Shaft medium-frequency electric heating control device and method

Abstract

The invention belongs to the technical field of pumping well electric heating, and particularly discloses a shaft medium-frequency electric heating control device and method. The shaft medium-frequency electric heating control method comprises the steps that the output current of a pumping unit frequency converter is monitored in real time; the upstroke and the downstroke of the pumping unit are judged based on the output current of the pumping unit frequency converter; determining the highest operation current of the pumping unit frequency converter during the upstroke and the downstroke of the pumping unit; the highest operation current of the pumping unit frequency converter during the upstroke and the downstroke of the pumping unit is compared with the upstroke current upper limit and the downstroke current upper limit of the pumping unit respectively; and controlling the shaft medium-frequency electric heating frequency converter based on the comparison result. According to the scheme, the shaft medium-frequency electric heating frequency converter is controlled based on the output current of the pumping unit frequency converter, the operation energy consumption of the shaft medium-frequency electric heating system can be reduced, and meanwhile the problems of excessive heating and insufficient heating temperature can be effectively avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of electric heating of oil pumping wells, and in particular relates to a wellbore medium-frequency electric heating control device and method. Background Art

[0002] Wellbore medium frequency electric heating technology is one of the commonly used technologies for heavy oil well exploitation. This technology has the following disadvantages in field application:

[0003] 1. The wellbore medium-frequency electric heating control cabinet is a high-energy-consuming equipment for crude oil production in heavy oil fields, with a monthly power consumption of more than 40,000 degrees. In order to improve quality and efficiency, this problem must be effectively solved. There are currently two control modes for the wellbore medium-frequency electric heating control cabinet, timing control and temperature control. The timing control mode uses manual setting of the heating operation time and stop time; the temperature control mode is to install the temperature sensor at the wellhead, and the collected temperature cannot truly reflect the bottom of the well working conditions. The above two control methods have little energy-saving effect. At the same time, there are also problems of overheating and insufficient heating temperature. Excessive heating increases the operating cost of the oil field, and insufficient heating temperature causes a sudden change in the load of the pumping unit. After the load mutation, it is very easy to cause the motor to overheat and burn out and the inverter to burn out.

[0004] 2. The high-order harmonics generated by the frequency converter in the wellbore medium-frequency electric heating control cabinet pose a hidden danger to the safe and stable operation of the power supply equipment. At the same time, it makes the oilfield automation control device unable to operate normally and interferes with the signals transmitted remotely by the control device.

[0005] 3. There is no alarm device when the neutral wire of the medium-frequency electric heating in the wellbore is broken, and it is difficult for employees to find it at night. After the neutral wire is broken, the heating cabinet is still running. At this time, if the neutral wire falls to the ground, it is very easy to cause an electric shock accident. At the same time, if the neutral wire contacts metal, it will generate electric sparks, which is easy to cause fire and explosion accidents at the wellhead. Summary of the invention

[0006] In order to solve at least one of the drawbacks of the wellbore medium-frequency electric heating control cabinet in use mentioned in the background technology, the main purpose of the present invention is to provide a wellbore medium-frequency electric heating control device and method.

[0007] According to a first aspect of the present invention, a method for controlling medium-frequency electric heating of a wellbore is provided, which comprises the following steps:

[0008] Real-time monitoring of the output current of the pumping unit inverter;

[0009] The upstroke and downstroke of the pumping unit are determined based on the output current of the pumping unit inverter;

[0010] Determine the maximum operating current of the pumping unit inverter during the upstroke and downstroke of the pumping unit;

[0011] The maximum operating current of the frequency converter of the oil pumping unit during the upstroke and downstroke of the oil pumping unit is compared with the upper current limit of the upstroke and downstroke of the oil pumping unit respectively;

[0012] The wellbore medium frequency electric heating inverter is controlled based on the comparison result.

[0013] According to some embodiments of the present invention, the output current of the frequency converter of the oil pumping unit is obtained via a current transmitter installed at the output end of the frequency converter of the oil pumping unit.

[0014] According to some embodiments of the present invention, the output current of the pumping unit frequency converter is obtained from the pumping unit frequency converter.

