On-site pressurized energy-saving oil field water injection device and water injection method

Abstract

The present invention discloses an on-site pressurized energy-saving oilfield water injection device and a water injection method thereof. The on-site pressurized energy-saving oilfield water injection device comprises: a first pipe network, the first pipe network is connected to a water injection station; a second pipe network, the second pipe network is connected to the first pipe network through a first control valve; a third pipe network, the third pipe network is connected to the second pipe network through a first water pump, a pressure difference detection device is arranged between the third pipe network and the second pipe network, and the third pipe network is connected to a water injection well, wherein the first water pump is driven by a first motor; a water storage tank, a second control valve and a second water pump are connected between the water storage tank and the second pipe network, a third control valve is connected between the water storage tank and the third pipe network, wherein the second water pump is driven by a second motor; a control system, the control system is electrically connected to the first motor, the second motor, the first control valve, the second control valve and the third control valve. The present invention also discloses a water injection method for an on-site pressurized energy-saving oilfield water injection device.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield exploitation, in particular to an on-site pressurized energy-saving oilfield water injection device and a water injection method thereof. Background Art

[0002] As a basic development method for onshore oil fields, oilfield water injection is often used in secondary oil recovery when the natural pressure of the reservoir is exhausted. It is one of the important measures to stabilize oil production and increase production in oilfield development. As the most important water injection parameters, water injection volume and water injection pressure directly affect water injection efficiency and effect.

[0003] At present, oilfield water injection is mostly done by pumping water from the water injection station to boost the pressure, then transporting it to each water distribution room through the water injection trunk line, and then injecting the boosted water into the injection well from the water distribution room. In this process, the water injection flow rate needs to be dynamically adjusted according to the changes in parameters such as the pressure and flow rate of the oil well water injection. This requirement will make the difference between the pressure required by the water injection well and the water pressure output by the water injection station in the existing oilfield water injection device shared by the pipe network, control valve, water injection pipe column and water nozzle. The greater the pressure difference between the two, the lower the efficiency of the water injection device. This will cause a lot of energy waste. Summary of the invention

[0004] Based on this, the object of the present invention is to provide an on-site pressurized energy-saving oil field water injection device and a water injection method thereof.

[0005] In a first aspect, the in-situ pressurized energy-saving oilfield water injection device of the present invention comprises:

[0006] a first pipe network, wherein the first pipe network is connected to a water injection station;

[0007] a second pipe network, the second pipe network being connected to the first pipe network through a first control valve;

[0008] a third pipe network, the third pipe network being connected to the second pipe network through a first water pump, pressure difference detection devices being arranged on both sides of the first water pump, and the third pipe network being connected to a water injection well, wherein the first water pump is driven by a first motor;

[0009] A water storage tank, wherein a second control valve and a second water pump are connected between the water storage tank and the second pipe network, and a third control valve is connected between the water storage tank and the third pipe network, wherein the second water pump is driven by a second motor;

[0010] A control system is electrically connected to the first motor, the second motor, the first control valve, the second control valve and the third control valve.

[0011] The on-site pressurized energy-saving oilfield water injection device of the present invention can be arranged on the on-site side of the water injection well. According to the real-time requirement of the desired pressure of the water injection well, the speed of the first motor can be adjusted and the switching of the second motor can be controlled. The operating speed of the first water pump and the partial pressure of the gas in the water storage tank can be dynamically adjusted to ensure that the water injection pressure input to the water injection well is consistent with the desired pressure. Moreover, being directly arranged on the on-site side can reduce the pressure difference between the pipeline network, the control valve, the water injection pipe column and the water nozzle, and has a significant energy-saving effect, which can effectively solve the problems of large energy loss and low energy utilization rate in the water injection process of the existing oilfield device.

[0012] In one implementation of the above technical solution, the control system includes a starting circuit, a speed regulating circuit, a protection circuit and a control circuit electrically connected to each other;

[0013] The starting circuit is electrically connected to the first motor;

[0014] The speed regulating circuit is electrically connected to the first motor;

[0015] The control circuit is electrically connected to the first motor, the second motor, the first control valve, the second control valve, and the third control valve.

