Pressure-relief-free channel well treatment method and equipment

Abstract

The invention relates to the technical field of oil field shaft unblocking processes, in particular to a treatment method and equipment for a non-pressure-relief channel well. According to the non-pressure-relief channel well treatment method and equipment, power frequency current is converted into low-frequency surge bidirectional pulse current, then the low-frequency surge bidirectional pulse current is input into a shaft oil casing to be heated and unblocked, after the underground oil casing is heated by current for a period of time, a cleaning agent is injected into an annular space of the oil casing at high pressure, and blockages in a well are washed and dissolved; a continuous well washing channel is cleaned in the pressure-relief-channel-free well, blockages are dissolved along the well washing channel and taken out of a well opening, and paraffin removal and blockage removal treatment on the pressure-relief-channel-free well is achieved. According to the non-pressure-relief channel well treatment method and equipment, the underground metal pipe is prevented from being damaged through the low-frequency surge bidirectional pulse current, a well washing channel can be cleaned by injecting the cleaning agent into the well in a matched mode, well washing and paraffin removal work is conducted on the target well, overhaul work is not needed, the work input cost is low, and the paraffin removal effect is good.

Description

Technical Field

[0001] This invention relates to the field of oilfield wellbore unblocking technology, and in particular to a method and equipment for treating wells without pressure relief channels. Background Art

[0002] During oilfield production, crude oil needs to be gradually lifted from a depth of more than 1 km to the surface. In high-wax wells, the wax in the crude oil gradually precipitates out and adheres to the metal pipe wall as the pressure and temperature decrease during the lifting process. When the wax on the well wall accumulates to a certain extent, it will block the oil well and cause wax blockage. Once wax blockage occurs in the well, the production well becomes a well without pressure relief channels, which means there are no pressure relief channels or well washing channels in the annular space of the oil casing. For oil well wax blockage, common methods used in oilfields include mechanical wax removal, heated wax removal, and chemical wax removal. However, when the underground tubing is blocked at depths of 500-600m or more, chemical wax removal methods cannot effectively force the chemicals and hot water into the casing and back out of the tubing to complete the hot washing and wax removal. Furthermore, conventional direct current heating wax removal methods require long working times due to severe blockage. During the wax removal process, the applied direct current creates a positive voltage between the underground metal tubing and the ground, causing rapid ion flow from the tubing to the ground and resulting in rapid corrosion. In severely blocked wells, casing leakage occurs before the blockage is cleared, causing significant economic losses to oilfield companies. In such cases, only major workover operations can restore normal production, resulting in high project costs and long construction times. Therefore, to address these shortcomings, a method and equipment for treating wells without pressure relief channels is proposed. Summary of the Invention

[0003] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a method and equipment for treating wells without pressure relief channels. This solves the problem that existing unblocking methods cannot remove wax from wax-blocked wells and can only restore normal production of blocked wells through major overhaul operations, resulting in high engineering costs and long construction time.

[0004] (II) Technical Solution To address the above problems, this invention provides a method for treating wells without pressure relief channels, comprising: Step S1: Install an electromagnetic heating generator at the oil pipe at the wellhead and pass a high-frequency current into the electromagnetic heating generator to heat the wellhead pipeline; Step S2: Observe the changes in equipment current and voltage and the heating and unblocking of the ground pipeline, and connect the injection equipment to the wellhead casing; Step S3: Convert the power supply current into a low-frequency surge bidirectional pulse current with a frequency range of 0.5-50Hz; Step S4: Pass the current obtained in step S3 into the wellhead tubing to heat the wellhead tubing. Step S5: Real-time acquisition of wellhead parameters and output parameters of low-frequency surge bidirectional pulse current from step S3; and adjustment of the waveform and frequency of pulse current based on the obtained parameters. Step S6: After heating for a period of time, inject cleaning agent into the casing through the injection equipment, and observe the changes in the injection pressure parameters of the target well to determine the degree of wax blockage in the wellbore; Step S7: Continuously inject cleaning agent into the casing until the well unblocking work is completed.

[0005] Furthermore, in step S1, the high-frequency current is 380V industrial power.

[0006] Furthermore, in step S2, the changes in current and voltage of the electrolysis equipment determine the unblocking status of the pipeline. When gas and liquid are discharged from the valve port and there are no solid blockages, it is determined that the unblocking of the ground pipeline is completed, and the output end of the injection equipment is connected to the well casing.

[0007] Furthermore, in step S3, the low-frequency surge bidirectional pulse current is a positive and negative pulse DC current, and its current frequency is automatically controlled by the controller.

[0008] Furthermore, in step S6, when the injection pressure in the target well decreases and fluid is discharged from the tubing, it is determined that the blockage has been successfully cleared.