[0015] According to some embodiments of the present invention, judging the upstroke and downstroke of the oil pump based on the output current of the oil pump inverter includes: determining the top dead center and the bottom dead center based on the output current of the oil pump inverter, and then judging the upstroke and downstroke of the oil pump based on the top dead center and the bottom dead center.

[0016] According to some embodiments of the present invention, controlling the wellbore medium frequency electric heating frequency converter based on the comparison result includes:

[0017] When the maximum operating current of the frequency converter of the oil pumping unit exceeds the corresponding first current upper limit during the upstroke or downstroke of the oil pumping unit, the medium frequency electric heating frequency converter of the wellbore is controlled to start and operate at the first gear power;

[0018] When the maximum operating current of the frequency converter of the oil pumping unit during the upstroke or downstroke of the oil pumping unit exceeds the corresponding second current upper limit but does not exceed the corresponding first current upper limit, the medium frequency electric heating frequency converter of the wellbore is controlled to start and operate at the second power level;

[0019] When the maximum operating current of the pumping unit inverter during the upstroke or downstroke of the pumping unit does not exceed the corresponding second current upper limit, the wellbore medium frequency electric heating inverter is controlled to be turned off.

[0020] Among them, the first power level is higher than the second power level, and the first current upper limit is higher than the second current upper limit.

[0021] According to some embodiments of the present invention, controlling the wellbore medium frequency electric heating frequency converter based on the comparison result further includes:

[0022] After the medium frequency electric heating inverter of the wellbore runs at the second power level for a set time, check whether the maximum operating current of the inverter of the pumping unit has a downward trend during the upstroke or downstroke of the pumping unit;

[0023] If there is a downward trend, adjust the medium-frequency electric heating inverter of the wellbore to operate at the third gear power;

[0024] If there is no downward trend, the medium frequency electric heating inverter of the wellbore is maintained to operate at the second power level.

[0025] Among them, the third gear power is lower than the first gear power and the second gear power.

[0026] According to some embodiments of the present invention, controlling the wellbore medium frequency electric heating frequency converter based on the comparison result further includes:

[0027] After the wellbore medium frequency electric heating inverter runs at the third gear power for a set time, it is detected whether the maximum operating current of the inverter of the pumping unit during the upstroke or downstroke of the pumping unit does not exceed the corresponding second current upper limit;

[0028] If the corresponding second current upper limit is not exceeded, the medium frequency electric heating inverter of the wellbore is controlled to be turned off;

[0029] If the corresponding second current upper limit is exceeded, the wellbore medium-frequency electric heating inverter is controlled to maintain the third power level operation.

[0030] According to some embodiments of the present invention, the wellbore medium frequency electric heating control method further includes:

[0031] After the medium frequency electric heating inverter of the wellbore runs at the first power level for a set time, check whether the maximum operating current of the inverter of the pumping unit has an upward trend during the upstroke or downstroke of the pumping unit;

[0032] If there is an upward trend, the frequency converter of the pumping unit is controlled to reduce the frequency;

[0033] If there is no upward trend, the pumping unit inverter is controlled to maintain the current power operation.

[0034] According to some embodiments of the present invention, the wellbore medium frequency electric heating control method further includes:

[0035] After the frequency converter of the oil pumping unit has been running at a reduced frequency for a set time, check whether the maximum operating current of the oil pumping unit's frequency converter has returned to normal;

[0036] If it returns to normal, the pumping unit inverter is controlled to accelerate to the set frequency.

[0037] According to some embodiments of the present invention, the wellbore medium frequency electric heating control method further includes:

[0038] When the medium frequency electric heating inverter of the wellbore is started, its current is monitored;

[0039] When the current drops below 10A, the medium-frequency electric heating inverter in the shaft is controlled to shut down, the operating parameters are uploaded to the monitoring terminal, and an alarm signal is output at the same time.

[0040] According to a second aspect of the present invention, there is provided a wellbore medium frequency electric heating control device, comprising:

[0041] A current acquisition device, wherein the current acquisition device is configured to acquire the output current of the frequency converter of the oil pumping unit in real time;

[0042] A controller is communicatively connected to the current acquisition device, and the controller is configured to execute the wellbore medium-frequency electric heating control method according to the first aspect of the present invention.

