 min, TS is reduced by 10 min; When TR≤40min and TS<90min, TS increases by 10min; When 40min<TR<50min, TS does not change.

4. The intermittent pumping control method of the oil pumping unit according to claim 3, characterized in that: The initial value of the pumping stop time TS within a working cycle is 60 minutes.

5. The intermittent pumping control method of an oil pumping unit according to any one of claims 1 to 2, characterized in that: The method further comprises: The detection circuit of the frequency converter detects the instantaneous voltage and instantaneous current of the motor; The inverter calculates the instantaneous power of the motor based on the instantaneous voltage and instantaneous current of the motor; The inverter sends the value of the instantaneous power of the motor to the controller.

6. The intermittent pumping control method of the oil pumping unit according to claim 5, characterized in that: The controller receives the value of the instantaneous power of the motor sent by the frequency converter, specifically including: The controller receives the instantaneous power value of the motor sent by the inverter through 485 communication.

7. An intermittent pumping control system for an oil pumping unit, characterized in that: include: A frequency converter and a controller for executing the intermittent pumping control method of an oil pumping unit according to any one of claims 1 to 6; The power supply end of the frequency converter is connected to the contactor of the main circuit, and the load end of the frequency converter is connected to the motor; the controller and the frequency converter are connected in communication; and the motor is set in the main circuit.

Images