[0009] The present invention also provides a device for treating wells without pressure relief channels, and the method for treating wells without pressure relief channels according to any one of the preceding claims includes: The wellhead assembly includes a casing, tubing, a heating coil, and a pulse heater. The casing and tubing are arranged concentrically at the wellhead, with the tubing located inside the casing. The heating coil is installed on the exposed portion of the tubing at the wellhead and wound around the tubing. The input of the heating coil is connected to a field power source, which powers the coil to heat the tubing. The input of the pulse heater is also connected to a field power source, converting the power into a low-frequency, bidirectional surge current. Its output is connected to the casing, and the converted current output is used to heat the casing. The pulse heater collects wellhead data and its own output current parameters, adjusting these parameters in real time to provide feedback regulation. A cleaning agent tank is located next to the casing, and its output is connected to a casing valve via an injection pump.

[0010] Furthermore, the pulse heater is equipped with an inverter, a data acquisition module, a current adjustment module, and a controller. The inverter converts the output current of the field power supply into DC power and inputs it into the current adjustment module to adjust the current waveform. The data acquisition module collects the operating parameters of the oil pipe, casing, and pulse heater and sends the collected parameters to the controller. The output terminal of the controller is connected to the current adjustment module, and controls the current adjustment module according to the data sent by the data acquisition module. The output terminal of the current adjustment module is connected to the casing to output current into the casing to achieve energized heating.

[0011] Furthermore, the current adjustment module is composed of an insulated gate bipolar transistor (IGBT) module integrated on the control chip, which converts the input DC current into a low-frequency surge bidirectional pulse current.

[0012] Furthermore, the data acquisition module includes a temperature sensor, a current measurement sensor, a pressure sensor, and a voltage sensor.

[0013] Furthermore, the controller is equipped with a touch screen, and the controller transmits the received signals to the touch screen to convert them into visual signals for display.

[0014] (III) Beneficial Effects This invention provides a method and equipment for treating wells without pressure relief channels. By inputting a low-frequency surge bidirectional pulse current into the casing, the direction of the current can be periodically changed while heating the casing, thereby preventing the downhole environment from corroding the casing and protecting it. Combined with the injection of cleaning agent into the well, a well-washing channel can be created to perform comprehensive well-washing and dewaxing of the target well without the need for major workover operations. The cost of operation is low and the dewaxing effect is good. Attached Figure Description

[0015] Figure 1 This is a flowchart of the treatment method for wells without pressure relief channels according to the present invention; Figure 2 This is a structural diagram of the pressure relief channel well treatment device of the present invention; Figure 3 This is a diagram showing the working relationship between the modules within the pulse heater of the pressure relief channel well treatment device of the present invention.

[0016] The components include: 1. casing; 2. oil pipe; 3. cleaning agent storage tank; 4. injection pump; 5. heating coil; and 6. pulse heater.

[0017] The detailed embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] In the description of this invention, it is necessary to understand that the orientation or positional relationship indicated by terms such as "upper", "lower", "inner", "outer", "top", and "bottom" are based on the orientation or positional relationship shown in the accompanying drawings. The purpose is only to facilitate the description of this invention and to simplify the description. It is not intended to indicate or imply that the component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention. Example

[0019] like Figure 1 As shown, the present invention provides a method for treating wells without pressure relief channels, characterized in that it includes: Step S1: Install an electromagnetic heating generator at the wellhead tubing and pass a high-frequency current into the electromagnetic heating generator to heat the wellhead tubing.

[0020] Typically, the high-frequency current used is the commonly available 380V industrial power. The heater is installed at the wellhead of the target well, and it heats the pipeline above the surface. As the pipeline heats up, the surface portion of the pipeline heats up, causing the wax adhering to the tubing to melt and flow downwards along the casing, creating space for the subsequent injection of cleaning agents. Simultaneously, comparing the heater's output power and the melting state of the wellhead blockage during the heating process provides data for subsequent power-on heating procedures.

[0021] For example, during the heating of the wellhead pipeline, if the electric heater outputs power according to the planned schedule, but the melting rate of the wax in the heated section of the pipeline is observed to be lower than the planned melting rate, then in subsequent heating processes, the output power of the heating pipeline needs to be increased based on the planned power output to ensure that the heating and unblocking efficiency meets the requirements of the plan. During the heating process, workers can open the observation port and valve port of the surface pipeline to directly determine the melting rate of the wax in the well by observing the melting state of the solids inside.

[0022] Step S2: Observe the changes in equipment current and voltage, and the heating and unblocking of underground tubing and surface pipelines. Connect the injection equipment to the wellhead casing. As mentioned above, during the heating process, the operator determines the unblocking status of the pipeline by observing the changes in current and voltage of the electrolysis equipment. By opening the ground valve or observation port and looking into the well, the operator determines the melting state of the wax in the ground pipeline, thus confirming the unblocking status of the ground section. During the process of energizing the ground heating section, as the pipeline gradually heats up, the current and voltage of the pipeline will change accordingly. Because the resistance of the metal increases with temperature, the operating current in the device decreases when the voltage is constant, and the operating voltage decreases when the current is constant. When the changes in current and voltage of the electrolysis equipment indicate that the device has reached a certain temperature under the influence of the current, the unblocking status of the ground section can be determined by observing the discharge from the ground valve.