[0043] According to some embodiments of the present invention, the wellbore medium frequency electric heating control device further includes:

[0044] An input device is communicatively connected to the controller, the input device is configured to receive a user's selection of a control mode for a wellbore medium frequency electric heating inverter, the control mode including manual control and automatic control, and the controller is configured to control the wellbore medium frequency electric heating inverter based on the control mode received from the user.

[0045] According to some embodiments of the present invention, the wellbore medium frequency electric heating control device further includes:

[0046] An active filter connected to a medium-frequency electric heating frequency converter in a wellbore is configured to eliminate harmonic currents generated by the medium-frequency electric heating frequency converter in the wellbore.

[0047] According to some embodiments of the present invention, the wellbore medium frequency electric heating control device further includes:

[0048] A wireless transmission module is communicatively connected to the controller, and the wireless transmission module is configured to upload operating parameters to a remote monitoring terminal.

[0049] According to some embodiments of the present invention, the current acquisition device is a current transmitter installed at the output end of the frequency converter of the oil pumping unit.

[0050] Due to the adoption of the above technical solution, the present invention has at least one of the following beneficial effects:

[0051] In the scheme of the present invention, by real-time monitoring of the output current of the pumping unit frequency converter, the wellbore medium-frequency electric heating frequency converter is controlled based on the output current of the pumping unit frequency converter, thereby realizing the automatic control of the start and stop of the wellbore medium-frequency electric heating frequency converter and the power regulation, which can reduce the operating energy consumption of the wellbore medium-frequency electric heating system, reduce the operating cost of the oil field, improve the oil well time rate, reduce the labor intensity of workers, and effectively avoid the problems of overheating and insufficient heating temperature;

[0052] In the scheme of the present invention, by setting an active filter, the high-order harmonics generated by the wellbore medium-frequency electric heating system during operation can be effectively reduced, the interference to other electrical equipment in the production system can be eliminated, and the safe and stable operation of high and low voltage electrical equipment can be ensured;

[0053] In the scheme of the present invention, by monitoring the current of the wellbore medium-frequency electric heating inverter, when the output current drops below 10A, the wellbore medium-frequency electric heating inverter is controlled to be shut down, the operating parameters are uploaded to the monitoring terminal, and an alarm signal is output at the same time, which can facilitate users to promptly discover and handle line break faults and effectively prevent accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0055] Figure 1 A flow chart of a wellbore medium frequency electric heating control method provided by one embodiment of the present invention;

[0056] Figure 2 A flow chart of a method for controlling a wellbore medium frequency electric heating frequency converter based on the output current of a pumping unit frequency converter provided in one embodiment of the present invention;

[0057] Figure 3 A block diagram of a wellbore medium frequency electric heating control device provided in one embodiment of the present invention;

[0058] Figure 4 A schematic diagram of a wellbore medium-frequency electric heating control device provided in another embodiment of the present invention. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0060] According to a first aspect of the present invention, a method for controlling medium-frequency electric heating of a wellbore is provided. Figure 1 As shown, in one embodiment, the method includes the following steps:

[0061] S1: real-time monitoring of the output current of the pumping unit inverter;

[0062] S2: judging the upstroke and downstroke of the pumping unit based on the output current of the pumping unit inverter;

[0063] S3: Determine the maximum operating current of the frequency converter of the pumping unit during the upstroke and downstroke of the pumping unit;

[0064] S4: comparing the maximum operating current of the frequency converter of the oil pumping unit during the upstroke and downstroke of the oil pumping unit with the upper current limit of the upstroke and downstroke of the oil pumping unit respectively;

[0065] S5: Control the wellbore medium frequency electric heating inverter based on the comparison result.

