Wellbore radio frequency electric heating control device and method

Abstract

The present application belongs to the technical field of electric heating of pumping wells, and specifically discloses a wellbore intermediate frequency electric heating control device and method. The wellbore intermediate frequency electric heating control method comprises: monitoring the output current of the pumping unit frequency converter in real time; determining the upstroke and downstroke of the pumping unit based on the output current of the pumping unit frequency converter; determining the highest operating current of the pumping unit frequency converter during the upstroke and downstroke of the pumping unit; comparing the highest operating current of the pumping unit frequency converter during the upstroke and downstroke of the pumping unit with the upper limit of the upstroke and downstroke current, respectively; and controlling the wellbore intermediate frequency electric heating frequency converter based on the comparison result. In the scheme of the present application, the wellbore intermediate frequency electric heating frequency converter is controlled based on the output current of the pumping unit frequency converter, which can reduce the operating energy consumption of the wellbore intermediate frequency electric heating system, and effectively avoid the problems of excessive heating and insufficient heating temperature.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electric heating of oil extraction wells, and particularly relates to a wellbore medium-frequency electric heating control device and method. BACKGROUND

[0002] Wellbore medium-frequency electric heating technology is one of the technologies commonly used in heavy oil well production, and the following disadvantages exist in the field application of this technology:

[0003] 1. The wellbore medium-frequency electric heating control cabinet is a high-energy-consumption equipment for heavy oil field crude oil production, and the monthly power consumption reaches more than 40,000 degrees. In order to improve the quality and efficiency, this problem must be effectively solved. The wellbore medium-frequency electric heating control cabinet currently has two control modes, namely, timing control and temperature control. The timing control mode uses manual setting of heating operation time and stop time; the temperature control mode installs a temperature sensor at the wellhead, and the collected temperature cannot truly reflect the bottom hole condition. The energy-saving effect of the above two control modes is very small. At the same time, there are problems of excessive heating and insufficient heating temperature. Excessive heating increases the operating cost of the oil field, and insufficient heating temperature causes sudden load change of the oil pumping unit, which easily causes over-temperature burning of the motor and burning of the frequency converter after the load change.

[0004] 2. The high-order harmonic generated by the frequency converter in the wellbore medium-frequency electric heating control cabinet poses a hidden danger to the safe and stable operation of the power supply equipment, and at the same time, it makes the oil field automatic control device unable to operate normally, and causes interference to the signal transmitted remotely by the control device.

[0005] 3. There is no alarm device after the zero line of the wellbore medium-frequency electric heating is broken, and it is difficult for employees to find it at night. After the zero line is broken, the heating cabinet is still running, and at this time, if the zero line falls to the ground, an electric shock accident is easily caused, and if the zero line contacts metal, an electric spark is generated, which easily causes a fire and explosion accident at the wellhead. SUMMARY

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

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

[0008] Real-time monitoring of the output current of the oil pumping unit frequency converter;

[0009] Judging the upstroke and downstroke of the oil pumping unit based on the output current of the oil pumping unit frequency converter;

[0010] Determining the highest operating current of the oil pumping unit frequency converter during the upstroke and downstroke of the oil pumping unit;

[0011] comparing the maximum running current of the pumping unit frequency converter during the upstroke and downstroke of the pumping unit with the upper limit of the upstroke and downstroke current of the pumping unit respectively;

[0012] controlling the frequency converter of the intermediate frequency electric heating of the wellbore based on the comparison result.

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

[0014] According to some embodiments of the present application, 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 application, determining the upstroke and downstroke of the pumping unit based on the output current of the pumping unit frequency converter comprises: determining the top dead center and the bottom dead center based on the output current of the pumping unit frequency converter, and then determining the upstroke and downstroke of the pumping unit based on the top dead center and the bottom dead center.

