A device for high-frequency induction heating and separation of cement-bonded sleeves

Abstract

This invention provides a device for high-frequency induction heating and separation of cement-bonded casing. A main control device, a cooling water reservoir, and a downhole position drive device are connected to the induction heating head via an umbilical cable. The induction heating head is divided into an electronics compartment and a heating compartment, located at the device connection end and free end of the induction heating head, respectively. The electronics compartment houses an electrical control device, and the heating compartment contains a plywood tube. A heating coil and an induction copper tube are located between the plywood tube and the inner wall of the heating compartment. The advantages of this invention are: the device heats the well casing using the induction heating head, causing the cement to undergo a qualitative change, cracking, or even pulverization due to the high temperature, effectively reducing the adhesion between the casing and the cement layer. The casing can then be directly retrieved in sections using retrieval tools, significantly improving construction efficiency. Compared to traditional processes, this equipment offers faster heating, shorter construction time, eliminates the need for expensive milling equipment, resulting in better economic efficiency; and generates less waste during operation.

Description

Technical Field

[0001] This invention relates to the field of efficient treatment technology for reuse casing in old wells in offshore oil fields, and more specifically to a device for high-frequency induction heating and separation of cement-bonded casing. Background Technology

[0002] With the continuous development of offshore oil and gas resources, oilfields are generating a large number of inefficient wells, such as those shut down due to malfunctions or those that have run out of resources, while constructing new production wells. To improve overall recovery efficiency and control development costs, reusing old wells on existing platforms and drilling adjustment wells on sidetracks has become an economical and efficient preferred solution.

[0003] To ensure the integrity of the original wellbore dimensions and structure, the casing, which is cemented inside the wellbore, needs to be removed. Currently, the industry commonly uses milling and grinding processes to remove the casing, but this method has many drawbacks, including low construction efficiency, long operation cycle, high overall cost, difficulty in cleaning mud and iron filings, and easy environmental pollution.

[0004] To address the above-mentioned industry pain points, this invention proposes a high-frequency induction heating separation device for cement consolidation sleeves. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and provides a device for high-frequency induction heating separation of cement-bonded sleeves.

[0006] A device for high-frequency induction heating and separation of cement-bonded casing includes a main control unit, a cooling water storage tank, and a downhole position drive unit connected to an induction heating head via an umbilical cable. The induction heating head is divided into an electronics compartment and a heating compartment, located at the device connection end and free end of the induction heating head, respectively. The electronics compartment contains an electrical control device, and the heating compartment contains a plywood tube. A heating coil and an induction copper tube are located between the plywood tube and the inner wall of the heating compartment. The heating coil is arranged around the outer wall of the plywood tube, and the induction copper tube and the heating coil are arranged parallel to each other in the vertical direction. The heating coil is electrically connected to the electrical control device, and the induction copper tube is physically attached to the heating element of the electrical control device. A coolant circulation path is provided inside the induction copper tube, which is connected to the cooling water storage tank via a liquid passage in the umbilical cable. A sensor group is provided on the outer wall of the induction copper tube.

[0007] The electronic control unit includes: a bridge rectifier, an algorithm board, a filter capacitor, and a resonant capacitor. The AC input terminal of the bridge rectifier is connected to the three-phase power supply, and the filter capacitor is connected in parallel to the DC output terminal of the bridge rectifier. The DC bus of the rectified output of the bridge rectifier is electrically connected to the inverter circuit. The AC output terminal of the inverter circuit is connected to both the resonant capacitor and the heating coil, and the resonant capacitor and the heating coil are connected in parallel. The algorithm board is electrically connected to the bridge rectifier, the filter capacitor, the resonant capacitor, and the sensor group. The algorithm board collects the voltage and current signals of the bridge rectifier, the filter capacitor, and the resonant capacitor, and outputs drive signals to the inverter circuit.

[0008] The inner walls at the top and bottom of the heating chamber are equipped with heat insulation plates.

[0009] The sensor group includes temperature sensors and ultrasonic detection sensors.

[0010] Multiple sliders are provided on the outer wall of the induction heating head.

[0011] The free end of the induction heating head is equipped with a guide head, and the guide head is equipped with a straightening and guiding device.

[0012] The induction heating head is provided with an inert gas passage. The inlet of the inert gas passage is connected to the gas passage provided in the umbilical cable, and the outlet of the inert gas passage is provided on the guide head.