[0066] The present invention controls the start and stop and power regulation of the medium-frequency electric heating frequency converter of the wellbore based on the change of the output current of the pumping unit frequency converter, thereby reducing the operating energy consumption of the medium-frequency electric heating system of the wellbore. Specifically, the change of the output current of the pumping unit frequency converter can reflect the magnitude of the movement resistance of the sucker rod column to a certain extent, and then reflect the crude oil viscosity information, especially the greater the maximum operating current of the pumping unit frequency converter during the upstroke and downstroke of the pumping unit, the greater the crude oil viscosity at this time, and it may be necessary to electrically heat the wellbore to reduce the crude oil viscosity at this time. On the contrary, the smaller the maximum operating current of the pumping unit frequency converter during the upstroke and downstroke of the pumping unit, the smaller the crude oil viscosity at this time, and it may be unnecessary to electrically heat the wellbore at this time. Based on this, the method of the present invention determines the maximum operating current of the pumping unit inverter during the upstroke and downstroke of the pumping unit by monitoring the output current of the pumping unit inverter in real time, and then controls the start and stop and power regulation of the wellbore medium frequency electric heating inverter based on the maximum operating current of the pumping unit inverter during the upstroke and downstroke of the pumping unit, thereby realizing the automatic control of the wellbore medium frequency electric heating, which can reduce the operating energy consumption of the wellbore medium frequency electric heating system, reduce the operating cost of the oil field, improve the oil well time rate, reduce the labor intensity of workers, and effectively avoid the problems of overheating and insufficient heating temperature.

[0067] In step S1 , the output current of the pumping unit inverter may be obtained via a current transducer installed at the output end of the pumping unit inverter or may be directly obtained from the pumping unit inverter via communication with the pumping unit inverter.

[0068] In step S2, judging the upstroke and downstroke of the oil pumping unit based on the output current of the oil pumping unit inverter includes: determining the top dead center and the bottom dead center based on the output current of the oil pumping unit inverter, and then judging the upstroke and downstroke of the oil pumping unit based on the top dead center and the bottom dead center. Because the current has two minimum values ​​when the oil pumping unit runs to the top dead center and the bottom dead center, the top dead center and the bottom dead center can be determined based on the minimum value of the identified output current. After the top dead center and the bottom dead center are determined, the stroke from a top dead center to the next bottom dead center is the downstroke, and the stroke from a bottom dead center to the next top dead center is the upstroke. Since the current change immediately after the minimum current appears at the top dead center is less than the current change after the minimum current appears at the bottom dead center, the top dead center and the bottom dead center can be distinguished based on the minimum value of the current combined with the current change.

[0069] In step S3, based on the output current of the pumping unit inverter monitored in real time in step S1 and the upstroke and downstroke of the pumping unit determined in step S2, the maximum operating current of the pumping unit inverter during the upstroke and downstroke of the pumping unit is determined.

[0070] In step S4, the maximum operating current of the frequency converter of the oil pumping unit during the upstroke and downstroke of the oil pumping unit determined in step S3 is compared with the predetermined upper and lower current limits of the oil pumping unit during the upstroke and downstroke, respectively. The upper and lower current limits of the oil pumping unit are predetermined based on the calculation of the balance of the rod and the oil pumping unit. Generally speaking, the upper current limit of the upstroke is different from the upper current limit of the downstroke.

[0071] In step S5, based on the comparison result of the maximum operating current of the frequency converter of the oil pumping unit during the upstroke and downstroke of the oil pumping unit with the corresponding upper limit, the start and stop and power regulation of the medium frequency electric heating frequency converter of the wellbore are controlled.