[0016] According to some embodiments of the present application, controlling the frequency converter of the intermediate frequency electric heating of the wellbore based on the comparison result comprises:

[0017] when the maximum running current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit exceeds the corresponding first current upper limit, controlling the frequency converter of the intermediate frequency electric heating of the wellbore to start and make it run at the first power;

[0018] when the maximum running current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit exceeds the corresponding second current upper limit but does not exceed the corresponding first current upper limit, controlling the frequency converter of the intermediate frequency electric heating of the wellbore to start and make it run at the second power;

[0019] when the maximum running current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit does not exceed the corresponding second current upper limit, controlling the frequency converter of the intermediate frequency electric heating of the wellbore to be closed,

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

[0021] According to some embodiments of the present application, controlling the frequency converter of the intermediate frequency electric heating of the wellbore based on the comparison result further comprises:

[0022] detecting whether there is a downward trend in the maximum running current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit after the frequency converter of the intermediate frequency electric heating of the wellbore runs at the second power for a set time;

[0023] if there is a downward trend, adjusting the frequency converter of the intermediate frequency electric heating of the wellbore to run at the third power;

[0024] if there is no downward trend, maintaining the frequency converter of the intermediate frequency electric heating of the wellbore to run at the second power,

[0025] wherein the third power is lower than the first power and the second power.

[0026] According to some embodiments of the present application, the wellbore medium-frequency electric heating frequency converter is further controlled based on the comparison result, and the wellbore medium-frequency electric heating control method comprises:

[0027] After the wellbore medium-frequency electric heating frequency converter runs at the third power for a set time, it is detected whether the highest operating current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit is not more than the corresponding second upper limit of current;

[0028] If the highest operating current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit is not more than the corresponding second upper limit of current, the wellbore medium-frequency electric heating frequency converter is controlled to be turned off;

[0029] If the highest operating current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit is more than the corresponding second upper limit of current, the wellbore medium-frequency electric heating frequency converter is controlled to maintain the third power.

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

[0031] After the wellbore medium-frequency electric heating frequency converter runs at the first power for a set time, it is detected whether there is an upward trend in the highest operating current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit;

[0032] If there is an upward trend, the pumping unit frequency converter is controlled to run at a lower frequency;

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

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

[0035] After the pumping unit frequency converter runs at a lower frequency for a set time, it is detected whether the highest operating current of the pumping unit frequency converter returns to normal;

[0036] If the highest operating current of the pumping unit frequency converter returns to normal, the pumping unit frequency converter is controlled to accelerate to a set frequency.

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

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

[0039] When the current is reduced to below 10A, the wellbore medium-frequency electric heating frequency converter is controlled to be turned off, the operating parameters are uploaded to a monitoring terminal, and an alarm signal is output.

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

[0041] A current collecting device configured to collect the output current of the pumping unit frequency converter in real time;

[0042] A controller in communication connection with the current collecting device, the controller being configured to execute the wellbore medium-frequency electric heating control method according to the first aspect of the present application.

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

[0044] An input device in communication connection with the controller, the input device being configured to receive the user's selection of the control mode of the wellbore medium-frequency electric heating frequency converter, the control mode including manual control and automatic control, and the controller being configured to control the wellbore medium-frequency electric heating frequency converter based on the received user-selected control mode.

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

[0046] An active filter connected to the wellbore medium-frequency electric heating frequency converter, the active filter being configured to eliminate the harmonic current generated by the wellbore medium-frequency electric heating frequency converter.

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

[0048] A wireless transmission module in communication connection with the controller, the wireless transmission module being configured to upload the operating parameters to a remote monitoring terminal.

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

[0050] As the above technical solutions are adopted, the present application has at least one of the following beneficial effects:

[0051] In the present application, by monitoring the output current of the pumping unit frequency converter in real time and controlling the wellbore medium-frequency electric heating frequency converter based on the output current of the pumping unit frequency converter, the automation control of the start-stop and power adjustment of the wellbore medium-frequency electric heating frequency converter is realized, the operating energy consumption of the wellbore medium-frequency electric heating system is reduced, the oilfield operating cost is reduced, the oil well time rate is improved, the labor intensity of workers is reduced, and the problems of excessive heating and insufficient heating temperature can be effectively avoided;

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

[0053] In the scheme of the present application, by monitoring the current of the wellbore intermediate frequency electric heating frequency converter, when the output current is reduced to below 10A, the wellbore intermediate frequency electric heating frequency converter is controlled to be closed, the running parameters are uploaded to the monitoring terminal, and an alarm signal is output, so that the user can find and handle the wire breakage fault in time, and the occurrence of accidents can be effectively prevented. BRIEF DESCRIPTION OF DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0055] Figure 1 The flow chart of the wellbore intermediate frequency electric heating control method provided by an embodiment of the present application is shown in the figure.

[0056] Figure 2 The flow chart of the method for controlling the wellbore intermediate frequency electric heating frequency converter based on the output current of the pumping unit frequency converter is shown in the figure.