[0016] In one implementation of the above technical solution, the starting circuit includes a first contactor KM1 and a starting current limiting resistor FR;

[0017] The stator coil of the first motor is connected to a three-phase power grid, and the rotor coil thereof is connected to the first contactor KM1 . The first contactor KM1 is connected to one end of the starting current limiting resistor FR, and the other end of the starting current limiting resistor FR is grounded.

[0018] In one implementation of the above technical solution, the speed regulating circuit includes a second contactor KM2, an uncontrolled rectifier DR, an inductor Ls, a power switch tube S, a diode D, an energy storage capacitor C, an inverter bridge B and a buffer inductor LD;

[0019] One end of the second contactor KM2 is connected to the rotor coil of the first motor, and the other end of the second contactor KM2 is connected to the input end of the uncontrolled rectifier DR. The high-voltage side of the output end of the uncontrolled rectifier DR is connected to the inductor Ls, and the inductor Ls is connected to the source of the power switch tube S. The inductor Ls is connected to the cathode of the diode D, and the anode of the diode D is connected to the positive electrode of the energy storage capacitor C and the high-voltage side of the input end of the inverter bridge B. The low-voltage side of the input end of the inverter bridge B is connected to one end of the buffer inductor LD, the low-voltage side of the uncontrolled rectifier DR is connected to the drain of the power switch tube S, the low-voltage side of the energy storage capacitor C is connected to the low-voltage side of the uncontrolled rectifier DR, and the low-voltage side of the uncontrolled rectifier DR is connected to the other end of the buffer inductor LD.

[0020] In one implementation of the above technical solution, the protection circuit includes a third contactor KM3 and a transformer T;

[0021] One end of the third contactor KM3 is connected to the output end of the inverter bridge B, and the other end of the third contactor KM3 is connected to the low-voltage side of the transformer T. The high-voltage side of the transformer T is connected to a three-phase power grid.

[0022] In one implementation of the above technical solution, the first motor is a winding motor or a doubly-fed motor.

[0023] In a second aspect, a water injection method of an on-site pressurized energy-saving oilfield water injection device of the present invention is applied to any of the on-site pressurized energy-saving oilfield water injection devices described above, comprising:

[0024] When the pressure required by the water injection well is greater than the water boost value when the first water pump is running at full speed, the control system controls the first water pump to run at full speed, closes the second control valve, and controls the opening of the third control valve according to the real-time requirements of the water injection pressure of the water injection well to ensure that the water injection pressure input to the water injection well is consistent with the expected pressure;

[0025] When the pressure required by the water injection well is less than the water boost value when the first water pump is running at full speed, the control system controls the closing of the third control valve, and adjusts the speed of the first motor according to the real-time requirements of the water injection pressure of the water injection well, and changes the operating speed of the first water pump to ensure that the water injection pressure input to the water injection well is consistent with the expected pressure;

[0026] When the gas pressure in the water storage tank does not reach the normal storage pressure value and when the pressure required by the injection well is less than the incoming water pressure value when the first water pump runs at full speed, the control system controls the opening of the second control valve and starts the second motor to put the second water pump into operation until the gas pressure in the water storage tank reaches the normal storage pressure value.

[0027] The water injection method of the on-site pressurized energy-saving oilfield water injection device of the present invention can adjust the speed of the first motor and control the switching of the second motor according to the real-time requirement of the expected pressure of the water injection well, dynamically adjust the operating speed of the first water pump and the partial pressure of the gas in the water storage tank to ensure that the water injection pressure input to the water injection well is consistent with the expected pressure, and the water injection process can be automatically adjusted, which has a significant energy-saving effect and can effectively solve the problems of large energy loss and low energy utilization rate in the water injection process of the existing oilfield device.