[0072] In one embodiment, Figure 2As shown, step S5 specifically includes: in step S50, it is determined whether the maximum operating current of the frequency converter of the oil pumping unit during the upstroke or downstroke of the oil pumping unit exceeds the corresponding first current upper limit; if it exceeds the corresponding first current upper limit, then in step S51, the medium-frequency electric heating frequency converter of the wellbore is controlled to start and operate according to the first gear power, so as to quickly heat the crude oil with high power and improve the heating efficiency; if it does not exceed the corresponding first current upper limit, then in step S52, it is determined whether the maximum operating current of the frequency converter of the oil pumping unit during the upstroke or downstroke of the oil pumping unit exceeds the corresponding second current upper limit, and the second current upper limit is lower than the first current upper limit; if it exceeds the corresponding second current upper limit, then in step S53, it is controlled The medium-frequency electric heating inverter of the wellbore is started and operated at the second power level, so as to heat the crude oil with a suitable medium power, thereby achieving energy saving while ensuring the heating effect, wherein the first power level is higher than the second power level; if it does not exceed the corresponding second current upper limit, then in step S54, the medium-frequency electric heating inverter of the wellbore is controlled to be turned off to save energy; after step S53, in step S55, it is determined whether the operation of the medium-frequency electric heating inverter of the wellbore at the second power level has reached the set time; if the set time has not been reached, it returns to step S55; if the set time has been reached, then in step S56, it is detected whether there is a decrease in the maximum operating current of the inverter of the pumping unit during the upstroke or downstroke of the pumping unit trend; if there is a downward trend, then in step S57, the medium-frequency electric heating frequency converter of the wellbore is adjusted to operate at the third power level, so as to heat the crude oil with a suitable medium power, thereby achieving energy saving while ensuring the heating effect, wherein the third power level is lower than the first power level and the second power level; if there is no downward trend, then in step S58, the medium-frequency electric heating frequency converter of the wellbore is maintained to operate at the second power level, so as to ensure the heating efficiency as high as possible; after step S57, in step S59, it is determined whether the medium-frequency electric heating frequency converter of the wellbore has been operating at the third power level for a set time; if the set time has not been reached, the process returns to step S59; if the set time has been reached, the process returns to step S59. In step S60, it is detected whether the maximum operating current of the frequency converter of the oil pump during the upstroke or downstroke of the oil pump does not exceed the corresponding second current upper limit; if it does not exceed the corresponding current upper limit, then in step S61, the medium-frequency electric heating frequency converter of the wellbore is controlled to be turned off to save energy; if it exceeds the corresponding second current upper limit, then in step S62, the medium-frequency electric heating frequency converter of the wellbore is maintained to operate at the third power level to ensure the balance between heating efficiency and energy saving as much as possible; after step S51, in step S63, it is determined whether the medium-frequency electric heating frequency converter of the wellbore has been operating at the first power level for a set time; if the set time has not been reached, return to step S63; if the set time has been reached, return to step S50.Although in this embodiment, a three-speed frequency adjustment of the medium-frequency electric heating frequency converter for the wellbore is provided, it should be understood that the medium-frequency electric heating frequency converter for the wellbore may have more or fewer speeds, and the adjustment method thereof is similar, and the present invention does not limit the number of speeds of the medium-frequency electric heating frequency converter for the wellbore. In the above method, the first upper current limit is determined based on the calculation of the balance of the rod, pipe and pumping unit, and the second upper current limit is set based on the calculation of the balance of the rod, pipe and pumping unit, crude oil characteristics, pumping unit characteristics, electric heating frequency converter characteristics, etc. The setting times mentioned in various places in the above method may not be equal, and technicians may set and adjust them according to actual needs.

[0073] In some embodiments, the frequency conversion of the pumping unit can also be controlled based on the power regulation of the medium frequency electric heating inverter in the wellbore, such as Figure 2 As shown, in step S63, after the medium-frequency electric heating inverter in the wellbore runs at the first power level for a set time, it is detected whether the maximum operating current of the inverter of the oil pumping unit has an upward trend during the upstroke or downstroke of the oil pumping unit; if there is an upward trend, then in step S65, the oil pumping unit inverter is controlled to run at a reduced frequency to protect the oil pumping unit from damage or reduced life caused by overload operation; if there is no upward trend, then in step S66, the oil pumping unit inverter is maintained to run at the current frequency; after step S65, in step S67, it is determined whether the pumping unit inverter has been running at a reduced frequency for a set time; if the set time has not been reached, the process returns to step S67; if the set time has been reached, then in step S68, it is detected whether the maximum operating current of the inverter of the oil pumping unit has returned to normal (i.e., whether the current is always within the rated current range of the motor); if it has returned to normal, then in step S69, the pumping unit inverter is controlled to accelerate to the set frequency to increase production capacity; if it has not returned to normal, the process returns to step S66. In the method of the present invention, through the coordinated control between the wellbore medium frequency electric heating inverter and the oil pumping unit inverter, the operating energy consumption of both the wellbore medium frequency electric heating system and the oil pumping unit system can be reduced, and the efficiency can be improved. At the same time, the damage of related components can be effectively prevented and the service life can be extended.