[0057] Figure 3 The block diagram of the wellbore intermediate frequency electric heating control device provided by an embodiment of the present application is shown in the figure.

[0058] Figure 4 The schematic diagram of the wellbore intermediate frequency electric heating control device provided by another embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0060] According to a first aspect of the present application, a wellbore intermediate frequency electric heating control method is provided. As shown in the figure, in one embodiment, the method comprises the following steps: Figure 1

[0061] S1: Real-time monitoring of the output current of the pumping unit frequency converter;

[0062] S2: Judging the upstroke and downstroke of the pumping unit based on the output current of the pumping unit frequency converter;

[0063] S3: Determining the highest running current of the pumping unit frequency converter during the upstroke and downstroke of the pumping unit;

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

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

[0066] The present application controls the start-stop and power adjustment of the wellbore medium frequency electric heating frequency converter based on the change of the pumping unit frequency converter output current, thereby reducing the operation energy consumption of the wellbore medium frequency electric heating system. Specifically, the change of the pumping unit frequency converter output current can reflect the size of the sucker rod string movement resistance to some extent, and in turn reflect the crude oil viscosity information. The greater the maximum running current of the pumping unit frequency converter during the pumping unit upstroke and downstroke, the greater the crude oil viscosity at this time, and the wellbore electric heating may be necessary to reduce the crude oil viscosity at this time. Conversely, the smaller the maximum running current of the pumping unit frequency converter during the pumping unit upstroke and downstroke, the smaller the crude oil viscosity at this time, and the wellbore electric heating may not be necessary at this time. Based on this, the method of the present application determines the maximum running current of the pumping unit frequency converter during the pumping unit upstroke and downstroke by monitoring the output current of the pumping unit frequency converter in real time, and then controls the start-stop and power adjustment of the wellbore medium frequency electric heating frequency converter based on the maximum running current of the pumping unit frequency converter during the pumping unit upstroke and downstroke, thereby realizing the automatic control of the wellbore medium frequency electric heating, reducing the operation energy consumption of the wellbore medium frequency electric heating system, reducing the oilfield operation cost, improving the oil well time rate, reducing the labor intensity of workers, and effectively avoiding the problems of excessive heating and insufficient heating temperature.

[0067] In step S1, the output current of the pumping unit frequency converter can be obtained through a current transmitter installed at the output end of the pumping unit frequency converter or can be directly obtained from the pumping unit frequency converter through communication with the pumping unit frequency converter.

[0068] In step S2, determining the pumping unit upstroke and downstroke based on the output current of the pumping unit frequency converter includes: determining the top dead center and the bottom dead center based on the output current of the pumping unit frequency converter, and then determining the pumping unit upstroke and downstroke based on the top dead center and the bottom dead center. Since the current appears two minimum values when the 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 identified minimum value of the output current. After the top dead center and the bottom dead center are determined, the stroke from one top dead center to the immediately adjacent bottom dead center is the downstroke, and the stroke from one bottom dead center to the immediately adjacent top dead center is the upstroke. Since the current change 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, the highest operating current of the pumping unit frequency converter during the upstroke and downstroke of the pumping unit is determined based on the output current of the pumping unit frequency converter monitored in real time in step S1 in combination with the upstroke and downstroke of the pumping unit determined in step S2.

[0070] In step S4, the highest operating current of the pumping unit frequency converter during the upstroke and downstroke of the pumping unit determined in step S3 is compared with the pre-determined upper limit of the upstroke and downstroke current of the pumping unit respectively. The upper limit of the upstroke and downstroke current of the pumping unit is pre-determined based on the rod string and the balance of the pumping unit. Generally, the upper limit of the upstroke current is different from the upper limit of the downstroke current.

[0071] In step S5, the start-stop and power adjustment of the frequency converter of the electric heating system in the wellbore is controlled based on the comparison result of the highest operating current of the pumping unit frequency converter during the upstroke and downstroke of the pumping unit and the corresponding upper limit.