[0013] The beneficial effects of this invention are as follows: This device heats the well casing using an induction heating head, causing the solidified cement to undergo qualitative changes, cracking, and even pulverizing at high temperatures, effectively reducing the adhesion between the casing and the cement layer. Subsequently, the casing can be directly retrieved in sections using retrieval tools, significantly improving construction efficiency. Compared to traditional processes, this equipment has a faster heating speed, shorter construction period, eliminates the need for expensive milling equipment, and is more economical; it generates less waste and has no significant mud pollution, making it environmentally friendly; at the same time, the non-mechanical contact operation method eliminates the risk of stuck drill pipe downhole, resulting in higher operational safety. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the structure of the induction heating head; Figure 3 This is a driving circuit diagram of the present invention; Figure 4 This is a plan view comparing the number of turns caused by the current in the electromagnetic induction heating head in this embodiment; Figure 5 This is a three-dimensional diagram comparing the number of turns caused by the current in the electromagnetic induction heating head in this embodiment. In the diagram: 1. Main control unit; 2. Cooling water storage tank; 3. Umbilical cable; 4. Umbilical cable winch; 5. Guide arm; 6. Piping system; 7. Induction heating head; 701. Electronic compartment; 702. Heating compartment; 703. Bridge rectifier; 704. Algorithm board; 705. Filter capacitor; 706. Resonant capacitor; 707. Phenolic resin tube; 708. Heating coil; 709. Induction copper tube; 710. Heat insulation board; 711. Inert gas passage; 712. Temperature sensor; 713. Ultrasonic detection sensor; 8. Slider; 9. Guide head; 10. Straightening and guiding device. Detailed Implementation

[0015] Example A device for high-frequency induction heating and separation of cement-bonded casing includes a main control unit 1, a cooling water storage tank 2, and a downhole position drive unit, which are connected to an induction heating head 7 via an umbilical cable 3. The induction heating head 7 is internally divided into an electronic compartment 701 and a heating compartment 702, located at the device connection end and free end of the induction heating head 7, respectively. The electronic compartment 701 contains an electrical control device, and the heating compartment 702 contains a plywood tube 707. A heat exchanger is installed between the plywood tube 707 and the inner wall of the heating compartment 702. A heating coil 708 and an induction copper tube 709 are provided. The heating coil 708 is arranged around the outer wall of the phenolic resin tube 707. The induction copper tube 709 is arranged in parallel with the heating coil 708 in a vertical direction. The heating coil 708 is electrically connected to the electronic control device. The induction copper tube 709 is physically attached to the heating element of the electronic control device. A coolant circulation passage is provided inside the induction copper tube 709. The coolant circulation passage is connected to the cooling water storage tank 2 through a liquid passage provided inside the umbilical cable 3. A sensor group is provided on the outer wall of the induction copper tube 709.

[0016] like Figure 1 and Figure 2 As shown, in this embodiment, the high-frequency induction heating separation device for cement-bonded casing uses an umbilical cable winch 4 and a guide arm 5 for the downhole position drive. The umbilical cable winch 4 is assembled from a drum and a drum support, with the umbilical cable 3 wound around the drum. The umbilical cable 3 has a steel strand structure on the outside and integrates power cables, air lines, water inlet lines, water return lines, and signal lines internally. The umbilical cable 3 is lowered into the wellbore via the guide arm 5, which guides the umbilical cable 3, preventing internal pipe bending during deployment and retraction, and ensuring the umbilical cable 3 runs smoothly along a parabolic trajectory. The pipeline system 6 is a ventilation duct used in conjunction with a fan. The ventilation duct delivers airflow into the duct via the fan, and the airflow reaches the bottom of the well through the pipeline, creating air pressure convection inside the well. This allows for the timely discharge of flammable and harmful gases from the wellbore, ensuring operational safety. The induction heating head 7 is internally divided into an electronic compartment 701 and a heating compartment 702. The outer side of the induction heating head 7 is equipped with a straightening and guiding device 10, which can limit radial swaying during equipment operation.

[0017] Furthermore, the main control device 1 is conventionally located in the main control room. The main control device 1 consists of a power distribution cabinet, power cables, atmospheric pressure cables, and a control console forming the power transmission circuit. The main control device 1 is divided into a control section and a monitoring section. The control section manages the inert gas supply through the control console, while the monitoring section consists of a downhole temperature sensor 712, an ultrasonic detection sensor 713, and signal decoding and display circuits within the control console. The cooling water storage tank 2 is used to supply circulating cooling water to the internal pipelines of the downhole induction heating head 7 to achieve equipment cooling.