[0074] In some embodiments, the wellbore medium frequency electric heating control method further includes: monitoring the current of the wellbore medium frequency electric heating inverter when it is started; when the current drops below 10A, it indicates that a line break accident has occurred, and at this time the wellbore medium frequency electric heating inverter is controlled to be turned off, and the operating parameters are uploaded to the monitoring terminal, and an alarm signal is output at the same time to prompt the inspection staff to pay attention. This can effectively prevent the heating cabinet from operating when the neutral line of the heating cable connected to the medium frequency bottom hole electric heating control cabinet is broken at the terminal connected to the hollow sucker rod at the wellhead of the oil well, thereby causing a safety accident.

[0075] According to a second aspect of the present invention, a wellbore medium frequency electric heating control device is provided. Figure 3 As shown, in one embodiment, the device includes: a current acquisition device 10, which is configured to acquire the output current of the pumping unit frequency converter in real time; and a controller 20 connected to the current acquisition device 10 in communication, and the controller 20 is configured to execute the wellbore medium frequency electric heating control method according to the first aspect of the present invention. No further details will be given here.

[0076] In some embodiments, the current collection device 10 is a current transmitter installed at the output end of the oil pump inverter.

[0077] In some embodiments, the wellbore medium frequency electric heating control device further includes: an input device 30 connected to the controller 20 in communication, the input device 30 is configured to receive a user's selection of a wellbore medium frequency electric heating inverter control mode, the control mode including manual control and automatic control. The controller 20 is configured to control the wellbore medium frequency electric heating inverter based on the control mode selected by the user.

[0078] In some embodiments, the wellbore medium frequency electric heating control device further includes: an active filter 40 connected to the wellbore medium frequency electric heating frequency converter, and the active filter 40 is configured to eliminate the harmonic current generated by the wellbore medium frequency electric heating frequency converter.

[0079] In some embodiments, the wellbore medium frequency electric heating control device further includes: a wireless transmission module 50 communicatively connected to the controller 20 , and the wireless transmission module 50 is used to upload operating parameters to the remote monitoring terminal 100 .

[0080] Figure 4A schematic diagram of a wellbore medium-frequency electric heating control device provided by another embodiment of the present invention. The wellbore medium-frequency electric heating control cabinet 1 includes an active filter 2, a frequency converter 3, a touch screen 4, a PLC (programmable logic controller) 7 and a LORA wireless transmission module 8. Among them, the PLC 7 can communicate with the pumping unit frequency conversion control cabinet 5, and the pumping unit frequency conversion control cabinet 5 includes a frequency converter 6. The output end of the frequency converter 6 is equipped with a current transmitter for real-time monitoring of the output current of the frequency converter 6 and transmitting it to the PLC 7, or in some cases, the PLC 7 can directly obtain the output current of the frequency converter 6 via the RS485 communication established with the frequency converter 6. The touch screen 4 is used to select the control mode of the frequency converter 3, that is, manual control and automatic control. When manual control is selected on the touch screen 4, the heating time and stop time of the frequency converter 3 are controlled through the RS485 communication established between the touch screen 4 and the PLC 7, and the continuous operation of the wellbore medium-frequency electric heating control cabinet 1 can also be realized. When the shaft medium frequency electric heating control cabinet 1 is working, the active filter 2 eliminates the harmonic current generated by the inverter 3. The LORA wireless transmission module 8 uploads the operating parameters (including medium frequency electric heating voltage, current, power, fault information, and alarm information) to the remote monitoring terminal, so that employees can obtain operating data in real time and remotely control the inverter 3.