[0072] In one embodiment, as Figure 2As shown, step S5 specifically comprises: in step S50, judging whether the highest operating current of the pumping unit frequency converter during the pumping unit upstroke or downstroke exceeds the corresponding first current upper limit; if the highest operating current of the pumping unit frequency converter during the pumping unit upstroke or downstroke exceeds the corresponding first current upper limit, then in step S51, the wellbore medium-frequency electric heating frequency converter is controlled to start and operate at the first gear power, so as to heat the crude oil at high power and improve the heating efficiency; if the highest operating current of the pumping unit frequency converter during the pumping unit upstroke or downstroke does not exceed the corresponding first current upper limit, then in step S52, judging whether the highest operating current of the pumping unit frequency converter during the pumping unit upstroke or downstroke exceeds the corresponding second current upper limit, the second current upper limit being lower than the first current upper limit; if the highest operating current of the pumping unit frequency converter during the pumping unit upstroke or downstroke exceeds the corresponding second current upper limit, then in step S53, the wellbore medium-frequency electric heating frequency converter is controlled to start and operate at the second gear power, so as to heat the crude oil at appropriate medium power, so as to save energy while ensuring the heating effect, wherein the first gear power is higher than the second gear power; if the highest operating current of the pumping unit frequency converter during the pumping unit upstroke or downstroke does not exceed the corresponding second current upper limit, then in step S54, the wellbore medium-frequency electric heating frequency converter is controlled to be turned off, so as to save energy; after step S53, in step S55, judging whether the wellbore medium-frequency electric heating frequency converter operating at the second gear power reaches the set time; if the wellbore medium-frequency electric heating frequency converter operating at the second gear power does not reach the set time, then returning to step S55; if the wellbore medium-frequency electric heating frequency converter operating at the second gear power reaches the set time, then in step S56, detecting whether there is a downward trend in the highest operating current of the pumping unit frequency converter during the pumping unit upstroke or downstroke; if there is a downward trend in the highest operating current of the pumping unit frequency converter during the pumping unit upstroke or downstroke, then in step S57, the wellbore medium-frequency electric heating frequency converter is adjusted to operate at the third gear power, so as to heat the crude oil at appropriate medium power, so as to save energy while ensuring the heating effect, wherein the third gear power is lower than the first gear power and the second gear power; if there is no downward trend in the highest operating current of the pumping unit frequency converter during the pumping unit upstroke or downstroke, then in step S58, the wellbore medium-frequency electric heating frequency converter is maintained to operate at the second gear power, so as to ensure the heating efficiency as high as possible; after step S57, in step S59, judging whether the wellbore medium-frequency electric heating frequency converter operating at the third gear power reaches the set time; if the wellbore medium-frequency electric heating frequency converter operating at the third gear power does not reach the set time, then returning to step S59; if the wellbore medium-frequency electric heating frequency converter operating at the third gear power reaches the set time, then in step S60, detecting whether the highest operating current of the pumping unit frequency converter during the pumping unit upstroke or downstroke does not exceed the corresponding second current upper limit; if the highest operating current of the pumping unit frequency converter during the pumping unit upstroke or downstroke does not exceed the corresponding current upper limit, then in step S61, the wellbore medium-frequency electric heating frequency converter is controlled to be turned off, so as to save energy; if the highest operating current of the pumping unit frequency converter during the pumping unit upstroke or downstroke exceeds the corresponding second current upper limit, then in step S62, the wellbore medium-frequency electric heating frequency converter is maintained to operate at the third gear power, so as to ensure the balance between the heating efficiency and energy saving as much as possible; after step S51, in step S63, judging whether the wellbore medium-frequency electric heating frequency converter operating at the first gear power reaches the set time; if the wellbore medium-frequency electric heating frequency converter operating at the first gear power does not reach the set time, then returning to step S63; if the wellbore medium-frequency electric heating frequency converter operating at the first gear power reaches the set time, then returning to step S50.Although three frequency adjustment gears of the frequency converter of the in- well frequency electric heating system are given in this embodiment, it should be understood that the frequency converter of the in-well frequency electric heating system can have more or less gears, and the adjustment method is similar, and the present application does not limit the number of gears of the frequency converter of the in-well frequency electric heating system. In the above method, the first upper limit of the current is determined based on the rod string and pumping unit balance calculation, and the second upper limit of the current is set based on the rod string and pumping unit balance calculation, crude oil characteristics, pumping unit characteristics, electric heating converter characteristics, etc. The set time mentioned in the above method is not necessarily equal, and the skilled person can set and adjust it according to actual needs.