[0023] Generally, when gas or liquid flows out of the valve port and there are no solid blockages, it is determined that the surface pipeline has been unblocked, and the output end of the injection equipment is connected to the wellhead casing valve. At this time, the output port of the injection equipment is connected to the casing valve through a pipeline. The injection equipment can be started at any time as needed to inject the agent into the blocked area in the annular space of the casing to melt and clean the waxy blockage in the wellhead tubing. Typically, when the operator observes into the well through the open valve port or observation port, if there are no obvious fixed blockages near the valve port and gas or liquid is flowing out, it is determined that the injection equipment can be connected.

[0024] Step S3: Convert the output current of the common power supply into a low-frequency surge bidirectional pulse current with a frequency range of 0.5-50 Hz. During the heating process, the heating effect in the pipe varies depending on the frequency of the current. The commonly used 50 Hz power frequency current will create a "skin effect" on the surface of the bushing during heating. When alternating current passes through a conductor, the current density will concentrate near the conductor surface. The higher the frequency, the more concentrated the current is on the conductor surface, and the current density at the center of the conductor approaches zero. This makes the heating effect mainly concentrated on the surface of the pipe, which is not effective for heating and unblocking pipes located underground, especially at depths of over 1000m, where the heating efficiency is greatly reduced due to the "skin effect." Therefore, when energizing the bushing for heating, it is necessary to reduce the frequency of the current to weaken the "skin effect" during operation. Normally, the current frequency is between 0.5-50 Hz. In actual operation, the current frequency can be intelligently and automatically modified according to work requirements and conditions.

[0025] Low-frequency surge bidirectional pulse current is formed by adding surge impact to bidirectional direct current. During the direct current output process, a high-frequency pulse current is input into the direct current, causing the output frequency current to suddenly increase and then decrease to the normal operating frequency, forming a surge-like current frequency change. When a surge occurs, the maximum frequency of the current is usually between 1-1000 Hz. Since the operating frequency during normal operation is 0.5-50 Hz, the maximum frequency of the surge is usually limited to between 500-1000 Hz to ensure the efficiency of the surge current. Each surge corresponds to a pulse current in the metal pipe. The pulse can generate mechanical waves on the underground metal pipe. Under the impact of the mechanical waves, the pipe can vibrate slightly, accelerating the shedding of impurities such as wax on the metal pipe wall.

[0026] In step S3, the low-frequency surge bidirectional pulse current is direct current (DC) with a periodic change in direction. Since the power supply used during operation is typically 220V or 380V AC, to ensure the stability of the converted current, the current from the power supply is not directly frequency-converted during the conversion process. Instead, the power supply output current is first filtered to convert the AC power to DC. Compared to the initial power supply, the DC power obtained from the first conversion is more stable. Then, an inverter is used to invert the DC power obtained from the first conversion, periodically changing its current direction to form a low-frequency bidirectional pulse current. A periodic high-frequency pulse current is then input into this low-frequency surge bidirectional pulse current.

[0027] Step S4: Input the current obtained in step S3 into the wellhead tubing to heat the tubing. Since the tubing is made of metal during operation, as the current flows into it, electrons move continuously, generating heat. With continuous current supply to the casing and tubing, both the surface tubing and the deeply buried casing and tubing gradually heat up. As the temperature rises, the wax adhering to the casing and tubing surface melts and falls off, gradually creating cracks in the blockage between the casing and tubing. As the cracks extend and widen, a well-washing channel is formed between the tubing and casing, allowing the well-washing fluid and cleaning agent to flow. At this point, the melted wax can be carried out of the tubing along the formed well-washing channel by injecting cleaning agent into the well.

[0028] Existing technologies also employ methods of electrically heating casing to achieve delamination and wax removal. However, these technologies typically use only direct current (DC) with a single flow direction as the heating source. Buried underground, the casing is constantly in contact with the surrounding soil. When DC current flows through the casing, it forms a battery-like structure underground. While this effectively heats the casing, the gradual outflow of electrons from the internal metal material under the influence of DC current accelerates corrosion from the surrounding geological environment, significantly shortening its lifespan. As the delamination depth increases, the heating time also increases. For casings at depths exceeding 1000m, using a single DC current for heating can lead to severe corrosion from the surrounding geological environment. Even if delamination and delamination are completed, normal production from subsequent wells cannot be guaranteed. This technology combines periodic changes in the direction of direct current flow with high-frequency pulsed current to create a low-frequency surge bidirectional pulsed current. During the heating process, the periodic change in current direction causes electrons to return to the casing after leaving it, driven by the current direction. This achieves effective heating of the casing while avoiding corrosion caused by the current flow. This allows unrelieved wells with wax blockage to return to a normal state without major overhauls, reducing the cost and workload of treating such wells. Simultaneously, the surge impact of the high-frequency pulsed current accelerates the removal of impurities from the metal casing wall, improving cleaning efficiency.