[0081] When automatic control is selected, PLC 7 can obtain the real-time current of inverter 6 through the current transmitter installed at the output end of inverter 6. Since the current has two minimum values ​​when the pumping unit runs to the upper dead center and the lower dead center, PLC 7 judges the upper and lower strokes of the pumping unit based on this current, and the upper and lower stroke current maximum limits are set by the internal program of PLC 7. When PLC 7 detects that the highest current of inverter 6 running during the upper or lower stroke of the pumping unit exceeds the upper current limit set by the internal program of PLC 7, the inverter 3 in the wellbore medium-frequency electric heating control cabinet 1 starts and runs according to the first power (highest gear) set by the program of PLC 7. When the highest current of inverter 6 running during the upper or lower stroke of the pumping unit is lower than the upper current limit set by the internal program of PLC 7, PLC 7 controls inverter 3 to run according to the second power (middle gear) set by the program. During the operation, when PLC 7 detects that the highest current of inverter 6 running has a downward trend, PLC 7 controls inverter 3 to run according to the third power (lowest gear) set by the program. When PLC 7 detects that the maximum operating current of inverter 6 during the up and down strokes of the sucker rod returns to normal (ie, lower than the upper current limit set by the internal program of PLC7), PLC7 controls inverter 3 to stop running and enter a standby state.

[0082] After the inverter 3 in the shaft medium frequency electric heating control cabinet 1 starts the first power gear (highest gear) and runs for the set time, when PLC 7 detects that the maximum current of the inverter 6 is rising, PLC 7 controls the inverter 6 to reduce the frequency through RS485 communication. After the frequency is reduced and the maximum current of the inverter 6 returns to normal (that is, the operating current of the inverter 6 is always within the rated current range of the motor), PLC 7 controls the inverter 6 to accelerate to the set frequency through RS485 communication.

[0083] When the neutral line of the heating cable connected to the medium frequency bottom hole electric heating control cabinet 1 is broken at the terminal connecting the wellhead of the oil well and the hollow sucker rod, when the current is reduced to 0A through the RS485 communication established by PLC 7 and the inverter 3, PLC 7 controls the inverter 3 to stop running, and uploads the operating parameters to the monitoring terminal through the LORA wireless transmission module 8, so that the employees can find the disconnection fault in time. At the same time, PLC 7 outputs an alarm signal, and the alarm installed on the on-site control cabinet sends an alarm signal to prompt the inspection employees to pay attention.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention, including the combination of various technical features in any other appropriate manner, these simple variations and combinations should also be regarded as the contents disclosed by the present invention and should be included in the protection scope of the present invention.

Claims

1. A method for controlling medium frequency electric heating in a wellbore, characterized in that: The following steps are involved: Real-time monitoring of the output current of the pumping unit inverter; The upstroke and downstroke of the pumping unit are determined based on the output current of the pumping unit inverter; Determine the maximum operating current of the pumping unit inverter during the upstroke and downstroke of the pumping unit; The maximum operating current of the frequency converter of the oil pumping unit during the upstroke and downstroke of the oil pumping unit is compared with the upper current limit of the upstroke and downstroke of the oil pumping unit respectively; The wellbore medium frequency electric heating inverter is controlled based on the comparison result.

2. The method for controlling medium frequency electric heating of a wellbore according to claim 1, characterized in that: The output current of the oil pumping unit inverter is obtained via a current transmitter installed at the output end of the oil pumping unit inverter.

3. The method for controlling medium frequency electric heating of a wellbore according to claim 1, characterized in that: The output current of the frequency converter of the oil pumping unit is obtained through communication with the frequency converter of the oil pumping unit.

4. The method for controlling medium frequency electric heating of a wellbore according to claim 1, characterized in that: Judging the upstroke and downstroke of the oil pump based on the output current of the oil pump inverter includes: determining the top dead center and the bottom dead center based on the output current of the oil pump inverter, and then judging the upstroke and downstroke of the oil pump based on the top dead center and the bottom dead center.

5. The method for controlling medium frequency electric heating of a wellbore according to claim 1, characterized in that: Controlling the wellbore medium frequency electric heating inverter based on the comparison results includes: When the maximum operating current of the frequency converter of the oil pumping unit exceeds the corresponding first current upper limit during the upstroke or downstroke of the oil pumping unit, the medium frequency electric heating frequency converter of the wellbore is controlled to start and operate at the first gear power; When the maximum operating current of the frequency converter of the oil pumping unit during the upstroke or downstroke of the oil pumping unit exceeds the corresponding second current upper limit but does not exceed the corresponding first current upper limit, the medium frequency electric heating frequency converter of the wellbore is controlled to start and operate at the second power level; When the maximum operating current of the pumping unit inverter during the upstroke or downstroke of the pumping unit does not exceed the corresponding second current upper limit, the wellbore medium frequency electric heating inverter is controlled to be turned off. Among them, the first power level is higher than the second power level, and the first current upper limit is higher than the second current upper limit.