[0073] In some embodiments, the frequency of the pumping unit converter can also be controlled based on the regulation of the power of the frequency converter of the in-well frequency electric heating system, as shown in FIG. 6. Figure 2 As shown in FIG. 6, in step S63, after the frequency converter of the in-well frequency electric heating system runs at the first gear power for a set time, it is detected whether there is an upward trend in the highest operating current of the pumping unit converter during the upstroke or downstroke of the pumping unit; if there is an upward trend, in step S65, the frequency of the pumping unit converter is controlled to run at a lower frequency, so as to protect the pumping unit from overloading operation and damage or reduce the service life; if there is no upward trend, in step S66, the pumping unit converter is maintained to run at the current frequency; after step S65, in step S67, it is judged whether the pumping unit converter running at a lower frequency reaches the set time; if the set time is not reached, return to step S67; if the set time is reached, in step S68, it is detected whether the highest operating current of the pumping unit converter returns to normal (i.e., whether the current is always within the rated current range of the motor); if it returns to normal, in step S69, the pumping unit converter is controlled to accelerate to the set frequency, so as to improve the production capacity; if it does not return to normal, return to step S66. In the method of the present application, through the cooperative control between the frequency converter of the in-well frequency electric heating system and the pumping unit converter, the operating energy consumption of both the in-well frequency electric heating system and the pumping unit system can be reduced, the efficiency can be improved, and at the same time, the damage to the related components can be effectively prevented, and the service life can be prolonged.

[0074] In some embodiments, the in-well frequency electric heating control method further comprises: monitoring the current of the frequency converter of the in-well frequency electric heating system when it is started; when the current is reduced to below 10A, it indicates that a broken wire accident has occurred, at which time the frequency converter of the in-well frequency electric heating system is controlled to be turned off, the operating parameters are uploaded to the monitoring terminal, and an alarm signal is outputted to prompt the inspection staff to pay attention. In this way, it can effectively avoid the safety accident caused by the fact that the heating cabinet is still running after the zero line of the heating cable connected to the in-well frequency electric heating control cabinet is broken at the terminal of the connection between the wellhead and the hollow sucker rod.

[0075] According to a second aspect of the present application, an in-well frequency electric heating control device is provided. As shown in FIG. 7, the in-well frequency electric heating control device comprises a frequency converter of the in-well frequency electric heating system, a pumping unit converter, a control unit, a current sensor, a power sensor, a temperature sensor, a pressure sensor, a flow sensor, a data storage unit, a data transmission unit, a data receiving unit, an alarm unit, and a power supply unit.Figure 3 As shown, in one embodiment, the device comprises: a current acquisition device 10 configured to acquire the output current of the pumping unit frequency converter in real time; and a controller 20 communicatively connected with the current acquisition device 10, the controller 20 being configured to execute the wellbore medium-frequency electric heating control method according to the first aspect of the present application. Details are not repeated here.

[0076] In some embodiments, the current acquisition device 10 is a current transmitter installed at the output end of the pumping unit frequency converter.

[0077] In some embodiments, the wellbore medium-frequency electric heating control device further comprises: an input device 30 communicatively connected with the controller 20, the input device 30 being configured to receive the user's selection of the control mode of the wellbore medium-frequency electric heating frequency converter, the control mode including manual control and automatic control. The controller 20 is configured to control the wellbore medium-frequency electric heating frequency converter based on the received user-selected control mode.

[0078] In some embodiments, the wellbore medium-frequency electric heating control device further comprises: an active filter 40 connected with the wellbore medium-frequency electric heating frequency converter, the active filter 40 being 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 comprises: a wireless transmission module 50 communicatively connected with the controller 20, the wireless transmission module 50 being configured to upload the operating parameters to a remote monitoring terminal 100.

[0080] Figure 4A schematic diagram of the wellbore medium frequency electric heating control device provided for another embodiment of the present application. The wellbore medium frequency electric heating control cabinet 1 comprises an active filter 2, a frequency converter 3, a touch screen 4, a PLC (programmable 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 comprises a frequency converter 6, and a current transmitter is installed at the output end of the frequency converter 6, which is used to monitor the output current of the frequency converter 6 in real time and transmit it to the PLC 7, or in some cases, the PLC 7 can directly obtain the output current of the frequency converter 6 via 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 the manual control is selected on the touch screen 4, the RS485 communication between the touch screen 4 and the PLC 7 is realized to control the heating time and the stopping time of the frequency converter 3, and the continuous operation of the wellbore medium frequency electric heating control cabinet 1 can also be realized. When the wellbore medium frequency electric heating control cabinet 1 works, the active filter 2 eliminates the harmonic current generated by the frequency converter 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 the employees can obtain the operating data in real time, and the frequency converter 3 can be remotely controlled.