[0028] Further preferably, the starting circuit short-circuits the rotor coil of the first motor during the starting process of the first motor, so that the first motor enters a starting state;

[0029] When the speed of the first motor reaches 60-80% of the rated speed, the rotor coil of the first motor is connected to the speed regulating circuit;

[0030] The control circuit calculates the pressure difference between the two sides of the first water pump and the expected pressure of the water injection well, and controls the speed regulating circuit to change the current value fed back to the stator coil of the first motor to adjust the speed of the first motor according to the calculation result;

[0031] The protection circuit ensures the normal operation of the entire circuit by detecting the rotor coil current of the first motor and feeding back the stator coil current of the first motor and the DC bus voltage in the speed regulation circuit.

[0032] Further preferably, the starting circuit short-circuits the rotor coil of the first motor during the starting process of the first motor, so that the first motor enters the starting state, including: when the first motor starts, the control circuit issues an instruction to close the first contactor KM1, disconnect the second contactor KM2, and disconnect the third contactor KM3, and the starting circuit short-circuits the rotor coil of the first motor during the starting process of the first motor, so that the first motor enters the starting state;

[0033] When the speed of the first motor reaches 60-80% of the rated speed, the rotor coil of the first motor is connected to the speed regulating circuit, including: when the control circuit detects that the speed of the first motor reaches 60-80% of the rated speed, the second contactor KM2 is closed, the third contactor KM3 is closed, and the control circuit issues an instruction to adjust the duty cycle of the power switch tube S drive signal PWM1 so that the current i' fed into the AC bus f The speed of the first motor is kept constant.

[0034] The control circuit calculates the pressure difference between the two sides of the first water pump and the expected pressure of the water injection well, and controls the speed regulation circuit to change the current value fed back to the stator coil of the first motor to adjust the speed of the first motor through the calculation result, including: the control circuit calculates the pressure difference between the two sides of the first water pump and the expected pressure of the water injection well, and changes the current i' fed into the AC bus by combining the curve of the speed, pressure and flow of the first water pump and adjusting the duty cycle of the power switch tube S drive signal PWM1. f The value of the first motor is maintained at a speed corresponding to a given pressure;

[0035] The protection circuit ensures the normal operation of the entire circuit by detecting the rotor coil current of the first motor, feeding back the stator coil current of the first motor and the DC bus voltage in the speed regulation circuit, including: when the control circuit detects the speed of the first motor, the output voltage and current of the speed regulation circuit, the DC link voltage and current and the current i' fed into the AC bus f In case of abnormality, a protection signal is sent to stop the operation of the oilfield water injection device.

[0036] Compared with the prior art, the on-site pressurized energy-saving oilfield water injection device and water injection method of the present invention, the water injection device can be arranged on the on-site side of the water injection well, and can adjust the speed of the first motor and control the switching of the second motor according to the real-time requirement of the desired pressure of the water injection well, and dynamically adjust the operating speed of the first water pump to ensure that the water injection pressure input to the water injection well is consistent with the desired pressure. The water injection device is directly arranged on the on-site side and the water injection process is automatically adjusted to reduce the pressure difference between the pipeline network, control valve, water injection pipe column and water nozzle, which has a significant energy-saving effect and can effectively solve the problems of large energy loss and low energy utilization rate in the water injection process of the existing oilfield device.

[0037] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a connection schematic diagram of the preferred structure of the on-site pressurized energy-saving oil field water injection device of the present invention.

[0039] Figure 2 It is the circuit connection diagram of the optimal structure of the control system. DETAILED DESCRIPTION

[0040] The directional terms such as up, down, left, right, front, back, front, back, top, bottom, etc. mentioned or may be mentioned in this specification are defined relative to their structure and are relative concepts. Therefore, they may change accordingly according to their different locations and different usage conditions. Therefore, these or other directional terms should not be interpreted as restrictive terms.

[0041] The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0042] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms of "a", "said" and "the" used in this disclosure and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0043] First, see Figure 1 , Figure 1 It is a connection schematic diagram of the preferred structure of the on-site pressurized energy-saving oil field water injection device of the present invention.

[0044] The on-site pressurized energy-saving oilfield water injection device of the present invention comprises a first pipe network 1, a second pipe network 2, a third pipe network 3, a water storage tank 4 and a control system.