[0018] The electronic compartment 701 of the induction heating head 7 is located at the equipment connection end, and the heating compartment 702 is located at the free end of the equipment. The electronic compartment 701 houses the electronic control device, which consists of a bridge rectifier 703, an algorithm board 704, a filter capacitor 705, and a resonant capacitor 706. The heating compartment 702 has heat insulation plates 710 at both ends. A plywood tube 707 is installed inside the heating compartment 702, and a heating coil 708 is wound between the plywood tube 707 and the heat insulation plate 710. The heating coil 708 is electrically connected to the inverter circuit inside the electronic compartment 701. An induction copper tube 709 is also installed in the interlayer formed by the plywood tube 707 and the inner wall of the heating compartment 702. The copper tube 709 and the heating coil 708 are arranged in parallel along the vertical direction. The induction copper tube 709 is provided with a coolant circulation passage. The induction copper tube 709 is connected to the cooling water storage tank 2 through the coolant circulation passage. The induction copper tube 709 cools the electronic control device through circulating cooling water to prevent the electronic control device from overheating. At the same time, the outer wall of the induction copper tube 709 is provided with a temperature sensor 712 and an ultrasonic detection sensor 713, which are used to monitor the temperature of the casing during heating and the state of the cement layer on the outside of the casing, the progress of cement separation, and the downhole working conditions, respectively.

[0019] Furthermore, a slider 8 and a straightening and guiding device 10 are fixed to the outer wall of the induction heating head 7. The straightening and guiding device 10 is composed of elastic rollers and is fixed to the outer tube of the induction heating head 7 by a pin.

[0020] Furthermore, the guide head 9 is positioned at the free end of the induction heating head 7 away from the umbilical cable 3. The guide head 9 has a conical structure, with an inert gas passage 711 running through the inside of the induction heating head 7. The inlet end of the inert gas passage 711 connects to the gas passage inside the umbilical cable 3, and the outlet end is located on the guide head 9. A guide cap is provided on the outside of the guide head 9 corresponding to the outlet position of the inert gas passage 711. The guide cap is fixed to the guide head 9 by a support frame, and the bending shape of the guide cap matches that of the guide head 9.

[0021] Preferably, the thickness of slider 8 is set to 5cm, and the material is OILES500 alloy copper.

[0022] The electrical control device includes: a bridge rectifier 703, an algorithm board 704, a filter capacitor 705, and a resonant capacitor 706. The AC input terminal of the bridge rectifier 703 is connected to a three-phase power supply, and the filter capacitor 705 is connected in parallel to the DC output terminal of the bridge rectifier 703. The DC bus of the rectified output of the bridge rectifier 703 is electrically connected to the inverter circuit. The AC output terminal of the inverter circuit is connected to both the resonant capacitor 706 and the heating coil 708, which are connected in parallel. The algorithm board 704 is electrically connected to the bridge rectifier 703, the filter capacitor 705, and the resonant capacitor 706. The algorithm board 704 acquires the voltage and current signals of the bridge rectifier 703, the filter capacitor 705, and the resonant capacitor 706, and outputs drive signals to the inverter circuit.

[0023] like Figure 3 As shown, in this embodiment, the bridge rectifier 703 is a three-phase bridge rectifier circuit composed of diodes VD1-VD6. The three-phase power supplies A, B, and C are respectively connected to the AC input terminal of the bridge rectifier 703. The positive DC output of the bridge rectifier 703 is connected to the positive DC bus via switch K1 and resistor R1, and the negative DC output of the bridge rectifier 703 is connected to the negative DC bus.

[0024] The filter capacitor 705 consists of capacitors C1 and C2 connected in series. The upper end of capacitor C1 is connected to the positive terminal of the DC bus, and the lower end of capacitor C2 is connected to the negative terminal of the DC bus. Resistors R2 and R3 are connected in series and then in parallel across capacitors C1 and C2.

[0025] The inverter circuit consists of a full-bridge structure composed of power transistors V1, V2, V3, and V4. Power transistors V1 and V2 form the first bridge arm, and power transistors V4 and V3 form the second bridge arm. The collectors of power transistors V1 and V4 are connected to the positive terminal of the DC bus, and the emitters of power transistors V2 and V3 are connected to the negative terminal of the DC bus. The connection points of power transistors V1 and V2, and power transistors V4 and V3 are respectively connected to the two ends of the primary winding of the high-frequency transformer TR. Capacitors C3 and C4 are connected in parallel between the positive terminal of the DC bus and the upper end of the primary winding of the high-frequency transformer TR, and between the negative terminal of the DC bus and the lower end of the primary winding of the high-frequency transformer TR, respectively.