[0081] When the automatic control is selected, the PLC 7 can obtain the real-time current of the frequency converter 6 through the current transmitter installed at the output end of the frequency converter 6. When the pumping unit runs to the top dead center and the bottom dead center, the current appears two minimum values, and the PLC 7 judges the upstroke and downstroke of the pumping unit according to the current. The PLC 7 sets the upper limit of the current of the upstroke and downstroke in the internal program. When the PLC 7 detects that the highest current of the frequency converter 6 during the upstroke or downstroke of the pumping unit exceeds the upper limit of the current set in the internal program of the PLC 7, the frequency converter 3 in the wellbore medium frequency electric heating control cabinet 1 starts to work and operates at the first gear power (the highest gear) set in the PLC 7 program. When the highest current of the frequency converter 6 during the upstroke or downstroke of the pumping unit is lower than the upper limit of the current set in the internal program of the PLC 7, the PLC 7 controls the frequency converter 3 to operate at the second gear power (the middle gear) set in the program. When the PLC 7 detects that the highest current of the frequency converter 6 during the upstroke or downstroke of the pumping unit has a downward trend, the PLC 7 controls the frequency converter 3 to operate at the third gear power (the lowest gear) set in the program. When the PLC 7 detects that the highest current of the frequency converter 6 during the upstroke or downstroke of the pumping unit returns to normal (i.e. lower than the upper limit of the current set in the internal program of the PLC 7), the PLC 7 controls the frequency converter 3 to stop working and be in standby state.

[0082] When the frequency converter 3 in the wellbore medium-frequency electric heating control cabinet 1 starts the first gear power (the highest gear) and runs to the set time, the PLC 7 detects that the highest current of the frequency converter 6 has an upward trend, and the PLC 7 controls the frequency converter 6 to reduce the frequency through RS485 communication. When the frequency converter 6 runs to the set time, the PLC 7 detects that the highest current of the frequency converter 6 returns to normal (that is, the current of the frequency converter 6 is always within the rated current range of the motor), and the PLC 7 controls the frequency converter 6 to accelerate to the set frequency through RS485 communication.

[0083] When the zero line of the heating cable connected to the medium-frequency well bottom electric heating control cabinet 1 is broken at the connection terminal of the oil well wellhead and the hollow sucker rod, at this time, the RS485 communication between the PLC 7 and the frequency converter 3 obtains that the current is reduced to 0A, the PLC 7 controls the frequency converter 3 to stop running, and uploads the running parameters to the monitoring terminal through the LORA wireless transmission module 8, so that the staff can find the broken wire fault in time, and the PLC 7 outputs an alarm signal, and the alarm installed on the field control cabinet sends an alarm signal to prompt the inspection staff.

[0084] The above only describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application, including the combination of various technical features in any other suitable way, should be considered as the disclosed content of the present application, and should be included in the protection scope of the present application.

Claims

1. A method of controlling the electric heating in a wellbore at medium frequency, characterized by, The method comprises the following steps: monitoring output current of the pumping unit frequency converter in real time; judging upstroke and downstroke of the pumping unit based on the output current of the pumping unit frequency converter; determining the highest operating current of the pumping unit frequency converter during the upstroke and downstroke of the pumping unit; comparing the highest operating current of the pumping unit frequency converter during the upstroke and downstroke of the pumping unit with the upper limit of the upstroke and downstroke current respectively; controlling the frequency converter of the wellbore medium-frequency electric heating based on the comparison result, controlling the frequency converter of the wellbore medium-frequency electric heating based on the comparison result comprises: when the highest operating current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit exceeds the corresponding first current upper limit, controlling the frequency converter of the wellbore medium-frequency electric heating to start and make it operate at the first power; when the highest operating current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit exceeds the corresponding second current upper limit but does not exceed the corresponding first current upper limit, controlling the frequency converter of the wellbore medium-frequency electric heating to start and make it operate at the second power; when the highest operating current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit does not exceed the corresponding second current upper limit, controlling the frequency converter of the wellbore medium-frequency electric heating to be closed, wherein the first power is higher than the second power, and the first current upper limit is higher than the second current upper limit.