[0029] Step S5: Real-time acquisition of wellhead parameters and low-frequency surge bidirectional pulse current output parameters from Step S3. Adjust the waveform and frequency of the pulse current based on the obtained parameters. During the energized heating process, to understand the device's operating status and unblocking progress, it is necessary to measure the output current and voltage, as well as the casing temperature, casing current, and casing resistance. During operation, measuring the casing temperature and resistance allows for assessment of the heating efficiency. Generally, as the conductor temperature rises, its resistance gradually decreases. Therefore, if the temperature change does not match the casing resistance change during measurement—for example, if the measured casing temperature gradually rises, but the casing resistance change does not match the temperature change—it indicates that the output current parameters are not stable. In this case, the pulse current frequency and waveform need to be adjusted before continuing measurement until the casing temperature and resistance change match and the device is in a heating state. There are no specific rules for adjusting the pulse current frequency and waveform during this process; judgment and experimentation based on the on-site conditions are required.

[0030] Generally, before performing heating and unblocking work, the operator sets a rated output power based on the site conditions and experience. During the heating process, if the output power is less than the rated output power and the measured resistance of the bushing remains unchanged for a period of time, it indicates that the current output power is insufficient to effectively heat the bushing. Initially, the frequency of the bidirectional pulse current is typically 5 Hz. After determining that effective heating is impossible during the above process, the output frequency is uniformly reduced, and the output power is measured in real time. As the frequency decreases, the current penetration increases, thus increasing the output power during the heating process. When the output power reaches 110% of the rated power, the output power of the device is uniformly reduced to avoid overloading the device. Simultaneously, during the process of reducing the frequency to increase the output power, the output current waveform can be adjusted to increase its duty cycle, further increasing the device's output power. Similarly, during the process of increasing the frequency to reduce the output power, the output current waveform can be changed to decrease its duty cycle, further reducing the output power and preventing device overload. During operation, as the frequency and waveform of the output current change, the output power of the heating and unblocking process also changes. During the adjustment process, the real-time output power of each parameter is recorded, and the parameter with the highest output power and safe operation is selected as the optimal operating parameter. Then, the output current parameter is adjusted to the optimal operating parameter and the parameter is kept stable for output.

[0031] Step S6: After heating for a period of time, inject cleaning agent into the casing using an injection device and observe the changes in target well parameters to determine the degree of wax blockage in the wellbore. After heating for a period of time, in order to verify the specific unblocking effect, it is necessary to inject cleaning agent into the casing and observe the state inside the well to determine the degree of wax blockage in the unblocked casing. At the same time, after the cleaning agent is injected into the casing, it can dissolve the melted wax blockage and prevent the melted wax from re-solidifying downhole and forming secondary blockage. Under normal circumstances, the cleaning agent is a wax dissolving agent or water. Wax dissolving agents include organic solvents such as gasoline and diesel. Wax can dissolve in organic solvents after contacting them. In addition, for some water-soluble organic solvents such as ethanol and ether, surfactants such as sodium dodecylbenzenesulfonate can be added to the wax dissolving agent to enhance the solubility of wax in organic solvents, thereby increasing the amount of wax dissolved and improving the wax removal and unblocking efficiency.

[0032] The target well parameters include the cleaning agent injection pressure and the wax content of the tubing backflow fluid. These two values ​​are compared with specified values; the closer the measured value is to the specified value, the lower the degree of wax blockage in the target well. After the casing is heated for a period of time, the wax dissolved in the casing and tubing gradually forms a connected well-washing channel. At this time, the cleaning agent injected from the casing flows along the well-washing channel and backflows from the tubing wellhead. During the backflow process, the cleaning agent gradually dissolves the decomposed wax and carries it back out from the tubing inlet. At this point, the staff can measure the wax content of the returned fluid. Generally, the wax content of the returned fluid gradually decreases as the wax in the well decreases. When the wax content is lower than the specified value, it indicates that the unblocking is complete. At the same time, the degree of unblocking can also be judged based on the injection pressure of the cleaning agent. When the cleaning agent is first injected, the well washing channel in the well is narrow. The cleaning agent flows in the narrow downhole space, causing pressure buildup at the output end of the injection equipment, and the cleaning agent injection pressure increases. As the wax gradually dissolves, the well washing channel in the well gradually expands, and the cleaning agent injection pressure also decreases. When the cleaning agent injection pressure reaches the normal pressure value at the wellhead, it indicates that the wax removal and unblocking work in the well is complete, and the degree of wax blockage is low.