[0026] The resonant capacitor 706 is a capacitor C located on the secondary side of the high-frequency transformer TR, and capacitor C is connected in parallel with the heating coil 708.

[0027] The drive output terminal of the algorithm board 704 is electrically connected to the bases b1-b4 of the power transistors V1-V4, respectively. The sampling terminal of the algorithm board 704 is electrically connected to the output terminal of the bridge rectifier 703, the two ends of the filter capacitor 705, and the resonant circuit, respectively.

[0028] When the equipment is working, the three-phase AC power is rectified by the three-phase bridge rectifier circuit composed of diodes VD1-VD6, and then filtered by the filter capacitor 705 composed of capacitors C1 and C2 to obtain a stable DC voltage to supply the full-bridge inverter circuit. The algorithm board 704 outputs a drive signal to control the orderly switching on and off of power transistors V1, V2, V3, and V4, inverting the DC power into alternating current. The alternating current is transformed by the high-frequency transformer TR and then sent to the secondary circuit, which operates using the resonant circuit formed by capacitor C and heating coil 708. The algorithm board 704 collects the voltage and current signals of the bridge rectifier 703, filter capacitor 705, and resonant circuit in real time, and dynamically adjusts the drive signal to ensure stable circuit operation.

[0029] Preferably, the bridge rectifier 703 adopts dual-path drive technology, with dual IGBT inverter modules to process the upper and lower half waves of AC power respectively, outputting a complete and stable high-frequency current waveform. The equipment has high power conversion efficiency, strong load capacity, and uniform overall heating.

[0030] IGBTs exhibit conduction losses and switching losses, the proportions of which vary with the switching frequency. Therefore, selection must be based on the operating frequency: for switching frequencies below 10kHz, Infineon's DLC and KE3 series low-saturation-drop IGBTs are recommended; for switching frequencies between 8kHz and 20kHz, Infineon's DN2 series IGBT modules are recommended; for switching frequencies above 20kHz, Infineon's KS4 high-frequency series IGBTs are recommended, with a maximum hard-switching frequency of 40kHz and a soft-switching frequency of 150kHz. This embodiment, considering voltage withstand, current, and operating conditions, selects the DN2 series IGBT module suitable for 5kHz to 15kHz.

[0031] like Figure 4 and Figure 5 As shown, the number of coil turns directly affects the heating temperature, and the coil inductance can be optimized using formulas.

[0032] The inductance formula is L=Ψ / I, which is used to characterize the magnetic flux corresponding to a unit current in a closed loop.

[0033] The formula for calculating coil inductance is: L=(μN2A) / l; where L is the inductance, μ is the absolute permeability of the material, N is the number of turns of the coil, A is the cross-sectional area of ​​the coil, and l is the length of the coil.

[0034] by Figure 4 For example, the table below shows the corresponding parameters in the effect diagram.

[0035]

[0036] The specific workflow of this device is as follows: The guide arm 5 is fixed at the wellhead position. The main control device 1, cooling water storage tank 2, and umbilical cable winch 4 are arranged in the designated area of ​​the offshore platform. The wiring and pipelines between the various devices are connected. Then, one end of the umbilical cable 3 is passed through the roller of the guide arm 5 and connected to the downhole induction heating head 7. The operator controls the operation of the umbilical cable winch 4 through the main control device 1, adjusts the lowering speed, and vertically sends the induction heating head 7 into the target depth of the casing along the guide arm 5. The straightening and guiding device 10 and the slider 8 on the outer wall ensure that the equipment is placed vertically and centered in the well.

[0037] The water circulation system is started. After being pressurized, the cooling water in the cooling water storage tank 2 is transported to the cooling liquid circulation passage of the induction copper tube 709 through the water inlet pipe inside the umbilical cable 3 to cool the electronic control device. The cooling water that has absorbed heat flows back to the cooling water storage tank 2 through the return water pipe of the liquid passage to form a continuous circulation, which is used to ensure that the electronic control device does not overheat and can work normally.