[0045] The first pipe network 1 is connected to the water injection station A. The second pipe network 2 is connected to the first pipe network 1 through a first control valve 5. The third pipe network 3 is connected to the second pipe network 2 through a first water pump 6, and pressure difference detection devices are provided on both sides of the first water pump 6. The third pipe network 3 is connected to the water injection well B, wherein the first water pump 6 is driven by a first motor 7.

[0046] A second control valve 8 and a second water pump 9 are connected between the water storage tank 4 and the second pipe network 2 , and a third control valve 10 is connected between the water storage tank 4 and the third pipe network 3 , wherein the second water pump 9 is driven by a second motor 11 .

[0047] The control system is electrically connected to the first motor 7 , the second motor 11 , the first control valve 5 , the second control valve 8 , and the third control valve 10 .

[0048] The on-site pressurized energy-saving oilfield water injection device of the present invention can be arranged on the on-site side of the water injection well. According to the real-time requirement of the desired pressure of the water injection well, the speed of the first motor can be adjusted and the switching of the second motor can be controlled. The operating speed of the first water pump and the partial pressure of the gas in the water storage tank can be dynamically adjusted to ensure that the water injection pressure input to the water injection well is consistent with the desired pressure. Moreover, being directly arranged on the on-site side can reduce the pressure difference between the pipeline network, the control valve, the water injection pipe column and the water nozzle, and has a significant energy-saving effect, which can effectively solve the problems of large energy loss and low energy utilization rate in the water injection process of the existing oilfield device.

[0049] In specific implementation, the water injection station A is located at the remote side, and the water injection station A does not need to pressurize the incoming water or pressurize it to a lower value. The on-site pressurization energy-saving oil field water injection device of the present invention is set on the on-site side of the water injection well B. The upper part of the water storage tank 4 is a sealed gas, and the lower part is a liquid, and the liquid level height of the liquid can fluctuate. The first control valve 5 is in a normally open state when working normally, and is in a closed state only when the on-site side part needs maintenance and overhaul.

[0050] For more details, please refer to Figure 2 , Figure 2 It is the circuit connection diagram of the optimal structure of the control system.

[0051] The control system includes a starting circuit, a speed regulating circuit, a protection circuit and a control circuit which are electrically connected to each other.

[0052] The starting circuit is electrically connected to the first motor 7 .

[0053] The speed regulating circuit is electrically connected to the first motor 7 .

[0054] The control circuit is electrically connected to the first motor 7 , the second motor 11 , the first control valve 5 , the second control valve 8 , and the third control valve 10 .

[0055] Preferably, the starting circuit includes a first contactor KM1 and a starting current limiting resistor FR.

[0056] The stator coil of the first motor 7 is connected to a three-phase power grid, and the rotor coil thereof is connected to the first contactor KM1 . The first contactor KM1 is connected to one end of the starting current limiting resistor FR, and the other end of the starting current limiting resistor FR is grounded.

[0057] Furthermore, the speed regulation circuit includes a second contactor KM2, an uncontrolled rectifier DR, an inductor Ls, a power switch tube S, a diode D, an energy storage capacitor C, an inverter bridge B and a buffer inductor LD.

[0058] One end of the second contactor KM2 is connected to the rotor coil of the first motor 7, and the other end of the second contactor KM2 is connected to the input end of the uncontrolled rectifier DR. The high-voltage side of the output end of the uncontrolled rectifier DR is connected to the inductor Ls, and the inductor Ls is connected to the source of the power switch tube S. The inductor Ls is connected to the cathode of the diode D, and the anode of the diode D is connected to the positive electrode of the energy storage capacitor C and the high-voltage side of the input end of the inverter bridge B. The low-voltage side of the input end of the inverter bridge B is connected to one end of the buffer inductor LD, the low-voltage side of the uncontrolled rectifier DR is connected to the drain of the power switch tube S, the low-voltage side of the energy storage capacitor C is connected to the low-voltage side of the uncontrolled rectifier DR, and the low-voltage side of the uncontrolled rectifier DR is connected to the other end of the buffer inductor LD.

[0059] Preferably, the protection circuit includes a third contactor KM3 and a transformer T.

[0060] One end of the third contactor KM3 is connected to the output end of the inverter bridge B, and the other end of the third contactor KM3 is connected to the low-voltage side of the transformer T. The high-voltage side of the transformer T is connected to a three-phase power grid.