6. The method for controlling medium frequency electric heating of a wellbore according to claim 5, characterized in that: Controlling the wellbore medium frequency electric heating inverter based on the comparison result also includes: After the medium frequency electric heating inverter of the wellbore runs at the second power level for a set time, check whether the maximum operating current of the inverter of the pumping unit has a downward trend during the upstroke or downstroke of the pumping unit; If there is a downward trend, adjust the medium-frequency electric heating inverter of the wellbore to operate at the third gear power; If there is no downward trend, the medium frequency electric heating inverter of the wellbore is maintained to operate at the second power level. Among them, the third gear power is lower than the first gear power and the second gear power.

7. The method for controlling medium frequency electric heating of a wellbore according to claim 6, characterized in that: Controlling the wellbore medium frequency electric heating inverter based on the comparison result also includes: After the wellbore medium frequency electric heating inverter runs at the third gear power for a set time, it is detected whether the maximum operating current of the inverter of the pumping unit during the upstroke or downstroke of the pumping unit does not exceed the corresponding second current upper limit; If the corresponding second current upper limit is not exceeded, the medium frequency electric heating inverter of the wellbore is controlled to be turned off; If the corresponding second current upper limit is exceeded, the wellbore medium-frequency electric heating inverter is controlled to maintain the third power level operation.

8. The method for controlling medium frequency electric heating of a wellbore according to claim 5, characterized in that: Also includes: After the medium frequency electric heating inverter of the wellbore runs at the first power level for a set time, check whether the maximum operating current of the inverter of the pumping unit has an upward trend during the upstroke or downstroke of the pumping unit; If there is an upward trend, the frequency converter of the pumping unit is controlled to reduce the frequency; If there is no upward trend, the pumping unit inverter is controlled to maintain the current power operation.

9. The method for controlling medium frequency electric heating of a wellbore according to claim 8, characterized in that: Also includes: After the frequency converter of the oil pumping unit has been running at a reduced frequency for a set time, check whether the maximum operating current of the oil pumping unit's frequency converter has returned to normal; If it returns to normal, the pumping unit inverter is controlled to accelerate to the set frequency.

10. The method for controlling medium frequency electric heating of a wellbore according to claim 1, characterized in that: Also includes: When the medium frequency electric heating inverter of the wellbore is started, its output current is monitored; When the output current drops below 10A, the medium-frequency electric heating inverter in the shaft is controlled to shut down, the operating parameters are uploaded to the monitoring terminal, and an alarm signal is output at the same time.

11. A medium frequency electric heating control device for a wellbore, characterized in that: include: A current acquisition device, wherein the current acquisition device is configured to acquire the output current of the frequency converter of the oil pumping unit in real time; A controller communicatively connected to the current acquisition device, wherein the controller is configured to execute the wellbore medium-frequency electric heating control method according to any one of claims 1-10.

12. The wellbore medium frequency electric heating control device according to claim 11, characterized in that: Also includes: An input device is communicatively connected to the controller, the input device is configured to receive a user's selection of a control mode for a wellbore medium frequency electric heating inverter, the control mode including manual control and automatic control, and the controller is configured to control the wellbore medium frequency electric heating inverter based on the control mode received from the user.

13. The wellbore medium frequency electric heating control device according to claim 11, characterized in that: Also includes: An active filter connected to a medium-frequency electric heating frequency converter in a wellbore is configured to eliminate harmonic currents generated by the medium-frequency electric heating frequency converter in the wellbore.

14. The medium frequency electric heating control device for a wellbore according to claim 11, characterized in that: Also includes: A wireless transmission module is communicatively connected to the controller, and the wireless transmission module is configured to upload operating parameters to a remote monitoring terminal.

15. The medium frequency electric heating control device for a wellbore according to claim 11, characterized in that: The current acquisition device is a current transmitter installed at the output end of the oil pumping unit frequency converter.

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