[0038] The inert gas delivery circuit is opened simultaneously. The inert gas enters the inert gas passage 711 through the gas passage inside the umbilical cable 3, and finally exits from the vent hole of the inert gas passage 711 set at the guide head 9. Under the guidance of the guide cap, it diffuses to the surroundings and flows upward, diluting and carrying out the flammable hydrocarbon gas generated by the heating of the inner wall of the casing, isolating the oil and gas from contact with oxygen, avoiding the risk of explosion. The mixed gas in the wellbore is finally discharged from the wellhead through the pipeline system 6 and the matching fan.

[0039] During this process, the main control device 1 connects to the power supply circuit, and electrical energy is transmitted to the electronic control device in the electronics compartment 701 via the umbilical cable 3. The alternating current passes through the bridge rectifier 703, filter capacitor 705, and resonant capacitor 706 in sequence to complete rectification, filtering, inversion, and frequency modulation. After the alternating current is passed into the heating coil 708, an alternating magnetic field is generated, which in turn generates eddy currents on the sleeve within the magnetic field. The energy of the eddy currents is converted into heat energy to heat the sleeve, and the sleeve heats the cement stone outside the sleeve through heat transfer. Due to the difference in the coefficients of thermal expansion between the sleeve and the cement stone, the bonding force between the sleeve and the cement stone is broken through the principle of thermal expansion and contraction.

[0040] During the operation, temperature sensor 712 and ultrasonic detection sensor 713 collect downhole working condition data in real time. Electrical parameters such as equipment voltage and current are collected simultaneously. All signals are aggregated to algorithm board 704, encoded, and transmitted back to ground main control device 1 via signal line. The staff can monitor the operation status in real time with the help of the display interface.

[0041] After heating a single section of casing, the induction heating head 7 is moved towards the wellhead using a traction device to separate the casing from the cement stone section by section. After all heating processes are completed, the casing can be removed in sections using a special retrieval tool, completing the downhole casing removal operation.

[0042] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A device for high-frequency induction heating and separation of cement-bonded sleeves, characterized in that: The main control unit, cooling water storage tank, and downhole position drive unit are connected to the induction heating head via an umbilical cable. The induction heating head is divided into an electronics compartment and a heating compartment, located at the equipment connection end and free end of the induction heating head, respectively. The electronics compartment contains an electronic control device, and the heating compartment contains a plywood tube. A heating coil and an induction copper tube are located between the plywood tube and the inner wall of the heating compartment. The heating coil is arranged around the outer wall of the plywood tube. The induction copper tube and the heating coil are arranged in parallel in the vertical direction. The heating coil is electrically connected to the electronic control device, and the induction copper tube is physically attached to the heating element of the electronic control device. The induction copper tube has a coolant circulation path, which is connected to the cooling water storage tank through a liquid passage in the umbilical cable. A sensor group is located on the outer wall of the induction copper tube.

2. The device for high-frequency induction heating and separation of cement-bonded sleeves according to claim 1, characterized in that, The electronic control unit includes: a bridge rectifier, an algorithm board, a filter capacitor, and a resonant capacitor. The AC input terminal of the bridge rectifier is connected to the three-phase power supply, and the filter capacitor is connected in parallel to the DC output terminal of the bridge rectifier. The DC bus output of the bridge rectifier is electrically connected to the inverter circuit. The AC output terminal of the inverter circuit is connected to both the resonant capacitor and the heating coil, and the resonant capacitor and the heating coil are connected in parallel. The algorithm board is electrically connected to the bridge rectifier, the filter capacitor, the resonant capacitor, and the sensor group, and outputs drive signals to the inverter circuit.

3. The device for high-frequency induction heating and separation of cement-bonded sleeves according to claim 1, characterized in that: The inner walls at the top and bottom of the heating chamber are equipped with heat insulation plates.

4. The device for high-frequency induction heating and separation of cement-bonded sleeves according to claim 1, characterized in that: The sensor group includes temperature sensors and ultrasonic detection sensors.

5. The device for high-frequency induction heating separation of cement-bonded sleeves according to claim 1, characterized in that: Multiple sliders are provided on the outer wall of the induction heating head.

6. The device for high-frequency induction heating separation of cement-bonded sleeves according to claim 1, characterized in that: The free end of the induction heating head is equipped with a guide head, and the guide head is equipped with a straightening and guiding device.

7. The device for high-frequency induction heating separation of cement-bonded sleeves according to claim 6, characterized in that: The induction heating head is provided with an inert gas passage. The inlet of the inert gas passage is connected to the gas passage provided in the umbilical cable, and the outlet of the inert gas passage is provided on the guide head.

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