[0061] In addition, the first motor 7 may be a winding motor or a double-fed motor.

[0062] In a second aspect, the water injection method of the on-site pressurized energy-saving oilfield water injection device of the present invention is applied to the on-site pressurized energy-saving oilfield water injection device, comprising:

[0063] S1. When the required pressure of injection well B is greater than the water boost value when the first water pump 6 runs at full speed, the control system controls the first water pump 6 to run at full speed, closes the second control valve 8, and controls the opening of the third control valve 10 according to the real-time requirements of the injection pressure of injection well B to ensure that the injection pressure input to injection well B is consistent with the expected pressure.

[0064] S2. When the required pressure of the injection well B is less than the water boost value when the first water pump 6 runs at full speed, the control system controls the closing of the third control valve 10, and adjusts the speed of the first motor 7 according to the real-time requirement of the injection pressure of the injection well B, and changes the operating speed of the first water pump 6 to ensure that the injection pressure input to the injection well B is consistent with the expected pressure.

[0065] S3. When the gas pressure in the water storage tank 4 does not reach the normal storage pressure value and when the pressure required by the injection well B is less than the incoming water pressure value when the first water pump 6 runs at full speed, the control system controls the opening of the second control valve 8 and starts the second motor 11 to put the second water pump 9 into operation until the gas pressure in the water storage tank 4 reaches the normal storage pressure value.

[0066] The water injection method of the on-site pressurized energy-saving oilfield water injection device of the present invention can adjust the speed of the first motor and control the switching of the second motor according to the real-time requirement of the expected pressure of the water injection well, dynamically adjust the operating speed of the first water pump and the partial pressure of the gas in the water storage tank to ensure that the water injection pressure input to the water injection well is consistent with the expected pressure, and the water injection process can be automatically adjusted, which has a significant energy-saving effect and can effectively solve the problems of large energy loss and low energy utilization rate in the water injection process of the existing oilfield device.

[0067] During the start-up and operation of the first motor 7:

[0068] S10. During the starting process of the first motor 7, the starting circuit short-circuits the rotor coil of the first motor 7, so that the first motor 7 enters the starting state.

[0069] S20. When the rotation speed of the first motor 7 reaches 60-80% of the rated rotation speed, the rotor coil of the first motor 7 is connected to the rotation speed regulating circuit.

[0070] S30. The control circuit calculates the pressure difference on both sides of the first water pump 6 and the expected pressure of the water injection well B, and controls the speed regulation circuit to change the current value fed back to the stator coil of the first motor 7 through the calculation result to adjust the speed of the first motor 7.

[0071] S40. The protection circuit ensures the normal operation of the entire circuit by detecting the rotor coil current of the first motor 7 and feeding back the stator coil current of the first motor 7 and the DC bus voltage in the speed regulation circuit.

[0072] The following describes the control process of the water injection method of the on-site pressurized energy-saving oil field water injection device of the present invention in combination with the specific circuit connection structure of the starting circuit, the speed regulating circuit and the control circuit:

[0073] S101. When the first motor 7 is started, the control circuit sends a command to close the first contactor KM1, disconnect the second contactor KM2, and disconnect the third contactor KM3. The starting circuit short-circuits the rotor coil of the first motor 7 during the starting process of the first motor 7, so that the first motor 7 enters the starting state.

[0074] S201. When the control circuit detects that the speed of the first motor 7 reaches 60-80% of the rated speed, the second contactor KM2 is closed, the third contactor KM3 is closed, and the control circuit issues an instruction to adjust the duty cycle of the power switch tube S drive signal PWM1 so that the current i' fed into the AC bus f The speed of the first motor 7 is kept constant.

[0075] S301. The control circuit calculates the pressure difference between the first pump 6 and the desired pressure of the injection well B, and by combining the speed, pressure and flow curve of the first pump 6, by adjusting the duty cycle of the power switch tube S drive signal PWM1, changes the current i' fed into the AC bus f The value of is used to maintain the rotation speed of the first motor 7 at a rotation speed corresponding to the given pressure.