[0033] Step S7: Continuously inject cleaning agent into the casing until the well unblocking work is completed. As described in step S6, during the dewaxing and unblocking process, cleaning agent needs to be continuously injected into the well until the wax content of the fluid flowing back from the wellhead decreases to below the specified value and the cleaning agent injection pressure reaches the normal cleaning agent injection pressure. Example

[0034] like Figure 2-3 As shown, the present invention also provides a treatment device for wells without pressure relief channels, which, using the treatment method for wells without pressure relief channels in the above embodiments, includes: The well consists of a casing 1, tubing 2, heating coil 5, and pulse heater 6. Casing 1 and tubing 2 are concentrically arranged at the wellhead, with tubing 2 located inside casing 1. Casing 1 and tubing 2 are part of the original structure of the target well. During normal production, tubing 2 serves as the main production channel, with underground oil being pumped into the well by the oil pump. Casing 1 primarily provides support, preventing the pressure of the surrounding formation from directly acting on tubing 2. It also forms an annular channel between casing 1 and tubing 2 to facilitate subsequent well processing. Downhole crude oil generally contains wax. During production, the wax in the oil gradually precipitates and adheres to the inner and outer walls of tubing 2 and the inner wall of casing 1, causing wax blockage in the well. After wax blockage, the well becomes a well without pressure relief channels due to the blockage of both the tubing and the annular channel.

[0035] The heating coil 5 is installed on the exposed portion of the oil pipe 2 and wound around its surface. The input end of the heating coil 5 is connected to a local power supply, which powers the coil to heat the oil pipe 2. The working principle of the heating coil 5 is similar to that of an induction cooker. During installation, the coil is typically wound around the exposed portion of the oil pipe 2. When current flows through the coil, an alternating magnetic field is generated. Eddy currents are generated within the oil pipe 2 at the contact point with the coil, and these currents, due to the pipe's resistance, generate heat, thus heating the portion of the pipe above ground. In most working environments, simply connecting the local power supply directly to the exposed portion of the oil pipe 2 is sufficient to heat and unblock the blockage. However, in low-temperature environments such as winter, the direct power supply may not provide sufficient heat. In such cases, the heating coil 5 must be installed on the exposed portion of the oil pipe 2 and powered through it for heating.

[0036] It is important to note that, to maintain the safety and stability of the device during operation, electrical components such as control switches and protective switches are typically installed between the heating coil 5 and the local power supply. The control switches can switch the operating and stopping states of the working coil 5 by closing and opening / closing them. Protective switches include common circuit breakers, overvoltage switches, and overheat switches to protect the circuit. Among the protective switches, circuit breakers, overvoltage switches, and overheat switches are connected between the heating coil 5 and the local power supply. When a short circuit occurs in the circuit, the circuit breaker trips to cut off the circuit; when the operating voltage exceeds a safe value, the overvoltage switch trips to cut off the circuit; and when the operating temperature exceeds a safe value, the overheat switch trips to cut off the circuit, thereby protecting the circuit.

[0037] During the heating process of the working coil 5, an ammeter and a ohmmeter can be additionally installed on the working coil 5. The output power of the working coil 5 can be obtained by measuring the values ​​of the ammeter and ohmmeter, and the obtained output power is denoted as P. 线圈 Simultaneously, observe the unblocking process and speed of the blockages inside the oil pipe 2 and the ground section of the casing 1, providing a reference for setting the rated output power during subsequent heating and unblocking processes. For example, in P... 线圈 Under the output power, the operator observed that the heating and unblocking speed inside the wellhead met the preset plan. Therefore, based on the ratio of the length of the surface portion of tubing 2 and casing 1 to the total length of casing 1, the rated output power for subsequent heating and unblocking processes was set, and the length of the surface portion was denoted as H. 地 The total length of sleeve 1 is denoted as H. 总 Then P 额定 =H 总 ·P 线圈 / H 地After calculating the rated power P, the rated power P is only a reference value. The operator can select a suitable output power near the reference value as the rated output power based on experience.

[0038] In this invention, the input end of the pulse heater 6 is connected to the field power supply, converting the field power supply into a low-frequency surge bidirectional pulse current. The output end is connected to the casing 1, and the converted current output value is used to heat the casing 1. The pulse heater 6 collects wellhead data and its own output current parameters and adjusts its own output current parameters in real time based on the collected data, forming feedback regulation. By converting the current of the field power supply through the pulse heater 6, the AC power with a field frequency of 50Hz or 60Hz is converted into a low-frequency surge bidirectional pulse current, which can improve the stability of the current. At the same time, the skin effect generated by the low-frequency current in the process of heating the casing 1 is greatly reduced compared with the field power supply directly heating the casing 1, which can better heat the casing 1 that is deep underground, thereby improving the heating efficiency in the process of heating the casing 1 by electricity.

[0039] The pulse heater 6 is equipped with an inverter, a data acquisition module, a current adjustment module, and a controller. The inverter converts the output current of the field power supply into DC power and inputs it into the current adjustment module to adjust the waveform of the current. The data acquisition module collects the operating parameters of the oil pipe, the casing, and the pulse heater 6 and sends the collected parameters to the controller. The output terminal of the controller is connected to the current adjustment module and controls the current adjustment module according to the data sent by the data acquisition module. The output terminal of the current adjustment module is connected to the casing 1 to output current to the casing 1 to achieve energized heating.