2. The wellbore radio frequency electric heating control method of claim 1, wherein, The output current of the pumping unit frequency converter is obtained via a current transmitter installed at the output end of the pumping unit frequency converter.

3. The wellbore radio frequency electric heating control method of claim 1, wherein, The output current of the pumping unit frequency converter is obtained via communication with the pumping unit frequency converter.

4. The wellbore radio frequency electric heating control method of claim 1, wherein, Judging the upstroke and downstroke of the pumping unit based on the output current of the pumping unit frequency converter comprises: determining the top dead center and the bottom dead center based on the output current of the pumping unit frequency converter, and then judging the upstroke and downstroke of the pumping unit based on the top dead center and the bottom dead center.

5. The wellbore radio frequency electric heating control method of claim 1, wherein, Controlling the frequency converter of the wellbore medium-frequency electric heating based on the comparison result further comprises: after the frequency converter of the wellbore medium-frequency electric heating operates at the second power for a set time, detecting whether there is a downward trend in the highest operating current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit; if there is a downward trend, adjusting the frequency converter of the wellbore medium-frequency electric heating to make it operate at the third power; if there is no downward trend, maintaining the frequency converter of the wellbore medium-frequency electric heating to operate at the second power, wherein the third power is lower than the first power and the second power.

6. The wellbore medium frequency electric heating control method of claim 5, wherein, Controlling the frequency converter of the wellbore medium-frequency electric heating based on the comparison result further comprises: after the frequency converter of the wellbore medium-frequency electric heating operates at the third power for a set time, detecting whether the highest operating current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit does not exceed the corresponding second current upper limit; if it does not exceed the corresponding second current upper limit, controlling the frequency converter of the wellbore medium-frequency electric heating to be closed; if it exceeds the corresponding second current upper limit, controlling the frequency converter of the wellbore medium-frequency electric heating to maintain the third power operation.

7. The wellbore radio frequency electric heating control method of claim 1, wherein, Further comprising: after the frequency converter of the wellbore medium-frequency electric heating operates at the first power for a set time, detecting whether there is an upward trend in the highest operating current of the pumping unit frequency converter during the upstroke or downstroke of the pumping unit; if there is an upward trend, controlling the pumping unit frequency converter to reduce the frequency; if there is no upward trend, controlling the pumping unit frequency converter to maintain the current power operation.

8. The wellbore medium frequency electric heating control method of claim 7, wherein, Further comprising: After the pumping unit frequency converter runs at a set frequency for a set time, whether the highest operating current of the pumping unit frequency converter returns to normal is detected; If it returns to normal, the pumping unit frequency converter is accelerated to the set frequency.

9. The wellbore radio frequency electric heating control method of claim 1, wherein, Also comprising: When the wellbore medium frequency electric heating frequency converter is started, the output current thereof is monitored; When the output current is reduced to below 10A, the wellbore medium frequency electric heating frequency converter is controlled to be turned off, the operating parameters are uploaded to a monitoring terminal, and an alarm signal is outputted.

10. A wellbore medium frequency electric heating control device, characterized in that, Comprising: A current collecting device configured to collect the output current of the pumping unit frequency converter in real time; A controller in communication connection with the current collecting device, the controller being configured to execute the wellbore medium frequency electric heating control method of any one of claims 1-9.

11. The wellbore medium frequency electric heating control device of claim 10, wherein, Also comprising: An input device in communication connection with the controller, the input device being configured to receive the user's selection of the control mode of the wellbore medium frequency electric heating frequency converter, the control mode including manual control and automatic control, and the controller being configured to control the wellbore medium frequency electric heating frequency converter based on the received user's selected control mode.

12. The wellbore medium frequency electric heating control apparatus of claim 10, wherein, Also comprising: An active filter connected to the wellbore medium frequency electric heating frequency converter, the active filter being configured to eliminate the harmonic current generated by the wellbore medium frequency electric heating frequency converter.

13. The wellbore medium frequency electric heating control apparatus of claim 10, wherein, Also comprising: A wireless transmission module in communication connection with the controller, the wireless transmission module being configured to upload the operating parameters to a remote monitoring terminal.

14. The wellbore medium frequency electric heating control apparatus of claim 10, wherein, The current collecting device is a current transmitter installed at the output end of the pumping unit frequency converter.

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