[0076] S401. When the control circuit detects the speed of the first motor 7, the speed regulation circuit output voltage and current, the DC link voltage and current and the current i' fed into the AC bus f In case of abnormality, a protection signal is sent to stop the operation of the oilfield water injection device.

[0077] Compared with the prior art, the on-site pressurized energy-saving oilfield water injection device and water injection method of the present invention, the water injection device can be arranged on the on-site side of the water injection well, and can adjust the speed of the first motor and control the switching of the second motor according to the real-time requirement of the desired pressure of the water injection well, and dynamically adjust the operating speed of the first water pump to ensure that the water injection pressure input to the water injection well is consistent with the desired pressure. The water injection device is directly arranged on the on-site side and the water injection process is automatically adjusted to reduce the pressure difference between the pipeline network, control valve, water injection pipe column and water nozzle, which has a significant energy-saving effect and can effectively solve the problems of large energy loss and low energy utilization rate in the water injection process of the existing oilfield device.

[0078] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A water injection method for an on-site pressurized energy-saving oilfield water injection device, characterized in that: The on-site pressurized energy-saving oilfield water injection device comprises: a first pipe network, wherein the first pipe network is connected to a water injection station; a second pipe network, the second pipe network being connected to the first pipe network through a first control valve; a third pipe network, the third pipe network being connected to the second pipe network through a first water pump, pressure difference detection devices being arranged on both sides of the first water pump, and the third pipe network being connected to a water injection well, wherein the first water pump is driven by a first motor; A water storage tank, wherein a second control valve and a second water pump are connected between the water storage tank and the second pipe network, and a third control valve is connected between the water storage tank and the third pipe network, wherein the second water pump is driven by a second motor; a control system, the control system being electrically connected to the first motor, the second motor, the first control valve, the second control valve, and the third control valve; The water injection method of the on-site pressurized energy-saving oilfield water injection device comprises: When the pressure required by the water injection well is greater than the water boost value when the first water pump is running at full speed, the control system controls the first water pump to run at full speed, closes the second control valve, and controls the opening of the third control valve according to the real-time requirements of the water injection pressure of the water injection well to ensure that the water injection pressure input to the water injection well is consistent with the expected pressure; When the pressure required by the water injection well is less than the water boost value when the first water pump is running at full speed, the control system controls the closing of the third control valve, and adjusts the speed of the first motor according to the real-time requirements of the water injection pressure of the water injection well, and changes the operating speed of the first water pump to ensure that the water injection pressure input to the water injection well is consistent with the expected pressure; When the gas pressure in the water storage tank does not reach the normal storage pressure value and when the pressure required by the injection well is less than the incoming water pressure value when the first water pump runs at full speed, the control system controls the opening of the second control valve and starts the second motor to put the second water pump into operation until the gas pressure in the water storage tank reaches the normal storage pressure value.

2. The water injection method of the on-site pressurized energy-saving oilfield water injection device according to claim 1 is characterized in that: The control system includes a starting circuit, a speed regulating circuit, a protection circuit and a control circuit which are electrically connected to each other; The starting circuit is electrically connected to the first motor; The speed regulating circuit is electrically connected to the first motor; The control circuit is electrically connected to the first motor, the second motor, the first control valve, the second control valve, and the third control valve.

3. The water injection method of the on-site pressurized energy-saving oil field water injection device according to claim 2 is characterized in that: The starting circuit includes a first contactor KM1 and a starting current limiting resistor FR; The stator coil of the first motor is connected to a three-phase power grid, and the rotor coil thereof is connected to the first contactor KM1 . The first contactor KM1 is connected to one end of the starting current limiting resistor FR, and the other end of the starting current limiting resistor FR is grounded.