[0040] It should be noted that the data acquisition module includes a temperature sensor, a current measuring device, a pressure sensor, and a voltage sensor. The input terminals of the current measuring device and the voltage measuring device are connected to the output terminals of the pulse heater 6, reading the voltage and current output of the pulse heater 6 and sending the read current and voltage signals to the controller. The input terminal of the temperature sensor is connected to the casing 1, and the output terminal is connected to the controller; it reads the real-time temperature of the casing 1 and sends the read signal to the controller. The input terminal of the pressure sensor is installed at the wellhead, and the output terminal is connected to the controller; it measures the wellhead pressure in real time and transmits the pressure to the controller. Additionally, a resistance measuring device can be installed on the casing 1 to measure the resistance of the casing 1 in real time and send the measured data to the controller.

[0041] During operation, the pulse heater 6 collects real-time data on wellhead pressure, casing 1 temperature, and its own output current parameters. Based on the collected data, it determines the heating efficiency and adjusts the output current parameters accordingly. Generally, during the heating process, the overall temperature of casing 1 increases with the heating time, and the resistance of casing 1 decreases as the temperature rises.

[0042] According to the formula P=I 2 R can be used to determine the real-time output frequency, where I is the output current of pulse heater 6, R is the resistance of bushing 1, and P is the output power.

[0043] After calculating the real-time output power, pulse heater 6 compares the output power with the rated output power. When the output power of pulse heater 6 is less than the rated output power and the resistance of casing 1 remains stable for a period of time, pulse heater 6 reduces the frequency of the output current and adjusts its waveform to increase the duty cycle, thereby increasing the output power. When the output power is greater than 110% of the rated output power, pulse heater 6 increases the frequency of the output current and adjusts the output current waveform to reduce its duty cycle, thereby reducing the output power and preventing overload of pulse heater 6. Typically, the initial frequency of the output current of pulse heater 6 is 5 Hz, and the frequency adjustment range is 1-5 Hz. In actual operation, the operator can adjust the frequency range and initial frequency according to the actual situation of the unblocked well.

[0044] In this invention, the inverter preferably uses an IGBT module, such as the FF400R12KT3P_E model inverter, which has a more stable output current waveform compared to traditional inverters.

[0045] The current regulation module is composed of Insulated Gate Bipolar Transistor (IGBT) modules integrated on the control chip. The current regulation module converts the input DC current into a low-frequency surge bidirectional pulse current. Typically, the current regulation module is a full-bridge inverter circuit with four arms, each containing two parallel IGBT modules. The four arms are designated IGBT1, IGBT2, IGBT3, and IGBT4. IGBT1 and IGBT2 are connected in parallel, with their outputs connected to the positive terminal of the inverter's DC bus and their inputs connected to bushing 1. IGBT1 and IGBT2 are designated as the upper arm. IGBT3 and IGBT4 are connected in parallel, with their outputs connected to the negative terminal of the inverter's DC bus and their inputs connected to bushing 1. IGBT3 and IGBT4 are designated as the lower arm. The control signal input terminal of each IGBT module is connected to a signal output pin on the control chip. Utilizing the bidirectional connectivity of the IGBT modules, the direction of the current can be changed by sending control signals to the IGBT modules to alter the switching states of the upper and lower arms. During operation, the control chip sends a control signal to the upper bridge arm to connect the IGBT module within it. Simultaneously, the IGBT module in the lower bridge arm disconnects, and current flows from the current adjustment module into bushing 1 and then into the bottom layer. Similarly, after sending a control signal to the lower bridge arm, the current flows from the bottom layer to bushing 1 and then to the current adjustment module. During operation, the control chip within the current adjustment module periodically sends control signals to the IGBT modules in both the upper and lower bridge arms, thus controlling the periodic change in the output current direction. The period of the control signals from the upper and lower bridge arms alters the frequency of the output current.

[0046] In this method, by controlling the current frequency and the operating duration of the IGBT modules in the upper and lower bridge arms in each cycle, the duty cycle of the positive and negative currents can be changed, thereby altering the current waveform.

[0047] It should be noted that, in order to simplify the workflow, the current adjustment module and the signal acquisition module can be integrated into the controller. The controller is usually a microcontroller (MCU) or a digital signal processor (DSP), which can be purchased directly. After connecting the data acquisition module and the current adjustment module to the corresponding pins in the controller, the calculation and processing program in the controller can be encoded to make it work according to the predetermined processing sequence and workflow.

[0048] In this invention, a cleaning agent storage tank 3 is provided next to the casing 1. The output end of the cleaning agent storage tank 3 is connected to the casing 1 via an injection pump 4. The cleaning agent storage tank 3 is used to hold the cleaning agent used in the unblocking process. The outlet of the cleaning agent storage tank 3 is provided with a drain pipe and connected to the casing 1 via a return pipe. The cleaning agent is injected into the casing 1 through the drain pipe. Since the well is in a wax-blocked state, the liquid pressure in the cleaning agent storage tank 3 alone is insufficient to smoothly inject the cleaning agent into the casing 1. Therefore, an injection pump 4 needs to be installed on the drain pipe. The input end of the injection pump 4 is connected to the pipe on the side of the cleaning agent storage tank 3, and the output end is connected to the drain pipe on the side of the casing 1. The cleaning agent is injected into the casing 1 through the output pressure of the injection pump 4. During the injection of the cleaning agent, the injection pressure is usually 25 MPa. The high-pressure liquid injected into the casing 1 can impact the blockage inside the casing 1, flushing away the loosely attached blockage from the inner wall of the casing 1. To improve the flushing effect on the blockage in the casing 1, the injection pump 4 can be started and stopped intermittently in the initial stage of injecting the cleaning agent. For example, the injection pump 4 can be started once every 30 seconds, and the running time of the injection pump 4 is 10 seconds each time. This creates periodic high-pressure liquid pulses in the casing 1, thereby improving the flushing and dissolving efficiency of the cleaning agent on the blockage.

[0049] In order to facilitate the control of the output volume and output power of the injection pump 4, a shut-off valve can be installed before the input end and after the output end of the injection pump 4, which are respectively called the pump inlet valve and the pump outlet valve. By adjusting the opening of the pump outlet valve, the outlet pressure and discharge volume of the injection pump 4 can be adjusted. When the pump outlet valve is closed, the outlet pressure of the injection pump 4 increases, and vice versa.

[0050] It is important to note that before continuously injecting the cleaning agent into casing 1, a period of time is required to allow the current to fully heat casing 1. Typically, the cleaning agent is injected into casing 1 24 hours after the pulse heater 6 powers on the casing to heat and unblock it. At this time, after a long period of heating and unblocking, the blockage in the well is filled with cracks caused by the heating and unblocking process. After the cleaning agent is injected, the pressure of the cleaning agent and its dissolution of the wax can be used to open up the cracks and form a continuous well-washing channel. The cleaning agent can be injected from casing 1 and then back out from tubing 2 to the surface.

[0051] In this invention, the controller is equipped with a touch screen. The controller transmits received signals to the touch screen and converts them into visual signals for display. By installing a touch screen on the controller, the information parameters collected within the controller can be directly converted into visual signals, allowing operators to directly read specific parameters on the touch screen, reducing the difficulty of operating the device. Simultaneously, the touch screen also functions as a control signal input. During operation, operators can send signals to the controller via the touch screen to switch the device's operating state between automatic and manual control modes. This is achieved by encoding the program within the controller. When switching to manual control mode, operators can directly input the required operating parameters into the controller. The controller then adjusts the output parameters of the current adjustment module to match the input parameters, thus enabling manual control of the device.

[0052] The method and equipment for treating wells without pressure relief channels provided by this invention can remove wax and form a new well-washing channel in wells without pressure relief channels by means of electric heating, without major overhaul operations. A cleaning agent is then injected to assist in the wax removal and unblocking process. The specific operation process of this invention is as follows: Step 1: Select a suitable cleaning agent based on the condition and parameters of the target well and load the cleaning agent into the cleaning agent storage tank.

[0053] Step 2: Wrap the heating coil around the portion of the tubing above ground and energize the coil to heat the tubing and casing. At this point, current flows into the heating coil, creating an induced electromotive force around it. Under the influence of this induced current, eddy currents are generated within the tubing and casing around the heating coil. These eddy currents gradually heat the tubing and casing, causing the waxy blockages adhering to the inner and outer walls of the tubing and casing above ground to gradually melt.

[0054] Step 3: Observe the melting state of the blockage in the tubing and casing at the wellhead. Once there is no obvious blockage, connect the cleaning agent storage tank to the casing through the drainage pipe of the drainage pump. At this point, the output end of the drainage pump is connected to the casing, and the blockage at the connection has been cleared. Start the drainage pump to inject the cleaning agent into the casing.

[0055] Step 4: Connect the output terminal of the pulse heater to the bushing. The measuring terminal of the data acquisition module inside the pulse heater is installed on both the bushing and the pulse heater. At this time, the pulse heater converts the normal power supply into a low-frequency surge bidirectional pulse current and injects it into the bushing. The current flowing in the bushing generates heat, raising the bushing temperature to perform the heating and dewaxing process. Simultaneously, the data acquisition module collects the operating parameters of the bushing and the output parameters of the pulse heater and sends the collection results to the control terminal. The control terminal adjusts the frequency and waveform of the pulse heater's output current based on the collected data, forming a feedback regulation.

[0056] Step 5: After continuous heating for a period of time, start the drainage pump to inject the cleaning agent into the casing. Once started, the drainage pump pressurizes the cleaning agent, which, when injected into the casing, dissolves and flushes away the blockages adhering to the inner wall of the casing and the outer wall of the tubing, thus performing dewaxing. Simultaneously, after prolonged heating, the blockages inside the well melt and create cracks. The pressurized cleaning agent injected by the drainage pump flows downwards along these cracks, dissolving and cleaning the blockages it passes through, gradually clearing a well-washing channel. The cleaning agent, after being injected into the casing, flows back out from the tubing outlet along this channel.