4. The water injection method of the on-site pressurized energy-saving oil field water injection device according to claim 3 is characterized in that: The speed regulating circuit includes a second contactor KM2, an uncontrolled rectifier DR, an inductor Ls, a power switch tube S, a diode D, an energy storage capacitor C, an inverter bridge B and a buffer inductor LD; One end of the second contactor KM2 is connected to the rotor coil of the first motor, and the other end of the second contactor KM2 is connected to the input end of the uncontrolled rectifier DR. The high-voltage side of the output end of the uncontrolled rectifier DR is connected to the inductor Ls, and the inductor Ls is connected to the source of the power switch tube S. The inductor Ls is connected to the cathode of the diode D, and the anode of the diode D is connected to the positive electrode of the energy storage capacitor C and the high-voltage side of the input end of the inverter bridge B. The low-voltage side of the input end of the inverter bridge B is connected to one end of the buffer inductor LD, the low-voltage side of the uncontrolled rectifier DR is connected to the drain of the power switch tube S, the low-voltage side of the energy storage capacitor C is connected to the low-voltage side of the uncontrolled rectifier DR, and the low-voltage side of the uncontrolled rectifier DR is connected to the other end of the buffer inductor LD.

5. The water injection method of the on-site pressurized energy-saving oil field water injection device according to claim 4 is characterized in that: The protection circuit includes a third contactor KM3 and a transformer T; One end of the third contactor KM3 is connected to the output end of the inverter bridge B, and the other end of the third contactor KM3 is connected to the low-voltage side of the transformer T. The high-voltage side of the transformer T is connected to a three-phase power grid.

6. The water injection method of the on-site pressurized energy-saving oilfield water injection device according to any one of claims 1 to 5, characterized in that: The first motor is a wound motor or a double-fed motor.

7. The water injection method of the on-site pressurized energy-saving oilfield water injection device according to any one of claims 1 to 5, characterized in that: The starting circuit short-circuits the rotor coil of the first motor during the starting process of the first motor, so that the first motor enters a starting state; When the speed of the first motor reaches 60-80% of the rated speed, the rotor coil of the first motor is connected to the speed regulating circuit; The control circuit calculates the pressure difference between the two sides of the first water pump and the expected pressure of the water injection well, and controls the speed regulating circuit to change the current value fed back to the stator coil of the first motor to adjust the speed of the first motor according to the calculation result; The protection circuit ensures the normal operation of the entire circuit by detecting the rotor coil current of the first motor and feeding back the stator coil current of the first motor and the DC bus voltage in the speed regulation circuit.

8. The water injection method of the on-site pressurized energy-saving oil field water injection device according to claim 7 is characterized in that: The starting circuit short-circuits the rotor coil of the first motor during the starting process of the first motor, so that the first motor enters the starting state, including: when the first motor starts, the control circuit issues an instruction to close the first contactor KM1, disconnect the second contactor KM2, and disconnect the third contactor KM3, and the starting circuit short-circuits the rotor coil of the first motor during the starting process of the first motor, so that the first motor enters the starting state; When the speed of the first motor reaches 60-80% of the rated speed, the rotor coil of the first motor is connected to the speed regulating circuit, including: when the control circuit detects that the speed of the first motor reaches 60-80% of the rated speed, the second contactor KM2 is closed, the third contactor KM3 is closed, and the control circuit issues an instruction to adjust the duty cycle of the power switch tube S drive signal PWM1 so that the current i' fed into the AC bus f The speed of the first motor is kept constant. The control circuit calculates the pressure difference between the two sides of the first water pump and the expected pressure of the water injection well, and controls the speed regulation circuit to change the current value fed back to the stator coil of the first motor to adjust the speed of the first motor through the calculation result, including: the control circuit calculates the pressure difference between the two sides of the first water pump and the expected pressure of the water injection well, and changes the current i' fed into the AC bus by combining the curve of the speed, pressure and flow of the first water pump and adjusting the duty cycle of the power switch tube S drive signal PWM1. f The value of the first motor is maintained at a speed corresponding to a given pressure; The protection circuit ensures the normal operation of the entire circuit by detecting the rotor coil current of the first motor, feeding back the stator coil current of the first motor and the DC bus voltage in the speed regulation circuit, including: when the control circuit detects the speed of the first motor, the output voltage and current of the speed regulation circuit, the DC link voltage and current and the current i' fed into the AC bus f In case of abnormality, a protection signal is sent to stop the operation of the oilfield water injection device.

Images