[0057] Step Six: Continuously inject cleaning agent into the well and monitor the wax content in the fluid returned from the tubing outlet until the wellhead pressure returns to normal and the wax content in the returned fluid is within the normal range. With continuous injection of cleaning agent, blockages in the casing and tubing are gradually cleared by the combined effect of heating and the cleaning agent, and then returned from the tubing outlet along with the cleaning agent. As the blockages decrease, the downhole space gradually increases, reducing the pressure build-up at the outlet of the drainage pump, and the wellhead pressure gradually decreases; simultaneously, the wax content in the fluid returned from the tubing outlet gradually decreases. When both the wellhead pressure and the wax content in the returned fluid are within the normal range, the well dewaxing process is complete.

[0058] Step 7: Power off the equipment and retrieve it.

[0059] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for treating wells without pressure relief channels, characterized in that, include: Step S1: Install an electromagnetic heating generator at the wellhead tubing and pass a high-frequency current into the electromagnetic heating generator to heat the wellhead tubing. Step S2: Observe the changes in equipment current and voltage and the heating and unblocking of the ground pipeline, and connect the injection equipment to the wellhead casing; Step S3: Convert the power supply current into a low-frequency surge bidirectional pulse current with a frequency in the range of 0.5-50 Hz. Step S4: Pass the current obtained in step S3 into the wellhead tubing to heat the underground tubing at the wellhead. Step S5: Real-time acquisition of wellhead parameters and output parameters of low-frequency surge bidirectional pulse current from step S3; and adjustment of the waveform and frequency of pulse current based on the obtained parameters. Step S6: After heating for a period of time, inject cleaning agent into the casing through the injection equipment, and observe the changes in the injection pressure parameters of the target well to determine the degree of wax blockage in the wellbore; Step S7: Continuously inject cleaning agent into the casing until the well unblocking work is completed.

2. The method for treating wells without pressure relief channels according to claim 1, characterized in that, In step S1, the high-frequency current is 380V industrial power.

3. The method for treating wells without pressure relief channels according to claim 1, characterized in that, In step S2, the unblocking status of the pipeline is determined by the changes in current and voltage of the electrolysis equipment. When gas and liquid flow out of the valve port and there are no solid blockages, it is determined that the unblocking of the above-ground part of the pipeline is completed, and the output end of the injection equipment is connected to the wellhead casing.

4. The method for treating wells without pressure relief channels according to claim 1, characterized in that, In step S3, the low-frequency surge bidirectional pulse current is a positive and negative pulse DC current, and the current frequency is automatically controlled by the controller, injecting high-frequency surges into the current at random intervals.

5. The method for treating wells without pressure relief channels according to claim 1, characterized in that, In step S6, when the injection pressure in the target well decreases and fluid is discharged from the tubing, it is determined that the blockage has been successfully cleared.

6. A treatment device for a well without pressure relief channel, using the treatment method for a well without pressure relief channel as described in any one of claims 1-5, characterized in that, include: The well consists of a casing (1), tubing (2), a heating coil (5), and a pulse heater (6). The casing (1) and tubing (2) are arranged concentrically at the wellhead, with the tubing (2) located inside the casing (1). The heating coil (5) is installed on the exposed portion of the tubing (2) at the surface wellhead and wound around the tubing (2). The input end of the heating coil (5) is connected to the field power supply, which powers the heating coil (5) to heat the tubing (2). The input end of the pulse heater (6) is connected to the field power supply. Next, the power supply on site is converted into a low-frequency surge bidirectional pulse current, and the output end is connected to the casing (1). The converted current output value is used to heat the casing (1). The pulse heater (6) collects wellhead data and its own output current parameters and adjusts its own output current parameters in real time according to the collected data to form feedback regulation. A cleaning agent storage tank (3) is provided next to the casing (1). The output end of the cleaning agent storage tank (3) is connected to the valve of the casing (1) through the injection pump (4).

7. The treatment equipment for non-pressure relief channel wells according to claim 6, characterized in that, The pulse heater (6) includes an inverter, a data acquisition module, a current adjustment module, and a controller. The inverter converts the output current of the field power supply into DC power and inputs it into the current adjustment module to adjust the waveform of the current. The data acquisition module collects the working parameters of the oil pipe, the casing, and the pulse heater (6) and sends the collected parameters to the controller. The output end of the controller is connected to the current adjustment module and controls the current adjustment module according to the data sent by the data acquisition module. The output end of the current adjustment module is connected to the casing (1) and outputs the adjusted current to the casing (1) to achieve power-on heating.

8. The treatment equipment for non-pressure relief channel wells according to claim 7, characterized in that, The current adjustment module is composed of an insulated gate bipolar transistor (IGBT) module integrated on the control chip, which converts the input DC current into a low-frequency surge bidirectional pulse current.

9. The treatment equipment for non-pressure relief channel wells according to claim 6, characterized in that, The data acquisition module includes a temperature sensor, a current measurement sensor, a pressure sensor, and a voltage sensor.

10. The treatment equipment for non-pressure relief channel wells according to claim 6, characterized in that, The controller is equipped with a touch screen, which transmits the received signals to the touch screen and converts them into visual signals for display.

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